Volume 43, Issue 9

Hexa-terf-butyldisiloxane (tBu 3 Si) 2 O (2), hexa-rerr-butyldisilazane (tBu 3 Si) 2 NH (3), and the disiloxane (tBu 3 SiNHSuBu 2 ) 2 O (4) are prepared from bis(silyl)triazene tBu 3 SiN=N-NHSirBu 3 by reaction with water (2) and by thermolysis (3), or from silanimine tBu 2 Si=NSirBu 3 by reaction with water (4). Structures of 2-4 have been determined by X-ray crystallography (for data cf. Tables II). As a consequence of the bulkiness of the silyl groups, the heavy atom frameworks SiOSi in 2 and 4 are linear, and the SiNSi angles in 3 (167 ± 2°) and 4 (157.1°) are comparatively large.

Crystal and molecular structure analysis of the title compound 1, a most electron rich carbosilane, exhibits a shallow boat conformation for the cyclohexadiene ring which is shielded by four bulky Me 3 Si groups. Multiple hyperconjugative interaction occurs between the two non-conjugated olefinic π systems and the four rather long (192 pm) carbon-silicon o bonds which form an angle of about 34° with the assumed π axis. The HOMO destabilization caused by this unique structural arrangement explains the energetically facile formation and subsequent reactivity of the cation radical 1+ which was found to undergo oxidative desilylation to the aromatic 1,4-bis(trimethylsilyl) benzene precursor in the single electron transfer reaction with TCNE.

The title compounds have been prepared by reactions of the metal acetates of zink, cadmium, and mercury with ethanolic solutions of sodium polyselenides in the presence of 15-crown-5. They form dark red crystals, which were characterized by their IR specta as well as by X-ray crystal structure determinations. All complexes [Na-15-crown-5] 2 [M(Se 4 ) 2 ] with M = Zn (1), Cd (2), Hg (3) crystallize isotypically in the space group C2/c with 4 formula units per unit cell. In the anions [M(Se 4 ) 2 ] 2- the metal atoms are coordinated tetrahedrally by four selenium atoms of two Se 4 2- units, thus forming a spiro-bicyclus. The complex cations [Na-15-crown-5] + have a Na---Se contact of approximately 299 pm with two selenium atoms of a MSe 4 group, allowing formulation of triple ion species.

Lithium-tris(diethylamino)hydridoaluminate, Lithium-bis(diisopropylamino)dihydridoaluminate. Lithium(tetramethylpiperidino)trihydridoaluminate, NMR Spectra, X-Ray Reactions of diethylamine, diisopropylamine and 2,2,6,6-tetramethylpiperidine with LiAlH 4 in various ethers have been studied. Only two well-defined products result from Et 2 NH, namely LiAlH(NEt 2 )- and LiAl(NEt 2 ) 4 . If molar ratios of Et 2 NH:LiAlH 4 smaller than 3:1 are employed all compounds of the series LiAlH 4-n (NEt 2 ) n (n = 0, 1, 2, 3) are present in solutions of tetra-hydrofuran and diglyme. In diethylether insoluble materials consisting predominantly of lithium diethylaminohydridoaluminates and, presumably, small quantities of Li 3 AlH 6 are also formed. At ambient temperature diisopropylamine reacts slowly with LiAlH 4 , and LiAlH 2 (N i Pr 2 ) 2 can be isolated as a well-defined substitution product. 2,2,6,6-tetramethylpiperidine (tmpH) replaces only a single hydride from LiAlH 4 with formation of LiAlH 3 (tmp). The reactions have been monitored by 7 Li, 13 C and 27 Al NMR spectroscopy, and the structure of LiAlH(NEt 2 ) 3 has been determined by X-ray analysis. The monoclinic compound contains chains of AlHN 3 and LiHN 3 tetrahedra linked through common edges.

The reaction of chloro-bis[bis(trimethylsilyl)methyl]alane (1) with potassium yields the title compound 2.2 crystallizes in the triclinic space group P1̄ and shows an aluminium -aluminium bond length of 266.0(1) pm. The core of the molecule is almost planar.

N,N,N'-Tris(trimethylsilyl)benzamidine, [C 6 H 5 -C(NSiMe 3 )N(SiMe 3 ) 2 ], reacts with antimony trichloride in CH 2 Cl 2 solution to form monomeric dichloroantimony-N,N'-bis(trimethylsilyl)- benzamidine, [SbCl 2 (NSiMe 3 ) 2 C-C 6 H 5 ]. Both benzamidine derivatives have been character­ized by crystal structure determinations. [C 6 H 5 -C(NSiMe 3 )N(SiMe 3 ) 2 ]: space group P2 1 /c, Z = 4, 2278 observed independent refle­xions, R = 0,038. Lattice dimensions (19 °C): a = 1521,0(1); b = 656.7(1); c = 2163,0(1) β = 94,21(1)°. The compound forms monomeric molecules with CN distances of 126,6 pm, and 141,0 pm, respectively, corresponding to C=N̄-SiMe3 and C-N(SiMe 3 ) 2 moieties. [SbCl 2 (NSiMe 3 ) 2 C-C 6 H 5 ]: space group P2 1 /c, Z = 4, 2707 observed independent reflexions, R = 0,027. Lattice dimensions (19 °C): a = 1212,7(1); b = 962,1(1); c = 1728,9(1) pm; β = 98,02(1)°. The compound forms monomeric molecules in which the antimony atom is surrounded by two chlorine atoms, and by the N atoms of the benzamidine chelate, forming a distorted trigonal bipyramidal arrangement, which is a consequence of the steric effect of the lone pair on the Sb atom.

[Na-15-Crown-5][MoF 5 (NCl)] has been prepared as yellow crystals by the reaction of NaF with MoF 4 (NCl) in the presence of 15-crown-5 in acetonitrile solution. The compound was charac­terized by its IR and 19 F NMR spectra as well as by an X-ray structure determination. Crystal data: space group P2 1 /n, Z = 4 (3736 observed, independent reflexions, R = 0.034). Lattice dimensions at -70 °C: a = 823.5(4). b = 1612.2(9), c = 1383.4(8), β = 99.35(3)°. The compound forms ion pairs, in which the sodium ion is seven-coordinated by the oxygen atoms of the crown ether molecule and by two fluorine ligands of the [MoF 5 (NCl)] - unit with Na-F distances of 228.3 and 249.6 pm. The Mo=N-Cl group of the anion is nearly linear (bond angle 175.8°) with bond lengths MoN = 172.9 and NCl = 161.8 pm.

Ph 3 P=NSiMe 3 (1) reacts with InCl 3 , SnCl 2 and FeCl 3 to yield (Ph 3 P=N) 2 (InCl 2 ) 2 • 2DMF (2a), (Ph 3 P=N) 2 Sn 2 Cl 4 • 2 CH 3 CN (3a) and (Ph 3 P=N) 2 (FeCl 2 ) 2 (4). The X-ray single crystal structures of 2a, 3a and 4 are reported. The compounds form four-membered rings consisting of alternating metal and nitrogen atoms. 2a and 4 are symmetrical, but 3a has both a Sn(II)Cl and a Sn(IV)Cl 3 group in the four-membered ring.

The crystal structure of (AsPh 4 )[Ni(dmid) 2 (dmid 2- = 1,3-dithia-2-one-4,5-dithiolato) has been determined by X-ray diffraction studies: crystals are monoclinic, space group P2 1 /n a = 14.724(2), b = 14.305(5), c = 15.570(3) Å, β = 92.20(1)°, V = 3277 Å 3 , ᵨ x = 1.63 g cm -3 for Z = 4, final conventional agreement indices R = 0.038 and R w = 0.049 for 2115 unique, observed reflections and 211 variable parameters. The asymmetric unit contains one (AsPh 4 ) + cation and one [Ni(dmid) 2 ] anion, both in general positions. The anions are isolated from each other by the bulky cations. The [Ni(dmid) 2 ] - ion deviates strongly from planarity: the dihedral angle between the two Ni(dmid) moieties is 10.7°; one of the dmid ligand is almost planar, while the second one is severely puckered. Polycristalline powder and single crystal EPR spectra have been recorded at room temperature. Only one signal was observed in all crystal orientations. The angular depend-ences of the linewidth and of the g values have been determined, as well as the principal g values and directions. These results have been compared to those previously obtained for the analogue (n-Bu 4 N)[Ni(dmit) 2 ] (drnit 2- = 1,3-dithia-2-thione-4,5-dithiolato), and discussed in terms of the localization of the unpaired electron on the ligands. leading to a formal (III) and actual (II) nickel oxidation state.

The reaction of SbI 3 with Me 4 NI, Me 3 SI. and Me 3 NCH 2 PhI in acetonitrile (molar ratios 2:1) yields (Me 4 N) 4 Sb 8 I 28 (I), (Me 3 S) 4 Sb 8 I 28 (2), and (Me 3 NCH 2 Ph)Sb 2 I 7 (3), respectively. The struc­tures of 1-3 were determined from single crystal X-ray diffraction data. 1-3 crystallize in the monoclinic space group P2 1 /n. 2: a = 1434.2(3). b = 1484.1(4). c = 2102.6(4) pm, β = 105.4(1)°, Z = 2. I: a = 1441.7(1). b = 1545.1(1). c = 2117.3(1) pm. β = 106.4(1)°, Z = 2. 3: a = 1004.4(1). b = 1378.8(1). c = 1899.3(2) pm. β = 94.2(1)°. Z = 4. The structures of I and 2 are very similar and consist of isolated cations and anions. The Sb 8 I 28 4- ions of 1 and 2 and the anion of the same stoichiometry of (Ph 4 P) 4 Sb 8 I 28 exhibit different struc­tures with a nearly identical Sb 4 I 16 core. The anions of 3 are built up of polymeric cfiains.

Titanocene pentasulfide reacts with sulfuryl chloride under suitable conditions to give a mixture of mainly S 10 , S 15 , and S 20 which can be separated by repeated crystallization and precipitation. Pure S 15 is obtained as a lemon-yellow powder at low temperatures which transforms to a sticky mass at 20 °C. Solutions of S 15 in CS 2 are stable at 20 °C for months. Pure S 15 does not decompose at 20 °C within a few hours. Raman spectra of S 15 show stretching vibrations at 409-480 cm -1 and bending and torsional modes at < 270 cm -1 .

The crystal structure of Na 5 SnSb 3 (monoclinic, P2 1 /c, a = 1859.4(6), b = 918.1(4), c = 1249.3(5) pm, β = 98.3°, Z = 8) contains SnSb 4 tetrahedra which form chains by sharing common vertices. Isolated tetrahedral units SnSb 4 8- are present in the crystal structure of K 8 SnSb 4 (cubic, Fd3m, a = 1627.9(3) pm, Z = 8). The compounds are in agreement with the Zintl concept.

By diffusion of methanolic solutions of hexamethylenetetramine into aqueous solutions of hexacyanoferrates(III) of sodium and potassium, resp., single crystals of the adducts were ob­tained. Na 3 [Fe(CN) 6 ] · 2C 6 H 12 N 4 -5H 2 O, orthorhombic, space group Pca2 1 . Z = 4, a = 14.122(4). b = 14.380(4), c = 14.381(4) Å, 3153 reflections, R = 0.044. K 3 [Fe(CN) 6 ]•2C 6 H 12 N 4 -4H 2 O, triclinic, space group P1̄, Z = 4, a = 14.125(4), b = 17.808(4), c =14.116(4) Å, α = 114.14(5), β = 94.91(4), γ = 108.36(5)°. 5550 reflections, R = 0.042. Both structures may be regarded as Elpasolite-Iike arrangements of [Fe(CN) 6 ] 3- ions, C 6 H 12 N 4 molecules and [M 2 (OH 2 ) x ] 3+ units (M = Na, K; x = 5, 4), linked together unsymmetrically by M-N contacts of metal ions and nitrogen atoms with mean distances of Na-N HMT = 264 pm. Na-N CY an = 243 pm, K-N HMT = 293 pm and K-N cyan = 290 pm. Stabilization of the crystal structures is obtained by N---H-O hydrogen bonds of coordination water molecules in three dimensions.

The crystal structure of the triclinic compound Ag 4 (NH 3 ) 5 Mo(CN) 8 - 1,5H 2 O could be refined in space group P1̄ (at T = 179 K: a = 974.6, b = 1477.6, C = 775.5 pm, α = 102.5, β = 94.6, y = 81.5°, Z = 2. Rg = 0.044 for 2744 independent reflections). The [Mo(CN) 8 ] 4_ -groups form distorted square antiprisms with mean distances Mo-C = 215.7, C-N = 115.1 pm. They are connected to a puckered layer via four of their nitrogen ends which are tetrahedrally coordinated to silver (Ag-N = 226.7 pm). In between these layers and more or less tightly coordinated to their free cyano-N atoms dumbbells [CNAgNH 3 ] and [Ag(NH 3 ) 2 ] + are embedded. Their variation of distances and angles (Ag-N: 213 ... 216 pm, N-Ag-N: 150 ... 174°) is discussed.

(PhN 3 ) 2 C 6 H 4 [(OH)Ni(PhN 3 H) 2 C 6 H 4 ] 2 · 2THF is obtained by the reaction of [(PhN 3 ) 2 C 6 H 4 ]Na 2 with aqueous NiCl 2 . It crystallizes from tetrahydrofuran/hexane in the monoclinic space group P2 1 /n, with a = 1574.6(3), b = 2498.5(2), c = 1629.2(2) pm, β = 93.909(3)°, and Z = 4. The Ni atoms are bridged by the bis(phenyltriazenidyl)benzene group and two hydroxyl groups. Two neutral bis(phenyltriazenyl)benzene groups chelate each Ni atom to complete the distorted co­ordination sphere.

Crystals of the title compound (2) are monoclinic with a = 905.5(3), b = 593.6(2). c - 3243.5(8) pm, β = 95.63(2)°, Z = 4, space group P2 1 /n. The molecule 2 neither has a C 2 -symmet-rical allene-type nor a D 2d -symmetrical cumulene-type structure, but it has a non-linear B-N = C= N - B arrangement and is nearly planar. The central N = C= N angle has a value of 171.9(3)°, the B - N = C angles are 145.9(2)° and 163.1(3)°.

The reaction of Fe(acac) 3 (acac = acetylacetonate, 2,4-pentanedionate) with 1,4,7-triazacyclo- nonane (L) in acetone in the presence of water and NaClO 4 yields green crystals of [L 2 Fe 2 III (acac) 2 (μ-O)](ClO 4 ) 2 (1) a μ-oxo bridged dimer of Fe(III) the crystal structure of which has been determined. Hydrolysis of this material in an acetone/water mixture in the presence of NaBr yields the green tetramer [L 4 Fe 4 III (μ-O) 2 (μ-OH) 4 ]Br 4 · 4H 2 O. Both compounds are strongly intramolecularly antiferromagnetically coupled. In contrast, the analogous reaction of Mn(acac) 3 with L or N,N',N"-trimethyl-1,4,7-triazacyclononane (L') in ethanol or methanol yields yellow- green monomeric complexes of the type [LMn III (acac)(OR)] + or [L'Mn(acac)(OR)] + (R = CH 3 , C 2 H 5 ) which were isolated as tetraphenylborate or hexafluorophosphate salts. The crystal struc­ture of [L'Mn(acac)(OC 2 H 5 )]BPh 4 (2) has been determined. If to the above reaction mixture cone. HClO 4 was added, red [L'Mn(acac)(H 2 O)](CLO 4 ) 2 (3) precipitated. In alkaline aqueous solution [L'Mn(acac)(OH)] + prevails. The crystal structure of 3 has also been determined. The new monomeric manganese(III) complexes have temperature independent (100-300 K) mag­netic moments of 4.8 to 5.1 μ B in agreement with a high spin (d 4 ) electronic configuration.

[(μ-N t C 4 H 9 ) 2 V 2 Cp 2 (O t C 4 H 9 ) 2 ] (2) and [(μ-Cl) 2 V 2 Cp 2 (N t C 4 H 9 ) 2 ] (6) have been prepared by reac­tion of Li t C 4 H 9 with t C 4 H 9 N=VCp(O t C 4 H 9 )Cl and t C 4 H 9 N=VCpCl 2 , respectively. The molecular structure has been investigated by X-ray diffraction analysis. NMR and ESR Spectra indicate two types of tert-butyliminovanadium(IV) complexes: 2 (diamagnetic) and 6 (paramagnetic).

The reactions of radiolytically generated hydroxyl radicals and H atoms with 1,4- and 1,3-cyclohexadiene were studied by pulse radiolysis and product analysis. Hydrogen abstraction from these substrates by the OH radical yields the cyclohexadienyl radical (ε (310 nm) = 4400 dm 3 mol -1 cm -1 from the reaction of the H atom with benzene) with an efficiency of 50% (0.29 ,μmol J -1 ) in the case of 1,4-cyclohexadiene and 25% (0.15 ,μmol J -1 ) in the case of 1,3-cyclohexadiene as determined by pulse radiolysis. The remaining OH radicals add to the olefin. In 1.4-cyclohexa- diene the yield of the resulting adduct radicals has been determined in a steady-state 60 Co-γ-irradiation experiment by reducing it with added 1.4-dithiothreitol (DTT) to 4-hydroxycyc- lohexene. There are two sites of OH radical attack in the case of 1.3-cyclohexadiene, and only the alkyl radical is reduced quantitatively by DTT (G(3-hydroxycyclohexene) = 0.15 ,μmol J -1 ). From material balance considerations it is concluded that the allylic radical must be formed with a G value of 0.28 ,μmol J -1 but largelv escapes reduction by DTT (G(4-hvdroxycyclohexene) = 0.03 ,μmol J -1 ). H atoms add preferentially to the double bonds of 1,4- and 1,3-cyclohexadiene (78% and 93%, respectively), while the O .- radical (the basic form of the OH radical) undergoes mainly H- abstraction (92% and 83%, respectively). The radicals formed in these systems decay bimolecularly (2k = 2.8 x 10 9 dm 3 mol -1 s -1 ). In their combination reactions the cyclohexadienyl radicals form the four possible dimers in propor­tions such that the dienyl radical moiety shows a 2:1 preference to react from its central (1a) rather than from a terminal carbon atom (1b). Cyclohexadienyl radicals and the OH- and H-adduct radicals also cross-tcrminate by disproportionation and dimerization. Material balance has been obtained for the 1,4-cyclohexadiene system in N 2 O-Saturated solution (10 -2 mol dm -3 ) at a dose rate of 0.14 Gy s -1 , the products (G values in ,μmol J -1 ) being: benzene (0.085), 4-hydroxycyclohexene (0.25), cyclohexadienyl-dimers (0.144). cvclohexadienyl-OH-adduct- dimers (0.02), OH-adduct-dimers (0.02). Some of the 4-hydroxycyclohcxene is formed in an H-abstraction reaction by the OH-adduct radical from 1,4-cyclohexadiene.

The crystal structure of [AsPh 4 ] 2 [Pb(N 3 ) 6 ] 2- has been determined by X-ray diffraction. The structure of [Pb(N 3 ) 6 ] 2- (C i symmetry) is analogous to that of [Sn(N 3 ) 6 ] 2- with covalent Pb-N bonds (222-226 pm) and angles Pb-N-N between 115 and 121°. Irridiation (daylight) of [AsPh 4 ] 2 [Pb(N 3 ) 6 ] in solution gives AsPh 4 [Pb(N 3 ) 3 ].

Iminoboranes RB≡NR' (1a,b; R/R' = iPr/iPr, Bu/tBu) have been allyloborated by triallylborane BAll 3 (All = allyl). The resulting diborylamines All(R)B-N(R')-BAll 2 undergo a thermal intra-molecular allyloboration to give azadiboracyclo-hexanes (3a, b).

Potassium graphite intercalate in THF is a reagent for the reduction of aryl halides and the reductive cleavage of aryl ethers.