Reactions of Al/P, Ga/P and P–H functionalized frustrated Lewis pairs with azides and a diazomethane – formation of adducts and capture of nitrenes

2.1 Azide complexes

Treatment of the FLPs Mes₂P–C(AlR₂)=CH-R′ (1, M=Al, R=^tBu [6]; 2, M=Al, R=CH₂^tBu [7], [8]; 3, M=Ga, R=^tBu [33]) or Mes(H)P–C{Al[CH(SiMe₃)₂]₂}=C(H)-^tBu 4 [32] with various azides R′-N=N=N at room temperature gave in good yields of 62–94% the corresponding adducts 5–7 (Scheme 2) and 8 (Scheme 3). The yellow (5, 6a–c, 7) to colourless (6d, 8) products were difficult to crystallise and only compounds 5, 6d, 7a [33] and 10a were obtained as crystalline, analytically pure products, that were fully characterised including X-ray crystallography. The other compounds yielded yellow-orange oils which contained only minor impurities, but did not crystallise from various solvents and were characterised by multinuclear NMR spectroscopy. All compounds feature four-membered PCMN heterocycles with the terminal N_γ atom of the azide bound to P and Al or Ga, respectively (see crystal structure determination, NMR discussion).

Scheme 2:

Reactions of FLPs 1–3 with azides. Syntheses of azametallaphosphetanes 5–7.

Scheme 3:

Reactions of the P–H functionalized FLP 4 with azides. Syntheses of compounds 8.

The NMR spectra of compounds 5–7 are very similar. They show a significant downfield shift of the ³¹P NMR resonances from about δ=−15 ppm for the starting FLPs to δ=34.6 (6d) to 45.0 (7b) ppm consistent with an increased coordination number at the phosphorus atoms from three to four. There is also a downfield shift in the ¹H NMR spectra for the signals of the vinylic hydrogen atoms from δ<7.40 ppm in the FLPs to δ=7.75–7.98 ppm for the azide adducts and an increase in the ³J_PH coupling constants from around 13 Hz to about 42 Hz which is indicative of the larger coordination number on phosphorus and a cis arrangement of phosphorus and vinylic hydrogen atoms across the C=C bonds. The difference arising for Al and Ga derivatives is small (compounds 7 have slightly larger downfield shifts and smaller coupling constants). The corresponding downfield shift in the ³¹P NMR spectra of compounds 8 in comparison to 4 is slightly larger (from δ=−80.8 to around δ=−12 ppm), the shift in the ¹H NMR spectra is similar (from δ=6.69 to about δ=7.20 ppm). The ³J_PH coupling constants of the adducts 8 (75 Hz) and the starting material 4 (31.8 Hz) are much larger compared to those of the dimesitylphosphorus compounds as a result of the trans orientation of phosphorus and vinylic hydrogen atoms and are consistent with the Karplus relation for J_PH coupling constants [41], [42]. Further evidence for adduct formation are the increased ³J_PC coupling constants (ipso-C, C=CPh) from about 13 Hz (1–3) to about 36 Hz (5–7) and increased ¹J_PC coupling constants (ipso-C, Mes) from around 23 Hz in 1–3 to >68 Hz in the adducts which is again consistent with the increase of the coordination number at phosphorus. Surprisingly there is simultaneously a significant decrease in the ¹J_PC coupling constants (PC=CH) from 46 (4) and 58 (1–3) Hz in the starting materials to <1 Hz (or not resolved; 8) and around 13 Hz (5 and 6, M=Al) or 30 Hz (7, M=Ga) in the azide adducts. The values of 1–4 may be influenced by an interaction of the lone pair at phosphorus with the vinylic carbon atom and the attached C–M bond (see also the structure discussion below). Compounds 8 additionally show large ¹J_PH coupling constants close to 470 Hz typical for hydrogen atoms directly bound to four-coordinate phosphorus atoms. Representative ¹H,¹H-ROESY spectra of 5a–c showed cross peaks between the o-hydrogen atoms of the aromatic azide substituents and both the Al^tBu groups and the o-Me groups of the mesityl substituents consistent with free rotation of the azide substituent and close contacts to both groups in solution. The presence of four different substituents on phosphorus introduces chirality in compounds 8 and results in highly complicated spectra with distinct signals for the mesityl substituents and the diastereotopic hydrogen and carbon atoms of CH(SiMe₃)₂ groups.

It is noteworthy that despite the multitude of different azides with a large variety of substituents that range from electron withdrawing [R′=C₆H₄(4-Cl), C₆H₄(4-CF₃)] to electron donating [R′=C₆H₄(4-Me), CH₂C₆H₄(4-^tBu), ^tBu] and that differ in steric bulk [e.g. C₆H₄(4-Cl) versus CH₂C₆H₄(4-Cl) or C₆H₄(2-CH=CHPh) or ^tBu] and the application of four different FLPs that differ in electronegativity and steric bulk of Lewis acid [Al, Ga; ^tBu, CH₂^tBu, CH(SiMe₃)₂] and base (Mes, H), exclusively azametallophosphetanes with four-membered heterocycles [structural motif (i)] and the terminal N atom of the azide in the bridging position were formed. The substituents on the metal and phosphorus atoms may be too bulky to favour a larger heterocycle with two or three nitrogen atoms in the ring (interaction of R′ with FLP substituents). The P–H functionalized compounds did not show the shift of the phosphorus-bound H atom to an azide N atom as observed previously for a Me₃SiN₃ adduct [32].

The molecular structures of six azide adducts were determined by X-ray crystallography and compounds 5a and 8a are shown as representative examples in Figs. 1 and 2 (Table 1). The azide adducts feature slightly puckered (angle MNP/MCP 5.6–12.6°) four-membered PCMN heterocycles with exocyclic N=N double bonds. The endocyclic angles range from 75° (C–M–N) over close to 90° (N–P–C and P–C–M) to 102° (M–N–P). Compounds 5 and 6d differ from 8a in the orientation of the vinylic H atom relative to phosphorus (cis in case of 5 and 6d, trans in case of 8a) which is in agreement with the observed difference in ³J_PH coupling constants discussed above. The N=N double bonds adopt in all compounds a trans configuration but the position of the substituent R′ at N_α differs, it is closer to the metal centre in case of compounds 5 and 6d and closer to the phosphorus atom in case of compound 8a. The reason for the different configurations may be the steric demand of the CH(SiMe₃)₂ groups and a minimisation of steric repulsion. The N–N bond lengths range from 134.7(2) pm (8a) to 138.1(2) pm (6d; N_β–N_γ) and 126.4(2) to 124.2(2) pm (N_β=N_α) and are consistent with partial delocalisation of electron density in the N₃ unit as is evident from a comparison with typical N–N single (140 pm) and N=N double bonds (122 pm) [43]. The Al–N and P–N distances of 195 and 166 pm are in the typical range of compounds with four-coordinate Al or P atoms. P–C and M–C bond lengths show the same trends as observed previously in other FLP adducts of 1–4 and are slightly shorter for the P–C bonds in the adducts compared to the free FLPs as a result of the increased oxidation number of the P atoms and longer for the M–C bonds due to the increase in coordination number at the metal atoms (Introduction). The latter effect is particularly significant for the Al–C=C bonds (ca. 207 pm versus 200 pm) and may be attributed to hyperconjugation of a lone pair of electrons from the nitrogen atom with the respective M–C σ* orbital [33].

Fig. 1:

Molecular structure and numbering scheme of compound 5a. Displacement ellipsoids are drawn at the 40% level. Hydrogen atoms (except H2) and a disordered solvent molecule have been omitted for clarity. Compounds 5b–d and 6d are similar.

Fig. 2:

Molecular structure and numbering scheme of compound (S)-8a. Displacement ellipsoids are drawn at the 40% level. Hydrogen atoms (except H1 and H2) have been omitted for clarity.

2.2 Nitrene adducts

Fragments corresponding to the loss of ^tBu or CH(SiMe₃)₂ groups and N₂ molecules were found as high intensity masses in the mass spectra of all azides indicating that N₂ may be released in vacuo without unselective degradation of the compounds. We therefore heated representative azides (5a, 5c, 6a, 6b, 8c) in solution (8c, 80°C, benzene, normal pressure) or in the melt in vacuo to temperatures between 170 and 280°C. All adducts lost selectively N₂ to yield the respective nitrene adducts Mes₂P–C(M^tBu₂)=CH-Ph(μ-NR′) (9, M=Al; 10, M=Ga, Scheme 4) and Mes(H)P–C{Al[CH(SiMe₃)₂]₂}=CH-^tBu (μ-NCH₂Ph) 11 as colourless solids in moderate (10b, 49%; 10a, NMR experiment only) to good yields (9, 11, 73–84%). When 3 was treated with Me₃SiN₃ at room temperature the direct elimination of nitrogen was observed and the nitrene adduct 10c was identified as the single product by multi-nuclear NMR spectroscopy, but the attempts to crystallise and isolate pure products was unsuccessful. This reaction is remarkable as it is only the second example [8] of a highly reactive nitrene to be formed from an azide at such moderate conditions which may likely be attributed to the unique donating capabilities of the SiMe₃ group and its ability to undergo 1,3-shifts. Other azide-FLP complexes (see Introduction and 8, 9, 11) require much higher reaction temperatures. The characteristic NMR spectroscopic parameters are similar to those of the azide adducts. There is a slightly lower downfield shift of the signals in the ³¹P NMR spectra to about δ=33 ppm (+10 ppm for compound 11), and the ³J_PH coupling constants of the vinylic H atoms are with 37 (10), 41 (9) and 51 Hz (11) very similar to the respective values of the azide adducts. The same is true for the ³J_PC (36 Hz, ipso-C, C=CPh) and ¹J_PC (68 Hz, ipso-C, Mes) coupling constants. The ¹J_PC coupling constants to the vinylic carbon atoms are with about 20 Hz (9) and 42 Hz (10) slightly larger than those of the azide adducts. The loss of nitrogen and the formation of nitrene adducts is evident from the observation of ^2/3/4/5J_PC, ^3/4J_PH and ²J_PSi (10c) coupling constants between phosphorus and the respective atoms of the substituents R′ directly bound to the nitrogen atom. The ¹J_PH coupling constant of compound 11 is reduced to 440 Hz.

Scheme 4:

Thermolysis of FLP-azide complexes.

The molecular structures of the nitrene adducts (compound 9a is shown as a representative example in Fig. 3) feature essentially planar PMCA heterocycles [largest deviation from the plane for P: 1 pm (9a) to 15 pm (11)]. The overall geometry and structural parameters of the molecules (endocyclic angles, M–C and P–C/N distances) are almost identical for all nitrene adducts (Table 2) and very similar to those of the azide complexes. The only exception is the Ga–N bond length of 10b which is with 209.4(7) pm significantly longer than the respective bond lengths of the Al derivatives (196 pm) but similar to the corresponding distance in the parent azide 7a (206.8 pm) [33]. This may reflect the lower Lewis acidity of gallium compared to aluminium. Several nitrene adducts of P/B based FLPs have been reported [39], [40], [44], [45], [46].

Fig. 3:

Molecular structure and numbering scheme of compound 9a. Displacement ellipsoids are drawn at the 40% level. Hydrogen atoms (except H2) have been omitted for clarity. Compounds 9b, 10b and 11 are similar.

2.3 Reactions with trimethylsilyldiazomethane

Diazoalkanes are isoelectronic to azides but as a result of the replacement of a nitrogen by a carbon atom the charge distribution on the atoms of the 1,3-dipole differs [47], [48]. To the best of our knowledge, diazoalkanes have not been reacted with FLPs previously. Solutions of FLPs 1 and 2 were treated at room temperature with Me₃Si–C(H)N₂ and stirred for several hours (Scheme 5). After recrystallisation of the crude products the adducts 12a and 12b were obtained as colourless solids in yields of about 90%. The results of the NMR spectroscopic investigations are consistent with those of crystal structure determinations that reveal that both compounds adopt structures similar to those of the azide adducts with an intact diazomethane moiety coordinated to the FLP, the terminal nitrogen atom being coordinated to phosphorus and aluminium, a planar four-membered PCAlN heterocycle [largest distance from average plane 6 pm (P, 12a), 1 pm (P, 12b)], a cis arrangement of phosphorus and vinylic hydrogen atoms, a trans conformation at the external C=N double bond (N and SiMe₃), and the C(H)SiMe₃ group pointing to the aluminium atom rather than to the sterically shielded phosphorus atom (Fig. 4). The chemical shifts of the phosphorus and the vinylic hydrogen atoms in the ³¹P and ¹H NMR spectra are in the same region as those of the azide adducts 5 and 6. Identical ³J_PH (PC=CH) and ³J_PC (ipso-C, C=CPh) coupling constants of 12 and 5 or 6 are in agreement with the observed cis orientation of phosphorus and vinylic hydrogen atoms, while ¹H,¹H ROESY spectra (12a) confirm the vicinity of N=C(H) and ^tBu₂Al as well as C=C(H) and o-Me(Mes) groups. The ¹J_PC (ipso-C, Mes) and ¹J_PC (PC=CPh) coupling constants show with ca. 67 and 17 Hz the same trends as observed for the azides. The characteristic resonances of the imine hydrogen atoms are found at around δ=8 ppm with geminal ²J_SiH coupling constants of 13 and 14.5 Hz. Adduct formation is also evident from the ¹⁵N shifts of δ=169 (N_β) and 386 (N_α) ppm in 12a as compared to δ=342 and 278 ppm in free Me₃Si–C(H)N₂ consistent with a three-coordinate N_β atom in 12a [49]. The N1–N2 bond lengths are with >139 pm (Table 2) longer than those of the azide adducts which indicates together with the short C6=N2 bond (127.7 pm) a lower degree of π delocalisation. In an exploratory experiment a solution of 12b in C₆D₆ was irradiated with polychromatic UV light. This led to the partial isomerisation of 12b at the C=C double bond and the formation of the isomer in which the vinylic hydrogen atom is trans to the phosphorus atom which is recognisable by a new signal in the ³¹P NMR spectrum at δ=30.6 ppm and the characteristic increase of the ³J_PH coupling constant to 72.0 Hz. The reaction was, however, incomplete and after 8 h a 1:1 mixture of the two isomers was obtained which was unaffected by further irradiation or prolonged standing of the sample at room temperature. N₂ elimination was not observed and did also not occur upon heating of neat samples to about 150°C.

Scheme 5:

Reactions of FLPs 1 and 2 with Me₃Si–C(H)N₂.

Fig. 4:

Molecular structure and numbering scheme of compound 12a. Displacement ellipsoids are drawn at the 40% level. Hydrogen atoms (except H6 and H11) have been omitted for clarity. Compound 12b is similar.

In a secondary reaction compound 12a was treated with a solution of HCl in Et₂O which afforded the hydrazonephosphonium salt 13 by cleavage of the polar Al–N bond in 91% yield as a colourless solid (Scheme 5). The ³¹P NMR spectrum shows a signal at δ=53.5 ppm (slightly downfield compared to 5–12) and coupling constants in the typical region as discussed above. Characteristic for the formation of 13 is the proton attached to nitrogen which is found in the downfield region of the ¹H NMR spectrum at δ=9.99 ppm (²J_PH=22.5 Hz). This value is consistent with the presence of a weak intramolecular N–H···Cl hydrogen bond [50], [51], [52], [53], [54], [55] as observed in the solid state structure (see Fig. 5). The N–H stretching frequency centred at 3356 cm⁻¹ is very broad and shifted to lower wave numbers compared to free N–H bonds which also indicates hydrogen bonding [54], [55], [56], [57]. The ¹⁵N chemical shifts of δ=134 and 362 ppm are similar to those of the diazomethane adduct 12a. Compound 13 is zwitterionic in the solid state with four-coordinate phosphorus and aluminium atoms in tetrahedral environments (Fig. 5, Table 2). The vinyl group and the attached phosphorus and aluminium atoms are approximately coplanar with the hydrazine and chlorine substituents on opposite sides of the plane. This allows the formation of an intramolecular N–H···Cl hydrogen bond (H1···Cl1 250.6 pm; N1–H1···Cl1 140.7°) [54], [58] that is comparable to that of the HCl adduct of 1 [23] and consistent with the results of IR and NMR spectroscopy. The P1–N1 (166.0(2) pm), N1–N1 (138.8(2) pm) and N2=C6 (127.1(3) pm) distances are comparable to [Ph₃P–N(H)–N=C(H)-Ph]Cl [59], [Ph₃P–N(H)–NMe₂]Br [60] or IndZrCp₂(2-PPh₂)·[N₂=C(H)–CO₂Et] [61] and in agreement with fairly localised P–N, N–N single and N=C double bonds.

Fig. 5:

Molecular structure and numbering scheme of compound 13. Displacement ellipsoids are drawn at the 40% level. Hydrogen atoms (except H1, H6, H11) have been omitted for clarity.

4.1 {Mes₂PC(Al^tBu₂)=C(H)Ph}{N₃C₆H₄(4-Cl)} (5a)

N₃C₆H₄(4-Cl) (1.1 mL, 0.55 mmol, 0.5 m in t-butyl methyl ether) was transferred into a Schlenk flask. The solvent was removed in vacuo and the residue treated with a solution of compound 1 (0.27 g, 0.53 mmol) in toluene (15 mL). The mixture was stirred overnight, the solvent was removed in vacuo and the residue recrystallised from 1,2-difluorobenzene at −45°C affording yellow crystals of compound 5a. Yield (0.31 g, 81%); m.p. (dec., sealed capillary): 190°C. – IR (CsI, paraffin): ν=1605 m, 1553 w, 1506 w ν(C=C), Aryl; 1454 vs, 1398 s, 1377 vs (paraffin); 1321 vs, 1290 m, 1273 m, 1240 m δ(CH₃); 1148 vs, 1101 s, 1061 vs, 1030 m, 1015 s, 928 w, 889 vw, 849 s, 808 m, 800 m, 750 s δ(CH), ν(CC), ν(CCl), ν(CN); 721 vs (paraffin); 691 vw, 673 vw δ(CH_Ph); 642 m, 619 m, 584 w, 554 w, 517 vw, 496 vw, 473 m, 473 m, 461 w cm⁻¹ν(PC), ν(AlC), ν(AlN), δ(CC). – ¹H NMR (400 MHz, C₆D₆, 300 K): δ=7.98 (d, ³J_HP=41.7 Hz, 1 H, PC=CH), 7.62 [d, ³J_HH=7.4 Hz, 2 H, o-H(Ph)], 7.42 [d, ³J_HH=7.4 Hz, 2 H, o-H(NAr)], 7.16 [m, 2 H, m-H(Ph)], 7.07 [m overlap, 1 H, p-H(Ph)], 7.07 [m overlap, 2 H, m-H(NAr)], 6.59 [d, ⁴J_HP=3.5 Hz, 4 H, m-H(Mes)], 2.42 (s, 12 H, o-Me), 1.92 (s, 6 H, p-Me), 1.43 ppm (s, 18 H, CMe₃). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=155.8 (PC=CH), 150.3 (d, ¹J_CP=13.2 Hz, PC=CH), 149.5 [ipso-C(NAr)], 142.3 [d, ⁴J_CP=2.8 Hz, p-C(Mes)], 141.3 [d, ²J_CP=10.2 Hz, o-C(Mes)], 140.8 [d, ³J_CP=36.3 Hz, ipso-C(Ph)], 133.6 [p-C(NAr)], 132.0 [d, ³J_CP=10.8 Hz, m-C(Mes)], 130.0 [p-C(Ph)], 129.5 [m-C(NAr)], 128.9 [m-C(Ph)], 128.3 [o-C(Ph)], 126.8 [d, ¹J_CP=68.4 Hz, ipso-C(Mes)], 123.1 [o-C(NAr)], 32.2 (CMe₃), 25.2 (d, ³J_CP=3.9 Hz, o-Me), 20.8 (p-Me), 17.2 ppm (s br, CMe₃). – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=40.2 ppm. – ¹⁵N NMR (40.5 MHz, C₆D₆, 300 K): δ=417 (N=NAr) ppm. – MS (EI; 25 eV; 443 K): m/z (%)=608 (83) [M–^tBu]⁺, 580 (100) [M–^tBu–N₂]⁺, 524 (16) [M–Al^tBu₂]⁺, 470 (16) [M–H₂C=CMe₂–N₂C₆H₄Cl]⁺.–C₄₀H₅₀AlClN₃P·0.5C₆H₄F₂ (723.3): calcd. C 71.4, H 7.2, N 5.8; found C 71.1, H 7.1, N 5.4.

4.2 {Mes₂PC(Al^tBu₂)=C(H)Ph}{N₃C₆H₄(4-CF₃)} (5b)

N₃C₆H₄(4-CF₃) (2.2 mL, 1.11 mmol, 0.5 m in t-butyl methyl ether) was transferred into a Schlenk flask. The solvent was removed in vacuo, the residue was dissolved in toluene (2 mL) and the solution was added at room temperature to a solution of compound 1 (0.57 g, 1.11 mmol) in toluene (15 mL). The mixture was stirred overnight, the solvent was removed in vacuo, the residue was washed with n-hexane (6 mL) and recrystallised from 1,2-difluorobenzene at −15°C to give yellow crystals of compound 5b. Yield (0.66 g, 85%); m.p. (dec., sealed capillary): 193°C. – IR (CsI, paraffin): ν=1603 m, 1580 w, 1558 m, 1543 w, 1524 w ν(C=C), Aryl; 1456 vs, 1395 m, 1377 vs (paraffin); 1306 m, 1288 m, 1269 s δ(CH₃); 1238 m, 1229 m, 1207 m, 1142 vs, 1098 m, 1086 m, 1063 m, 1030 m, 1015 s, 984 w, 964 w, 926 w, 891 w, 853 m, 835 s, 810 s, 799 m, 760 w sh, 750 vs ν(CC), ν(CF), δ(CH), ν(CN); 721 m (paraffin); 692 m δ(CH_Ph); 669 vw, 644 s, 623 m, 590 m, 573 w, 556 m, 546 w, 525 m, 496 vw, 471 m, 459 w cm⁻¹ν(PC), ν(AlC), ν(AlN), δ(CC). – ¹H NMR (400 MHz, C₆D₆, 300 K): δ=7.90 (d, ³J_HP=41.7 Hz, 1 H, PC=CH), 7.62 [d, ³J_HH=7.6 Hz, 2 H, o-H(Ph)], 7.46 (d, ³J_HH=8.3 Hz, 2 H, o-H(NAr)], 7.30 [d, ³J_HH=8.2 Hz, 2 H, m-H(NAr)], 7.16 [m overlap, 2 H, m-H(Ph)], 7.07 [t, ³J_HH=7.4 Hz, 1 H, p-H(Ph)], 6.61 [d, ⁴J_HP=3.3 Hz, 4 H, m-H(Mes)], 2.42 (s, 12 H, o-Me), 1.92 (s, 6 H, p-Me), 1.44 ppm (s, 18 H, CMe₃). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=156.1 (s, PC=CH), 153.3 [s, ipso-C(NAr)], 149.9 (d, ¹J_CP=13.0 Hz, PC=CH), 142.5 [d, ⁴J_CP=2.9 Hz, p-C(Mes)], 141.3 [d, ²J_CP=10.8 Hz, o-C(Mes)], 140.7 [d, ³J_CP=36.9 Hz, ipso-C(Ph)], 132.1 [d, ³J_CP=10.8 Hz, m-C(Mes)], 130.1 [p-C(Ph)], 129.3 [q, ²J_CF=32.3 Hz, p-C(NAr)], 129.0 [m-C(Ph)], 128.3 [o-C(Ph)], 126.6 [d, ¹J_CP=68.4 Hz, ipso-C(Mes)], 126.5 [q, ³J_CF=4.0 Hz, m-C(NAr)], 125.0 (q, ¹J_CF=271.8 Hz, CF₃), 122.0 [o-C(NAr)], 32.2 (CMe₃), 25.2 (d, ³J_CP=3.9 Hz, o-Me), 20.8 (p-Me), 17.2 ppm (s br, CMe₃). – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=40.9 ppm. – ¹⁹F NMR (376.4 MHz, C₆D₆, 300 K): δ=−61.9 ppm. – MS (EI; 20 eV; 413 K): m/z (%)=642 (100) [M–^tBu]⁺, 614 (64) [M–^tBu–N₂]⁺, 558 (18) [M–Al^tBu₂]⁺, 470 (12) [M–H₂C=CMe₂–N₂C₆H₄CF₃]⁺.

4.3 {Mes₂PC(Al^tBu₂)=C(H)Ph}{N₃CH₂C₆H₄(4-Cl)} (5c)

N₃CH₂C₆H₄(4-Cl) (1.3 mL, 0.64 mmol, 0.5 m in CH₂Cl₂) was added to a solution of compound 1 (0.33 g, 0.64 mmol) in n-hexane (20 mL). The mixture was stirred overnight, the solution concentrated and then stored at −45°C to yield yellow crystals of compound 5c. Yield (0.28 g, 64%); m.p. (dec., sealed capillary): 175°C. – IR (CsI, paraffin): ν=1601 w, 1553 w, 1506 m ν(C=C), Aryl; 1460 vs, 1402 m, 1375 vs (paraffin); 1304 s, 1288 s, 1273 m, 1246 s δ(CH₃); 1211 w, 1153 m, 1121 s, 1090 m, 1076 w, 1065 w, 1030 vw, 982 m, 941 w, 926 w, 903 m, 889 w 851 s, 808 m, 795 vs, 773 m ν(CC), δ(CH), ν(CCl), ν(CN); 721 vs (paraffin); 687 s δ(CH_Ph); 638 vs, 608 m, 577 m, 556 s, 544 m, 525 m, 500 w, 469 s, 451 m, 420 vw, 399 vw, 355 vw, 338 vw, 309 m, 297 w, 280 vw cm⁻¹ν(PC), ν(AlC), ν(AlN), δ(CC). – ¹H NMR (400.1 MHz, C₆D₆, 300 K): δ=7.84 (d, ³J_HP=41.5 Hz, 1 H, PC=CH), 7.60 [d, ³J_HH=7.4 Hz, 2 H, o-H(Ph)], 7.14 (pseudo-t overlap, ³J_HH=7.5 Hz, 2 H, m-H(Ph)], 7.07 [m overlap, 2 H, m-H(NAr)], 7.04 [t overlap, ³J_HH=7.5 Hz, 1 H, p-H(Ph)], 6.95 [d, ³J_HH=8.5 Hz, 2 H, o-H(NAr)], 6.61 [d, ⁴J_HP=2.4 Hz, 4 H, m-H(Mes)], 4.61 (s, 2 H, NCH₂), 2.38 (s, 12 H, o-Me), 1.94 (s, 6 H, p-Me), 1.33 ppm (s, 18 H, CMe₃). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=155.3 (PC=CH), 150.6 (d, ¹J_CP=13.1 Hz, PC=CH), 142.0 [d, ⁴J_CP=3.0 Hz, p-C(Mes)], 141.3 [d, ²J_CP=9.9 Hz, o-C(Mes)], 140.8 [d, ³J_CP=36.3 Hz, ipso-C(Ph)], 136.4 [ipso-C(NAr)], 133.1 [p-C(NAr)], 132.0 [d, ³J_CP=10.8 Hz, m-C(Mes)], 130.6 [o-C(NAr)], 129.9 [p-C(Ph)], 128.9 [m-C(Ph)], 128.7 [m-C(NAr)], 128.2 [o-C(Ph)], 127.3 [d, ¹J_CP=68.6 Hz, ipso-C(Mes)], 65.4 (NCH₂), 32.2 (CMe₃), 25.1 (d, ³J_CP=3.8 Hz, o-Me), 20.8 (d, ⁵J_CP=1.0 Hz, p-Me), 17.0 ppm (s br, CMe₃). – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=38.8 ppm. – ¹⁵N NMR (40.5 MHz, C₆D₆, 300 K): δ=479 ppm (N=NCH₂). – MS (EI; 20 eV; 413 K): m/z (%)=622 (55) [M–^tBu]⁺, 594 (100) [M–^tBu–N₂]⁺, 538 (8) [M–Al^tBu₂]⁺. – C₄₁H₅₂AlClN₃P (680.3): calcd. C 72.4, H 7.7, N 6.2; found C 72.3, H 7.8, N 6.1.

4.4 {Mes₂PC(Al^tBu₂)=C(H)Ph}{N₃CH₂C₆H₄(4-^tBu)} (5d)

N₃CH₂C₆H₄(4-^tBu) (0.11 mL, 0.12 g, 0.63 mmol) was added to a solution of compound 1 (0.32 g, 0.63 mmol) in toluene (20 mL). The mixture was stirred overnight, the solvent removed in vacuo and the residue recrystallised from pentafluorobenzene (5 mL) at 5°C to yield compound 5d as yellow crystals. Yield (0.37 g, 84%); m.p. (dec., sealed capillary): 155°C. – IR (CsI, paraffin): ν=1728 vw, 1641 vw, 1603 m, 1564 w, 1553 s, 1531 m, 1512 m ν(C=C), Aryl; 1454 vs, 1400 m, 1377 m (paraffin); 1308 m, 1288 s, 1267 s, δ(CH₃); 1238 vs, 1209 s, 1179 s, 1153 s, 1123 vs, 1069 m, 1028 m, 999 w, 982 w, 959 w, 924 m, 889 vw; 851 m, 833 w, 806 s, 797 s, 746 s δ(CH), ν(CC), ν(CN); 718 vs (paraffin); 689 s δ(CH_Ph); 640 vs, 611 s, 571 s, 554 vs, 500 s, 469 vs, 432 m, 409 m, 363 m, 347 w, 322 m, 309 w, 297 vw cm⁻¹ν(PC), ν(AlC), ν(AlN), δ(CC). – ¹H NMR (400.1 MHz, C₆D₆, 300 K): δ=7.85 (d, ³J_HP=41.8 Hz, 1 H, PC=CH), 7.61 [d, ³J_HH=7.3 Hz, 2 H, o-H(Ph)], 7.25 [s, 4 H, o,m-H(NAr)], 7.13 [t overlap, ³J_HH=7.7 Hz, 2 H, m-H(Ph)], 7.04 [t, ³J_HH=7.3 Hz, 1 H, p-H(Ph)], 6.62 [d, ⁴J_HP=3.6 Hz, 4 H, m-H(Mes)], 4.84 (s, 2 H, NCH₂), 2.42 (s, 12 H, o-Me), 1.94 (s, 6 H, p-Me), 1.37 (s, 18 H, AlCMe₃), 1.20 ppm (s, 9 H, CMe₃). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=155.1 (PC=CH), 151.1 (d, ¹J_CP=13.3 Hz, PC=CH), 149.8 [p-C(NAr)], 141.9 [d, ⁴J_CP=2.8 Hz, p-C(Mes)], 141.4 [d, ²J_CP=10.0 Hz, o-C(Mes)], 140.9 [d, ³J_CP=36.2 Hz, ipso-C(Ph)], 135.0 [ipso-C(NAr)], 131.9 [d, ³J_CP=10.5 Hz, m-C(Mes)], 129.8 [p-C(Ph)], 128.9 [overlap, m-C(Ph), o-C(NAr)], 128.2 [overlap, o-C(Ph)], 127.5 [d overlap, ¹J_CP≈64 Hz, ipso-C(Mes)], 125.5 [m-C(NAr)], 66.2 (NCH₂), 34.4 (CMe₃), 32.2 (AlCMe₃), 31.5 (CMe₃), 25.1 (d, ³J_CP=3.6 Hz, o-Me), 20.9 (d, ⁵J_CP≈1 Hz, p-Me), 17.1 ppm (s br, AlCMe₃). – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=38.4 ppm. – ¹⁵N NMR (40.5 MHz, C₆D₆, 300 K): δ=477 ppm (N=NCH₂). – MS (EI; 20 eV; 413 K): m/z (%)=644 (23) [M–^tBu]⁺, 616 (100) [M–^tBu–N₂]⁺, 560 (8) [M–Al^tBu₂]⁺. – C₄₅H₆₁AlN₃P (702.0): calcd. C 77.0, H 8.8, N 6.0; found C 76.3, H 8.5, N 5.9.

4.5 {Mes₂PC(Al^tBu₂)=C(H)Ph}{N₃C₆H₄(2-CH=CHPh)} (5e)

A solution of N₃C₆H₄(2-CH=CHPh) (0.10 g, 0.45 mmol) and compound 1 (0.23 g, 0.45 mmol) in toluene (20 mL) was stirred overnight. The solvent was removed in vacuo and the residue recrystallised from 1,2-difluorobenzene at 5°C to yield compound 5e as yellow crystals. Yield (0.26 g, 79%); m.p. (dec., sealed capillary): 203°C. – IR (CsI, paraffin): ν=1601 vw, 1580 vw, 1558 vw, 1541 vw, 1520 vw, 1504 w ν(C=C), Aryl; 1456 vs, 1377 vs (paraffin); 1342 s, 1306 s, 1287 s, 1261 s δ(CH₃); 1240 vs, 1207 s, 1186 s, 1136 vs, 1094 m, 1063 m, 1026 w, 1007 s, 982 m, 964 m, 926 w, 889 vw, 849 w, 835 w, 810 w, 797 m, 750 s δ(CH), ν(CC), ν(CN); 723 s (paraffin); 691 w, 669 w δ(CH_Ph); 640 m, 619 m, 581 w, 569 w, 554 m, 519 m, 494 w, 471 w, 397 vw, 366 vw cm⁻¹ν(PC), ν(AlC), ν(AlN), δ(CC). – ¹H NMR (400.1 MHz, C₆D₆, 300 K): δ=8.50 (d, ³J_HH=16.8 Hz, 1 H, CH=CHPh), 7.91 (d, ³J_HP=41.6 Hz, 1 H, PC=CH), 7.66 [d, ³J_HH=7.4 Hz, 2 H, o-H(C=CPh)], 7.61 [d, ³J_HH=7.7 Hz, 2 H, o-H(Ph)], 7.59 [m, 1 H, 3-H(NAr)], 7.44 [m, 1 H, 6-H(NAr)], 7.23 [t, ³J_HH=7.7 Hz, 2 H, m-H(C=CPh)], 7.14 [t overlap, ³J_HH=7.5 Hz, 2 H, m-H(Ph)], 7.06 [m overlap, 1 H, p-H(Ph), 5-H(NAr)], 7.05 [m overlap, 1 H, 4-H(NAr), p-H(C=CPh), C=CHPh], 6.59 [d, ⁴J_HP=3.8 Hz, 4 H, m-H(Mes)], 2.42 (s, 12 H, o-Me), 1.91 (s, 6 H, p-Me), 1.45 ppm (s, 18 H, CMe₃). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=155.9 (PC=CH), 149.9 (d, ¹J_CP=13.1 Hz, PC=CH), 148.7 [ipso-C(NAr)], 142.2 [d, ⁴J_CP=2.9 Hz, p-C(Mes)], 141.5 [d, ²J_CP=10.2 Hz, o-C(Mes)], 140.8 [d, ³J_CP=35.9 Hz, ipso-C(Ph)], 138.2 [ipso-C(C=CPh)], 134.5 [2-C(NAr)], 132.0 [d, ³J_CP=11.0 Hz, m-C(Mes)], 130.6 (C=CPh), 130.0 [5-C(NAr)], 128.9 [m-C(Ph)], 128.8 [m-C(C=CPh)], 128.3 [overlap, o-C(Ph)], 128.1 [4-C(NAr), p-C(C=CPh)], 127.9 [overlap, p-C(Ph)], 127.5 [o-C(C=CPh)], 126.9 [d, ¹J_CP=68.2 Hz, ipso-C(Mes)], 126.3 [3-C(NAr)], 125.4 (C=CPh), 118.3 [6-C(NAr)], 32.3 (CMe₃), 25.3 (d, ³J_CP=3.8 Hz, o-Me), 20.9 (d, ⁵J_CP=1.4 Hz, p-Me), 17.3 ppm (s br, CMe₃). – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=41.2 ppm. – MS (EI; 20 eV; 413 K): m/z (%)=676 (24) [M–^tBu]⁺, 648 (21) [M–^tBu–N₂]⁺, 592 (3) [M–Al^tBu₂]⁺.

4.6 {Mes₂PC[Al(CH₂^tBu)₂]=C(H)Ph}{N₃C₆H₄(4-Cl)} (6a)

N₃C₆H₄(4-Cl) (1.3 mL, 0.65 mmol, 0.5 m in t-butyl methyl ether) was transferred to a Schlenk flask. The solvent was removed in vacuo, the residue dissolved in n-hexane (10 mL) and the solution combined with a solution of compound 2 (0.35 g, 0.65 mmol) in n-hexane (20 mL). The mixture was stirred for 6 h at room temperature. Compound 6a was unambiguously identified by NMR spectroscopy as the sole product, but attempts to crystallise or further purify the crude product were not successful. ¹H NMR (400 MHz, C₆D₆, 300 K): δ=7.87 (d, ³J_HP=42.2 Hz, 1 H, PC=CH), 7.57 [d, ³J_HH=7.3 Hz, 2 H, o-H(Ph)], 7.44 (d, ³J_HH=8.7 Hz, 2 H, o-H(NAr)], 7.15 [m overlap, 2 H, m-H(Ph)], 7.06 [m overlap, 1 H, p-H(Ph)], 7.06 [m overlap, 2 H, m-H(NAr)], 6.58 [d, ⁴J_HP=3.7 Hz, 4 H, m-H(Mes)], 2.41 (s, 12 H, o-Me), 1.93 (s, 6 H, p-Me), 1.38 (s, 18 H, CMe₃), 1.03 and 0.97 ppm (each d, ²J_HH=13.7 Hz, 2 H, CH₂CMe₃). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=154.9 (PC=CH), 153.3 (d, ¹J_CP=12.3 Hz, PC=CH), 149.5 [ipso-C(NAr)], 142.1 [d, ⁴J_CP=2.9 Hz, p-C(Mes)], 141.1 [d, ²J_CP=10.0 Hz, o-C(Mes)], 140.5 [d, ³J_CP=36.8 Hz, ipso-C(Ph)], 133.4 [p-C(NAr)], 131.8 [d, ³J_CP=10.7 Hz, m-C(Mes)], 129.6 [p-C(Ph)], 129.4 [m-C(NAr)], 128.8 [d, ⁴J_CP=5.1 Hz, o-C(Ph)], 128.3 [m-C(Ph)], 127.9 [overlap, ipso-C(Mes)], 123.1 [o-C(NAr)], 35.5 (CH₂CMe₃), 33.4 (CH₂CMe₃), 32.2 (CH₂CMe₃), 25.0 (d, ³J_CP=4.4 Hz, o-Me), 20.8 ppm (d, ⁵J_CP=1.2 Hz, p-Me). – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=39.3 ppm. – ¹⁵N NMR (40.5 MHz, C₆D₆, 300 K): δ=418 ppm (N=NAr).

4.7 {Mes₂PC[(AlCH₂^tBu)₂]=C(H)Ph}{N₃CH₂C₆H₄(4-Cl)} (6b)

N₃CH₂C₆H₄(4-Cl) (1.1 mL, 0.55 mmol, 0.5 m in CH₂Cl₂) was added to a solution of compound 2 (0.30 g, 0.56 mmol) in n-hexane (10 mL). The mixture was stirred for 6 h at room temperature. Compound 6b was unambiguously identified by NMR spectroscopy as the sole product, but crystallisation or further purification of the crude product was not successful. – ¹H NMR (400.1 MHz, C₆D₆, 300 K): δ=7.82 (d, ³J_HP=42.1 Hz, 1 H, PC=CH), 7.55 [d, ³J_HH=7.3 Hz, 2 H, o-H(Ph)], 7.13 (pseudo-t overlap, ³J_HH=7.7 Hz, 2 H, m-H(Ph)], 7.08 [d overlap, ³J_HH=8.5 Hz, 2 H, m-H(NAr)], 7.02 [t overlap, ³J_HH=7.5 Hz, 1 H, p-H(Ph)], 6.92 [d, ³J_HH=8.5 Hz, 2 H, o-H(NAr)], 6.60 [d, ⁴J_HP=4.1 Hz, 4 H, m-H(Mes)], 4.63 (s, 2 H, NCH₂), 2.38 (s, 12 H, o-Me), 1.95 (s, 6 H, p-Me), 1.30 (s, 18 H, CH₂CMe₃), 0.91 and 0.87 ppm (each d, ²J_HH=13.7 Hz, 2 H, CH₂CMe₃). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=154.5 (PC=CH), 153.8 (d, ¹J_CP=12.4 Hz, PC=CH), 141.8 [d, ⁴J_CP=2.8 Hz, p-C(Mes)], 141.1 [d, ²J_CP=9.9 Hz, o-C(Mes)], 140.5 [d, ³J_CP=36.8 Hz, ipso-C(Ph)], 136.5 [ipso-C(NAr)], 133.1 [p-C(NAr)], 131.7 [d, ³J_CP=10.7 Hz, m-C(Mes)], 130.6 [o-C(NAr)], 129.5 [p-C(Ph)], 128.7 [m-C(Ph), o-C(Ph)], 128.6 [m-C(NAr)], 128.1 [d overlap, ¹J_CP≈60 Hz, ipso-C(Mes)], 65.2 (NCH₂), 35.5 (CH₂CMe₃), 33.3 (s br., CH₂CMe₃), 32.1 (CH₂CMe₃), 24.8 (d, ³J_CP=4.3 Hz, o-Me), 20.8 ppm (d, ⁵J_CP=1.1 Hz, p-Me). – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=37.7 ppm. – ¹⁵N NMR (40.5 MHz, C₆D₆, 300 K): δ=478 ppm (N=NAr).

4.8 {Mes₂PC[AlCH₂^tBu)₂]=C(H)Ph}{N₃CH₂C₆H₄(4-^tBu)} (6c)

N₃CH₂C₆H₄(4-^tBu) (0.13 mL, 0.14 g, 0.74 mmol) was added to a solution of compound 2 (0.41 g, 0.76 mmol) in n-hexane (20 mL). The mixture was stirred for 6 h at room temperature. Compound 6c was unambiguously identified by NMR spectroscopy as the sole product, but could not be crystallised or further purified. – ¹H NMR (400.1 MHz, C₆D₆, 300 K): δ=7.83 (d, ³J_HP= 42.0 Hz, 1 H, PC=CH), 7.57 [d, ³J_HH=7.4 Hz, 2 H, o-H(Ph)], 7.24 [m, 2 H, m-H(NAr)], 7.23 [m, 2 H, o-H(NAr)], 7.14 [t overlap, ³J_HH=7.7 Hz, 2 H, m-H(Ph)], 7.02 [t, ³J_HH=7.4 Hz, 1 H, p-H(Ph)], 6.61 [d, ⁴J_HP=3.7 Hz, 4 H, m-H(Mes)], 4.85 (s, 2 H, NCH₂), 2.43 (s, 12 H, o-Me), 1.95 (s, 6 H, p-Me), 1.32 (s, 18 H, CH₂CMe₃), 1.21 (s, 9 H, CMe₃), 0.94 and 0.90 ppm (each d, ²J_HH=13.7 Hz, 2 H, CH₂CMe₃). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=154.3 (s br., PC=CH), 154.2 (PC=CH), 149.8 [p-C(NAr)], 141.6 [d, ⁴J_CP=2.9 Hz, p-C(Mes)], 141.2 [d, ²J_CP=10.0 Hz, o-C(Mes)], 140.6 [d, ³J_CP=36.4 Hz, ipso-C(Ph)], 135.0 [ipso-C(NAr)], 131.7 [d, ³J_CP=10.8 Hz, m-C(Mes)], 129.4 [p-C(Ph)], 129.0 [o-C(NAr)], 128.7 [overlap, o-C(Ph), m-C(Ph)], 128.4 [overlap, ipso-C(Mes)], 125.4 [m-C(NAr)], 66.1 (NCH₂), 35.5 (CH₂CMe₃), 34.4 (CMe₃), 33.2 (s br., CH₂CMe₃), 32.1 (CH₂CMe₃), 31.5 (CMe₃), 24.9 (d, ³J_CP=4.3 Hz, o-Me), 20.9 ppm (d, ⁵J_CP≈1 Hz, p-Me). – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=37.5 ppm. – ¹⁵N NMR (40.5 MHz, C₆D₆, 300 K): δ=476 ppm (N=NCH₂).

4.9 {Mes₂PC[Al(CH₂^tBu)₂]=C(H)Ph}{N₃^tBu} (6d)

A solution of N₃^tBu (0.78 mL, 0.39 mmol, 0.5 m in n-hexane) was added at room temperature to a solution of compound 2 (0.21 g, 0.39 mmol) in n-hexane (10 mL). The mixture was stirred for 6 h at room temperature, the solution concentrated and stored at −30°C to yield colourless crystals of compound 6d. Yield (0.23 g, 92%); m.p. (dec., sealed capillary): 168°C. – IR (KBr pellet): ν=3061 w, 3024 s, 2951 vs, 2934 vs, 2895 vs, 2841 vs, 2791 m, 2764 m, 2731 w ν(C–H); 1605 vs, 1558 vs, 1501 s ν(C=C), Ar; 1443 vs, 1404 s, 1381 s, 1358 vs, 1290 m, 1277 w, 1250 s δ(CH); 1225 vs, 1105 vs, 1069 vs, 1051 s, 1030 s, 1013 s, 926 s, 849 vs, 793 vs, 750 vs δ(CH), ν(CC), ν(CN); 677 vs, 654 vs δ(CH_Ph); 623 vs, 604 s, 571 m, 554 s, 525 s, 500 w, 469 vs, 457 s, 401 vs cm⁻¹ν(PC), ν(AlC), ν(AlN), δ(CC). – ¹H NMR (400.1 MHz, C₆D₆, 300 K): δ=7.81 (d, ³J_HP=41.9 Hz, 1 H, PC=CH), 7.57 [d, ³J_HH=7.4 Hz, 2 H, o-H(Ph)], 7.14 [t overlap, ³J_HH=7.7 Hz, 2 H, m-H(Ph)], 7.02 [t, ³J_HH=7.4 Hz, 1 H, p-H(Ph)], 6.60 [d, ⁴J_HP=3.7 Hz, 4 H, m-H(Mes)], 2.42 (s, 12 H, o-Me), 1.94 (s, 6 H, p-Me), 1.37 (s, 18 H, CH₂CMe₃), 1.23 (s, 9 H, NCMe₃), 0.94 and 0.89 ppm (each d, ²J_HH=14 Hz, 2 H, CH₂CMe₃). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=154.6 (d, ¹J_CP=12.4 Hz, PC=CH), 154.0 (PC=CH), 141.5 [d, ⁴J_CP=2.9 Hz, p-C(Mes)], 141.0 [d, ²J_CP=9.9 Hz, o-C(Mes)], 140.7 [d, ³J_CP=36.8 Hz, ipso-C(Ph)], 131.6 [d, ³J_CP=10.7 Hz, m-C(Mes)], 129.3 [p-C(Ph)], 128.7 [m-C(Ph)], 128.6 [o-C(Ph)], 128.6 [d overlap, ¹J_CP>64 Hz, ipso-C(Mes)], 63.1 (NCMe₃), 35.6 (CH₂CMe₃), 33.3 (s br., CH₂CMe₃), 32.5 (CH₂CMe₃), 28.7 (NCMe₃), 24.7 (d, ³J_CP=4.4 Hz, o-Me), 20.8 ppm (d, ⁵J_CP=1.4 Hz, p-Me), – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=34.6 ppm. – ¹⁵N NMR (40.5 MHz, C₆D₆, 300 K): δ=457 ppm (N=NCMe₃). – MS (EI; 20 eV; 323 K): m/z (%)=568 (56) [M–CH₂^tBu]⁺, 540 (1) [M–N₃^tBu]⁺, 484 (100) [M–CH₂^tBu–N₂–H₂C=CMe₂]⁺, 469 (2) [M–N₃^tBu–CH₂^tBu]⁺. – C₄₀H₅₉AlN₃P (639.9): calcd. C 75.1, H 9.3, N 6.6; found C 75.1, H 9.5, N 6.3.

4.10 {Mes₂PC(Ga^tBu₂)=C(H)Ph}{N₃C₆H₄(4-CF₃)} (7b)

N₃C₆H₄(4-CF₃) (0.80 mL, 0.40 mmol, 0.5 m in t-butyl methyl ether) was transferred into a Schlenk flask. The solvent was removed in vacuo, the residue was dissolved in toluene (5 mL), and the solution was added at room temperature to a solution of compound 3 (0.22 g, 0.40 mmol) in toluene (5 mL). The mixture was stirred overnight, and the solvent was removed in vacuo to yield an orange solid which was analytically pure according to NMR spectroscopy. Attempts to crystallise compound 7b from a variety of solvents were not successful. Yield (0.28 g, 94%); m.p. of the crude material (dec., argon, sealed capillary): 124°C. – IR (KBr pellet): ν=3056 w, 3024 m, 2952 vs, 2929 vs, 2867 vs, 2827 vs, 2759 w, 2698 w ν(CH); 2635 vw, 2275 vw, 2100 w; 1945 vw, 1911 vw, 1764 vw, 1735 vw, 1671 vw, 1606 vs, 1558 s, 1509 w ν(C=C), Aryl; 1492 w, 1465 vs, 1436 vs, 1399 vs, 1359 m, 1322 vs δ(CH₃); 1288 s, 1241 vs, 1145 vs, 1124 vs, 1102 vs, 1062 vs, 1029 s, 1008 vs, 923 m, 848 vs, 805 vs, 746 vs, 717 w δ(CH), ν(CC), ν(CN); 692 s, 665 s δ(CH_Ph); 640 vs, 603 s, 572 s, 553 m, 518 m, 491 m, 470 vs, 445 m cm⁻¹ν(PC), ν(GaC), ν(GaN), δ(CC). – ¹H NMR (400 MHz, C₆D₆, 300 K): δ=7.93 (d, ³J_HP=37.9 Hz, 1 H, PC=CH), 7.52 [d, ³J_HH=7.3 Hz, 2 H, o-H(Ph)], 7.46 [d, ³J_HH=8.3 Hz, 2 H, o-H(NAr)], 7.33 [d, ³J_HH=8.4 Hz, 2 H, m-H(NAr)], 7.12 [m overlap, 2 H, m-H(Ph)], 7.06 [t, ³J_HH=7.4 Hz, 1 H, p-H(Ph)], 6.62 [d, ⁴J_HP=3.8 Hz, 4 H, m-H(Mes)], 2.44 (s, 12 H, o-Me), 1.93 (s, 6 H, p-Me), 1.48 ppm (s, 18 H, CMe₃). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=154.1 [ipso-C(NAr)], 153.6 (d, ²J_CP=2.8 Hz, PC=CH), 153.0 (d, ¹J_CP=30.9 Hz, PC=CH), 142.2 [d, ⁴J_CP=2.9 Hz, p-C(Mes)], 141.3 [d, ²J_CP=10.0 Hz, o-C(Mes)], 140.8 [d, ³J_CP=34.9 Hz, ipso-C(Ph)], 132.0 [d, ³J_CP=10.9 Hz, m-C(Mes)], 129.8 [p-C(Ph)], 129.0 [m-C(Ph)], 128.4 (q overlap, ²J_CF=32.0 Hz, p-C(NAr)], 128.0 [o-C(Ph)], 127.1 [d, ¹J_CP=68.3 Hz, ipso-C(Mes)], 126.4 [q, ³J_CF=3.8 Hz, m-C(NAr)], 125.1 (q overlap, ¹J_CF=272.0 Hz, CF₃), 121.9 [o-C(NAr)], 32.3 (CMe₃), 25.3 (d, ³J_CP=3.8 Hz, o-Me), 25.2 (GaCMe₃), 20.8 ppm (d, ⁵J_CP=1.3 Hz, p-Me). – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=45.0 ppm. – ¹⁹F NMR (376.4 MHz, C₆D₆, 300 K): δ=−61.8 ppm. – MS (EI; 20 eV; 373 K): m/z (%)=684 (12) [M–^tBu]⁺, 656 (11) [M–^tBu–N₂]⁺, 497 (29) [M–^tBu–N₃C₆H₄CF₃]⁺.

4.11 {Mes₂PC(Ga^tBu₂)=C(H)Ph}{N₃C₆H₄(4-Me)} (7c)

N₃C₆H₄(4-Me) (0.80 mL, 0.40 mmol, 0.5 m in t-butyl methyl ether) was transferred into a Schlenk flask. The solvent was removed in vacuo, the residue was dissolved in toluene (5 mL) and the solution was added at room temperature to a solution of compound 3 (0.22 g, 0.40 mmol) in toluene (5 mL). The mixture was stirred overnight, and the solvent was removed in vacuo to yield an orange solid. Attempts to crystallise compound 7c from a variety of solvents were not successful, but the crude material was NMR spectroscopically characterised, and 7c was identified as the major product. – ¹H NMR (400.0 MHz, C₆D₆, 300 K): δ=7.93 (d, ³J_HP=37.7 Hz, 1 H, PC=CH), 7.65 [d, ³J_HH=8.2 Hz, 2 H, o-H(NAr)], 7.55 [d, ³J_HH=7.4 Hz, 2 H, o-H(Ph)], 7.14 [pseudo-t, ³J_HH=7.4 Hz, 2 H, m-H(Ph)], 7.06 [t, ³J_HH=7.4 Hz, 1 H, p-H(Ph)], 7.00 [d, ³J_HH=8.2 Hz, 2 H, m-H(NAr)], 6.61 [d, ⁴J_HP=3.7 Hz, 4 H, m-H(Mes)], 2.49 (s, 12 H, o-Me), 2.08 [s, 3 H, Me(NAr)], 1.93 [s, 6 H, p-Me(Mes)], 1.51 ppm (s, 18 H, GaCMe₃). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=154.1 (d, ¹J_CP=31.2 Hz, PC=CH), 152.9 (d, ²J_CP=2.7 Hz, PC=CH), 149.6 [ipso-C(NAr)], 141.8 [d, ⁴J_CP=2.6 Hz, p-C(Mes)], 141.3 [d, ²J_CP=9.7 Hz, o-C(Mes)], 141.0 [d, ³J_CP=34.8 Hz, ipso-C(Ph)], 137.0 [p-C(NAr)], 131.9 [d, ³J_CP=10.9 Hz, m-C(Mes)], 129.9 [m-C(NAr)], 129.6 [p-C(Ph)], 128.9 [m-C(Ph)], 128.0 [o-C(Ph)], 127.7 [d overlap, ¹J_CP=68.0 Hz, ipso-C(Mes)], 121.9 [o-C(NAr)], 32.4 (GaCMe₃), 25.3 (d, ³J_CP=3.7 Hz, o-Me), 25.1 (d, ³J_CP=4.3 Hz, GaCMe₃), 21.1 [Me(NAr)], 20.9 ppm [d, ⁵J_CP=2.0 Hz, p-Me(Mes)]. – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=43.3 ppm.

4.12 {Mes(H)PC{Al[CH(SiMe₃)₂]₂}=C(H)^tBu}{N₃C₆H₄(4-Cl)} (8a)

N₃C₆H₄(4-Cl) (0.82 mL, 0.41 mmol, 0.5 m in t-butyl methyl ether) was transferred into a Schlenk flask. The solvent was removed in vacuo and the residue dissolved in n-pentane (5 mL). The solution was added at −78°C to a solution of compound 4 (0.24 g, 0.42 mmol) in n-pentane (20 mL). The mixture was allowed to warm to room temperature and stirred overnight. The solvent was removed in vacuo and the residue recrystallised from 1,2-difluorobenzene at −30°C affording colourless crystals of compound 8a. Yield (0.19 g, 62 %); m.p. (dec., sealed capillary): 86°C. – IR (KBr, paraffin): ν=1605 ν(C=C), Aryl; 1483 w, 1460 s, 1433 m, 1377 m (paraffin); 1364 w, 1296 vw, 1242 m δ(CH₃); 1148 s, 1088 w, 1074 vw; 1007 m ν(CHSi₂); 988 w, 974 w, 930 w, 914 w, 843 vs, 779 m, 750 m ρ(SiCH₃), δ(CH), ν(CC), ν(CN); 725 w (paraffin); 706 vw, 669 m ν(SiC), δ(CH_Ph); 611 vw, 557 vw, 527 m, 505 w, 459 vw, 442 vw, 419 w cm⁻¹ν(PC), ν(AlC), ν(AlN), δ(CC). – ¹H NMR (400 MHz, C₆D₆, 300 K): δ=8.68 (d, ¹J_HP=472. 9Hz, 1 H, PH), 7.30 [d, ³J_HH=8.7 Hz, 2 H, o-H(NAr)], 7.21 (d, ³J_HP=75.7 Hz, 1 H, PC=CH), 6.96 [d, ³J_HH=8.7 Hz, 2 H, m-H(NAr)], 6.55 [d, ⁴J_HP=4.2 Hz, 1 H, m-H(Mes)], 6.39 [d, ⁴J_HP=2.0 Hz, 1 H, m-H(Mes)], 2.61 and 2.53 (each s, 3 H, o-Me), 1.85 (s, 3 H, p-Me), 0.81 (s, 9 H, CMe₃), 0.51, 0.49, 0.40 and 0.39 (each s, 9 H, SiMe₃), −0.55 and −0.60 ppm (each s, 1 H, AlCH). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=171.7 (d, ²J_CP=6.8 Hz, PC=CH), 148.1 [ipso-C(NAr)], 143.6 [d, ⁴J_CP=2.5 Hz, p-C(Mes)], 142.6 [d, ²J_CP=12.0 Hz, o-C(Mes)], 141.9 [d, ²J_CP=9.1 Hz, o-C(Mes)], 133.7 [p-C(NAr)], 131.1 [d, ³J_CP=11.7 Hz, m-C(Mes)], 130.7 [d, ³J_CP=10.0 Hz, m-C(Mes)], 130.5 (s br. overlap, PC=CH), 129.5 [m-C(NAr)], 122.5 [o-C(NAr)], 121.1 [d, ¹J_CP=70.1 Hz, ipso-C(Mes)], 38.0 (d, ³J_CP=14.2 Hz, CMe₃), 28.4 (CMe₃), 24.5 (d, ³J_CP=6.5 Hz, o-Me), 21.8 (d, ³J_CP=9.1 Hz, o-Me), 21.0 (p-Me), 6.1 (s br., CHSi₂) 5.3 and 5.2 (SiMe₃), 5.1 (s br. overlap, CHSi₂), 5.0 and 4.7 ppm (SiMe₃). – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=−11.5 ppm. – ²⁹Si NMR (79.5 MHz, C₆D₆, 300 K): δ=−1.9, −1.7, −1.3 ppm. – ¹⁵N NMR (40.5 MHz, C₆D₆, 300 K): δ=406 (N=NAr), 187 ppm (PN). – MS (EI; 20 eV; 373 K): m/z (%)=688 (3) [M–CH₃–N₂]⁺, 572 (6) [M–CH(SiMe₃)₂]⁺, 544 (100) [M–CH(SiMe₃)₂–N₂]⁺. – C₃₅H₆₄AlClN₃PSi₄ (732.7): calcd. C 57.4, H 8.8, N 5.7; found C 56.9, H 8.6, N 5.5.

4.13 {Mes(H)PC{Al[CH(SiMe₃)₂]₂}=C(H)^tBu}{N₃Ph)} (8b)

N₃Ph (0.98 mL, 0.49 mmol, 0.5 m in t-butyl methyl ether) was transferred into a Schlenk flask. The solvent was removed in vacuo and the residue dissolved in n-hexane (10 mL). This solution was added at −30°C to a solution of compound 4 (0.28 g, 0.48 mmol) in n-hexane (20 mL). The mixture was allowed to warm to room temperature and stirred overnight. Compound 8b was unambiguously identified by NMR spectroscopy as the sole product, but could not be crystallised or further purified. – ¹H NMR (400 MHz, C₆D₆, 300 K): δ=8.72 (d, ¹J_HP=472.9 Hz, 1 H, PH), 7.57 [m, 2 H, o-H(NAr)], 7.21 (d, ³J_HP=75.1 Hz, 1 H, PC=CH), 7.06 [pseudo-t, ³J_HH=7.8 Hz, 2 H, m-H(NAr)], 6.91 [t, ³J_HH=7.4 Hz, 1 H, p-C(Ph)], 6.56 [d, ⁴J_HP=4.4 Hz, 1 H, m-H(Mes)], 6.40 [d, ⁴J_HP=2.0 Hz, 1 H, m-H(Mes)], 2.63 and 2.60 (each s, 3 H, o-Me), 1.84 (s, 3 H, p-Me), 0.82 (s, 9 H, CMe₃), 0.51, 0.50, 0.42 and 0.41 (each s, 9 H, SiMe₃), −0.54 and −0.59 ppm (each s, 1 H, AlCH). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=171.4 (d, ²J_CP=6.7 Hz, PC=CH), 149.7 [ipso-C(NAr)], 143.4 [d, ⁴J_CP=2.9 Hz, p-C(Mes)], 142.6 [d, ²J_CP=11.9 Hz, o-C(Mes)], 141.9 [d, ²J_CP=9.0 Hz, o-C(Mes)], 131.0 [d, ³J_CP=11.5 Hz, m-C(Mes)], 130.7 (s br. overlap, PC=CH), 130.6 [d, ³J_CP=9.8 Hz, m-C(Mes)], 129.3 [m-C(NAr)], 128.3 [p-C(NAr)], 121.4 [o-C(NAr)], 121.3 [d, ¹J_CP=70.4 Hz, ipso-C(Mes)], 38.7 (d, ³J_CP=14.5 Hz, CMe₃), 28.4 (CMe₃), 24.4 (d, ³J_CP=6.6 Hz, o-Me), 21.8 (d, ³J_CP=8.9 Hz, o-Me), 21.0 (d, ⁵J_CP=1.3 Hz, p-Me), 6.0, (s br., CHSi₂), 5.3 (SiMe₃), 5.2 (s br. overlap, CHSi₂), 5.2, 5.0, 4.7 ppm (SiMe₃). – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=−11.8 ppm. – ²⁹Si NMR (79.5 MHz, C₆D₆, 300 K): δ=−2.0, −1.9, −1.4 ppm.

4.14 {Mes(H)PC{Al[CH(SiMe₃)₂]₂}=C(H)^tBu}{N₃CH₂Ph)} (8c)

N₃CH₂Ph (0.82 mL, 0.41 mmol, 0.5 m in CH₂Cl₂) was transferred into a Schlenk flask. The solvent was removed in vacuo and the residue dissolved in n-hexane (10 mL). This solution was added at −30°C to a solution of compound 4 (0.24 g, 0.42 mmol) in n-hexane (20 mL). The mixture was warmed to room temperature and stirred overnight. Compound 8c was unambiguously identified by NMR spectroscopy as the sole product, but could not be crystallised or further purified. – ¹H NMR (400 MHz, C₆D₆, 300 K): δ=8.45 (d, ¹J_HP=472.1 Hz, 1 H, PH), 7.15 (d, ³J_HP=74.6 Hz, 1 H, PC=CH), 7.00 [m overlap, 2 H, m-H(NAr)], 6.99 [m overlap, 1 H, p-H(NAr)], 6.79 [m, 2 H, o-H(NAr)], 6.41 [d, ⁴J_HP=2.0 Hz, 1 H, m-H(Mes)], 6.34 [d, ⁴J_HP=4.0 Hz, 1 H, m-H(Mes)], 4.66 and 4.55 (each d, ²J_HH=13.9 Hz, 1 H, CH₂) 2.63 and 2.21 (each s, 3 H, o-Me), 1.88 (s, 3 H, p-Me), 0.78 (s, 9 H, CMe₃), 0.51, 0.50, 0.44 and 0.41 (each s, 9 H, SiMe₃), −0.57 and −0.63 ppm (s, 1 H, AlCH). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=170.8 (d, ²J_CP=7.0 Hz, PC=CH), 142.9 [d, ⁴J_CP=2.9 Hz, p-C(Mes)], 142.4 [d, ²J_CP=5.1 Hz, o-C(Mes)], 142.3 [d, ²J_CP=7.7 Hz, o-C(Mes)], 137.6 [ipso-C(NAr)], 131.1 (s br. overlap, PC=CH), 130.8 [d, ³J_CP=10.7 Hz, m-C(NMes)], 128.6 [o-C(NAr)], 128.4 [m-C(NAr)], 127.0 [p-C(Ph)], 121.0 [d, ¹J_CP=71.0 Hz, ipso-C(Mes)], 64.9 (NCH₂), 38.6 (d, ³J_CP=14.4 Hz, CMe₃), 28.4 (d, ⁴J_CP=1.0 Hz, CMe₃), 24.4 (d, ³J_CP=6.6 Hz, o-Me), 21.4 (d, ³J_CP=8.7 Hz, o-Me), 21.0 (⁵J_CP=1.3 Hz, p-Me), 5.9 (s br., CHSi₂) 5.3, 5.2 and 5.0 (SiMe₃), 5.0 (s br. overlap, CHSi₂), 4.8 ppm (SiMe₃). – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=−11.6 ppm. – ²⁹Si NMR (79.5 MHz, C₆D₆, 300 K): δ=−2.1, −2.0, −1.9, −1.4 ppm. – ¹⁵N NMR (40.5 MHz, C₆D₆, 300 K): δ=478 ppm (N=NAr).

4.15 Nitrene adduct {Mes₂PC(Al^tBu₂)=C(H)Ph}{NC₆H₄(4-Cl)} (9a)

Compound 5a (0.13 g, 0.20 mmol) was heated in vacuo for 15 min to 170°C. The solid melted, and a vigorous gas evolution was visible. The melt was cooled to room temperature and the solid dissolved in a small amount of pentafluorobenzene. The solution was stored at room temperature to yield colourless crystals of compound 8a. Yield (0.10 g, 78%); m.p. (dec., sealed capillary): 216°C. – IR (CsI, paraffin): ν=1603 w, 1580 w, 1557 w ν(C=C), Aryl; 1454 vs, 1375 vs (paraffin); 1308 m, 1271 vs, 1242 vs δ(CH₃); 1155 s, 1096 w, 1061 w, 1026 w, 999 w, 974 m, 922 w, 887 vw, 854 w, 837 w, 799 w, 772 m, 745 m δ(CH), ν(CC), ν(CN); 721 vs (paraffin); 689 m δ(CH_Ph); 637 m, 602 vw, 573 w, 554 m, 529 w, 517 w, 469 vw, 465 m, 428 w, 420 vw, 397 w, 357 vw, 327 vw, 303 vs cm⁻¹ν(PC), ν(AlC), ν(AlN), δ(CC). – ¹H NMR (400.1 MHz, C₆D₆, 300 K): δ=7.78 (d, ³J_HP=41.4 Hz, 1 H, PC=CH), 7.57 [d, ³J_HH=7.2 Hz, 2 H, o-H(Ph)], 7.15 [pseudo-t overlap, ³J_HH=7.7 Hz, 2 H, m-H(Ph)], 7.05 [t, ³J_HH=7.4 Hz, 1 H, p-H(Ph)], 6.99 [dd, ³J_HH=8.9 Hz, ⁴J_HP=1.3 Hz, 2 H, o-H(NAr)], 6.93 [d, ³J_HH=8.9 Hz, 2 H, m-H(NAr)], 6.57 [d, ⁴J_HP=3.7 Hz, 4 H, m-H(Mes)], 2.23 (s, 12 H, o-Me), 1.96 (s, 6 H, p-Me), 1.31 ppm (s, 18 H, CMe₃). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=153.6 (d, ¹J_CP=20 Hz, PC=CH), 153.0 (PC=CH), 145.4 [d, ²J_CP=5.5 Hz, ipso-C(NAr)], 141.5 [d, ⁴J_CP=2.8 Hz, p-C(Mes)], 141.1 [d, ³J_CP=36.8 Hz, ipso-C(Ph)], 140.9 [d, ²J_CP=10.1 Hz, o-C(Mes)], 131.8 [d, ³J_CP=10.5 Hz, m-C(Mes)], 130.7 [d, ¹J_CP=66.7 Hz, ipso-C(Mes)], 129.5 [p-C(Ph)], 128.8 [m-C(Ph), m-C(NAr)], 128.6 [d, ⁵J_CP=2.5 Hz, p-C(NAr)], 128.3 [o-C(Ph)], 127.4 [d, ³J_CP=8.4 Hz, o-C(NAr)], 32.8 (CMe₃), 25.1 (d, ³J_CP=3.8 Hz, o-Me), 20.8 (d, ⁵J_CP=1.4 Hz, p-Me), 18.1 ppm (s br, CMe₃). – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=32.9 ppm. – MS (EI; 20 eV; 353 K): m/z (%)=580 (100) [M–^tBu]⁺. – C₄₀H₅₀AlClNP (638.3): calcd. C 75.3, H 7.9, N 2.2; found C 75.1, H 8.0, N 2.1.

4.16 Nitrene adduct {Mes₂PC(Al^tBu₂)=C(H)Ph}{NCH₂C₆H₄(4-Cl)} (9b)

Compound 5c (0.15 g, 0.22 mmol) was heated in vacuo for 15 min to 175°C. The solid melted, and a vigorous gas evolution was visible. The melt was cooled to room temperature, the solid dissolved in a small amount of pentafluorobenzene and the solution stored at room temperature to give colourless crystals of compound 9b. Yield (0.12 g, 84%); m.p. (dec., sealed capillary): 185°C. – IR (CsI, paraffin): ν=1601 w, 1555 m, 1491 s ν(C=C), Aryl; 1458 vs, 1406 m, 1377 vs (paraffin); 1352 m, 1341 m, 1310 w, 1287 w δ(CH₃); 1244 m, 1211 w, 1173 vw, 1136 s, 1101 w, 1086 w, 1063 w, 1051 w, 1026 m, 1016 m, 988 m, 959 vw, 924 m, 889 vw, 853 s, 824 m, 802 vs, 746 vs δ(CH), ν(CC), ν(CN); 721 m (paraffin); 714 m, 689 m δ(CH_Ph); 667 w, 633 vs, 623 s, 584 s, 554 vs, 513 w, 500 m, 480 s, 463 vs, 440 w, 409 m, 384 vw, 355 w, 332 w, 303 w cm⁻¹ν(PC), ν(AlC), ν(AlN), δ(CC). – ¹H NMR (400.1 MHz, C₆D₆, 300 K): δ=7.64 (d overlap, ³J_HP=43.2 Hz, 1 H, PC=CH), 7.59 [d overlap, ³J_HH=6.8 Hz, 2 H, o-H(Ph)], 7.12 [pseudo-t, ³J_HH=7.7 Hz, 2 H, m-H(Ph)], 7.06 [d, ³J_HH=8.4 Hz, 2 H, m-H(NCH₂Ar)], 7.02 [t overlap, ³J_HH=7.7 Hz, 1 H, p-H(Ph)], 6.95 [d, ³J_HH=8.4 Hz, 2 H, o-H(NCH₂Ar)], 6.62 [d, ⁴J_HP=3.3 Hz, 4 H, m-H(Mes)], 4.22 (d, ³J_HP=14.5 Hz, 2 H, NCH₂), 2.35 (s, 12 H, o-Me), 2.00 (s, 6 H, p-Me), 1.22 ppm (s, 18 H, CMe₃). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=154.1 (d, ¹J_CP=13.7 Hz, PC=CH), 152.4 (d, ²J_CP=2.0 Hz, PC=CH), 141.0 [d, ³J_CP=36.9 Hz, ipso-C(Ph)], 141.0 [d, ⁴J_CP=2.7 Hz, p-C(Mes)], 140.2 [d, ²J_CP=9.4 Hz, o-C(Mes)], 139.0 [d, ³J_CP=11.9 Hz, ipso-C(NCH₂Ar)], 133.4 [p-C(NCH₂Ar)], 131.8 [d, ³J_CP=10.0 Hz, m-C(Mes)], 131.6 [o-C(NCH₂Ar)], 129.9 [d, ¹J_CP=66.2 Hz, ipso-C(Mes)], 129.3 [p-C(Ph)], 128.6 [d, ⁵J_CP=0.9 Hz, m-C(Ph)], 128.5 [m-C(NCH₂Ar)], 128.4 [d, ⁴J_CP=1.2 Hz, o-C(Ph)], 50.4 (d, ²J_CP=4.2 Hz, NCH₂), 32.7 (CMe₃), 24.6 (d, ³J_CP=4.0 Hz, o-Me), 20.8 (d, ⁵J_CP=1.4 Hz, p-Me), 17.8 ppm (s br, CMe₃). – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=37.8 ppm. – MS (EI; 20 eV; 313 K): m/z (%)=594 (100) [M–^tBu]⁺. – C₄₁H₅₂AlClNP (652.3): calcd. C 75.5, H 8.0, N 2.1; found C 75.3, H 8.0, N 2.1.

4.17 Nitrene adduct {Mes₂PC(Ga^tBu₂)=C(H)Ph}{NC₆H₄(4-Cl)} (10a)

In an NMR experiment a small quantity of solid compound 7a was heated to 200°C in vacuo. After the gas evolution had stopped, the brown solid was dissolved in C₆D₆ and characterised by NMR spectroscopy which showed compound 10a as the major product in solution. – ¹H NMR (400.1 MHz, C₆D₆, 300 K): δ=7.79 (d, ³J_HP=37.4 Hz, 1 H, PC=CH), 7.47 [d, ³J_HH=7.4 Hz, 2 H, o-H(Ph)], 7.13 [m overlap, 2 H, m-H(Ph)], 7.02 [t, ³J_HH=7.4 Hz, 1 H, p-H(Ph)], 6.94 [d overlap, 4 H, o-H(NAr), m-H(NAr)], 6.60 [d, ⁴J_HP=3.3 Hz, 4 H, m-H(Mes)], 2.28 (s, 12 H, o-Me), 1.97 (s, 6 H, p-Me), 1.34 ppm (s, 18 H, CMe₃). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=157.2 (d, ¹J_CP=42.3 Hz, PC=CH), 149.9 (d, ²J_CP=1.3 Hz, PC=CH), 147.4 [d, ²J_CP=4.9 Hz, ipso-C(NAr)], 141.3 [d, ⁴J_CP=3.0 Hz, p-C(Mes)], 141.1 [d overlap, ³J_CP=35.0 Hz, ipso-C(Ph)], 141.0 [d, ²J_CP=10.1 Hz, o-C(Mes)], 131.8 [d, ³J_CP=10.4 Hz, m-C(Mes)], 131.4 [d overlap, ¹J_CP=68.0 Hz, ipso-C(Mes)], 129.2 [p-C(Ph)], 128.9 [m-C(Ph)] 128.8 [m-C(NAr)], 128.0 [o-C(Ph)], 127.1 [d, ⁵J_CP=2.0 Hz, p-C(NAr)], 126.6 [d, ³J_CP=9.8 Hz, o-C(NAr)], 32.8 (CMe₃), 26.0 (d, ³J_CP=3.3 Hz, CMe₃), 25.1 (d, ³J_CP=4.0 Hz, o-Me), 20.8 ppm (d, ⁵J_CP=1.2 Hz, p-Me). – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=32.5 ppm.

4.18 Nitrene adduct {Mes₂PC(Ga^tBu₂)=C(H)Ph}{NC₆H₄-(4-CF₃)} (10b)

Solid compound 7b (0.30 g, 0.40 mmol) was melted at 280°C in vacuo until the gas evolution subsided. The obtained residue was recrystallised from cyclopentane at −15°C to afford yellow crystals of compound 10b. Yield (0.14 g, 49%); m.p. (dec., sealed capillary): 192°C. – IR (CsBr, paraffin): ν=1607 s, 1580 m, 1555 m ν(C=C), Aryl; 1445 vs, 1433 vs, 1371 vs (paraffin); 1321 vs 1296 vs, 1276 vs, 1246 vs δ(CH₃); 1184 s, 1157 vs, 1116 vs, 1070 vs, 1028 s, 1008 s, 979 vs, 935 s, 918 s, 885 vs, 827 m, 806 s, 785 vs, 771 m, 748 vs δ(CH), ν(CC), ν(CN); 725 vs (paraffin); 690 m, 657 s δ(CH_Ph); 635 vs, 600 m, 570 m, 556 m, 544 m, 528 m, 517 m, 494 w, 475 m, 461 s, 444 m cm⁻¹ν(PC), ν(GaC), ν(GaN), δ(CC). – ¹H NMR (400 MHz, C₆D₆, 300 K): δ=7.78 (d, ³J_HP=37.4 Hz, 1 H, PC=CH), 7.45 [d, ³J_HH=7.2 Hz, 2 H, o-H(Ph)], 7.21 (d, ³J_HH=8.4 Hz, 2 H, m-H(NAr)], 7.13 [pseudo-t, ³J_HH=7.2 Hz, 2 H, m-H(NPh)], 7.04 [t overlap, ³J_HH=7.2 Hz, 1 H, p-H(Ph)], 7.03 [d overlap, ³J_HH=8.4 Hz, 2 H, o-H(NAr)], 6.61 [d, ⁴J_HP=3.8 Hz, 4 H, m-H(Mes)], 2.25 (s, 12 H, o-Me), 1.98 (s, 6 H, p-Me), 1.31 ppm (s, 18 H, CMe₃). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=156.0 [d, ¹J_CP=42.2 Hz, PC=CH), 152.7 (d, ²J_CP=4.3 Hz, ipso-C(NAr)], 149.9 (PC=CH), 141.6 [d, ⁴J_CP=2.8 Hz, p-C(Mes)], 141.4 [d, ²J_CP=10.2 Hz, o-C(Mes)], 141.0 [d, ³J_CP=35.2 Hz, ipso-C(Ph)], 131.9 [d, ³J_CP=10.2 Hz, m-C(Mes)], 130.8 [d, ¹J_CP=68.3 Hz, ipso-C(Mes)], 129.3 [p-C(Ph)], 128.9 [m-C(Ph)], 128.0 [o-C(Ph)], 126.1 [q, ³J_CF=3.6 Hz, m-C(NAr)], 125.5 (q overlap, ¹J_CF=272.0 Hz, CF₃), 124.3 [d, ³J_CP=11.0 Hz, o-C(NAr)], 123.0 [q, ²J_CF=32.8 Hz, p-C(NAr)], 32.8 (CMe₃), 26.2 (d, ³J_CP=3.7 Hz, GaCMe₃), 25.3 (d, ³J_CP=4.2 Hz, o-Me), 20.8 ppm (p-Me). – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=32.5 ppm. – ¹⁹F NMR (376.4 MHz, C₆D₆, 300 K): δ=−61.0 ppm. – MS (EI; 20 eV; 403 K): m/z (%)=656 (100) [M–^tBu]⁺. – C₄₁H₅₀F₃ GaNP·(C₅H₁₀)_0.5 (749.6): calcd. C 69.7, H 7.4, N 1.9; found C 70.3, H 7.4, N 1.9.

4.19 Nitrene adduct {Mes₂PC(Ga^tBu₂)=C(H)Ph}(NSiMe₃) (10c)

A solution of N₃SiMe₃ (0.05 mL, 0.042 g, 0.36 mmol) in toluene (5 mL) was added at room temperature to a solution of compound 3 (0.20 g, 0.36 mmol) in toluene (5 mL). The mixture was stirred overnight and the solvent removed in vacuo to yield a brown solid. Attempts to crystallise compound 10c from a variety of solvents were unsuccessful, but the crude material was NMR spectroscopically characterised, and 10c was identified as the major product. – ¹H NMR (400 MHz, C₆D₆, 300 K): δ=7.55 (d, ³J_HP=40.1 Hz, 1 H, PC=CH), 7.49 [d, ³J_HH=7.3 Hz, 2 H, o-H(Ph)], 7.11 [pseudo-t, ³J_HH=7.3 Hz, 2 H, m-H(Ph)], 7.02 [t, ³J_HH=7.3 Hz, 1 H, p-H(Ph)], 6.63 [d, ⁴J_HP=3.8 Hz, 4 H, m-H(Mes)], 2.42 (s, 12 H, o-Me), 2.00 (s, 6 H, p-Me), 1.42 (s, 18 H, CMe₃), 0.23 ppm (s, 9 H, SiMe₃). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=160.8 (d, ¹J_CP=34.2 Hz, PC=CH), 148.3 (PC=CH), 140.9 [d, ³J_CP=35.0 Hz, ipso-C(Ph)], 140.6 [d, ²J_CP=9.8 Hz, o-C(Mes)], 140.4 [d, ⁴J_CP=2.8 Hz, p-C(Mes)], 132.4 [d, ¹J_CP=72.7 Hz, ipso-C(Mes)], 131.8 [d, ³J_CP=10.1 Hz, m-C(Mes)], 128.9 [p-C(Ph)], 128.6 [m-C(Ph)], 128.3 [o-C(Ph)], 33.2 (CMe₃), 25.9 (d, ³J_CP=2.1 Hz, CMe₃), 25.4 (d, ³J_CP=4.4 Hz, o-Me), 20.8 (d, ⁵J_CP=1.3 Hz, p-Me), 5.2 ppm (d, ³J_CP=3.6 Hz, SiMe₃). – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=33.5 ppm. – ²⁹Si NMR (79.5 MHz, 300 K, C₆D₆): δ=−3.5 ppm (d, ²J_PSi=1.0 Hz). – ¹⁵N NMR (40.1 MHz, 300 K, C₆D₆): δ=59.0 ppm.

4.20 Nitrene adduct {Mes(H)PC{Al[CH(SiMe₃)₂]₂}=C(H)^tBu}{NCH₂Ph)} (11)

A solution of compound 8c (0.29 g, 0.42 mmol) in benzene (20 mL) was heated for 8 h at 80°C. The solvent was removed in vacuo and the residue recrystallised from cyclopentane at −30°C to yield colourless crystals of compound 11. Yield (0.21 g, 73%); m.p. (dec., sealed capillary): 120°C. – IR (KBr, paraffin): ν=1607 vw, 1558 vw ν(C=C), Aryl; 1456 vs, 1377 vs (paraffin); 1364 w δ(CH₃); 1148 w, 1078 vw; 1000 w ν(CHSi₂); 936 w, 841 s, 774 w δ(CH), ν(CC), ν(CN), ρ(SiCH₃); 700 w, 669 w ν(SiC), δ(CH_Ph); 451 w cm⁻¹ν(PC), ν(Al–C). – ¹H NMR (400 MHz, C₆D₆, 300 K): δ=7.97 (d, ¹J_HP=440.3 Hz, 1 H, PH), 7.11 [m, 2 H, o-H(NAr)], 6.81 [m, 1 H, p-H(NAr)], 6.80 [m, 2 H, m-H(NAr)], 6.49 (d, ³J_HP=51.3 Hz, 1 H, PC=CH), 6.48 [s br., 1 H, m-H(Mes)], 6.26 [s br., 1 H, m-H(Mes)], 4.43 (dd, ³J_HP=16.6 Hz, ²J_HH=13.9 Hz, 1 H, CH₂), 4.29 (dd, ³J_HP=19.4 Hz, ²J_HH=13.9 Hz, 1 H, CH₂), 2.53 (s, 3 H, o-Me), 1.88 (s, 3 H, p-Me), 1.76 (s, 3 H, o-Me), 1.09 (s, 9 H, CMe₃), 0.53 and 0.49 (each s, 18 H, SiMe₃), −0.54 ppm (s, 2 H, AlCH). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=166.4 (d, ²J_CP=4.1 Hz, PC=CH), 143.8 [br., o-C(Mes)], 143.3 [o-C(Mes)], 142.9 [d, ⁴J_CP=2.7 Hz, p-C(Mes)], 140.5 (PC=CH), 139.3 [d, ³J_CP=8.1 Hz, ipso-C(NAr)], 130.6 [d overlap, m-C(Mes)], 130.5 [d overlap, m-C(Mes)], 129.7 [o-C(Ph)], 128.3 [m-C(Ph)], 127.6 [p-C(Ph)], 120.5 [d, ¹J_CP=67.1 Hz, ipso-C(Mes)], 51.3 (d, ²J_CP=5.8 Hz, NCH₂), 37.4 (d, ³J_CP=32.0 Hz, CMe₃), 28.8 (d, ⁴J_CP=1.7 Hz, CMe₃), 23.2 (d, ³J_CP=5.7 Hz, o-Me), 21.6 (d, ³J_CP=8.5 Hz, o-Me), 20.9 (⁵J_CP=1.0 Hz, p-Me), 6.3, 6.1, 5.8 and 5.5 (SiMe₃), 5.5 and 4.4 ppm (s br. overlap, CHSi₂). – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=10.0 ppm. – ²⁹Si NMR (79.5 MHz, C₆D₆, 300 K): δ=−2.7, −2.6, −2.4, −2.0 ppm. – MS (EI; 20 eV; 333 K): m/z (%)=668 (3) [M–Me]⁺, 525 (100) [M+H–CH(SiMe₃)₂]⁺. – C₃₆H₆₇AlNPSi₄ (684.2): the carbon value was always found 1% below the calculated value; C 63.2, H 9.9, N 2.1; found C 62.2, H 9.8, N 1.9.

4.21 {Mes₂PC(Al^tBu₂)=C(H)Ph}(NN=C(H)SiMe₃) (12a)

A solution of 1 (0.18 g, 0.35 mmol) in toluene (10 mL) was treated with N₂C(H)–SiMe₃ (0.18 mL, 0.35 mmol, 2.0 m in n-hexane) at room temperature. The mixture was stirred for 21 h. The solvent was removed in vacuo, and the residue was recrystallised from 1,1,1-trifluorotoluene (2 mL) at −32°C to yield colourless crystals of compound 12a. Yield (0.19 g, 87%); m.p. (dec., sealed capillary): 105°C. – IR (KBr, paraffin): ν=1603 vs, 1555 vs, 1535 s, 1516 s ν(C=C), Aryl, ν(C=N); 1466 vs, 1454 vs, 1435 vs, 1406 vs, 1373 vs (paraffin); 1337 s, 1323 vs, 1314 vs sh, 1290 vs, 1246 vs δ(CH₃); 1211 s, 1171 vs, 1157 vs, 1132 vs, 1094 vs, 1071 vs, 1028 vs, 1001 s, 963 s, 943 vs, 910 s, 887 s, 851 vs, 808 vs, 793 s, 770 s, 743 vs δ(CH), ν(CC), ν(CC), ρ(SiCH₃); 723 vs (paraffin); 692 s, 640 vs ν(SiC), δ(CH_Ph); 627 m, 602 vs, 579 s, 556 m, 529 s, 500 s, 469 vs, 430 m, 407 w cm⁻¹ν(PC), ν(AlC), ν(AlN), δ(CC). – ¹H NMR (400 MHz, C₆D₆, 300 K): δ=8.03 (d, ⁴J_HP=1.3Hz, ²J_HSi=13.0 Hz, 1 H, CHSi), 7.82 (d, ³J_HP=40.3 Hz, 1 H, PC=CH), 7.60 [d, ³J_HH=7.6 Hz, 2 H, o-H(Ph)], 7.14 [pseudo-t overlap, ³J_HH=7.6 Hz, 2 H, m-H(Ph)], 7.05 [t, ³J_HH=7.3 Hz, 1 H, p-H(Ph)], 6.63 [d, ⁴J_HP=3.5 Hz, 4 H, m-H(Mes)], 2.47 (s, 12 H, o-Me), 1.93 (s, 6 H, p-Me), 1.38 (s, 18 H, CMe₃), 0.15 ppm (s, ²J_HSi=6.7 Hz, 9 H, SiMe₃). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=158.1 (d, ³J_CP=26.4 Hz, C=N), 154.5 (PC=CH), 149.8 (d, ¹J_CP=16.7 Hz, PC=CH), 141.5 [d, ⁴J_CP=2.9 Hz, p-C(Mes)], 141.4 [d, ²J_CP=9.8 Hz, o-C(Mes)], 141.1 [d, ³J_CP=35.2 Hz, ipso-C(Ph)], 131.7 [d, ³J_CP=10.7 Hz, m-C(Mes)], 129.6 [p-C(Ph)], 128.8 [m-C(Ph)], 128.2 [overlap, o-CPh)], 128.2 [d overlap, ¹J_CP=67.3 Hz, ipso-C(Mes)], 32.4 (CMe₃), 25.0 (d, ³J_CP=3.4 Hz, o-Me), 20.8 (d, ⁵J_CP=1.2 Hz, p-Me), 17.4 (s br. CMe₃), −2.0 ppm (SiMe₃). – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=39.5 ppm. – ²⁹Si NMR (79.5 MHz, 300 K, C₆D₆): δ=−7.7 ppm. – ¹⁵N NMR (40.1 MHz, 300 K, C₆D₆): δ=386 (N=CH), 169 ppm (³J_NH=9.5 Hz, PN). – MS (EI; 25 eV; 298 K): m/z (%)=569 (89) [M–^tBu]⁺, 470 (20) [M–NCHSiMe₃–H₂C=CMe₂]⁺. – C₃₈H₅₆AlN₂PSi (626.92): calcd. C 72.8, H 9.0; found C 72.5, H 9.0.

4.22 {Mes₂PC[Al(CH₂^tBu)₂]=C(H)Ph}(NN=C(H)SiMe₃) (12b)

A solution of 2 (0.24 g, 0.44 mmol) in n-pentane (10 mL) was treated with N₂C(H)–SiMe₃ (0.22 mL, 0.44 mmol, 2.0 m in n-hexane). The mixture was stirred for 12 h. The solvent was removed in vacuo and the residue recrystallised from 1,1,1-trifluorotoluene (2 mL) at 0°C to afford colourless crystals of compound 12b. Yield (0.26 g, 90%); m.p. (dec., sealed capillary): 132°C. – IR (KBr, paraffin): ν=1603 w, 1650 vw, 1531 vw ν(C=C), Aryl, ν(C=N); 1462 vs, 1402 vw, 1377 s (paraffin); 1358 m, 1306 vw, 1288 vw, 1246 w δ(CH₃); 1223 w, 1121 w, 1092 m, 1061 w, 1028 w, 959 vw, 945 w, 928 vw, 907 w, 851 m, 841 m, 795 w, 743 w δ(CH), ν(CC), ν(CC), ρ(SiCH₃); 723 m (paraffin); 694 w, 638 w ν(SiC), δ(CH_Ph); 629 w, 602 vw, 563 w, 552 vw, 500 vw, 461 w, 401 w cm⁻¹ν(PC), ν(AlC), ν(AlN), δ(CC). – ¹H NMR (400 MHz, C₆D₆, 300 K): δ=8.07 (d, ⁴J_HP=1.5Hz, ²J_HSi=14.5 Hz, 1 H, CHSi), 7.81 (d, ³J_HP=40.5 Hz, 1 H, PC=CH), 7.55 [d, ³J_HH=7.2 Hz, 2 H, o-H(Ph)], 7.16 [pseudo-t overlap, ³J_HH=7.6 Hz, 2 H, m-H(Ph)], 7.04 [t, ³J_HH=7.4 Hz, 1 H, p-H(Ph)], 6.62 [d, ⁴J_HP=3.7 Hz, 4 H, m-H(Mes)], 2.47 (s, 12 H, o-Me), 1.94 (s, 6 H, p-Me), 1.30 (s, 18 H, CH₂CMe₃), 0.93 (s, 4 H, CH₂CMe₃) 0.14 ppm (s, ²J_HSi=7.0 Hz, 9 H, SiMe₃). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=158.4 (d, ³J_CP=25.9 Hz, C=N), 153.4 (PC=CH), 153.0 (d, ¹J_CP=17.0 Hz, PC=CH), 141.2 [d, ⁴J_CP=3.0 Hz, m-C(Mes)], 141.1 [d, ²J_CP=9.6 Hz, o-C(Mes)], 141.0 [d, ³J_CP=35.2 Hz, ipso-C(Ph)], 131.4 [d, ³J_CP=10.6 Hz, m-C(Mes)], 129.2 [p-C(Ph)], 129.2 [d, ¹J_CP=67.7 Hz, ipso-C(Mes)], 128.7 [m-C(Ph)], 128.6 [o-C(Ph)], 35.4 (CH₂CMe₃), 34.0 (s br., CH₂CMe₃), 32.0 (CH₂CMe₃), 24.7 (d, ³J_CP=3.9 Hz, o-Me), 20.8 (d, ⁵J_CP=1.4 Hz, p-Me), −1.9 ppm (¹J_CSi=53.0 Hz, SiMe₃). – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=37.6 ppm. – ²⁹Si NMR (79.5 MHz, 300 K, C₆D₆): δ=−7.9 ppm. – MS (EI; 20 eV; 298 K): m/z (%)=583 (50) [M–CH₂^tBu]⁺. – C₄₀H₆₀AlN₂PSi (655.0): calcd. C 73.3, H 9.2, N 4.3; found C 73.1, H 9.1, N 3.9.

4.23 {Mes₂PC[Al(Cl)^tBu₂]=C(H)Ph}{NHN=C(H)SiMe₃} (13)

A solution of 12a (0.27 g, 0.43 mmol) in toluene (10 mL) was treated with HCl·Et₂O (0.43 mL, 0.43 mmol, 1.0 m in Et₂O). The mixture was stirred for 15 h. The solvent was removed in vacuo, the residue dissolved in n-pentane (1 mL), the solvent again removed in vacuo, and the residue recrystallised from pentafluorobenzene (2 mL) at −45°C to afford colourless crystals of compound 13. Yield (0.26 g, 91%); m.p. (dec., sealed capillary): 153°C. – IR (KBr, paraffin): ν=3356 vw br. (NH); 3142 vw, 2951 vs, 2920 vs, 2851 vs, 2752 s sh, 2725 s, 2687 s (paraffin); 1599 vs, 1578 vs, 1555 vs, 1541 vs, 1505 s ν(C=C), Aryl, ν(C=N); 1456 vs, 1402 vs, 1375 vs (paraffin); 1341 vs, 1306 vs, 1290 vs, 1248 vs δ(CH₃); 1207 s, 1171 s, 1157 s, 1045 vs, 936 m, 905 m, 849 s, 812 s, 787 s, 748 s δ(CH), ν(CC), ν(CC), ρ(SiCH₃); 721 vs (paraffin); 694 s, 648 m ν(SiC), δ(CH_Ph); 611 w, 590 w, 561 m, 513 w, 496 w, 471 m, 417 s cm⁻¹ν(PC), ν(AlC), ν(AlN), δ(CC). – ¹H NMR (400 MHz, C₆D₆, 300 K): δ=9.99 (d, ²J_HP=22.5 Hz, 1 H, NH), 8.00 (d, ³J_HP=48.8 Hz, 1 H, PC=CH), 7.61 [d, ³J_HH=7.4 Hz, 2 H, o-H(Ph)], 7.48 (s, 1 H, N=CH), 7.22 [pseudo-t, ³J_HH=7.7 Hz, 2 H, m-H(Ph)], 7.09 [t, ³J_HH=7.5 Hz, 1 H, p-H(Ph)], 6.66 [d, ⁴J_HP=3.7 Hz, 4 H, m-H(Mes)], 2.33 (s, 12 H, o-Me), 1.95 (s, 6 H, p-Me), 1.28 (s, 18 H, CMe₃), −0.15 ppm (s, 9 H, SiMe₃). – ¹³C NMR (100.6 MHz, C₆D₆, 300 K): δ=160.2 (d, ²J_CP=2.3 Hz, PC=CH), 157.2 (d, ³J_CP=13.6 Hz, N=CH), 144.2 (d, ²J_CP=10.3 Hz, o-C(Mes)], 143.7 [d, ⁴J_CP=2.6 Hz, p-C(Mes)], 140.1 [d, ³J_CP=37.3 Hz, ipso-C(Ph)], 138.5 (s br., PC=CH), 132.5 [d, ³J_CP=11.5 Hz, m-C(Mes)], 129.6 [p-C(Ph)], 129.1 [m-C(Ph)], 128.8 [d, ⁴J_CP=1.5 Hz, o-C(Ph)], 122.1 [d, ¹J_CP=83.5 Hz, ipso-C(Mes)], 32.7 (CMe₃), 25.3 (d, ³J_CP=3.8 Hz, o-Me), 20.8 (d, ⁵J_CP=1.5 Hz, p-Me), 18.1 (s br. CMe₃), −2.5 ppm (SiMe₃). – ³¹P NMR (161.9 MHz, C₆D₆, 300 K): δ=53.5 ppm. – ²⁹Si NMR (79.5 MHz, 300 K, C₆D₆): δ=−6.7 ppm. – ¹⁵N NMR (40.1 MHz, 300 K, C₆D₆): δ=362 (N=CH), 134 ppm (PN). – MS (EI; 25 eV; 298 K): m/z (%)=605 (1) [M–^tBu]⁺, 569 (19) [M–^tBu–HCl]⁺, 547 (6) [M–NHN=C(H)SiMe₃)]⁺. – C₃₈H₅₇AlClN₂PSi (663.4): calcd. C 68.8, H 8.7, N 4.2; found C 69.0, H 8.4, N 3.9.

4.24 Crystal structure determinations

Crystals suitable for X-ray crystallography were obtained by crystallisation from a 1,2-difluorobenzene (5a, 5b, 5e, 8a, 13), pentafluorobenzene (9), CH₂Cl₂ (5c), cyclopentane (10b, 11), 1,1,1-trifluorotoluene (12) and n-hexane (6d). Intensity data was collected on Bruker D8 Venture (5a–c, 5e, 6d, 8a, 9b, 10b, 11–13) or Quazar (9a) diffractometers with multilayer optics and MoKα radiation. The collection method involved ω scans. Data reduction was carried out using the programme Saint+ [63], [64]. The crystal structures were solved by Direct Methods using Shelxtl [65], [66], [67]. Non-hydrogen atoms were first refined isotropically followed by anisotropic refinement by full-matrix least-squares calculations based on F² using Shelxtl. Hydrogen atoms were positioned geometrically and allowed to ride on their respective parent atoms. Compounds 5a and 5e cocrystallised with one molecule of 1,2-difluorobenzene which was disordered (5a, three positions 0.434: 0.311: 0.254; 5e, F2 and F6 refined on split positions 0.87: 0.13). Compound 11 cocrystallised with two molecules of cyclopentane which were disordered and refined in two positions (0.47: 0.53; 0.50: 0.50). Compounds 8a and 11 also incorporated solvent molecules, but these were heavily disordered and treated as diffuse contribution to the overall scattering without specific atom positions by using the routine SQUEEZE in Platon [68] (8a, 5.5 molecules 1,2-difluorobenzene, 12a, three molecules of 1,1,1-trifluorotoluene). The CF₃ groups of compounds 5b and 10b, one neopentyl and the SiMe₃ group of compound 12b were disordered and refined in split positions (5b has two independent molecules, 0.90: 0.10 and 0.72: 0.28; 10b, 0.83: 0.17; 12b, C60 0.69: 0.31, SiMe₃ 0.48: 0.52).

CCDC 1557572 (5a), 1557573 (5b), 1557574 (5c), 1557575 (5d), 1557576 (5e), 1557577 (8a), 1557578 (9a), 1557579 (9b), 1557580 (10b), 1557581 (11), 1557582 (12a), 1557583 (12b) and 1557584 (13) contain the supplementary crystallographic data for this paper. This data can be obtained free of charge from The Cambridge Crystallographic Data Centre viawww.ccdc.cam.ac.uk/data_request/cif.