Synthese,Eigenschaften und Struktur von Amin-Addukten der Lithium-tris[bis(trimethylsilyl)methyl]zinkate

Synthesis, Properties, and Structure of the Amine Adducts of Lithium Tris[bis(trimethylsilyl)methyl]zincates . Bis[bis(trimethylsilyl)methyl]zinc and the aliphatic amine 1,3,5-trimethyl-1,3,5-triazinane (tmta) yield in n-pentane the 1:1 adduct, the tmta molecule bonds as an unidentate ligand to the zinc atom. Bis[bis(trimethylsilyl)methyl]zinc · tmta crystallizes in the triclinic space group P1 with {a = 897.7(3); b = 1 114.4(4); c = 1 627.6(6) pm; α = 90.52(1); β = 103.26(1); γ = 102.09(1)°; Z = 2}. The central C₂ZnN moiety displays a nearly T-shaped configuration with a CZnC angle of 157° and Zn? C bond lengths of 199 pm. The Zn? N distances of 239 pm are remarkably long and resemble the loose coordination of this amine; a nearly complete dissociation of this complex is also observed in benzene. The addition of aliphatic amines such as tmta or tmeda to an equimolar etheral solution of lithium bis(trimethylsilyl)methanide and bis[bis(trimethylsilyl)methyl]zinc leads to the formation of the amine adducts of lithium tris[bis(trimethylsilyl)methyl]zincate. Lithium tris[bis(trimethylsilyl)methyl]zincate · tmeda · 2 Et₂O crystallizes in the orthorhombic space group Pbca with {a = 1 920.2(4); b = 2 243.7(5); c = 2 390.9(5) pm; Z = 8}. In the solid state solvent separated ions are observed; the lithium cation is distorted tetrahedrally surrounded by the two nitrogen atoms of the tmeda ligand and the oxygen atoms of both the diethylether molecules. The zinc atom is trigonal planar coordinated; the long Zn? C bonds with a value of 209 pm can be attributed to the steric and electrostatic repulsion of the three carbanionic bis(trimethylsilyl)methyl substituents.     

Tris(trimethylsilyl)silylamin und seine lithiierten und silylierten Derivate — Kristallstruktur des dimeren Lithium-trimethylsilyl-[tris(trimethylsilyl)silyl]amids

Tris(trimethylsilyl)silylamine and the lithiated and silylated Derivatives — X-Ray Structure of the dimeric Lithium Trimethylsilyl-[tris(trimethylsilyl)silyl]amide The ammonolysis of the chlor, brom or trifluormethanesulfonyl tris(trimethylsilyl)silane yields the colorless tris(trimethylsilyl)silylamine, destillable at 51°C and 0.02 Torr. The subsequent lithiation, reaction with chlor trimethylsilane and repeated lithiation lead to the formation of lithium tris(trimethylsilyl)silylamide, trimethylsilyl-[tris(trimethylsilyl)silyl]amine and finally lithium trimethylsilyl-[tris(trimethylsilyl)silyl]amide, which crystallizes in the monoclinic space group P2₁/n with a = 1 386.7(2); b = 2 040.2(3); c = 1 609.6(2) pm; β = 96.95(1)° and Z = 4 dimeric molecules. The cyclic Li₂N₂ moiety with Li? N bond distances displays a short transannular Li …? Li contact of 229 pm. The dimeric molecule shows nearly C₂-symmetry, so that one lithium atom forms agostic bonds to both the trimethylsilyl groups, the other one to the tris(trimethylsilyl)silyl substituents. However, the ⁷Li{¹H}-NMR spectrum displays a high field shifted singlet at —1.71 ppm. The lithiation of trimethylsilyl-[tris(trimethylsilyl)silyl]amine leads to a high field shift of the ²⁹Si{¹H} resonance of about 12 ppm for the Me₃SiN group, whereas the parameters of the tris(trimethylsilyl)silyl ligand remain nearly unaffected.     

Bis(trimethylsilyl)amide und -methanide des Yttriums — Molekülstrukturen von Tris(diethylether-O)lithium-(μ-chloro)-tris[bis(trimethylsilyl) methyl]yttriat,solvensfreiem Yttrium-tris[bis(trimethylsilyl)amid] sowie dem Bis(benzonitril)-Komplex

Bis(trimethylsilyl)amides and -methanides of Yttrium — Molecular Structures of Tris(diethylether-O)lithium-(μ-chloro)-tris[bis(trimethylsilyl)methyl]yttriate, solvent-free Yttrium Tris[bis(trimethylsilyl)amide] as well as the Bis(benzonitrile) Complex The reaction of yttrium(III) chloride with the three-fold molar amount of LiE(SiMe₃)₂ (E = N, CH) yields the corresponding yttrium derivatives. Yttrium tris-[bis(trimethylsilyl)amide] crystallizes in the space group P3 1c with a = 1 636,3(2), c = 849,3(2) pm, Z = 2. The yttrium atom is surrounded trigonal pyramidal by three nitrogen atoms with Y? N-bond lengths of 222 pm. Benzene molecules are incorporated parallel to the c-axes. The compound with E = CH crystallizes as a (Et₂O)₃LiCl-adduct in the monoclinic space group P2₁/n with a = 1 111,8(2), b = 1 865,2(6), c = 2 598,3(9) pm, β = 97,41(3)° and Z = 4. The reaction of yttrium tris[bis(trimethylsilyl)amide] with benzonitrile yields the bis(benzonitrile) complex, which crystallizes in the triclinic space group P1 with a = 1 173,7(2), b = 1 210,3(2), c = 1 912,4(3) pm, α = 94,37(1), β = 103,39(1), γ = 117,24(1)° and Z = 2. The amido ligands are in equatorial, the benzonitrile molecules in axial positions.     

Molekül- und Kristallstruktur des Dimeren Magnesium-bis[bis(trimethylsilyl)amids]

Molecular and Crystal Structure of the dimeric Magnesium bis[bis(trimethylsilyl)-amide] The magnesium bis[bis(trimethylsilyl)amide] crystallizes as a dimeric molecule in the space group C2/c with {a = 1821.0(4); b = 1494.4(4); c = 1859.6(6) pm; β = 121.10(2)°; Z = 4 dimers}. The cyclic planar Mg₂N₂ moiety shows endocyclic NMgN angles of 95.8°. The bond lengths within this ring system to the four-coordinate, bridging nitrogen atoms N^b are 215 pm, whereas the distances between the magnesium atom and the terminal, three-coordinate nitrogen atom N^t display values of approximately 198 pm. These different coordination numbers of the nitrogen atoms affect the NSi bond length (N^tSi 171, N^bSi 177 pm).     

Über die Synthese von Tris(trimethylsilyl)silyl-kalium, -rubidium und -caesium und die Molekülstrukturen zweier Toluolsolvate

About the Synthesis of Tris(trimethylsilyl)silyl Potassium, Rubidium and Cesium and the Molecular Structures of two Toluene Solvates . Solventfree tris(trimethylsilyl)silyl potassium ( 1 ), rubidium ( 2 ) and cesium ( 3 ) are obtained by the reaction of the zink group bis[tris(trimethylsilyl)silyl] derivatives with the appropriate alkali metal in n-pentane. Addition of benzene or toluene to the colourless powders yields deeply coloured solutions. From these solutions single crystals of tris(trimethylsilyl)silyl rubidium—toluene (2/1) ( 2 a ) and tris(trimethylsilyl)silyl cesium—toluene (2/3) ( 3 a ) suitable for X-ray structure analysis are iso- lated [ 2a : orthorhombic; P2₁2₁2₁; a = 1 382.1(3); b = 1 491.7(5); c = 2 106.3(6) pm; Z = 4 (dimers); 3a : orthorhombic; P2₁2₁2₁; a = 2 131.0(6); b = 2 833.1(2); c = 925.2(2) pm; Z = 4 (dimers)]. The central structure moieties are folded four-membered Rb₂Si₂ and Cs₂Si₂ rings, respectively. Small Si? Si? Si angles (100 to 104°) on the one hand and extreme highfield ²⁹Si-NMR shifts of the central silicon atoms on the other hand indicate a strong charge transfer from the alkali metal atoms to the tris(trimethylsilyl)silyl fragments, i.e. mainly ionic interactions between alkalimetal and silicon atoms.     

Molekül- und Kristallstruktur von Magnesium-bis[bis(trimethylsilyl)phosphanid] · DME

Molecular and Crystal Structure of Magnesium Bis[bis(trimethylsilyl)phosphide] · DME Magnesium bis[bis(trimethylsilyl)phosphide] crystallizes in the tetragonal space group I4 c2 with a = 1652.9(2); c = 2282.6(5) pm and Z = 8. The magnesium atom is distorted tetrahedrally surrounded by two oxygen and two phosphorus atoms with Mg? P- and Mg? O-bond lengths of 248.7(2) and 204.7(5) pm, respectively. The phosphorus atom displays a trigonal pyramidal coordination.     

Synthesis of novel bis(chromenes) and bis(chromeno[3,4-C]pyridine) incorporating piperazine moiety

Novel bis(2-oxo-2H-chromene) as well as bis(2-imino-2H-chromene) derivatives incorporating piperazine moiety were prepared by the cyclocondensation reaction of bis(2-hydroxybenzaldehyde) with two equivalents of each of the appropriate β-ketoesters or acetonitrile derivatives. The bis(2-imino-2H-chromene-3-carbothioamide) derivative was used as a key synthon for construction of novel bis(3-(4-substituted thiazol-2-yl)-2H-chromen-2-one) derivatives via its cyclocondensation with a series of the appropriate α-halocarbonyl derivatives. Moreover, the bis(2-hydroxybenzaldehyde) reacted with four equivalents of the appropriate acetonitrile derivatives to afford the corresponding bis(3H-chromeno[3,4-c]pyridine) derivatives. Elucidation of the structure of the novel bis(chromenes) bearing piperazine nucleus was established by the spectral data and elemental analyses.     

Strontium- und Barium-bis[N,N′ -bis(trimethylsilyl)benzamidinate] aus der Additionsreaktion der Erdalkalimetall-bis[bis(trimethylsilyl)amide] mit Benzonitril

Strontium and Barium Bis[N,N′-bis(trimethylsilyl)benzamidinates] from the Addition Reaction of the Alkaline Earth Metal Bis[bis(trimethylsilyl)amides] and Benzonitrile The reaction of strontium bis[bis trimethylsilyl)amide] with benzonitrile yields strontium bis[N,N′- bis(trimethylsilyl)benzamidinate] · 2THF, which crystallizes in the orthorhombic space group Pbcn (a = 1845.4(3); b = 131 1,3(2); c = 1838,(3) pm; Z = 4). During the similar reaction of barium bis[bis(trimethylsilyl)amide] with benzonitrile the benzonitrile adduct barium bis[N,N′-bis(trimethylsilyl)benzamidinate] · 2 THF · benzonitrile is formed. After the addition of diphenylacetylene to the strontium di(benzamidinate) in diglyme a clathrate of the composition strontium bis[N,N′-bis(trimethylsilyl)benzamidinate] · diglyme · diphenylacetylene could be isolated; the spectroscopic data as well as the X-ray structure (monoclinic, C2/c, a = 1492.2(2); b = 1539.1(2); c = 2337.8(3)pm; Z = 4) confirm the isolated appearance of the acetylene molecule without interaction to the metal center in solution and in the solid state, respectively.     

Synthese,Kristallstruktur, Elektronenstruktur,spektroskopische und magnetische Eigenschaften von [VOCl2{P(SiMe3)3}2]: Ein Phosphankomplex mit fehlgeordneter VOCl2-Einheit

Synthesis, Crystal Structure, Electronic Structure, Spectroscopic and Magnetic Properties of [VOCl₂{P(SiMe₃)₃}₂]: A Phosphane Complex with a Disordered VOCl₂ Group VOCl₃ reacts with P(SiMe₃)₃ to form blue green crystals of [VOCl₂{P(SiMe₃)₃}₂] ( 1 ). The X-ray crystal structure analysis of 1 (cubic space group P2₁3: a = 1541.4(1) pm, Z = 4) reveals a slightly distorded trigonal bipyramidal coordination environment for the disordered vanadium(IV) center. Density functional calculations on the compound [VOCl₂{P(SiH₃)₃}₂] ( 2 ) are in accord with this observation. 1 has been characterized by ESR, vibrational (IR and Raman) and electronic absorption spectroscopy and magnetic measurements. The ESR spectra of 1 in a toluene solution (293 K and frozen solution at 6 K) exhibit hyperfine interactions of the unpaired electron with the ⁵¹V center (I = 7/2) and the ³¹P centers (I = 1/2) of the two equivalent phosphane ligands. The ligand-field transitions of the VOCl₂{P}₂ chromophore observed in the electronic absorption spectrum have been assigned on the basis of density functional calculations on 2 .     

Aufbau von Trimethylsilyl-substituierten Polyedern aus Calcium,Zinn(II) und Phosphor

Synthesis of Trimethylsilyl Substituted Polyhedra of Calcium, Tin(II), and Phosphorus The reaction of calcium-bis[bis(trimethylsilyl)amide] with bis(trimethylsilyl)phosphane in thf yields the heteroleptic, dimeric (tetrahydrofuran-O)calcium-bis(trimethylsilyl)amidebis(trimethylsilyl)phosphanide 1 (triclinic, P 1 , a = 1066,6(2), b = 1141,3(2), c = 1226,6(2)pm, α = 97,78(3)°, β = 107,47(3)°, γ = 101,12(3)°, Z = 1 dimer). The bridging phosphanide-substituent displays with Ca? P bond lengths of 292,6 and 300,5 pm a distortion of the four-membered Ca₂P₂-cycle. The reaction with another equivalent of HP(SiMe₃)₂ in thf leads to the formation of tetrakis(tetrahydrofuran-O)calcium-bis[bis(trimethylsilyl)phosphanide] 2 mit Ca? P distances of 292 pm (monoclinic, P2₁/c, a = 1626,0(3), b = 1295,3(4), c = 2039,5(5) pm, β = 102,60(2)°, Z = 4). The performance of the reaction in the presence of bis[bis(trimethylsilyl)amino]stannylene yields heterobimetallic compounds with a central polyhedron of Ca-, Sn- and P-atoms. Dependent on the Sn/Ca ratio the isolation of tris(trimethylsilyl)phosphane as well as bis[tris(tetrahydrofuran-O)calcium]-ditin(II)-tetrakis(μ₃-trimethylsilylphosphandiide) 3 with a central dicalcia-distanna-tetraphosphacubane-fragment or (thf)₂CaSn₂[μ-P(SiMe₃)₂]₂[μ₃-PSiMe₃]₂ 4 (orthorhombic, Pnma, a = 2247,7(2), b = 1868,9(1), c = 1168,0(1) pm, Z = 4), respectively, succeeds. The Ca? P distances lie at 291 pm.     

Tris(trimethylsilyl)methanselenenylhalogenide und -chalkogenide

Tris(trimethylsilyl)methaneselenenyl Halides and Chalcogenides . Ditrisyldiselenide ( 1 ) (trisyl = TSi = (Me₃Si)₃C) reacts with SOCl₂, Br₂ and I₂ to provide trisylselenenyl halides TSiSeX ( 2 : X = Cl; 3 : X = Br, 4 : X = I). Insertion of S and Se into the Se? Se bond of 1 to yield (TSiSe)₂S_n ( 5 : n = 1; 6 : n = 2) and (TSiSe)₂Se_n ( 7 : n = 1; 8 : n = 2) was catalysed by iodine. 5 was isolated in pure state and examined by X-ray diffraction. Triselenide 7 can be cleaved by I₂ in CS₂ to give 4 and Se₂I₂ ( 9 ). From 2 with Me₃SiCN and Me₃SiNCS, the new selenenyl pseudohalides TSiSeCN ( 10 ) and TSiSeSCN ( 11 ) were prepared. The compounds were characterised by ¹H, ¹³C- and ⁷⁷Se n.m.r. spectra.     

Das unterschiedliche Reaktionsverhalten von basefreiem Tris(trimethylsilyl)methyl‐Lithium gegenüber den Trihalogeniden der Erdmetalle und des Eisens

The Variable Reaction Behaviour of Base‐free Tris(trimethylsilyl)methyl Lithium with Trihalogenides of Earth‐Metals and Iron Base‐free tris(trimethylsilyl)methyl Lithium, Tsi–Li, reacts with the earth‐metal trihalogenides (MHal₃ with M = Al, Ga, In and Hal = Cl, Br, I) primarily to give the metallates [Tsi–MHal₃]Li. Simultaneous to this simple metathesis a methylation also takes place, mainly with heavier halogenides of Ga and In with excess Tsi–Li, forming the mono and dimethyl compounds Tsi–M(Me)Hal (M = Ga, In; Hal = I), Tsi–MMe₂ (M = Ga), and the bis(trisyl)derivative (Tsi)₂InMe, respectively and the main by‐product 1,3‐disilacyclobutane. Representatives of each type of compound have been isolated by fractionating crystallizations or sublimations and characterized by spectroscopic methods (¹H, ¹³C, ²⁹Si NMR, IR, Raman) and X‐ray elucidations. Reduction takes place, when FeCl₃ reacts with Tsi–Li (1 : 3 ratio) in toluene at 55–60 °C, yielding red‐violet Fe(Tsi)₂, 1,1,1‐tris(trimethylsilyl)‐2‐phenyl ethane and low amounts of Tsi–Cl. Fe(Tsi)₂ is monomeric, crystallizes in the monoclinic space group C2/c and consists of a linear C–Fe–C skeleton with d(Fe–C) of 204,5(4) pm.     

Preparation of samarimm(ii) sulfide by the reaction of samarium(II) bis[bis(trimethylsilyl)amide] with hydrogen sulfide

X-ray amorphous samarium(II) sulfide was prepared by the reaction of H₂S with samarium(II) bis[bis(trimethylsilyl)amide] (1) in THF at 10^–2 Torr. Compound1 was prepared by two methods: 1) the reaction of SmI₂ with lithium bis(trimethylsilyl)amide and 2) the reaction of samarium naphthalide with bis(trimethylsilyl)amine. SmS was transformed to the polycrystalline state with the lattice parametera = 5.92 Å by annealing at 400–500 °C.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 241–243, February, 1995.     

Metallderivate von Molekülverbindungen. IV. Synthese,Struktur und Reaktivität des Lithium-[tris-(trimethylsilyl)silyl]tellanids · DME

Metal Derivatives of Molecular Compounds. IV Synthesis, Structure, and Reactivity of Lithium [Tris(trimethylsilyl)silyl]tellanide · DME Lithium tris(trimethylsilyl)silanide · 1,5 DME [3] and tellurium react in 1,2-dimethoxyethane to give colourless lithium [tris(trimethylsilyl)silyl]tellanide · DME ( 1 ). An X-ray structure determination {-150 · 3·C; P2₁/c; a = 1346.6(4); b = 1497.0(4); c = 1274.5(3) pm; β = 99.22(2)·; Z = 2 dimers; R = 0.030} shows the compound to be dimeric forming a planar Li? Te? Li? Te ring with two tris(trimethylsilyl)silyl substituents in a trans position. Three-coordinate tellurium is bound to the central silicon of the tris(trimethylsilyl)silyl group and to two lithium atoms; the two remaining sites of each four-coordinate lithium are occupied by the chelate ligand DME {Li? Te 278 and 284; Si? Te 250; Li? O 200 pm (2X); Te? Li? Te 105°; Li? Te? Li 75°; O? Li? O 84°}. The covalent radius of 154 pm as determined for the DME-complexed lithium in tellanide 1 is within the range of 155 ± 3 pm, also characteristic for similar compounds. In typical reactions of the tellanide 1 [tris(trimethylsilyl)silyl]tellane ( 2 ), methyl-[tris(trimethylsilyl)silyl]tellane ( 4 ) and bis[tris(trimethylsilyl)silyl]ditellane ( 5 ) are formed.     

Synthesen und Eigenschaften neuer Tris(fluorphenyl)antimon- und -bismut-Verbindungen. Kristallstruktur von Tris(2,6-difluorphenyl)bismut

Syntheses and Properties of Some New Tris(fluorophenyl)antimony and -bismuth Compounds. Crystal Structure of Tris(2,6-difluorophenyl)bismuth (2,6-F₂C₆H₃)₃Bi, (2,4,6-F₃C₆H₂)₃Bi, and (2,6-F₂C₆H₃)₃Sb are prepared via Grignard reactions with BiBr₃ and SbBr₃, respectively. The syntheses and properties of the new compounds and the crystal structure of (2,6-F₂C₆H₃)₃Bi are described. From the reaction of BiBr₃ with Ag(OCOC₆H₃F₂) the bismuth benzoate Bi(OCOC₆H₃F₂)₃ is formed in 83% yield. Attempts to prepare (2,6-F₂C₆H₃)₃Bi by decarboxylation of the bismuth benzoate failed.     

Reactions at the B–B Bond of Bis(trisyl)oxadiborirane: Ring Extensions

The B–B bond of bis(trisyl)oxadiborirane OB₂R₂ (R = C(SiMe₃)₃) is opened by amides R′CO(NHR″) to give the dioxaazadiboracyclohexanes [–BR–O–BR–NR″–CHR′–O–] (R′/R″ = H/H, H/Me, H/Et, Me/H: 5 a – d ). The amide MeCO(NHMe) yields 5 e (R′/R″ = Me/Me), when an excess of the amide is applied for 24 h, but yields an isomeric 1 : 1 adduct ( 6 e ), when a stoichiometric amount of the amide is applied for 15 h; upon refluxing this isomer in hexane, it is transformed into 5 e .     

Synthese,Eigenschaften und Struktur von [Li(OC4H8)4][((CH3)3Si)3C–InBr3]

Synthesis, Properties, and X-Ray Structure Determination of [Li(OC₄H₈)₄][((CH₃)₃Si)₃C–InBr₃] The reaction of InBr₃ with LiR* · (THF)_n (R* = –C(SiMe₃)₃, THF = OC₄H₈) in a 1 : 1 molar ratio forms [Li(THF)₄][R*InBr₃] in good yield. The properties and some spectroscopic data (¹H, ¹³C, ²⁹Si, ⁷Li–NMR, IR and Raman) of this trisyl-tribromoindate are given and the crystal structure has been determined.     

Monomere Bis- und Tris(amide) des Indiums

Monomeric Bis and Tris(amides) of Indium The synthesis of tris(2,2,6,6-tetramethylpiperidino)indium 1 and of bis(2,2,6,6-tetramethylpiperidino)indium bromide 2 are described. Both compounds were characterized by NMR and mass spectroscopy. They are monomeric in solution and gasphase. A crystal structure analysis of 1 , also described in this work, proofs monomeric 1 in the solid state, too.     

Darstellung und Einkristall-Strukturanalyse von Hexachloro-μ-dichloro-bis[N-(trimethylsilyl)imidazol]dititan-Chloroform (1/2) [Ti2Cl8(C6H12N2Si)2] · 2 CHCl3

Synthesis and Crystal Structure Determination of Hexachloro-μ-dichloro-bis[N-(trimethylsilyl)imidazol]dititanium Chloroform (1/2) Hexachloro-μ-dichloro-bis[N-(trimethylsilyl)-imidazol]dititanium chloroform (1/2) 1 has been prepared by the reaction of titanium tetrachloride with N-trimethylsilylimidazole (NTMSI) in chloroform solution as orange crystals. The structure consists of two distorted TiCl₅N octahedrons, which are connected by two chlorine atoms via common edges to a centrosymmetric dimer [Ti₂Cl₈(NTMSI)₂] · 2 CHCl₃. The N-trimethylsilylimidazole ligands each are located at one axial position of each octahedron, whereas the equatorial positions are occupied by the chloro ligands. The results presented are discussed assuming a gradual formation of an 1 : 1 and 1 : 2 adduct.     

Synthese von Magnesium-bis[N,N′-bis(trimethylsilyl)benzamidinat] als Bis(THF)- und Benzonitril-Addukt

Synthesis of Magnesium Bis[N,N′ -bis(trimethylsilyl)benzamidinate] as both Bis(THF) and Benzonitrile Adduct Magnesium bis[bis(trimethylsilyl)amide] 1 , reacts with benzonitrile in toluene at room temperature to yield magnesium bis[N,N′-bis(trimethylsilyl)benzamidinate]-benzonitrile(1/1) 2 . Addition of THF leads to a quantitative substitution of the benzonitrile ligand by two THF molecules. The performance of the addition reaction in THF yields magnesium bis[N,N′-bis(trimethylsilyl)benzamidinate] · THF(1/2) 3 . The upper benzonitrile complex 2 , crystallizes in the orthorhombic space group Pbcn with {a = 1383.2(2); b = 2589.1(4); c = 1133.7(1) pm; Z = 4}. The magnesium atom is coordinated distorted trigonal-bipyramidal, where the benzonitrile ligand lies within the equatorial plane. The axial bound nitrogen atom of the benzamidinate substitution shows with a value of 213 pm a slightly longer bond distance to the metal center than the one in the equatorial plane (210 pm). The steric strain within the benzamidinate ligand leads to an elongation of the silicon atoms out of the 1,3-diazaallylic moiety under an enlargement of the C? N? Si angle to 131°.