The Reaction of Transient 1,1‐Bis(trimethylsilyl)silenes with Tris(trimethylsilyl)silyllithium – Synthesis and Structure of Sterically Congested 1‐Trimethylsilylalkylpolysilanes

Tris(trimethylsilyl)silyllithium ( 3 ) reacted with aldehydes and ketones (molar ratio 2 : 1) according to a modified Peterson mechanism under formation of transient silenes, which were immediately trapped by excess 3 to give the organolithium derivatives (Me₃Si)₃SiSi(SiMe₃)₂C(Li)R¹R² ( 7 ). Hydrolysis of 7 afforded the alkylpolysilanes (Me₃Si)₃SiSi(SiMe₃)₂CHR¹R² ( 8 ). Depending on the substituents R¹ and R², 7 proved to be rather unstable in THF solution and underwent a rapid rearrangement, involving a 1,3‐Si,C‐trimethylsilyl migration, resulting in the formation of the lithium silanides (Me₃Si)₂Si(Li)Si(SiMe₃)₂C(SiMe₃)R¹R² ( 9 ), which were hydrolized during the aqueous workup to give the H‐silanes (Me₃Si)₂Si(H)Si(SiMe₃)₂C(SiMe₃)R¹R² ( 10 ). Reaction of 9 with chlorotrimethylsilane produced the 1‐trimethylsilylalkylpolysilanes (Me₃Si)₃SiSi(SiMe₃)₂C(SiMe₃)R¹R² ( 11 ). The structures of the products described were elucidated by comprehensive spectral analyses. The results of X‐ray crystal structure analyses, performed for 8 l (R¹ = H, R² = 2,4,6‐(MeO)₃C₆H₂), 10 d (R¹ = H, R² = Mes) and 11 d (R¹ = H, R² = Mes) are discussed and confirm the expected extreme sterical congestion of the molecules.     

Reaction of Hexamethyldisilazane with Borane in Tetrahydrofuran

Hexamethyldisilazane 1 reacts with borane in tetrahydrofuran (THF? BH₃, 2 ) first by formation of an adduct (Me₃Si)₂NH? BH₃ ( 3 ), and then either to the N,N-bis-(trimethylsilyl)-μ-aminodiborane 5 or to the mixture of 5 and N-trimethylsilyl-μ-aminodiborane(6) 6 , depending on the reaction conditions. The compounds 5 and 6 can be quantitatively converted to the N,N′,N″-tris(trimethylsilyl)borazine 4 . Three intermediates can be identified, namely N,N-bis(trimethylsilyl)borane 7 , N,N-bis(trimethylsilyl)amino(N′-trimethylsilylamino)borane 8 and N-trimethylsilylaminoborane-trimer. All products and intermediates were characterized by multinuclear NMR spectroscopy, and coupling constant ¹J(²⁹Si, ¹⁵N) were measured from ²⁹Si NMR spectra by using the Hahn-echo-extended (HEED) INEPT pulse sequence.     

Preparation and Synthetic Utility of 1-Trimethylsiloxyalkyl-bis(trimethylsilyl)silanes, (Me3Si)2SiH–C(OSiMe3)R1R2

1-Trimethylsiloxyalkyl-bis(trimethylsilyl)silanes ( 5 ), obtained by a base induced isomerization of easily accessable 1-hydroxyalkyl-tris(trimethylsilyl)silanes ( 1 ) were hydrolized to give 1-hydroxyalkyl-bis(trimethylsilyl)silanes ( 6 ), which in presence of sodium hydride underwent a further 1,3-Si,O-trimethylsilyl migration resulting in the formation of 1-trimethylsiloxyalkyl-disilanes Me₃SiSiH₂–C(OSiMe₃)R¹R² ( 7 ). Under acidic conditions, the alkoxysilanes 5 isomerized in a Me₃Si/OSiMe₃ exchange under formation of the 1-trimethylsilylalkyldisiloxanes 10 , which were hydrolyzed affording the silanols 11 . Chlorination of the H-silanes 5 with CCl₄ gave the chlorosilanes 12 , which underwent rapid thermal isomerizations to give via the 1-chloroalkyldisiloxanes 13 the 1-trimethylsilylalkyl-chlorodisiloxanes 15 . Hydrolysis of 12 or 15 , resp., finally afforded the 1-trimethylsilylalkyl-silanediols 18 . Possible mechanisms of the various isomerization processes are discussed. The structures of the products described were elucidated by full spectral analyses. For 18 a the results of an X-ray structural analysis are given.     

Synthese und spektroskopische Charakterisierung einiger Pentacarbonylwolfram(0)‐Komplexe mit monound bicyclischen Phosphiran‐Liganden: Kristallstruktur von [{(Me3Si)2HCPC(H)H–C(H)Ph}W(CO)5]

Synthesis and Spectroscopic Characterisation of some Pentacarbonyltungsten(0) Complexes with Mono‐ and Bicyclic Phosphirane Ligands: Crystal Structure of [{(Me₃Si)₂HCPC(H)H–C(H)Ph}W(CO)₅] The tungsten(0) complex [{(Me₃Si)₂HCPC(Ph)=N}W(CO)₅] ( 1 ) reacts upon heating with alkene derivatives 2 , 6 , 8 , and 10 in toluene to form benzonitrile and the complexes [{(Me₃Si)₂HCPC(R¹,R²)–C(R³,R⁴}W(CO)₅] ( 4 , 7 a , b , 9 a , b , 11 a , b ) ( 4 (trans): R¹,R³ = Ph, R²,R⁴ = H, 7 a , b (cis, meso and rac): R¹,R³ = Ph, R²,R⁴ = H, 9 a , b (RR und SS): R¹ = Ph, R²,R³,R⁴ = H, 11 a , b : R¹=R³ = (CH₂)₄, R²,R⁴ = H). Spectroscopic and mass spectrometric data are discussed. The structure of the complex 9 a was determined by X‐ray single crystal structure analysis showing characteristic data for the phosphirane ring such as a narrow angle at phosphorus (49,2(2)°), different P–C distances (P–C(6) 182,1(5) and P–C(7) 185,2(4) pm) and 152,9(6) pm for the basal C–C bond.     

Dimethyl(tetramethylcyclopentadienyl)silyl-, -germyl- und -stannyl-phosphane. Röntgenstrukturanalyse von Chloro(dimethyl)tetramethylcyclopentadienylstannan und Tetracarbonyl[1-dimethyl-(tetramethylcyclopentadienyl)germyl-3,4-dimethylphospholen]eisen(0)

Dimethyl(tetramethylcyclopentadienyl)silyl-, -germyl-, and -stannylphosphanes. X-Ray Structures of Chloro(dimethyl)tetramethylcyclopentadienyl-stannane and Tetracarbonyl[1-dimethyl(tetramethylcyclopentadienyl)germyl-3,4-dimethyl-phospholene]iron(0) Me₂Cp′SiCl ( 1 ) (Cp′ = C₅HMe₄) reacts with magnesium and R₂PCl (R = Ph, ^tBu) as well as PCl₃ in tetrahydrofurane yielding Me₂Cp′SiPPh₂ ( 4 ), Me₂Cp′SiP^tBu₂ ( 5 ) and (Me₂Cp′Si)₃P ( 6 ) respectively. The reaction of Me₃SiPPh₂ ( 7 ) or Me₃SiPC₄H₄Me₂ ( 10 ) with Me₂Cp′GeCl ( 2 ) and Me₂Cp′SnCl ( 3 ) leads to the formation of Me₂Cp′EPPh₂ (E = Ge ( 8 ), Sn ( 9 )) and Me₂Cp′EPC₄H₄Me₂ (E = Ge ( 11 ), Sn ( 12 )). 11 reacts with Fe(CO)₅ with formation of Fe(CO)₄[(PC₄H₄Me₂)GeCp′Me₂] ( 13 ). 3 crystallizes in the space group P2₁/n with a = 986,7(1), b = 1247,3(2), c = 1028,2(1) pm, β = 92,71(1)°, Z = 4 and V = 1264,1(2) 10^?30 m³. The final refinement resulted in R₁ = 0,0249 for 2097 observed reflexions with F_o ≥ 4σ(F_o). 13 crystallizes in the space group P2₁/n with a = 967,7(3), b = 1298,70(16), c = 1832,7(3) pm, β = 95,810(19)°, Z = 4 and V = 2291,4(8) 10^?30 m³ (R₁ = 0,0444 for 4043 observed reflexions with F_o ≥ 4σ(F_o). 13 forms a trigonal bipyramide with the phosphane ligand 11 in an axial position.     

Zum Reaktionsverhalten lithiierter Aminosilane RR′ Si(H)N(Li)SiMe3

The Reaction Behaviour of Lithiated Aminosilanes RR′Si(H)N(Li)SiMe₃ The bis(trimethylsilyl)aminosubstituted silances RR′Si(H)N(SiMe₃)₂ 11 – 16 (R,R′ = Me, Me₃SiNH, (Me₃Si)₂N) are obtained by the reaction of the lithium silylamides RR′Si(H)N(Li)SiMe₃ 1 – 10 (R,R′ = Me₃SiNLi, Me, Me₃SiNH, (M₃Si)₂N) with chlorotrimethylsilane in the polar solvent tetrahydrofurane (THF). In the reaction of the lithium silylamides [(Me₃Si)₂N]₂(Me₃SiNLi)SiH 10 with chlorotrimethylsilane in THF the rearranged product 1,1,3-tris[bis(trimethylsilyl)amino]-3-methyl-1,3-disila-butane [(Me₃Si)₂N]₂Si(H)CH₂SiMe₂N(SiMe₃)₂ 17 is formed. The reaction of the lithium silyamides RR′ Si(H)N(Li)SiMe₃ 1 – 3 (1: R = R′ = Me; 2: R = Me, R′ = Me₃SiNH; 3: R = Me, R′ = Me₃SiNLi) with chlorotrimethylsilane in the nonpolar solvent n-hexane gives the cyclodisilazanes [RR′ Si? NSiMe₃]₂ 18 – 22 (R = Me, Me₃SiNH, (Me₃Si)₂N; R′ = Me, Me₃SiNH, (Me₃Si)₂N, N(SiMe₃)Si · Me(NHSiMe₃)₂) and trimethylsilane. The lithium silylamides 4 , 5 , 6 , 9 , 10 (4: R = R′ = Me₃SiNH; 5: R = Me₃SiNH, R′ = Me₃SiNLi; 6: R = R′ = Me₃SiNLi; 9: R = (Me₃Si)₂N, R ′ = Me₃SiNLi; 10: R = R′ = (Me₃Si)₂N) shows with chlorotrimethylsilane in n-hexane no reaction. The crystal structure of 17 and 21 are reported.     

Lithiierte Siloxy-silylamino-silane – Darstellung und Reaktionen mit Chlordimethylsilan

Lithiated Siloxy-silylamino-silanes — Preparation and Reactions with Chlorodimethylsilane The siloxy-silylamino-silanes (Me₃SiO)Me_3–nSi(NHSiMe₃)_n ( 1 : n = 1, 2 : n = 2, 3 : n = 3) are obtained by coammonolysis of the chlorosiloxysilanes (Me₃SiO)Me_3–nSiCl_n (n = 1–3) with chlorotrimethylsilane. The reaction of 1, 2 , and 3 with n-butyllithium in appropriate molar ratio in n-hexane gives the siloxy-silylamido-silanes (Me₃SiO)Me_3–nSi(NLiSiMe₃)_n ( 4 : n = 1, 5 : n = 2, 6 : n = 3), which were spectroscopically characterized (IR, ¹H-, ⁷Li-, ²⁹Si-NMR) and allowed to react in solution (n-hexane, THF) with Me₂Si(H)Cl. 4 reacts to the N-substitution product (Me₃SiO)Me₂SiN(SiMe₃)SiMe₂H 7, 5 to (Me₃SiO)MeSi[N(SiMe₃)SiMe₂H](NHSiMe₃) 8 , (Me₃SiO)MeSi[N(SiMe₃)SiMe₂H]₂ 9 and to the cyclodisilazane 10. 6 gives in THF the cyclodisilazanes 11 : R = H; 12 : R = HMe₂Si) and ( 13 , in n-hexane only 11 in small amounts. An amide solution of 2 with n-butyllithium in the molar ratio 1:1 in n-hexane leads to 8 (main product), 2 and 10; in THF 10 and 2 are obtained nearly in same amounts and 8 and 9 as byproducts. The amide solutions of 3 with n-butyllithium in the molar ratio 1:1 and 1:2, resp., show nearly the same behaviour in n-hexane and THF. In THF 3, 11 , and 12 and in n-hexane 3, 11, 12 , and (Me₃SiO)Si[N(SiMe₃)SiMe₂H](NHSiMe₃)₂ 14 are formed.     

Transient Silenes as Versatile Synthons – The Reaction of Dichloromethyl‐tris(trimethylsilyl)silane with Organolithium Reagents

Treatment of dichloromethyl‐tris(trimethylsilyl)silane (Me₃Si)₃Si–CHCl₂ ( 1 ), prepared by the reaction of tris(trimethylsilyl)silane with chloroform in presence of potassium tertbutoxide, with organolithium reagents (molar ratio 1 : 3) affords the bis(trimethylsilyl)methyl‐disilanes Me₃SiSiR₂–CH(SiMe₃)₂ ( 12 a–d ) ( a : R = Me, b : R = n‐Bu, c : R = Ph, d : R = Mes). The formation of 12 a–d is discussed as proceeding through an exceptional series of isomerization and addition reactions involving intermediate silyl substituted carbenoids and transient silenes. The carbenoid (Me₃Si)₂PhSi–C(SiMe₃)LiCl ( 8 c ) is moderately stable at low temperature and was trapped with water to give (Me₃Si)₂PhSi–CH(SiMe₃)Cl ( 9 c ) and with chlorotrimethylsilane affording (Me₃Si)₂PhSi–CCl(SiMe₃)₂ ( 7 c ). For 12 d an X‐ray crystal structure analysis was performed, which characterizes the compound as a highly congested silane with bond parameters significantly deviating from standard values.     

Kristallstruktur des Bis[lithium-tris(trimethylsilyl)-hydrazids] und Reaktionen mit Fluorboranen, -silanen und -phosphanen

Crystal Structure of Bis[lithium-tris(trimethylsilyl)hydrazide] and Reactions with Fluoroboranes, -silanes, and -phospanes Tris(trimethylsilyl)hydrazine reacts with n-butyllithium in n-hexane to give the lithium-derivative 1 . The reaction of 1 with SiF₄, PhSiF₃, BF₃ · OEt₂, F₂BN(SiMe₃)₂ and PF₃ leads to the substitution products 2–6 . The 1,2-diaza-3-bora-5-silacyclopentane 7 is formed by heating (Me₃Si)₂N? N(SiMe₃)(BFNSiMe₃)₂ ( 5 ) at 250°C. In the reaction of (Me₃Si)₂N? N(SiMe₃)PF₂ ( 6 ) with lithiated tert.-butyl(trimethylsilyl)amine the hydrazino-iminophosphene (Me₃Si)₂N? N = P? N(SiMe₃)(CMe₃) ( 8 ) is obtained. In the molar ratio 2:1 1 reacts with SiF₄ and BF₃ · OEt₂ to give bis[tris(trimethylsilyl)hydrazino]silane 9 and -borane 10 .     

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.     

Metallorganische diazoalkane : XVI. Synthese von silyldiazoalkanen Me3Si(LnM)CN2

Silyldiazoalkanes Me₃Si(L_nM)CN₂ (L_nM = Me₃Si, Me₃Ge, Me₃Sn, Me₃Pb; Me₃As, Me₃Sb, Me₃Bi) have been synthesized by three different routes: (a) reactions of the Me₃SiCHN₂ with metal amides L_nMNR¹R² of Group IVB and VB elements, using Me₃SnCl as catalyst; (b) reactions of the in situ prepared organolithium compound Me₃SiC(Li)N₂ with organometallic chlorides Me₃MCl (M = Si, Ge); (c) tincarbon bond cleavage reaction of (Me₃Sn)₂CN₂ with Me₃SiN₃, affording Me₃SnN₃, traces of bis(trimethylsilyl)diazomethane (Me₃Si)CN₂, trimethylsilyl(trimethylstannyl)diazomethane Me₃Si(Me₃Sn)CN₂ and bis(trimethylsilyl)aminoisocyanide (Me₃Si)₂NNC as the major reaction products. IR and NMR data (¹H, ¹³C, ²⁹Si, ¹¹⁹Sn, ²⁰⁷Pb) of the new heterometal-diazoalkanes are reported and discussed in comparison to relevant compounds of the organometallic diazoalkane series.     

Alkoxylierung von bis(trimethylsilyl)-aminofluorsilanen,sowie siloxanbildung unter äthereliminierung

The reaction of bis(trimethylsilyl)aminofluorsilanes, (Me₃Si)₂NSiF₂R (R = CH₃ or F), with sodium alcoholates or sodium phenylate yields under elimination of NaF alkoxy- and aryloxy-aminofluorosilanes of the composition (Me₃Si)₂NSiF(R)OR′(R′ = CH₃, C₂H₅, C₃H₇, C₆H₅). A disiloxane is formed by thermal elimination of diethyl ether from bis(trimethylsilyl)aminomethylfluoroethoxysilane. The IR, mass, ¹H and ¹⁹F NMR spectra of the above-mentioned compounds are reported. ab]Die Reaktion von Bis(trimethylsilyl)-aminofluorsilanen des Typs (Me₃Si)₂NSiF₂R (R = F, CH₃) mit Natriumalkoholaten und Natriumphenolat führt unter NaF-Abspaltung zu Alkyl- und Aryloxyaminofluorsilanen der Zusammensetzung: (Me₃Si)₂NSiF(R)OR′ (R′ = CH₃, C₂H₇, C₆H₅, C₆H₅). Ein Disiloxan könnte durch die thermische Eliminierung von Diäthyläther aus Bis(trimethylsilyl)aminomethyl-fluor-äthoxy-silylarnin erhalten werden.Die IR-, Massen-, ¹H- und ¹⁹F-NMR-Spektren der dargestellten Verbindungen werden mitgeteilt.     

Synthese von Bis- und Tris(trimethylsilyl)methyl-aminofluorsilanen

Synthesis of Bis- and Tris(trimethylsilyl)-methyl-aminofluorosilanes Lithium-tris(trimethylsilyl)methane reacts with fluoro-silanes to give (Me₃Si)₃C—SiF₂R ( 1—3 , R = F, C₆H₅, CMe₃). 1 and 2 react with lithiated amines to aminofluorosilanes 4 a, 5 a, 6 a , and with a 1, 3-migration of a silyl group to the structure isomeric trimethylsilylaminofluorsilanes 4 b, 5 b, 6 b, 7, 8 . The disubstituted NH-compound 9 is obtained in the reaction of 1 with LiNH₂.     

1‐Silacyclopent‐2‐enes and 1‐silacyclohex‐2‐enes bearing functionally substituted silyl groups in 2‐positions. Novel electron‐deficient Si?H?B bridges

The reactions of alkyn‐1‐yl(vinyl)silanes R₂Si[C?C‐Si(H)Me₂]CH?CH₂ [R = Me (1a), Ph (1b)], Me₂Si[C?C‐Si(Br)Me₂]CH?CH₂ (2a), and of alkyn‐1‐yl(allyl)silanes R₂Si[C?C‐Si(H)Me₂]CH₂CH?CH₂ (R = Me (3a), R = Ph (3b)] with 9‐borabicyclo[3.3.1]nonane in a 1:1 ratio afford in high yield the 1‐silacyclopent‐2‐ene derivatives 4a, b and 5a, and the 1‐silacyclohex‐2‐ene derivatives 6a, b, respectively, all of which bear a functionally substituted silyl group in 2‐position and the boryl group in 3‐position. This is the result of selective intermolecular 1,2‐hydroboration of the vinyl or allyl group, followed by intramolecular 1,1‐organoboration of the alkynyl group. In the cases of 4a, b, potential electron‐deficient Si? H? B bridges are absent or extremely weak, whereas in 6a,b the existence of Si? H? B bridges is evident from the NMR spectroscopic data (¹H, ¹¹B, ¹³C and ²⁹Si NMR). The molecular structure of 4b was determined by X‐ray analysis. Copyright © 2005 John Wiley & Sons, Ltd.     

Neue Hypersilanide der Erdmetalle Aluminium,Gallium und Indium

New Hypersilanides of the Earth Metals Aluminium, Gallium, and Indium The dialkylaluminiumchlorides R₂AlCl (with R = Me, Et; Me = CH₃, Et = C₂H₅) react with base‐free lithium‐tris(trimethylsilyl)silanide (Li–Hsi; Hsi = –Si(SiMe₃)₃), forming the pyrophoric dialkyl aluminiumhypersilanides R₂Al–Hsi. The methyl compound is dimeric in solid state (triclinic space group P1, Z = 1 dimer), as in Al₂Me₆ the association takes place by two Al–Me–Al bridges, forming a centrosymmetric molecule of approximately C_2h point‐symmetry. Contrary to this (Me₂GaCl)₂ and Li–Hsi form a mixture of (MeGa(Hsi)Cl)₂ and [Me₃Ga–Hsi]Li. The monochloride again is a centrosymmetric, chlorine‐bridged dimer (monoclinic space group P2₁/n, Z = 2 dimers). The extremely air sensitive gallate can be prepared from GaMe₃ and Li–Hsi (1 : 1 ratio), as well as the homologous [Me₃Ga–Hsi]Na and [Me₃Ga–Hsi]K from GaMe₃ and the corresponding alkalimetal hypersilanides. The 1 : 1 toluene‐solvat of the sodium salt crystallizes in the orthorhombic space group Pbca (Z = 8) with polymeric zig‐zag‐chains, in which the toluene‐capped Na‐ions act as GaMe…Na…Me₂Ga‐bridges between [Me₃Ga–Hsi]^– anions. The reaction of InCl₃ with Li–Hsi (1 : 3 ratio) mainly gives LiCl, metallic In and the “dihypersilyl” Hsi–Hsi. Ruby‐red (Hsi)₂In–In(Hsi)₂ could also be obtained in low yield and characterized by X‐ray structure elucidation (space group P2₁/c, Z = 4). The ¹H, ¹³C, ²⁹Si and ⁷Li NMR‐ and the vibrational spectra of the hypersilanides have been measured and discussed.     

SYNTHESIS AND NMR CHARACTERIZATION OF P-VINYL SUBSTITUTED PHOSPHAZENE PRECURSORS1

Abstract

The reactions of either PhPCl₂ or PCl₃ with (Me₃Si)₂NLi followed by H₂C[dbnd]CHMgBr were used to prepare the new P-vinyl substituted [bis(trimethylsilyl)amino]phosphines, (Me₃Si)₂NP(R)CH[dbnd]CH₂ [1: R=Ph, 2: CH[dbnd]CH₂, 3: R=Me, and 4: R=N(SiMe₃)₂]. Oxidative bromination of phosphines 3–1 afforded the P-bromo-P-vinyl-N-(trimethylsilyl)phosphoranimines, Me₃SiN[dbnd]P(CH[dbnd]CH₂)(R)Br [5: R=Ph, 6: R=CH[dbnd]CH₂, 7: R=Me], which, upon treatment with CF₃CH₂OH/Et₃N, were subsequently converted to the P-trifluoroethoxy derivatives, Me₃SiN[dbnd]P(CH[dbnd]CH₂)(R)OCH₂CF₃ [8: R=Ph, 9: R=CH[dbnd]CH₂, 10: R=Me]. Compounds 1–10, which are of interest as potential precursors to P-vinyl substituted poly(phosphazenes), were fully characterized by elemental analyses (except for the thermally unstable P-Br derivatives 5–7) and NMR spectroscopy (¹H, ¹³C, and ³¹P) including complete analysis of the vinylic proton splitting patterns via HOM2DJ experiments.     

Synthese und Struktur eines Pentaalkylchlorohexastibans Sb6R5Cl [R = (Me3Si)2CH]

Synthesis and Structure of Pentaalkylchlorohexastibane Sb₆R₅Cl [R = (Me₃Si)₂CH] The reaction of RSbCl₂ [R = (Me₃Si)₂CH] with Na‐K alloy in tetrahydrofuran gives besides the known rings Sb_nR_n (n = 3, 4), (Me₃Si)₂CH₂ and the pentaalkylchlorohexastibane Sb₆R₅Cl ( 1 ). 1 was characterized by spectroscopic methods (MS, ¹H‐, ¹³C‐NMR, X‐ray diffraction). The structure of 1 consists of a folded four membered antimony ring in the all‐trans configuration with three alkyl groups and one Sb(R)—Sb(R)Cl fragment as substituents.     

Komplexchemie P-reicher Phosphane und Silylphosphane. IX. Chromcarbonyl-Komplexe silyliert-alkylierter Triphosphane

Transition Metal Complexes of P-rich Phosphanes and Silylphosphanes. IX. Chromium Carbonyl Complexes of Silylated and Alkylated Triphosphanes . To investigate the influence of the substituents on the formation of complex compounds of triphosphanes several derivatives were synthesized which differ in the number and position of the Me₃Si and tBu groups at the primary P atoms and which bear H, Me₃Si, Me of Ph groups at the secondary P atom. These are [(Me₃Si)₂P]₂PH 1 , [(Me₃Si)₂P]₂P(SiMe₃) 2 , (MeSi)(tBu)P? P(H)? P(SiMe₃)₂ 3 , (tBu)₂P? P(SiMe₃)? P(tBu)(SiMe₃) 4 , [(tBu)₂P]₂PH 5 , [(tBu)₂P]₂P(SiMe₃) 6 , [(Me₃Si)₂P]₂PMe 7 , [(Me₃Si)₂P]₂P(Ph) 8 . When reacting these compounds with Cr(CO)₅THF 9 the following groups of products are obtained: Compounds 1, 3, 5, 7 and 8 at first yield products of group A and react on to B; however this second step is not important for 7 and even less for 8. Compounds 2, 4 and 6 bearing a Me₃Si group at the secondary P atom yield C, but their reactivity is strongly reduced and they tend to give byproducts. Using a molar ratio of triphosphane: Cr(CO),THF 9 = 1 : 2 A forms also D in addition to B . Further reactions may occur from A and B , e. g., at 50°C 1 b ( B ) decomposes to 1 and lc (E). With Cr(CO),NBD the compounds 1, 5, 7 and 8 form products of groups E and F. At ?18°C 7 forms 7c (E) which rearranges at 75°C to 7d (F). The compounds are characterized by ³¹P and ¹H NMR spectra, mass spectra and elemental analysis.     

13C and 29Si chemical shifts and coupling constants involving tris[(trimethylsilyl)methyl] silicon compounds

Silicon-29(δ²⁹Si) NMR chemical shifts are reported for the first time of tris[(trimethylsilyl)methyl] silicon compounds (disilylated derivatives) (Me₃Si^A)₃ C_αL, where L = Si^BR₁R₂R₃ and where R varies widely in electronegativity. ²⁹Si chemical shifts exhibit good correlation with the electronegativities of the groups bonded to the silicon atom. The ¹³C NMR spectra of these compounds have been recorded and assigned. δ¹³C_α is shown to depend on the type of substitutent on Si^B. The variation of ²⁹SiH coupling constants with electronegativity of R is studied.     

The Non-Ancillary Nature of Trimethylsilylamide Substituents in Boranes and Borinium Cations

The known boranes (R(Me₃Si)N)₂BF (R=Me₃Si 1 , tBu 2 , C₆F₅ 3 , o-tol 4 , Mes 5 , Dipp 6 ) and borinium salts (R(Me₃Si)N)₂B][B(C₆F₅)₄] (R=Me₃Si 7 , tBu 8 ) are prepared and fully characterized. Compound 7 is shown to react with phosphines to generate [R₃PSiMe₃]⁺ and [R₃PH]⁺ (R=Me, tBu). Efforts to generate related borinium cations via fluoride abstraction from (R(Me₃Si)N)₂BF (R=C₆F₅ 3 , o-tol 4 , Mes 5 ) gave complex mixtures suggesting multiple reaction pathways. However for R=Dipp 6 , the species [(μ-F)(SiMe₂N(Dipp))₂BMe][B(C₆F₅)₄] was isolated as the major product, indicating methyl abstraction from silicon and F/Me exchange on boron. These observations together with state-of-the-art DFT mechanistic studies reveal that the trimethylsilyl-substituents do not behave as ancillary subsitutents but rather act as sources of proton, SiMe₃ and methyl groups.