Volume 72, Issue 11 - Special Issue: Dedicated to Professor Dietrich Gudat on the occasion of his 60th birthday

Attempts to synthesize Pr 4 Mo 7 O 27 using Pr, Pr 6 O 11 and MoO 3 in a molar ratio of 8:6:77 led to a main product of scheelite-type Pr 0.667 [MoO 4 ] and few single crystals of the triclinic A-type Pr 6 Mo 10 O 39 . The latter crystallizes in space group P 1̅ ( a =945.25(1), b =1058.49(2), c =1815.16(3) pm; α =104.149(1), β =95.220(1), γ =102.617(1)°, Z =2). Its crystal structure comprises six crystallographically independent Pr 3+ cations, eight tetrahedral [MoO 4 ] 2− units, and one [Mo 2 O 7 ] 2− entity. The cations display coordination numbers of seven (1×) and eight (5×), while the [MoO 4 ] 2− tetrahedra are surrounded by five Pr 3+ cations each. The [Mo 2 O 7 ] 2− anions exhibit a coordination environment of seven Pr 3+ cations. The attempt to synthesize PrF[MoO 4 ] using PrOF (from in situ thermal decomposition of PrF[CO 3 ]) as reagent did not lead to the desired product but to monoclinic B-type Pr 6 Mo 10 O 39 . This slightly less dense modification compared to its triclinic analogue crystallizes in space group C 2/ c ( a =1247.93(3), b =1989.68(6), c =1392.52 (4) pm, β =100.505(2)°, Z =4) with three crystallographically independent Pr 3+ cations, four [MoO 4 ] 2− tetrahedra, and again one [Mo 2 O 7 ] 2− unit in the crystal structure. Thus, both Pr 6 Mo 10 O 39 modifications are better described with the structured formula Pr 6 [MoO 4 ] 8 [Mo 2 O 7 ]. The coordination numbers around the Pr 3+ cations are seven (1×) and eight (2×) while all four [MoO 4 ] 2− anions are again surrounded by five Pr 3+ cations each. Six of the latter represent the coordination environment around the [Mo 2 O 7 ] 2− entities. Besides the thorough comparison of the crystal structures single crystal Raman spectra were recorded for both Pr 6 Mo 10 O 39 phases.

Polycrystalline RE Rh 6 Si 4 ( RE= La, Nd, Tb, Dy, Er, Yb) samples can be synthesized by arc-melting of the elements. Single crystals of LaRh 6 Si 4 , NdRh 6 Si 4 and YbRh 6 Si 4 were synthesized from the elements in bismuth fluxes (non-reactive flux medium). The structures were refined on the basis of single-crystal X-ray diffractometer data: LiCo 6 P 4 type, P 6̅ m 2, a =700.56(3), c =380.55(1) pm, wR 2=0.0257, 317 F 2 values, 19 variables for LaRh 6 Si 4 , a =698.4(5), c =377.7(2) pm, wR 2=0.0578, 219 F 2 values, 19 variables for NdRh 6 Si 4 and a =696.00(3), c =371.97(1) pm, wR 2=0.0440, 309 F 2 values, 19 variables for YbRh 6 Si 4 . The rhodium and silicon atoms build up three-dimensional, covalently bonded [Rh 6 Si 4 ] δ− polyanionic networks with Rh–Si distances ranging from 239 to 249 pm. The rare earth atoms fill larger cavities within channels of these networks and they are coordinated by six silicon and twelve rhodium atoms in the form of hexa-capped hexagonal prisms.

A chloro-bridged dimeric copper(I) complex with the ambiphilic phosphinoborane ligand t Bu 2 PCH 2 BPh 2 is reported. The molecular structure was determined by single-crystal X-ray diffraction analysis, revealing a secondary η 1 -C interaction of the ligand with the metal center. The complex exhibits green fluorescence when exposed to UV light at 366 nm.

The 1,1′-diaminoferrocene derivatives [Fe( η 5 -C 5 H 4 –NHAd) 2 ] (Ad=2-adamantyl) and [Fe( η 5 -C 5 H 4 –NH t Bu) 2 ] were investigated in terms of their suitability for the synthesis of N-heterocyclic tetrylenes of the type [{Fe( η 5 -C 5 H 4 –NR) 2 }E] (E=Ge, Sn). The synthesis of these target compounds was easily achieved with R= t Bu, but failed with R=Ad. In the latter case, the stannylene was not sufficiently stable for isolation and decomposed to the aminoiminoferrocene derivative [Fe( η 5 -C 5 H 4 –NHAd)( η 5 -C 5 H 4 –N=Ad′)] (Ad′=adamant-2-ylidene). Attempts to synthesise [{Fe( η 5 -C 5 H 4 –NAd) 2 }Ge] afforded intractable material, from which the unusual compound [ μ 2 -{Fe( η 5 -C 5 H 4 –NAd) 2 }Ge 2 ( μ 3 -O)(GeCl 2 )] was obtained by serendipity. It contains GeO, stabilised by adduct formation with GeCl 2 and the target germylene. [Fe( η 5 -C 5 H 4 –NH t Bu) 2 ], [Fe( η 5 -C 5 H 4 –NHAd) 2 ], [Fe( η 5 -C 5 H 4 –NHAd)( η 5 -C 5 H 4 –N=Ad′)], [ μ 2 -{Fe( η 5 -C 5 H 4 –NAd) 2 }Ge 2 ( μ 3 -O)(GeCl 2 )] and [{Fe( η 5 -C 5 H 4 –N t Bu) 2 }E] (E=Ge, Sn) were structurally characterised by single-crystal X-ray diffraction.

The syntheses and crystal structures of the two isotypic europium(II) oxide halides Eu 2 OBr 2 and Eu 2 OI 2 are reported. They crystallize orthorhombically in the space group Ibam ( Z =4; Eu 2 OBr 2 : a =709.86(5), b =1200.34(9), c =628.71(4) pm; Eu 2 OI 2 : a =739.78(5), b =1295.13(9), c =644.82(4) pm). The unit cell parameters presented here, and thus the interatomic distances of Eu 2 OI 2 , are significantly smaller than the ones reported in the literature, which is explained by the substitution of europium with larger barium cations due to the synthesis route described in the early study. Central building blocks of both crystal structures are trans -edge-connected [OEu 4 ] 6+ tetrahedra forming straight ∞1{[OEu4/2e]2+}$_\infty ^1\{ {[{\text{OEu}}_{{\text{4/2}}}^{\text{e}}]^{2 + }}\} $ chains running parallel to the [001] direction. Bundled like a hexagonal rod packing, their interaction is achieved by Br − or I − anions for charge compensation.

A series of bis(phenylacetylido)(porphyrinato) E(IV) (E=Si, Ge, Sn) derivatives were obtained by reacting lithium phenylacetylide with the corresponding bis(chlorido)(porphyrinato) E(IV) precursors. Crystal structure determinations demonstrated that the trans -coordinated acetylide ligands deviate from their expected ideal geometry. Density functional theory calculations and comparison of the packing of the molecules among the homologous series of Si(IV), Ge(IV) and Sn(IV) revealed causes for the deviation from the simple valence shell electron pair repulsion model. Fluorescence and phosphorescence of these organometallic group 14 derivatives were studied and the results are compared to the literature-known properties of the related bis(chlorido)(porphyrinato) E(IV) compounds (E=Si, Ge, Sn). The first crystal structure of a porphyrinato Ge(IV) compound with σ-bonded acetylide ligands is reported.

A series of new heteroleptic divalent germaniun and tin complexes of the general type L 1,4 GeN(SiMe 3 ) 2 ( 1 , 2 ) and L 1−4 SnN(SiMe 3 ) 2 ( 3 – 6 ) were synthesized by reaction of β -ketimines L 1−4 H with Ge[N(SiMe 3 ) 2 ] 2 and Sn[N(SiMe 3 ) 2 ] 2 , respectively. The reaction of 3 with the strong Mg(I) reductant L 5 Mg yielded the heteroleptic complex L 1 MgL 5 7 after ligand transfer from tin to magnesium, whereas analogous reactions of L 4 GeN(SiMe 3 ) 2 2 and L 4 SnN(SiMe 3 ) 2 6 with L 5 Mg occurred with formation of insoluble precipitates, transfer of the amido substituent from the group 14 metal to magnesium and subsequent formation of the heteroleptic magnesium complex L 5 MgN(SiMe 3 ) 2 ( 8 ). 1–8 were characterized by heteronuclear NMR ( 1 H, 13 C, 119 Sn) and IR spectroscopy, elemental analysis and single-crystal X-ray diffraction (L 4 SnN(SiMe 3 ) 2 6 , L 1 MgL 5 7 ).

The Al- and Ga-based frustrated Lewis pairs (FLPs) Mes 2 P–C(MR 2 )=CH-R′ ( 1 , M=Al, R= t Bu; 2 , M=Al, R=CH 2 t Bu; 3 , M=Ga, R= t Bu) and the unique P–H functionalized FLP Mes(H)P–CH(AlR 2 )=C(H)- t Bu [ 4 , R=CH(SiMe 3 ) 2 ] were treated with a variety of azides R′-N=N=N [R′= t Bu, SiMe 3 , Ph, CH 2 Ph, C 6 H 4 (4-Cl), C 6 H 4 (4-CF 3 ), C 6 H 4 (4-Me), CH 2 C 6 H 4 (4-Cl), CH 2 C 6 H 4 (4- t Bu), C 6 H 4 (2-CH=CHPh)] in order to study systematically the influence of the substituents at nitrogen, phosphorus and the metal atoms on the reaction courses and the thermal stability of the products. Azide adducts ( 5–8 ) were isolated in which the terminal nitrogen atoms of the azides (N γ γ ) were bound to the phosphorus and the respective metal atoms resulting in four-membered PCMN heterocycles as the sole structural motif despite the wide range of substituents and the variation in the metal atoms of the FLPs. Thermal activation of selected azide adducts led to the elimination of N 2 and the formation of the nitrene adducts 9–11 in which formally a transient, highly reactive nitrene N–R with an electron sextet nitrogen atom is trapped by the FLPs. For the first time FLPs were treated with a diazomethane, Me 3 Si–C(H)=N=N. Reactions with 1 and 2 afforded the adducts [Mes 2 P–C(AlR 2 )=CH-Ph](μ-N 2 CH–SiMe 3 ) 12 (R= t Bu, CH 2 t Bu) which had structures and spectroscopic properties similar to those of the corresponding azides. These compounds are thermally stable and do not eliminate dinitrogen upon warming or irradiation. Protonation of 12a with HCl in Et 2 O resulted in cleavage of the Al–N bond and formation of the zwitterionic phosphonium salt Mes 2 P[NH–N=C(H)–SiMe 3 ]–C(AlCl t Bu 2 )=C(H)-Ph 13 with an intramolecular N–H···Cl hydrogen bond.

The compounds [W(CO) 5 (btd)], [W(CO) 5 (bsd] and [Re(CO) 3 (bpy)(bsd)](BF 4 ), btd=2,1,3-benzothiadiazole and bsd=2,1,3-benzoselenadiazole were isolated and characterized experimentally (crystal structure, spectroscopy, spectroelectrochemistry) and by density functional theory calculations. The results confirm single N-coordination in all cases, binding to Se was calculated to be less favorable. Studies of one-electron reduced forms indicate that the N-coordination is maintained during electron transfer.

Single crystals of the compounds Li 2 AeTt ( Ae =Ca, Ba, Tt =Si, Ge, Sn, Pb) were grown in reactive lithium melts in sealed tantalum ampoules from an equimolar ratio of the alkaline earth metal and the respective group 4 element. All compounds, with the exception of Li 2 CaSn and Li 2 CaPb, are isotypic and crystallize in an orthorhombic unit cell (space group Pmmn , no. 59). The crystal structure can be characterized as superimposed corrugated networks of Li 2 Tt connected by calcium or barium atoms within the third dimension. Li 2 CaSn and Li 2 CaPb crystallize in the cubic space group Fm 3̅ m (no. 225) in a Heusler-type (MnCu 2 Al) structure. According to magnetic susceptibility and electric resistivity measurements, the compounds Li 2 BaGe, Li 2 BaSn, and Li 2 BaPb represent diamagnetic activated semiconductors.

The germanides RE 3 Pt 4 Ge 6 ( RE =Y, Pr, Nd, Sm, Gd–Dy) have been synthesized by arc-melting of the elements followed by inductive annealing to improve the crystallinity and allow for structural order. The compounds have been studied by powder X-ray diffraction; additionally the structure of Y 3 Pt 4 Ge 6 has been refined from single-crystal X-ray diffractometer data. It exhibits a (3+1)D modulated structure, indicating isotypism with Ce 3 Pt 4 Ge 6 . The crystal structure can be described as an intergrowth between YIrGe 2 - and CaBe 2 Ge 2 -type slabs along [100]. Temperature-dependent magnetic susceptibility measurements showed Pauli paramagnetism for Y 3 Pt 4 Ge 6 and Curie-Weiss paramagnetism for Pr 3 Pt 4 Ge 6 and Nd 3 Pt 4 Ge 6 . Sm 3 Pt 4 Ge 6 exhibits van Vleck paramagnetism, while antiferromagnetic ordering at T N =8.1(1) K and T N =11.0(1) K is observed for Gd 3 Pt 4 Ge 6 and Tb 3 Pt 4 Ge 6 , respectively.

In a search for stable phosphinonitrenes generated by thermally induced decomposition of the azidophosphines 8a , b , different cyclodiphosp(V)azene products were generated. While in the case of 8a the expected phosphinonitrene dimer 10 could be obtained, from 8b , which has the sterically more demanding TMP substituents, product 11 , was obtained and characterized. DFT calculations have revealed that the primarily formed phosphinonitrene 9b is unstable against loss of TMP˙, and the resulting radical dimerizes to the biradicaloid 1,3-diaza-2,4-diphosphetane-2,4-diyl 13 . Compound 13 then dimerizes after ring opening, yielding in the ring system, which provides the final product upon reaction with the starting azidophosphine.

Three P -chloro-substituted diazaphosphasiletidines, Me 2 Si(N t Bu) 2 PCl ( 1 ) and Me 2 Si(N t Bu) 2 P(E)Cl (E=BCl 3 ( 2 ); W(CO) 5 ( 3 )), are presented for comparison. 1 was first prepared more than 30 years ago and studied by means of spectroscopic methods, however, no crystal structure has been reported until now. In the presence of the comparatively weak Lewis acid BCl 3 and the labile metal carbonyl complex [W(CO) 5 (THF)], 1 can be easily converted into its corresponding adducts 2 and 3 . All products were characterized by single-crystal X-ray diffraction studies. The structures of the new compounds 2 and 3 reveal a remarkable P–Cl bond contraction caused by the coordination of 1 to the Lewis acid or the Lewis acidic W(CO) 5 fragment. Although the coordination number of the P atom is increased in 2 and 3 , the P–Cl bond length is reduced dramatically, some kind of bond length paradoxon. A computational study suggests that these P–Cl bond shortenings result from a less effective donation of electron density from the lone pairs at the nitrogen atoms to the antibonding σ * (P–Cl) orbital in 2 and 3 as compared to 1 .

Reaction of the chelating imino-pyridine ligand SIMPY, (SIMPY=2-(DippN=CH)-C 5 H 4 N), Dipp=2,6- i Pr 2 -C 6 H 3 , with germanium(II) and tin(II) halides provides the respective neutral complexes [SIMPY·EX 2 ] (EX 2 : E=Ge, X=Cl, Br; E=Sn, X=Cl, Br, I). The method is readily extendable to give the tin(II) triflate complex [SIMPY·Sn(OTf) 2 ] (OTf, triflate=CF 3 SO 3 − ). In the solid state, the neutral compounds [SIMPY·EX 2 ] exist as monomers, in which the four-coordinate tetrel atoms feature a slightly distorted disphenoidal geometry around germanium and tin. Reaction of the tridentate imino-pyridine ligand DIMPY, (DIMPY=2,6-(DippN=CH) 2 -C 5 H 3 N) with Sn(OTf) 2 provided access to a neutral tin(II) complex. Similar to the previously reported reactions leading to the germanium and tin chloride complexes [DIMPY·SnCl] + [SnCl 3 ] − , and [ Me2 DIMPY·EX] + [EX 3 ] − ( Me2 DIMPY=2,6-(DippN=C(Me)) 2 -C 5 H 3 N, E=Ge, Sn; X=Cl), the reactions of DIMPY with GeX 2 ·dioxane (X=Cl, Br) and SnX 2 (X=Br, I) yielded Ge(II) and Sn(II) based ion pairs [DIMPY·EX] + [EX 3 ] − (E=Ge, X=Cl, Br; E=Sn, X=Br, I) as a consequence of spontaneous dissociation of the group 14 dihalides. The tetrel atoms in the cationic parts in [DIMPY·EX] + [EX 3 ] − are four-coordinate as one halide substituent is replaced by the coordination of a second imino donor group from the ligand. The anionic fragments adopt a pyramidally, tri-coordinate geometry. In contrast, the DIMPY tin(II) ditriflate complex crystallizes with two independent, neutral molecules per asymmetric unit, in which one of the tin centers is five- coordinate by interaction with three donor sites of the chelating bis(imino)pyridine ligand and two additional contacts towards the oxygen atoms of the triflate counter-anions. In the second crystallographically independent complex the tin atom is six-coordinate with a slightly distorted octahedral geometry via interaction with THF as an additional donor molecule. All compounds reported were studied by means of multinuclear NMR spectroscopy. In addition, the solid state structures of the complexes [SIMPY·EX 2 ] (EX 2 : E=Ge, X=Cl, Br; E=Sn, X=Cl, Br, I), the ion pairs [DIMPY·EX] + [EX 3 ] − (E=Ge, X=Cl; E=Sn, X=Br) and the tin(II) ditriflate [DIMPY·Sn(OTf) 2 ] were authenticated by means of single-crystal X-ray diffraction analyses. Moreover, [DIMPY·Sn(OTf) 2 ] was investigated by 119 Sn Mössbauer spectroscopy.

As demonstrated by DFT calculations, the bonding situation of P-iodo, bromo and chloro-bis(imino)phosphoranes XP(NR) 2 , X=Cl, Br, I, differs from that of conventional amino-bis(imino)phosphoranes (X=NR 2 ). The monomers are highly reactive compounds with relatively small adiabatic singlet-triplet energy differences. They can dimerize by a mutual polarization mechanism between the electropositive iodine center of one monomeric unit and the more electronegative nitrogen centers of the other unit. It causes a slight depletion of p -electron density at iodine and an accumulation at the nitrogen atoms. The polarization induces electrostatic attraction, attenuated by stack formation into a one-dimensional array of monomers. The weak electrostatic binding is strongly superimposed by steric attraction among the bulky substituents of the stack array, which can end up essentially stronger than the electrostatic interaction forces. The factors which govern the dispersion forces are evaluated. The substituent effects for stack formation are studied in detail for the association of two monomers.

The new ansa -phosphinoborane (dicyclohexyl(2-(dimesitylboryl)phenyl)phosphine was synthesized via an one-pot protocol in 67% yield. The compound has been characterized by 1 H, 13 C, 11 B and 31 P NMR, and its solid-state structure determined by a single crystal X-ray diffraction analysis. The ansa -phosphinoborane does not react with molecular hydrogen or water at room or elevated temperature. According to performed DFT studies, heterolytic splitting of water or hydrogen by the phosphinoborane are both endergonic but close in thermodynamics. In polar solvents, such as in methanol or acetonitrile, addition of hydrogen is energetically more favorable than of water.

The aminosilanes Me n Si(NRR′) 4− n ( n =2,3) with NRR′=ethylamino (NHEt), n -propylamino (NH n Pr), sec -butylamino (NH s Bu), n -octylamino (NH n Oct), n -dodecylamino (NH n Dodec), allylamino (NHAll), tert -butylamino (NH t Bu), diethylamino (NEt 2 ), and anilino (NHPh) were synthesized and their reactions with phenyl isocyanate were studied. In all cases of these silanes Me 3 SiNRR′ and Me 2 Si(NRR′) 2 formal insertion of the –NCO group into their Si–N bonds was observed, i.e. formation of products with Si–N (rather than Si–O) bonds was found. In some cases, the products could be crystallized and their molecular structures have been elucidated with single-crystal X-ray diffraction analyses.