Reaktionen von R4Sb2 (R = Me,Et) mit (Me3SiCH2)3M (M = Ga,In) und Kristallstrukturen von [(Me3SiCH2)2InSbMe2]3 und [(Me3SiCH2)2GaOSbEt2]2

Reactions of R₄Sb₂ (R = Me, Et) with (Me₃SiCH₂)₃M (M = Ga, In) and Crystal Structures of [(Me₃SiCH₂)₂InSbMe₂]₃ and [(Me₃SiCH₂)₂GaOSbEt₂]₂ The reaction of (Me₃SiCH₂)₃In with Me₂SbSbMe₂ gives [(Me₃SiCH₂)₂InSbMe₂]₃ ( 1 ) and Me₃SiCH₂SbMe₂. [(Me₃SiCH₂)₂GaOSbEt₂]₂ ( 2 ) is formed by the reaction of (Me₃SiCH₂)₃Ga with Et₂SbSbEt₂ and oxygen. The syntheses and the crystal structures of 1 and 2 are reported.     

Synthesis and characterization of [(Me3SiCH2)2GaP(SiMe3)2]2, an example of a gallium-phosphorus dimer obtainable only through an indirect reaction pathway

The dimeric gallium-phosphorus compound [(Me₃Si-CH₂)₂GaP(SiMe₃)₂]₂ ( 1 ) was prepared from the 1:1 mole ratio lithium-halide elimination reaction of (Me₃SiCH₂)₂GaP(SiMe₃)₂Ga(CH₂SiMe₃)₂Cl with LiP-(SiMe₃)₂ in benzene solution and has been characterized through multinuclear solution NMR, partial elemental analysis, and single-crystal X-ray analysis. Compound 1 could not be obtained from the direct reactions of (Me₃SiCH₂)₂GaCl with P(SiMe₃)₃ or LiP(SiMe₃)₂. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:147–150, 1998     

Reaktionen eines Dibismutans und von Cyclobismutanen mit Metallcarbonylen ‐ Synthesen von Komplexen mit R2Bi‐, RBi‐, Bi2‐ und Bin‐Liganden (R = Me3CCH2, Me3SiCH2)

Reactions of a Dibismuthane and of Cyclobismuthanes with Metal Carbonyls ‐ Syntheses of Complexes with R₂Bi‐, RBi‐, Bi₂‐ and Bi_n‐ligands (R = Me₃CCH₂, Me₃SiCH₂) Reactions of [Fe₂(CO)₉] with [(Me₃CCH₂)₄Bi]₂ or cyclo‐(Me₃SiCH₂Bi)_n (n = 3 ‐ 5) lead to the complexes [(R₂Bi)₂Fe(CO)₄], [RBiFe(CO)₄]₂[R = Me₃CCH₂, Me₃SiCH₂] and [Bi₂Fe₃(CO)₉]. [Bi₂{Mn(CO)₂C₅H₄CH₃}₃] forms in a photochemical reaction of [Mn(CO)₃C₅H₄CH₃] with cyclo‐(Me₃SiCH₂Bi)_n.     

[μ‐(Me3SiCH2Sb)5–Sb1,Sb3–{W(CO)5}2] und [{(Me3Si)2CHSb}3Fe(CO)4] – zwei cyclische Komplexe mit Antimon‐Liganden

Syntheses and Crystal Structures of [μ‐(Me₃SiCH₂Sb)₅–Sb¹,Sb³–{W(CO)₅}₂] and [{(Me₃Si)₂CHSb}₃Fe(CO)₄] – Two Cyclic Complexes with Antimony Ligands cyclo‐(Me₃SiCH₂Sb)₅ reacts with [(THF)W(CO)₅] (THF = tetrahydrofuran) to form cyclo‐[μ‐(Me₃SiCH₂Sb)₅–Sb¹,Sb³–{W(CO)₅}₂] ( 1 ). The heterocycle cyclo‐ [{(Me₃Si)₂CHSb}₃Fe(CO)₄] ( 2 ) is formed by an insertion reaction of cyclo‐[(Me₃Si)₂CHSb]₃ and [Fe₂(CO)₉]. The crystal structures of 1 and 2 are reported.     

Unerwartete Reduktion von [Cp*TaCl4(PH2R)] (R = But,Cy, Ad,Ph, 2,4,6‐Me3C6H2; Cp* = C5Me5) durch Reaktion mit DBU – Molekülstruktur von [(DBU)H][Cp*TaCl4] (DBU = 1,8‐Diazabicyclo[5.4.0]undec‐7‐en)

Unexpected Reduction of [Cp*TaCl₄(PH₂R)] (R = Bu^t, Cy, Ad, Ph, 2,4,6‐Me₃C₆H₂; Cp* = C₅Me₅) by Reaction with DBU – Molecular Structure of [(DBU)H][Cp*TaCl₄] (DBU = 1,8‐diazabicyclo[5.4.0]undec‐7‐ene) [Cp*TaCl₄(PH₂R)] (R = Bu^t, Cy, Ad, Ph, 2,4,6‐Me₃C₆H₂ (Mes); Cp* = C₅Me₅) react with DBU in an internal redox reaction with formation of [(DBU)H][Cp*TaCl₄] ( 1 ) (DBU = 1,8‐diazabicyclo[5.4.0]undec‐7‐ene) and the corresponding diphosphane (P₂H₂R₂) or decomposition products thereof. 1 was characterised spectroscopically and by crystal structure determination. In the solid state, hydrogen bonding between the (DBU)H cation and one chloro ligand of the anion is observed.     

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.     

Crystallographic report: 1,3‐Bis[(trimethylsilylmethyl)dichlorostannyl]propane, [(Me3SiCH2)Cl2Sn]2(CH2)3

The dinuclear molecule of [(Me₃SiCH₂)Cl₂Sn]₂(CH₂)₃ adopts an extended conformation and features distorted tetrahedral tin centres, with the greatest distortion manifested in the C? Sn? C angles of approximately 128 °. The distortions are ascribed to the influence of intermolecular Sn···Cl interactions. Copyright © 2002 John Wiley & Sons, Ltd.     

Die Hydroaluminierung von 1,1,4,4‐Tetramethyl‐2,3‐diazabutadien mit Dialkylaluminiumhydriden – Synthese von Dialkylaluminiumhydrazoniden

The Hydroalumination of 1,1,4,4‐Tetramethyl‐2,3‐diazabutadiene by Dialkylaluminium Hydrides – Synthesis of Dialkylaluminium Hydrazonides 1,1,4,4‐Tetramethyl‐2,3‐diazabutadiene reacted with dimethylaluminium hydride by hydroalumination of only one C=N double bond. The hydrazone derivative [Me₂Al–N(CHMe₂)–N=CMe₂]₂ ( 1 ) was formed which gave a dimer possessing a six‐membered Al₂N₄ heterocycle. The hydroalumination of both C=N double bonds was not observed. Also an excess of di(tert‐butyl)‐ or bis(trimethylsilylmethyl)aluminium hydride afforded only the product of a single hydroalumination step, a second dialkylaluminium hydride molecule was attached via a coordinative interaction between its central aluminium atom and the nitrogen atom of the C=N double bond and in addition via a 3 c‐2 e Al–H–Al bond. Compounds [(Me₃C)₂Al][(Me₃C)₂AlH]N(CHMe₂)NCMe₂ ( 2 ) and [(Me₃SiCH₂)₂Al][(Me₃SiCH₂)₂AlH]N(CHMe₂)NCMe₂ ( 3 ) were formed which have five‐membered Al₂N₂H heterocycles. Thermolysis of 2 gave by C–H activation compound [(Me₃C)₂Al]₂[CH₂C(Me)=N–]₂ ( 4 ) in trace amounts which possesses two anellated AlN₂C₂ rings with a common N–N bond. In contrast, the thermal decomposition of 3 yielded by the cleavage of the N–N bond a dimeric dialkylaluminium methylideneamide ( 5 ) which has two intact C=N double bonds. Up to now our attempts to insert a C=N double bond into an Al–C bond remained unsuccessful, and only the formation of an adduct [(Me₃C)₃Al(–N=CMe₂)₂] ( 6 ) was observed upon treatment of tri(tert‐butyl)aluminium with the diazabutadiene derivative.     

Reactions of Distibanes with [Fe2(CO)9]: Synthesis,Structure and DFT Calculations of [(Et2Sb)4Fe4(CO)14], [(nPr2Sb)4Fe3(CO)10], [{(Me3SiCH2)2Sb}4Fe2(CO)6], and [2‐(Me2NCH2)C6H4SbFe2(CO)8]

The iron complexes [(Et₂Sb)₄Fe₄(CO)₁₄] ( 1 ), [(nPr₂Sb)₄Fe₃(CO)₁₀] ( 2 ), [{(Me₃SiCH₂)₂Sb}₄Fe₂(CO)₆] ( 3 ), and [2‐(Me₂NCH₂)C₆H₄SbFe₂(CO)₈] ( 4 ) were prepared by reactions of distibanes with Fe₂(CO)₉. Compounds 1 – 4 were characterized by X‐ray diffraction, ¹H NMR and IR spectroscopy as well as mass spectrometry; complex 1 was additionally characterized by density functional calculations.     

Pentamethylcyclopentadienyl-rhodium and -iridium complexes : XXVIII. Properties and x-ray crystal structures of [(RhC5Me5)3(H)3O]+ and [(RhC5Me5)2(H)2OAc]+ prepaerd from reactions of [RhC5Me5)2(OH)3]+ with alcohols

The triμ-hydroxo-dirhodium complexes [(RhC₅Me₅)₂(OH)₃]X (X  Cl. PF₆, BF₄) react in isopropanol to give the tri-μ-hydrido-trirhodium complexes [(RhC₅Me₅)₂(H)₃O]X (X  PF₆, BF₄, BPh₄). A combination of X-ray crystal structure determination and ¹H and ¹³CNMR spectroscopy of [RhC₅Me₅)₃-(H)₃O][PF₆] showed it to contain an equilateral triangle of rhodium, each η⁵-bonded to a C₅Me₅, capped on one sid by an oxygen and with each pair of rhodiums bridged on the other side by a hydride (RhH mean 1.7(1) Å). The molecule is quite rigid and the barrier to movement of the hydrides, ΔG3, is at least 21 kcal mol^-1 at +100°C. Reasons for this rigidity are considered. The known tetrahydride complex[(RhC₅Me₅)₄]²⁺ is obtained from [(RhC₅Me₅)₂(OH)₃]Cl in isopropanol using longer reaction times. Reaction of [RhC₅Me₅)₂(HO)₃]PF₆ with primary alcohols (RCH₂OH) gave mixtures of [(RhC₅Me₅)₂H(O₂CR)₂PF₆ and [(RhC₅Me₅)₂(H)₂(O₂CR)₂PF₆, but only the latter could be easily isolated. A single crystal X-ray structure of [(RhC₅Me₅)₂-(H)₂(O₂CMe)]PF₆ showed it to be dinuclear with two rhodiums each η⁵-binded to C₅Me₅ and bridged by two hydrides (mean RhH, 1.72(10) Å) and one acetate.     

Diamino-di-tert-butylsilane als Bausteine cyclischer (SiN)2−, (SiNBN)2−, (SiN2Sn)- und spirocyclischer (SiN2)2Si-, (SiN2Sn)2S-Verbindungen

Diamino-di-tert-butylsilanes - Building Blocks for Cyclic (SiN)₂, (SiNBN)₂, (SiN₂Sn), and Spirocyclic (SiN₂)₂Si, (SiN₂Sn)₂S Compounds The aminochlorosilanes (Me₃C)₂SiClNHR ( 1 : R?H, 2 : R?Me) are obtained by the ammonolysis ( 1 ) respectively aminolysis ( 2 ) of di-tert-butyldichlorosilane in the n-hexane. The dilithium derivative of diamino-di-tert-butylsilane reacts with FSiMe₂R′ ( 3 : R′?Me, 4 : R′?F) in a molar ratio 1 : 2 to give the 1,3,5-trisilazanes 3 and 4 , (Me₃C)₂SiNHSiMe₂R′, in a molar ratio 1 : 1 with F₃SiN(SiMe₃)₂ to give the 1,3-diaza-2,4-disilacyclobutane 5 , (Me₃C)₂Si(NH)₂SiFN(SiMe₃)₂, and with F₂BN(SiMe₃)₂ to give the 1,3,5,7-tetraaza-2,6-dibora-4,8-disilacyclooctane 6 , [(Me₃C)₂SiNH-BN(SiMe₃)₂-NH]₂. The dilithium derivative of di-tert-butyl-bis(methylamino)silane reacts with SiF₄ with formation of the 1,3,5-trisilazane 7 , (Me₃C)₂Si(NMeSiF₃)₂, and the spirocycic compound 8 , [(Me₃C)₂Si(NMe)₂]₂Si, with SnCl₂ the cyclosilazane 9 , (Me₃C)₂SiNMe₂ is obtained. The dilithium derivative of 3 reacts with SnCl₂ to give the cyclo-1,3-diaza-2-sila-4-stannylen 10 , (Me₃C)₂Si(NSiMe₃)₂Sn. The oxidation of 10 with elemental sulfur leads to the formation of the spirocyclus 11 , [(Me₃C)₂Si(NSiMe₃)₂SnS]₂.     

Synthesis of bulky tris[(dimethyl(alkyl/aryl)silyl)methyl]stannanes as radical based reducing agents

The synthesis of novel bulky tris[dimethyl(ethyl/benzyl/p-tolyl/α-naphthyl)silylmethyl]stannanes (1-4) is described. Alkylation of SnCl₄ with Me₂(ethyl/p-tolyl)SiCH₂MgBr (10-11) gave mainly the triorganotin chlorides [(Me₂(ethyl/p-tolyl)SiCH₂)]₃SnCl 14 and 15, which were isolated by silica gel chromatography. Reduction of 14 and 15 with LiAlH₄ in THF gave the corresponding triorganotin hydrides 1 and 2, respectively. [Me₂(benzyl/α-naphthyl)SiCH₂]₃SnCl 16 and 17, generated by the alkylation of SnCl₄ with Me₂(benzyl/α-naphthyl)SiCH₂MgBr 12 and 13, were inseparable from the minor product [Me₂(benzyl/α-naphthyl)SiCH₂]₂SnCl₂18 and 19, respectively. Treatment of the mixtures of 16/18 and 17/19 with NaOH furnished the corresponding mixtures of stannoxanes, from which the hexakisdistannoxanes [Me₂(benzyl/α-naphthyl)SiCH₂]₆Sn₂O 20 and 22 were isolated from the minor dialkyltin oxide derivatives [Me₂(benzyl/α-naphthyl)SiCH₂]₂SnO in good yields. Reduction of 20 and 22 with BH₃ in THF gave [Me₂(benzyl/α-naphthyl)SiCH₂]₃SnH (3 and 4), respectively in good yields. ¹H, ¹³C, ¹¹⁹Sn, ²⁹Si NMR characteristics of the newly synthesized compounds are included.     

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.     

Neue Synthesen von Me2SbX (X = Cl,I) und Kristallstrukturen von Me2SbI und [(Me3Si)2CH]2SbCl

Novel Syntheses of Me₂SbX (X = Cl, I) and Crystal Structures of Me₂SbI and [(Me₃Si)₂CH]₂SbCl The crystal structures of Me₂SbI (Me = CH₃) and [(Me₃Si)₂CH]₂SbCl have been determined by X‐ray methods. Both molecules are pyramidal. The Me₂SbI molecules are associated to chains through short intermolecular Sb…I distances (366,7(1) pm) with linear I–Sb…I units (171,87(4)°) and bent Sb–I…Sb bridges (116,83(3)°).     

Transients from a mixture of [(R(O)Sn)2C(CH3)2]2 and (RCl2Sn)2C(CH3)2 [R = (SiMe3)2CH]: an identification in situ by 1D 119Sn and 2D 1H?119Sn HMQC NMR spectroscopy and electrospray mass spectrometry

The reaction of the 2,2‐bis(organodichlorostannyl)propane [(Me₃Si)₂CH(Cl₂)Sn]₂CMe₂ (A) with the corresponding organotin oxide {[(Me₃Si)₂CH(O)Sn]₂CMe₂}₂ (B) does not provide the corresponding normally expected tetraorganodistannoxane {[(Me₃Si)₂CH(Cl)SnCMe₂Sn(Cl)CH(SiMe₃)₂]O}_n but a complex reaction mixture. One major product, namely the 2,4,6,8‐tetraorgano‐2,6‐dichloro‐1,5,9‐trioxa‐2,4,6,8‐tetrastannabicyclo[3.3.1]nonane derivative [(Me₃Si)₂CHSnCMe₂Sn(Cl)CH(SiMe₃)₂]₂O₃ (C) was identified in situ by 2D ¹H? ¹¹⁹Sn and ¹H? ¹³C heteronuclear multiple quantum coherence and heteronuclear multiple bond correlation NMR spectroscopy as well as electrospray mass spectrometry. Compound C is proposed to be in equilibrium with an ionic species C′, the cation of which has an adamantane‐type structure. Copyright © 2003 John Wiley & Sons, Ltd.     

Synthesis, characterization, and X-ray crystal structure of the octabromodiosmate(III) salt [(C5Me4H)2OsBr]2[Os2Br8] and its conversion to [(C5Me4H)2OsBr][Os2HBr4(cod)2]

Treatment of hexabromoosmic acid, H₂OsBr₆, with 4 equiv. of tetramethylcyclopentadiene (C₅Me₄H₂) in tert-butanol at reflux for 8 h affords the unusual salt [(C₅Me₄H)₂OsBr]₂[Os₂Br₈], 1, which is the bis(tetramethylcyclopentadienyl)bromoosmocinium(IV) salt of the octabromodiosmate(III) dianion. The brown color of the salt suggests that the anion adopts an eclipsed conformation (D_4h symmetry) and this conclusion has been confirmed by a single-crystal X-ray diffraction experiment. The X-ray crystal structure indicates that the osmium atoms in the anion are disordered over two sites. The bromine atoms show no evidence of disorder and are disposed in a quasi-cubic arrangement; the two Os-Os vectors are almost exactly orthogonal to each other and each vector points toward a different pair of opposite square faces of the Br₈ cube. The Os-Os bond distances are 2.219(5) and 2.229(1) Å; the average Os-Br distance in the anion is 2.417(2) Å. Treatment of [(C₅Me₄H)₂OsBr]₂[Os₂Br₈] with excess 1,5-cyclooctadiene in ethanol at gentle reflux for 3 h affords [(C₅Me₄H)₂OsBr][Os₂HBr₄(cod)₂], 2. An X-ray crystallographic study was carried out on a sample in which the cation was a mixture of [(C₅Me₄H)₂OsBr⁺] and [(C₅Me₄H)₂OsH⁺]. The results demonstrate that the anion adopts a confacial bioctahedral structure in which the hydride ligand and two bromides bridge between the two osmium centers. The CC bonds of the cod ligands are trans to the bridging bromide groups. The Os-Os bond distance in the anion is 2.874(1) Å. The average Os-Br distance is 2.596(2) Å for the bridging bromides and 2.565(2) Å for the terminal bromides. Compound 2 is the first example of an anionic diosmium complex containing a bridging hydride. The reaction of 1 with cod also results in the formation of bis(tetramethylcyclopentadienyl)osmocene, (C₅Me₄H)₂Os, 3, which has been isolated and characterized. Treatment of (C₅Me₄H)₂Os with 1.0 equiv. of HBF₄ · Et₂O affords the osmocinium salt [(C₅Me₄H)₂OsH][BF₄].     

Small Molecule Activation with Intramolecular “Inverse” Frustrated Lewis Pairs

The intramolecular “inverse” frustrated Lewis pairs (FLPs) of general formula 1-BR₂-2-[(Me₂N)₂C=N]-C₆H₄ ( 3 – 6 ) [BR₂=BMes₂ ( 3 ), BC₁₂H₈, ( 4 ), BBN ( 5 ), BBNO ( 6 )] were synthesized and structurally characterized by multinuclear NMR spectroscopy and X-ray analysis. These novel types of pre-organized FLPs, featuring strongly basic guanidino units rigidly linked to weakly Lewis acidic boryl moieties via an ortho-phenylene linker, are capable of activating H−H, C−H, N−H, O−H, Si−H, B−H and C=O bonds. 4 and 5 deprotonated terminal alkynes and acetylene to form the zwitterionic borates 1-(RC≡C-BR₂)-2-[(Me₂N)₂C=NH]-C₆H₄ (R=Ph, H) and reacted with ammonia, BnNH₂ and pyrrolidine, to generate the FLP adducts 1-(R₂HN→BR₂)-2-[(Me₂N)₂C=NH]-C₆H₄, where the N-H functionality is activated by intramolecular H-bond interactions. In addition, 5 was found to rapidly add across the double bond of H₂CO, PhCHO and PhNCO to form cyclic zwitterionic guanidinium borates in excellent yields. Likewise, 5 is capable of cleaving H₂, HBPin and PhSiH₃ to form various amino boranes. Collectively, the results demonstrate that these new types of intramolecular FLPs featuring weakly Lewis acidic boryl and strongly basic guanidino moieties are as potent as conventional intramolecular FLPs with strongly Lewis acidic units in activating small molecules.     

Zur Reaktion von Metall-koordinierten Kohlenmonoxid mit Yliden XXII. Bis(diphenylphosphino)methanid-Eisen-Komplexe Cp(L)Fe(Ph2PCHPPh2) (L = CO,Me3P)

The reaction of [Cp(CO)(dppm)Fe]BF₄ (1a) with the phosphorus ylide Me₃PCH₂ yields the novel bis(phosphino)methanideiron complex Cp(CO)Fe(Ph₂PCHPPh₂) (2), which upon photolysis in the presnece of Me₃P is converted into Cp(Me₃P)Fe(Ph₂PCHPPh₂ (3). Reaction of 2 with MeOSO₂CF₃ gives a mixture of the iron salts [(Cp(CO)Fe(Ph₂PCR(R′)PPh₂)]CF₃SO₃ (R = R′ = H (1b), R = R′ = Me (6) and R = H, R′ = Me (syn/anti-4)).     

Crystal and molecular structure of [i-Pr2Si]4 and [(Me3SICH2)2Si]4 and some structural properties of cyclopolysilanes, [R1R2Si]n (n = 3-6)

The crystal structures of octaisopropylcyclotetrasilane [i-Pr₂Si]₄ (1) and octakis(trimethylsilylmethyl)cyclotetrasilane [(Me₃SiCH₂)₂Si]₄ (2) have been determined by means of X-ray diffraction analysis. Various crystallographic and structural data for the two compounds were recorded. The Si₄ rings of the compounds are nonplanar with quite large dihedral angles of 37.1° in (1) and 36.6° in (2), being comparable to that (36.8)° for [t-BuMeSi]₄ reported previously and other characteristic features in the structures of (1) and (2) were described. Some structural properties of the cyclic catenation systems, [R¹R²Si]_n (n = 3–6), including (1) and (2) were also discussed from a comparative viewpoint with respect to the ring shape and the relationship between ring size and Si-Si bond length.     

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.