Destruction reactions of some σ-derivatives of vanadium

The interactions of (Me₃SiCH₂)₄V and (Me₃SiCH₂)₃V·THF with cyclopentadiene have been studied. Me₄Si and Cp₂V were isolated. A scheme of the reactions was proposed which involves formation of unstable monocyclopentadienyl derivatives of vanadium. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1542–1544, August, 1997.     

μ-Oxo-bis(triorganoantimon- und -bismutsulfonate). Kristallstruktur von {(CH3)3SbOH2]2}O3SC6H5)2

μ-Oxo-bis(triorganoantimony- and -bismuthsulfonates) (R₃MO₃Sr′)₂O[M  Sb, R  Ph, benzyl, M  Bi, R  Ph; R′  Me, CH₂CH₂OH, CF₃, Ph, 4-CH₃C₆H₄, 2,4-(NO₂)₂C₆H₃] and (Me₃SbO₃SR′)₂O · nH₂O (n  2, R′  CF₃, Ph, 4-CH₃C₆H₄; n  0, R′  CH₃, CH₂CH₂OH) have been prepared by reaction of (Ph₃SbO)₂ and Me₃Sb(OH)₂, respectively, with appropriate sulfonic acids or with (R₃MX)₂O (R  Ph, benzyl; X  Br) and R′SO₃H in the presence of Ag₂O. The anhydrous compounds (Me₃SbO₃SR′)₂O are obtained by heating the hydrates. Me₃Sb(OH)₂ and 2,4-(NO₂)₂C₆H₃SO₃H react to give the hydroxosulfonate Me₃Sb(OH)O₃SR′. CH₃OH solvolyzes the products. A covalent structure, with pentacoordinated Sb or Bi atoms, unidentate O₃SR′ ligands and μ-oxygen in apical, and R in equatorial positions, is inferred from the vibrational data for all nonhydrated sulfonate compounds. A correlation between ν_as(SbOSb) vibration and SbOSb bond angles in hexaphenyl distiboxans was established, which indicates that the SbOSb bridges are linear in (Ph₃SbO₃SR′)₂O (R′  2,4-(NO₂)₂C₆H₃, 2,4,6-(NO₂)₃C₆H₂) and bent in the other compounds. Data also indicate that there is a linear BiOBi bridge in (Ph₃BiO₃SCH₂CH₂OH)₂O. The hydrated compounds have a distinctly different ionic structure one H₂O being coordinated apically to each of the pentacoordinated Sb atoms in the cation [(Me₂SbOH₂)₂O]²⁺. This proposal is verified by the crystal structure determination of (Me₃SbO₃SPh)₂O · 2H₂O which revealed an ionic structure: [(Me₃SbOH₂)₂O](O₃SPh)₂. The angles μ-OSbO(H₂O) of 171.7(2) and 171.0(2)° and μ-OSbC(CH₃) of 98.3° (mean) reflect the distortion of the trigonal bipyramidal surrounding of the Sb atoms, and the long SbO(H₂O) distance of 244.4(5) pm (mean) the rather weak bonding of the water molecules to Sb. The distances S [144.6(6) pm (mean)] and the angles OSO [112.6(4)° (mean)] in the sulfonate anion are essentially identical. Hydrogen bonds exist between the water ligands and O atoms of the anions.     

Half-sandwich dibenzyl complexes of scandium: Synthesis, structure, and styrene polymerization activity

Half-sandwich dibenzyl complexes of scandium have been prepared by stepwise treatment of scandium trichloride with lithium derivatives of silyl-functionalized tetramethylcyclopentadienes (C₅Me₄H)SiMe₂R (R = Me, Ph) and benzyl magnesium chloride. The resulting complexes [Sc(η⁵-C₅Me₄SiMe₃)(CH₂Ph)₂(THF)] and [Sc(η⁵-C₅Me₄SiMe₂Ph)(CH₂Ph)₂(1,4-dioxane)] show structure related to that of the corresponding bis(trimethylsilylmethyl) compounds [Sc(η⁵-C₅Me₄SiMe₂R)(CH₂SiMe₃)₂(THF)]. The four-coordinate complexes display η¹-coordinated benzyl ligands without significant interaction of the ipso-carbon of the phenyl moiety. Conversion of [Sc(η⁵-C₅Me₄SiMe₃)(CH₂Ph)₂(THF)] into the cationic species by treatment with triphenylborane in THF led to the formation of a stable charge separated complex [Sc(η⁵-C₅Me₄SiMe₃)(CH₂Ph)(THF)_x][BPh₃(CH₂Ph)]. Benzyl cation formed using [Ph₃C][B(C₆F₅)₄] in toluene resulted in a moderately active syndiospecific styrene polymerization catalyst.     

Bimetallic Rare Earth Alkyl Complexes Bearing Bridged Amidinate Ligands: Synthesis and Activity for L-Lactide Polymerization

Four novel bridged‐amidines H₂L {1,4‐R¹[C(=NR²)(NHR²)]₂ [R¹=C₆H₄, R²=2,6‐ⁱPr₂C₆H₃ (H₂L¹); R¹=C₆H₄, R²=2,6‐Me₂C₆H₃ (H₂L²); R¹=C₆H₁₀, R²=2,6‐ⁱPr₂C₆H₃ (H₂L³); R¹=C₆H₁₀, R²=2,6‐Me₂C₆H₃ (H₂L⁴)]} were synthesized in 65%–78% isolated yields by the condensation reaction of dicarboxylic acid with four equimolar amounts of amines in the presence of PPSE at 180°C. Alkane elimination reaction of Ln(CH₂SiMe₃)₃(THF)₂ (Ln=Y, Lu) with 0.5 equiv. of amidine in THF at room temperature afforded the corresponding bimetallic rare earth alkyl complexes (THF)(Me₃SiCH₂)₂LnL¹Ln(CH₂SiMe₃)₂(THF) [Ln=Y ( 1 ), Lu ( 2 )], (THF)(Me₃SiCH₂)₂LnL²Ln‐ (CH₂SiMe₃)₂(THF) [Ln=Y ( 3 ), Lu ( 4 )], (THF)(Me₃SiCH₂)₂YL³Y(CH₂SiMe₃)₂(THF) ( 5 ), (THF)(Me₃SiCH₂)₂YL⁴‐ Y(CH₂SiMe₃)₂(THF) ( 6 ) in 72% –80% isolated yields. These neutral complexes showed activity towards L‐lactide polymerization in toluene at 70°C to give high molecular weight (M>10⁴) and narrow molecular weight distribution (M_w/M_n≦1.40) polymers     

Organometallic Compounds of the Lanthanides. 157 [1] The Molecular Structure of Tris(trimethylsilylmethyl)samarium, ‐erbium, ‐ytterbium,and ‐lutetium

SmCl₃ reacts with Me₃SiCH₂Li in THF yielding Sm(CH₂SiMe₃)₃(THF)₃ ( 1 ). The single crystal X‐ray structural analyses of 1 , Er(CH₂SiMe₃)₃(THF)₂ ( 2 ), Yb(CH₂SiMe₃)₃(THF)₂ ( 3 ), and Lu(CH₂SiMe₃)₃(THF)₂ ( 4 ) show the Sm atom in a fac‐octahedral coordination and the heavier lanthanides Er, Yb, and Lu trigonal bipyramidally coordinated with the three alkyl ligands in equatorial and two THF molecules in axial positions.     

Carbon-13 and proton NMR parameters of neopentyl-and trimethylsilylmethyl-thallium(III) derivatives and the x-ray crystal structure of bis(trimethylsilylmethyl)chlorothallium(III)

Carbon-13 and proton NMR spectra have been determined for organothallium (III) derivatives of the types RTlX₂ and R₂ TlX (R  (CH₃)₃CCH₂ or (CH₃)₃SiCH₂; X  Cl, Br or O₂CCH(CH₃)₂). The dependence of coupling of ¹³C and ¹H to thallium on the number and nature of R groups is discussed in terms of the Fermi contact mechanism for spinspin coupling.The crystal structure of [(CH₃)₃SiCH₂]₂ TlCl has been determined. The compound crystallises in the monoclinic space group P2₁/n, with a 10.618, b 24.492, c 6.017 Å, β 99.76°. The molecule is dimeric with each four-coordinate thallium atom bonded unequally to two bridging chlorine atoms. The CTlC angle is 168°.     

Preparation and reactivity of the new cyclopentadienyl-bridged complex (Me2SiCH2CH2SiMe2)(C5H4Fe(CO)2)2

A new metal-metal bonded binuclear iron system [Me₂SiCH₂CH₂SiMe₂][η⁵-C₅H₄Fe(CO)₂]₂ (2) has been prepared by treating two equivalents of NaCp with one equivalent of ClSi(Me)₂CH₂CH₂SiClMe₂ obtaining the intermediate (C₅H₅)Si(Me)₂CH₂CH₂Si(Me)₂(C₅H₅) which then is directly allowed to react with Fe(CO)₅ given 2 in 30% yield. From this cyclopentadienyldisilyl linked system three new binuclear irom complexes are formed. Treatment of 2 with Na/Hg in THF produced the dianion [Me₂SiCH₂CH₂SiMe₂][η⁵-C₅H₄Fe(CO)₂^?]₂ which is quenched with CH₃I giving [Me₂SiCH₂CH₂SiMe₂][η⁵-C₄H₄Fe(CO)₂CH₃]₂ (4) in 76% yield. Complex 2 is oxidized with 1.2 equivalent of I₂ to give [Me₂SiCH₂CH₂SiMe₂][η⁵-C₅H₄Fe(CO)₂I]₂ (5) in 85% yield. Photolysis of 5 (1 equiv.) and PPh₃ (3 equiv.) results in the formation of the bis-substituted compound [Me₂SiCH₂CH₂SiMe₂][η⁵-C₅H₄Fe(CO)(PPh₃)I]₂ (6). These four new binuclear iron complexes are characterized by ¹H, ¹³C, and ³¹P NMR and IR spectroscopy.     

Strukturen zweifach metallierter Derivate von 3, 3‐Dimethyl‐1, 5‐bis(trimethylsilyl)‐1, 5‐diaza‐pentan mit Lithium und Aluminium sowie zweier Donor‐substituierter Digallane

Structural Characterization of Bis(metallated) Derivatives of 3, 3‐Dimethyl‐1, 5‐bis(trimethylsilyl)‐1, 5‐diaza‐pentane with Lithium and Aluminum and of two Donor‐substituted Digallanes The diaminopropane derivative Me₂C[CH₂N(H)SiMe₃]₂ is metallated with n‐butyllithium and lithium tetrahydridoaluminate to obtain Me₂C[CH₂N(Li)SiMe₃]₂ and Me₂C[CH₂N(Li)SiMe₃][CH₂N(AlH₂)SiMe₃], respectively. Both compounds exhibit a central eight‐membered ring, Li₄N₄ or Li₂Al₂N₄. Me₂C[CH₂N(Li)SiMe₃]₂ reacts with Ga₂Cl₄ · 2dioxane under formation of the corresponding tetra(amino)digallane. This is monomeric, in contrast to a dimeric tetraalkoxy‐substituted digallane, Ga₄O^tBu₈. All compounds were characterized by single crystal X‐ray crystallography.     

Synthese von sulfinsäureimidamidostannanen

N-Lithiomethanesulfinicacidimide amides of the general composition MeS(NR)NRLi (II) are prepared by addition of methyllithium to sulfur diimides RNSNR (I) (R  t-Bu or SiMe₃. The corresponding reaction with Me₃SnNSNSnMe₃ yields the N-lithio salt (Me₃SnNSN)Li (III) and tetramethylstannane; addition compounds are not formed. Methatetical reactions of II with chlorostannanes, Me₃SnCl or Me₂SnCl₂, leads to the formation of the sulfinicacidimideamidostannanes MeS(NR)NRSnMe₃ (IV) and MeS(NR)NRSnClMe₂ (Va), respectively.     

Darstellung,Charakterisierung und Reaktionsverhalten von Natrium‐ und Kaliumhydridosilylamiden R2(H)Si—N(M)R′ (M = Na,K) — Kristallstruktur von [(Me3C)2(H)Si—N(K)SiMe3]2·THF

Preparation, Characterization and Reaction Behaviour of Sodium and Potassium Hydridosilylamides R₂(H)Si—N(M)R′ (M = Na, K) — Crystal Structure of [(Me₃C)₂(H)Si—N(K)SiMe₃]₂ · THF The alkali metal hydridosilylamides R₂(H)Si—N(M)R′ 1a‐Na — 1d—Na and 1a‐K — 1d‐K ( a : R = Me, R′ = CMe₃; b : R = Me, R′ = SiMe₃; c : R = Me, R′ = Si(H)Me₂; d : R = CMe₃, R′= SiMe₃) have been prepared by reaction of the corresponding hydridosilylamines 1a — 1d with alkali metal M (M = Na, K) in presence of styrene or with alkali metal hydrides MH (M = Na, K). With NaNH₂ in toluene Me₂(H)Si—NHCMe₃ ( 1a ) reacted not under metalation but under nucleophilic substitution of the H(Si) atom to give Me₂(NaNH)Si—NHCMe₃ ( 5 ). In the reaction of Me₂(H)Si—NHSiMe₃ ( 1b ) with NaNH₂ intoluene a mixture of Me₂(NaNH)Si—NHSiMe₃ and Me₂(H)Si—N(Na)SiMe₃ ( 1b‐Na ) was obtained. The hydridosilylamides have been characterized spectroscopically. The spectroscopic data of these amides and of the corresponding lithium derivatives are discussed. The ²⁹Si‐NMR‐chemical shifts and the ²⁹Si—¹H coupling constants of homologous alkali metal hydridosilylamides R₂(H)Si—N(M)R′ (M = Li, Na, K) are depending on the alkali metal. With increasing of the ionic character of the M—N bond M = K > Na > Li the ²⁹Si‐NMR‐signals are shifted upfield and the ²⁹Si—¹H coupling constants except for compounds (Me₃C)(H)Si—N(M)SiMe₃ are decreased. The reaction behaviour of the amides 1a‐Na — 1c‐Na and 1a‐K — 1c‐K was investigated toward chlorotrimethylsilane in tetrahydrofuran (THF) and in n‐pentane. In THF the amides produced just like the analogous lithium amides the corresponding N‐silylation products Me₂(H)Si—N(SiMe₃)R′ ( 2a — 2c ) in high yields. The reaction of the sodium amides with chlorotrimethylsilane in nonpolar solvent n‐pentane produced from 1a‐Na the cyclodisilazane [Me₂Si—NCMe₃]₂ ( 8a ), from 1b‐Na and 1‐Na mixtures of cyclodisilazane [Me₂Si—NR′]₂ ( 8b , 8c ) and N‐silylation product 2b , 2c . In contrast to 1b‐Na and 1c‐Na and to the analogous lithium amides the reaction of 1b‐K and 1c‐K with chlorotrimethylsilane afforded the N‐silylation products Me₂(H)Si—N(SiMe₃)R′ ( 2b , 2c ) in high yields. The amide [(Me₃C)₂(H)Si—N(K)SiMe₃]₂·THF ( 9 ) crystallizes in the space group C2/c with Z = 4. The central part of the molecule is a planar four‐membered K₂N₂ ring. One potassium atom is coordinated by two nitrogen atoms and the other one by two nitrogen atoms and one oxygen atom. Furthermore K···H(Si) and K···CH₃ contacts exist in 9 . The K—N distances in the K₂N₂ ring differ marginally.     

Contributions to the chemistry of halosilane adducts: XVIII. On the nature of compounds of trimethylhalosilanes with 1,1,3,3-tetramethylguanidine and 2-trimethylsilyl-1,1,3,3-tetramethylguanidine: preparation and characterization of mono- and bis-(2-trimethylsilyl)-1,1,3,3-tetramethylguanidinium halides

1,1,3,3-Tetramethylguanidine (TMG) and 2-(trimethylsilyl)-1,1,3,3-tetramethylguanidine (TMSTMG) react with trimethylhalosilanes Me₃SiHal in equimolar ratio with ionization of the Sihalogen bond to give the stable guanidinium salts [(Me₂N)₂CNHSiMe₃]Hal (Hal  Cl (1), Br (2)) and [(Me₂N)₂CN(SiMe₃)₂]Hal (Hal  Cl (3), Br (4), I (5)), respectively, involving tetracoordinate silicon. No reaction occurs with Me₃SiF. The same ionic species are present in CHCl₃ or CH₃CN solutions (IR, ¹H, ²⁹Si NMR), thus establishing for the first time, the formation of an ionic solid derivative of Me₃SiCl stable towards dissociation. Reaction with an excess of TMG gives an equilibrium mixture of TMSTMG and TMG · HHal. The bis(silyl)guanidinium salts are less stable towards dissociation than the mono(silyl) derivatives, the stability sequence being Cl⁻ < Br⁻ < I⁻ within the series. The reactions of both types of compound have been investigated. The implications of the present and earlier results for the mechanisms of racemization and nucleophilic substitution at silicon are discussed.     

Über die Si---N-bindung : XLIV. Die umsetzung von benzophenon mit bis- und tris(trimethylsilyl)amin

The thermal LiHal elimination of

- and

functional compounds provides a simple synthetic route to four-membered SiC and SiN rings. In attempts to inhibit dimerisation sterically, bulky silylmethyl and silylamino substituents were introduced (I–III). (Me₃Si)₃CSiF₂R reacts with LiNHR′, 1,3- migration of a silyl group from carbon to the nitrogen (I, R′= 2,4,6-Me₃C₆H₂) taking place. Substitution occurs for R′ = SiMe₂CMe₂, (II, III) only.Dichloro-bis(trimethylsilyl)methane reacts with halogenosilanes and lithium in THF to give bis(trimethylsilyl)-halogenosilaethanes (Me₃Si)₂CHSi(Hal)RR′; R= Me, R′ = N(SiMe₃)₂, IV, Hal = F; V, Hal = Cl. However a reductive THF cleavage accompanied by a silyl group migration to the oxygen occurs and 1-halogenosilyl-1- trimethylsilyl-5-trimethylsiloxi-pent-1-ene,(Me₃Si)(RR′SiHal)CCH(CH₂)₃OSiMe₃, Are The main products (VII–X) of these reactions. Disubstitution occurs with F₃Si-i-Pr (VI). (Me₃Si)₃CSiFNHSiMe₂CMe₃ (II) reacts with C₄H₉Li in a molar ratio $\text{1}\text{2}$ to give an 1-aza-2,3-disilacyclobutane (XI), involving substitution, LiF elimination, and nucleophilic migration of a methanide ion of the unsaturated precusor.(Me₃Si)₂CHSiFMeN (2,4,6-Me₃C₆H₂)SiMe₃ cyclizes under comparable conditions in the reaction with MeLi via a methylene group of the mesityl group (XII).     

1,1,2,2-Tetramethyl-3-trimethylsilyl-1,2-disilacyclobutane: synthesis and spontaneous polymerization

Gas-phase dehalogenation of 1,2-bis[chloro(dimethyl)silyl]-2-trimethylsilylethane with alkali metals gave 1,1,2,2-tetramethyl-3-trimethylsilyl-1,2-disilacyclobutane (3). Its spontaneous ring-opening polymerization at room temperature afforded an amorphous linear polymer with T _g = ?8.9°C, M _w = 3.47·10⁵–3.85·10⁵, and M _w /M _n = 2.43—2.86. According to spectroscopic data (IR and ¹H, ¹³C, and ²⁹Si NMR), the backbone of the polymer consists of alternating monomer units joined in the “head-to-tail” ([Me₂SiCH(SiMe₃)CH₂SiMe₂SiMe₂CH-(SiMe₃)CH₂SiMe₂]) and “head-to-head” ways ([Me₂SiCH₂CH(SiMe₃)SiMe₂SiMe₂CH-(SiMe₃)CH₂SiMe₂]).     

Komplexchemie P-reicher Phosphane und Silylphosphane. VIII. Zur unterschiedlichen Tendenz der Bildung von Chromcarbonyl-Komplexen silylierter-alkylierter Phosphane und Diphosphane

Transition Metal Complexes of P-rich Phosphanes and Silylphosphanes. VIII. Concerning the Different Tendencies of Silylated and Alkylated Phosphanes and Diphosphanes to Form Chromium Carbonyl Complexes The influence of the substituents Me₃Si tBu and Me in phosphanes and diphosphanes on the formation of complex compounds with Cr(CO)₅THF is investigated. tBu(Me₃Si)P? P(SiMe₃)₂ 1 and (tBu)₂P? P(SiMe₃)₂ 2, resp., react with Cr(CO)₅THF 4 at ?18°C by coordinating Cr(CO)₅ to the P(SiMe₃)₂ group to give tBu(Me₃Si)P? P^IV(SiMe₃), · Cr(CO)₅ 1 a, tBu(Me₃Si)P^IV? P^IV(SiMe₃)₂ · Cr(CO)₄ 1b and (tBu)₂P? P^IV(SiMe₃)₂ · Cr(CO)₅ 2a . In the reaction of 1 with 4 using a molar ratio of 1:2 at first 1 a is formed which reacts on to yield completely 1 b. In a mixture of the dissolved compounds (Me₃Si)₃P 5, (tBu)₃P 6 and (tBu)₃P? P(SiMe₃)₂ 2 only 5 and 6 react with Cr(CO)₅THF yielding (Me₃Si)₃P · Cr(CO)₅ and (tBu)₃P · Cr(CO)₅, but 2 does not yet react. In a solution of (Me₃Si)₃P 5, P₂Me₄ 7 and (Me₃Si)₂P? PMe₂ 3 only 5 and 7 react with Cr(CO)₅THF (0.25 to 1.5 equivalents with respect to 3) to give (Me₃Si)₃P · Cr(CO)₅, P₂Me₄ · Cr(CO)₅ and P₂Me₄ · 2Cr(CO)₅. The formation of complexes with Cr(CO)₅THF of the phosphanes 5 and 6 is clearly favoured as compared to the silylated diphosphanes 2 and 3 (not to P₂Me₄); the PR₂ groups (R = tBu, Me in 2 or 3 ) don't have a strong influence.     

Tetrahedral Coordination in the First Structurally Characterized Dichlorooxovanadium(V) Alkoxide

Reaction of VOCl₃ with 2‐phenoxyethanol in n‐hexane in a 1:1 fashion gives dichlorooxo(2‐phenoxyethanolato)vanadium(V). HCl elimination yields the orange vanadium(V) complex, which is the first structurally characterized dichlorooxovanadium(V) alkoxide. The structure analysis reveals an unexpected tetrahedral coordination around the vanadium atom in the monomeric compound. Alcoholysis and hydrolysis reactions of [VOCl₂(OCH₂CH₂OPh)] are monitored by ⁵¹V NMR spectroscopy. Activated with Me₃SiCH₂MgCl or ⁿBu₂Mg the complex catalyses the polymerisation of styrene.     

Olefin polymerization catalyzed by amide vanadium(IV) complexes: The stereo‐ and regiochemistry of propylene insertion

The reaction of VCl₃(THF)₃ with 1 equiv of the lithium salt of ligand ArNH(Me₂SiCH₂CH₂SiMe₂)NHAr or ArNH(SiMe₃) (Ar = 2,6‐Me₂C₆H₃) afforded the corresponding V(IV) amide complexes, [1,2‐CH₂CH₂(Me₂SiNAr)₂]VCl₂ ( 3 ) and (Me₃SiNAr)₂VCl₂ ( 4 ). The activation of 3 and 4 with the alkyl aluminum compound Al₂Et₃Cl₃ or AlEt₂Cl produced active ethylene polymerization catalysts exhibiting productivity values among the highest reported for vanadium amide based catalysts. Moreover, syndiotactic specific propylene polymerization was successfully conducted at ?40 °C in the presence of 3 /Al₂Et₃Cl₃ and 4 /Al₂Et₃Cl₃. Syndiotactic polypropylenes with moderate stereoregularity ([rr] = 0.66) and a concentration of regioirregular propylene of 6.9 mol % were obtained. Monomodal molecular weight distributions and polydispersity indices lower than 2 were observed in the polymerization runs carried out in heptane solutions. Thus, ethylene–propylene copolymers with propylene concentrations up to 45 mol % were synthesized and characterized by ¹³C NMR and thermal analysis. Good alternation and random distribution of the two monomers were actually obtained. Samples with elevated concentrations of propylene were completely amorphous, with a glass‐transition temperature of ?50 °C. The properties and structure of the copolymers produced with amide vanadium catalysts 3 and 4 were similar to those reported for ethylene–propylenes produced with industrial vanadium‐based catalysts, suggesting the presence of the same active catalyst species. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3279–3289, 2006     

Synthesis and molecular structure of chlorotris(trimethylsilylmethyl)trimethylsilyl-methylidyne rhenium(VII)

The complex Re(CSiMe₃)(CH₂SiMe₃)₃Cl has been isolated as yellow crystals in low yield from the reaction of ReCl₄(THF)₂ with Me₃SiCH₂MgCl and characterised by X-ray crystallography. The molecule has a trigonal bipyramidal geometry with the alkylidyne and chlorine ligands axial.     

Spektroskopische Untersuchungen zu Substituenteneffekten in Silylmethylsilanen

Spectroscopic Investigations on Substituent Effects in Silylmethylsilanes The silanes Me_3?n(Me₃SiCH₂)_nSiH (n = 1–3), (RMe₂SiCH₂)₃SiH (R = n-Bu, n-Pr, Et, PhCH₂, Ph) and Me₃ElCH₂SiMe₂H (El = Ge, Sn) were prepared. The frequencies of the Si? H stretching vibration, the ²⁹Si? ¹H coupling constants and the ²⁹Si n.m.r. chemical shifts were measured. The ?(SiH) and J(²⁹Si? ¹H) values in the silanes Me_3?n(Me₃SiCH₂)_nSiH depend on the number of trimethylsilymethyl groups. There is hardly an influence of the substituents R on these values in the silanes (RMe₂SiCH₂)₃SiH. The frequencies of the Si? H stretching vibrations in the silanes Me₃ElCH₂SiMe₂H (El = Si, Ge, Sn) show the order Si?Ge > Sn. The ₂₉Si n.m.r. chemical shifts of the Si(H) signals are approximately equal in the silanes Me_3?n(Me₃SiCH₂)_nSiH and (RMe₂SiCH₂)₃SiH.     

Cumulated double bond systems as ligands : IV. 1H and 13C NMR studies of the intra- and inter-molecular exchange processes of cationic dialkylsulfurdiimine compounds of RhI,IrI and PtII

The preparation and properties are described of trans-[(Ph₃P)₂(CO)M(RNSNR)] [ClO₄] (M  Rh^I, Ir^I; R  Me, Et, i-Pr, t-Bu) and of cis- or trans-[L₂Pt(RNSNR)X] [ClO₄] (X  Cl^?, L  Et₂S, PhMe₂As, PhMe₂P, R  Me, t-Bu; X  CH₃, L  PhMe₂P, R  Me).¹H and ¹³C NMR data show the existence of various isomers in solution which may interconvert via intra- and inter-molecular exchange processes. A general reaction scheme for the intramolecular exchange processes is discussed.     

Synthese eines Titana-Oxacyclohexanringes durch kontrollierte Ringöffnung von Tetrahydrofuran. Kristallstrukturen von [Ti(CH2)4O{Me2Si(NBut)2}]2, [TiCl{Me2Si(NBut)2}]3(μ3-O)(μ3-Cl) und [Li2(THF)3{Me2Si(NBut)2}]

Synthesis of a Titana-Oxacyclohexane Ring by Controlled Ring Opening of Tetrahydrofurane. Crystal Structures of [Ti(CH₂)₄O{Me₂Si(NBu^t)₂}]₂, [TiCl{Me₂Si(NBu^t)₂}]₃(μ₃-O)(μ₃-Cl), and [Li₂(THF)₃{Me₂Si(NBu^t)₂}] [TiCl₃(THF)₃] reacts with [(Bu^tNLi)₂SiMe₂]₂ in diethyl ether at –35 °C under redox disproportionation and formation of the yellow titana(IV)-oxacyclohexane complex [Ti(CH₂)₄O{Me₂Si(NBu^t)₂}]₂. According to the crystal structure analysis the titanium atoms are linked to form centrosymmetric dimers via the oxygen atoms of the Ti(CH₂)₄O six-membered rings, which are in chair conformation. Along with the nitrogen atoms of the chelating [Me₂Si(NBu^t)₂]^2– ligands the titanium atoms obtain a distorted trigonal-bipyramidal surrounding. While [TiCl{Me₂Si(NBu^t)₂}]₃(μ₃-O)(μ₃-Cl) with a cluster-like structure is obtained as a by-product. According to the crystal structure analysis of [Li₂(THF)₃ · {Me₂Si(NBu^t)₂}], which is involved in the synthesis reaction, the two lithium atoms are connected with both the nitrogen atoms of the t-butyl amide groups and bridged via an oxygen atom of one of the THF molecules.