Bildung siliciumorganischer Verbindungen. 89. Selektive Photobromierung von Si-methylierten Carbosilanen

Formation of Organosilicon Compounds. 89. Selective Photobromination of Si-methylated Carbosilanes A selective photobromination of the C atoms in the skeleton of Si-methylated carbosilanes is reported. (me₃Si? CH₂)₂Sime₂ reacts to me₃Si? CBr₂? Sime₂? CH₂? Sime₃ in good yields (me = CH₃); the second CH₂ group is considerably slower brominated. Photobromination of (me₂Si? CH₂)₃ consecutively yields a and b . Also from (me₂Si? CH₂)₄ the derivative with one CBr₂ group is accessible. Bromination of tertiary CH groups is highly preferred; this is shown by the selective formation of c . The C-bromination of SiBr-substituted carbosilanes is significantly more difficult; nevertheless (Brme₂Si)₂CH₂ selectively forms (Brme₂Si)₂CBr₂. Brme₂Si? CH₂? Sime₂? CH₂? Sime₃ forms Brme₂Si? CH₂? Sime₂? CBr₂? Sime₃, i. e., only the CH₂ group non-adjacent to SiBr is attacked. The formation of CHBr groups could not be detected. Higher temperatures and longer reaction times increase the formation of polymers.     

Bildung siliciumorganischer Verbindungen. XXX. Metallorganische Synthese cyclischer Carbosilane

This paper contains:

• 1 The synthesis of the 1.3-disilacyclopentenes (a)(b)⁽²⁾ and of the 1.3-disilacyclo-butane (c); formulas see above.
• 2 The synthesis of the 1.3-disilacyclopentane skeleton (d) and of the SiCl-functional derivatives (e) (f ) (g) (h) (i) as well as of SiH-containing derivatives, e.g. (j).
• 3 The chlorination of (i) with SO₂,Cl₂, yielding (k) and (l), and the formation of (m) from (k) with K-methypyrrolidine.
• 4 The synthesis of the spirane (n).
• 5 The synthesis of the ten-membered ring(o) and of the unsaturated derivatives (p)and (q). Besides the synthetic routes, spectroscopic data (ir, pmr, and mass spectra) of the cyclic compounds as well as of the intermediate products are given.

     

Bildung siliciumorganischer Verbindungen. 84 [1]. Synthese und thermische Umlagerung von verschieden substituierten linearen und cyclischen Silanen

Formation of organosilicon compounds. 84. Synthesis and thermal rearrangement of some substituted linear and cyclic silanes In part IR we report on the synthesis of substituted silanes, and in part II on their thermal rearrangement. I: me₃i--Sime₃(me = CH₃) is formed by dropwise addition of THF to a suspension of Li powder in me₃SiCl; yield ～ 80%. The mixture me₃Si--Sime₂Cl, me₃SiCl, Li powder and THF reacts analogously to form me₂Si(Sime₃)₂; yield 80%. By the same type of reaction the following compounds are obtained: compound 1 from Brme₂Si? CH₂? Sime₂Br, 1 from Brme₂Si? CH₂? Sime₂Br, 2 from Brme₂Si? Sime₂? CH₂? Sime₂Br 16 and 3 from Bret₂Si? CH₂? CH₂? Siet₂Br (et = C₂H₅). 2 decomposes during its isolation from THF. 16 is formed from phme₂Si? Sime₂? CH₂? Sime₂ph 17 (ph = C₆H₅) by reaction with HBr, 17 either from phme₂SiLi and Clme₂SiCH₂Cl or from phme₂Si? Sime₂Br and LiCH₂? Sime₂ph. II: me₂Si(Sime₃)₂ rearranges at 440 °C (56 h) with insertion of the CH₂ group (Si? H formation) into the Si? Si bond and the formation of me₃Si? Sime₂? CH₂? Sime₂H, me₂HSi? CH₂? Sime₂? CH₂? SiHme₂, and me₃Si? CH₂? Sime? CH₂? Sime₂H. 1 reacts analogously. Methylated halogenated disilanes like Brme₂Si? Sime₂Br react with separation of: Sime₂ and its insertion into the Si-halogen bond to form trisilanes. Different from both are the phenylated derivatives, though phme₂Si? Sime₂ph still forms phme₂Si? Sime₂? Sime₂ph. 3 reacts with separation of C₂H₄, formation of the Si? H group and insertion of C₂H₄ into the Si? Si bond.     

Bildung siliciumorganischer Verbindungen. 83. Bildung,Reaktionen und Struktur von Yliden aus perchlorierten Carbosilanen

Formation of Organosilicon Compounds. 83. Formation, Reactions, and Structure of Ylides Generated from Perchlorinated Carbosilanes The CCl-moiety in perchlorinated carbosilanes as (Cl₃Si)₂ a, Cl₃Si? CH₂? SiCl₂? CCl₂? SiCl₃ b, (Cl₃Si? CCl₂)₂SiCl₂ c or (Cl₂Si? CCl₂)₃ d, e.g., cleaves the Si? P bond of me₃Si? Pme₂ e (me = CH₃); and by subsequent rearrangement ylides are formed. Such, treating e with a yields (Cl₃Si)₂CPme₂Cl 1, which also results from the reaction of me₂P? Pme₂ with a. The ylides also can be obtained by means of treating the carbosilanes a, b, c or d with LiPme₂. Thus, c with one mole of LiPme₂ yields Cl₃Si? CCl₂? SiCl₂? C(Pme₂Cl)? SiCl₃ or Cl₃Si? C(Pme₂Cl)? SiCl₂? C(Pme₂Cl)? SiCl₃, resp., with two moles of LiPme₂. The corresponding Si-methylated derivates do not form ylides; (me₃Si)₂CCl₂, e.g., with e in benzene yields me₃Si? CH(Pme₂)? Sime₃. One mole of Lime methylates 1 to yield (Cl₃Si)₂CPme₃ 11. With either LiPme₂, me₃Si? Pme₂ or Me₂P? Pme₂ 1 forms (Cl₃Si)₂CPme₂-Pme₂. Reacting 1 with CH₃OH/(C₂H₅)₂NH, (Cl₃Si)[SiCl₂(OCH₃)]CPme₂(OCH₃) is formed. Ylides also result from the reactions of partially C-chlorinated 1,1,3,3,5,5-hexachloro-1,3,5-trisilacyclohexanes with me₃Si? Pme₂, (Cl₂Si? CCl₂)₃ with three moles of me₃Si? Pme₂ or LiPme₂, resp., yields (Cl₂Si? CPme₂Cl)₃ 16, the 1,1,3,3,5,5-Hexachlor-2,4,6-tris(chlordimethylphosphoranyliden)-1,3,5-trisilacyclohexan, which crystallizes with one mole of monoglyme. X-ray structure determinations revealed that 1, 11 and 16 are planar. As well the (P? C) as the (Si? C) bond lengths are remarkably shortened; in 1 (P? C) to 173.3 pm, (Si? C) to 173.3 pm, (Si? C) to 179.5 pm, in 16 (P? C) to 168.7 pm, (Si? C) to 180 pm. The (Si? C) and (P? C) bond orders amount to about 1.33, and are relatively equally distributed. Therefore, the charge of the formal carbanion is equally distributed, which shall be expressed by means of the following kind of writing for 1 and 16 see “Inhaltsübersicht”.     

Bildung siliciumorganischer Verbindungen LXIII. Synthese und thermische Umlagerung des 1,1,3,3,4,4-Hexamethyl-1,3,4-trisilacyclopentan

Formation of Organosilicon Compounds. LXIII. Synthesis and Thermal Rearrangement of 1,1,3,3,4,4-Hexamethyl-1,3,4-trisilacyclopentane 1,1,3,3,4,4-Hexamethyl-1,3,4-trisilacyclopentane undergoes rearrangement at 500°C to form 1,1,3,5,5-Pentamethyl-1,3,5-trisilacyclohexane. The synthesis of 1,3,4-Trisilacyclopentane is reported.     

Bildung siliciumorganischer Verbindungen. 90. Synthese C-verbrückter Carbosilane

Formation of Organosilicon Compounds. 90. Synthesis of C-linked Carbosilanes n-buLi metallates 1 to give 2 , which with phme₂SiCl (ph = C₆H_5, me = CH₃) forms 3 . This compound yields 4 with Br₂. Lithiation of 3 yields 5 which for sterical reasons cannot be substituted with phme₂SiCl. The spiro compounds 10 and 11 are available by treating 2 with (Brme₂Si)₂CH₂ or (Brme₂SiCH₂)₂-Sime₂, resp. By means of n-buLi the CBr group in 4 can be metallated. On warming to 20°C the lithiated compound eliminates LiBr via an highly reactive intermediate to form 12 , 12 shows an extraordinary stability of the Si? C fourmembered ring against HBr or Br₂     

Bildung siliciumorganischer Verbindungen. 77. Zur Bildung von Carbosilanen aus Methylsilanen

Formation of Organosilicon Compounds. 77. Formation of Carbosilanes from Methylsilanes The products formed by pyrolysis of me₃SiH, me₂SiH₂, and meSiH₃ are reported. Sime₄ and the mentioned methylsilanes were reacted in a plasma, and the products are compared to those of the pyrolysis. The pyrolysis of me₃SiH and me₂SiH₂ essentially yields the same groups of carbosilanes which are accessible by thermal decomposition of Sime₄, if the range is restricted to compounds with 4 Si atoms at most. Cylic carbosilanes are the main products of the pyrolysis of me₃SiH, and amoung these, 1,3,5-trisilacyclohexanes and 1,3,5,7-tetrasilaadamantanes are preferrently formed. From me₂SiH₂ above all linear compounds as 1,3-disilapropanes are obtained. This is attributed to the chosen experimental procedure in which they not subject to further reaction. In the pyrolysis of meSiH₃ a yellow solid is formed besides little amounts of meH₂Si? SiH₂me. Compared to the compounds formed by pyrolysis of Sime₄, the carbosilasen obtained from me₃SiH and me₂SiH₂ possess more SiH substituents. Also the decomposition of Sime₄ in a plasma preferrently yields carbosilanes, mainly linear compounds with 2 or 3 Si atoms.     

Bildung siliciumorganischer Verbindungen. LVIII. Die Synthese eines Carbosilans mit Propellan-Struktur

Formation of Organosilicon Compounds. LVIII. Synthesis of a Carbosilane with Propellane Structure 1 (· ? C resp. CH₂; x ? Si(CH₃)₂ resp. Si) is formed by a coupling reaction of BrSi(CH₂? Sime₂? CH₂? Sime₂Br)₃ 2 with CCl₄ and Li. The reaction of C₆H₅me₂Si? CH₂Li with Clme₂Si? CH₂Br leads to C₆H₅me₂Si? CH₂? Sime₂? CH₂Br. Metallation with lithium and succeeding reaction with Cl₃SiC₆H₅ produces compound C₆H₅Si(CH₂? Sime₂? CH₂? Sime₂C₆H₅)₃, which than forms 2 by cleavage with bromine.     

Bildung siliciumorganischer Verbindungen. 92 [1]. Bildung und Struktur des Oktamethyl-hexasila-hexascaphans

Formation of Organosilicon Compounds. 92. Formation and Structure of Octamethylhexasila-hexascaphane By rearrangement and abstraction of CH₄ at the presence of AlBr₃ 2 forms 3 , and 6 forms 7 , which is also obtained reacting 8 and 9 under the same condition. Lithination of 1, 1, 3, 5, 5, 7, 7, 9, 9-Nonamethyl-1, 3, 5, 7, 9-pentasiladecaline yields 12 , which is trapped with me₃SiCl to form 6 . Convertation of 13 to 14 leads to 8 by reaction with ClSi(CH₂—Sime₃)₃. Compound 7 is characterized by NMR and mass spectroscopy as well as X-ray structural analysis. 1, 3, 5, 7, 9, 9, 11, 11-Octamethyl-1, 3, 5, 7, 9, 11-hexasila-hexascaphane 7 crystallizes in the monoclinic space group P2₁/n (No. 14) with a = 3296.7 pm, b = 1536.2 pm, c = 891.9 pm, β 91.71° and Z = 8 formular units. Both crystallographic independent molecules have approximately the symmetry C₂. The differences of corresponding bond lengths, bond angles and torsion angles are unimportant. But there is a distinct dependence of the Si? C bond length relative to the function of the bond in the molecule (Averages: Si? C) (endo) = 188.4 pm, Si? C (exo) = 187.6 (pm).     

Bildung Siliciumorganischer Verbindungen. 103. Bildung und Struktur von cis- und trans-2,4-Dichloro-2,4-bis(trimethyl-silyl)-1,1,3,3-tetramethyl-1,3-disilacyclobutan

Formation of Organosilicon Compounds. 103. Formation and Structure of cis and trans 2,4-Dichloro-2,4-bis(trimethylsilyl)-1,1,3,3-tetramethyl-1,3-disilacyclobutane The reaction of Me₃Si? CCl₂? SiMe₂Cl with LiBu in THF yields 1,1,3,3-Tetramethyl-2,4-bis(trimethylsilyl) 1,3-disilabicyclo[1.1.0]butane. The product of the first reaction stage is Me₃Si? CCl(Li)-SiMe₂Cl. The 1,3-Disilacyclobutane 2 and 3 were isolated, when Me₃Si? CCl₂? SiMe₂Cl was treated with LiBu in Et₂O. This way the proof is given that 2 and 3 are intermediates of the formation of product 1 . The further products are 4 and 5 (CCl in 2 and 3 substituted by CH) and Me₃Si? CH₂? C(SiMeCl)₂SiMe₃. 2 crystallizes orthorhombically in the space group Fdd 2 (no. 43) with a = 2149.1 pm, b = 2229.2 pm, c = 1763.6 pm and Z = 16 molecules per cell. The central ring of disilacyclobutane is slightly folded (17.9°). The configuration of the C-Atoms in this four membered ring gets closer to a sp² configuration built up by three Si? C bonds. The Cl-atoms approximately have orthogonal positions to these CSi₃ arrangements. The extension of the C? Cl bonds (184.6 pm) and the mutual approximations of the Cl-atoms in the cis-position indicate a high reactivity of the molecule.     

Bildung siliciumorganischer Verbindungen. 86. Si-phenylierte und butylierte 1,3,5-Trisilacyclohexane

Formation of Organosilicon Compounds. 86. Si-phenyl and Si-butyl Substituted 1,3,5-Trisilacyclohexanes By treating (BrHSi? CH₂)₃ with phMgBr or t-buLi, resp., and subsequent separation of the isomers, the pure cis-cis substituted 1,3,5-trisilacyclohexanes I are accessible which yield II (Formula see Inhaltsübersicht) by reaction with Br₂. (F₂Si? CH₂)₃ 8 can be transferred into (ph₂Si? CH₂)₃ 7 with phLi. With HCl/AlCl₃ 7 forms (Cl₂Si? CH₂)₃, whereas even with an excess of Br₂ it only yields (phBrSi? CH₂)₃. Cleavage of 7 with one equivalent of Br₂ yields (H₂C? Si)₃ph₅Br 14, which with LiAlH₄ forms (H₂C? Si)₃ph₅H 10. 10 is not so easy to obtain via (H₂C? Si)₃ph₅F 9 from the reaction of 8 with 5 equivalents of phLi. All of the SiH and SiBr groups in I and II, resp., occupy axial positions as well as the Br atom in 14 the H atom at Si in 10 and the F atom in 9.     

Bildung siliciumorganischer Verbindungen. LXII. Teilbromierte Carbosilane

Formation of Organosilicon Compounds. LXII. Partial Brominated Carbosilanes The photobromination of 1 leads to compound 2 as well as to C-chlorinated derivatives if the time of reaction is prolonged. Compound 2 is also formed from (Br₂Si–CH₂)₃; Gl. (1) see ?Inhaltsübersicht”?. In a corresponding reaction (Cl₃Si–CH₂)₂SiCl₂ gives successively Cl₃Si–CHBr–SiCl₂–CH₂–SiCl₃, Cl₃Si–CBr₂–SiCl₂–CH₂–SiCl₃ and Cl₃Si–CCl₂–SiCl₂–CH₂–SiCl₃. (Cl₃Si)₂CBr₂ is accessible through the photobromination of (Cl₃Si)₂CH₂. The reactivity of the CBr₂-group is quite obvious in the reaction of Cl₂Si–CBr₂–SiCl₂–CH₂–SiCl₃ with LiAlH₄ yielding (H₃Si–CH₂)₂SiCl₂ as well as in the reaction of compound 2 with CH₃MgCl yielding [(CH₃)₂Si–CH₂]₃. By treatment of the SiH groups with bromine the preparation of compounds with the general formulas CH₃SiH_nBr_3?n; (H_3?nSiBr_n)₂CH₂; (H_3?nSiBr_n? CH₂)₂SiH_2?nBr_n; (H_2?nBr_nSi? CH₂)₃ and (H_3?nSiBr_n)₂CCl₂ is possible. Analysis of the nmr spectra shows that 1,3-Dibromo-1,3,5-trisilacyclohexane is formed to 67% in the trans and to 33% in the cis configuration; 1,3,5-Tribromo-1,3,5-trisilacyclohexane is formed to 80–90% in teh cis-trans configuration. The results of ¹H and ²⁹Si NMR investigations are reported.     

Bildung siliciumorganischer Verbindungen. XXXIX. Teilchlorierte Carbosilane

1. Photochlorination in CCl₄ of the Si-chlorinated carbosilanes (Cl₃Si? CH₂)₂SiCl₂ and (Cl₂Si? CH₂)₃ leads to totally chlorinated compounds, e. g. (Cl₃Si? CCl₂)₂SiCl₂. After chlorination has started at one CH₂ group, formation of a CCl₂ group is preferred before another CH₂ group is involved into the reaction. Thus preparation of compounds a, b, c is possible. Cl₃Si? CCl₂? SiCl₂? CH₂? SiCl₃ (a) for (b) and (c) (see “Inhaltsübersicht”). SO₂Cl₂ (benzoyl peroxide) as chlorinating agent reacts more slowly, and opens an access to carbosilanes containing CHCl groups such as (d), Cl₃Si-CHCl? SiCl₂? CH₂? SiCl₃ (e). Reactions of compounds (a) to (d) with LiAlH₄ yields carbosilanes with SiH groups, and partially chlorinated C atoms. 2. By the high reactivity of Si? CCl₂? Si groups an exchange of Cl atoms of CCl groups in perchlorinated carbosilanes is possible for H atoms of Si? H groups in perhydrogenated carbosilanes, thus allowing the preparation of compounds containing CHCl and SiHCl groups, e. g. according to Gl.(1) (Inhaltsübersicht). Further reactions, formulated as the last equations in Inhaltsübersicht, are reported as well as the rearrangement of H₃Si? CHCl? SiH₃.     

Bildung siliciumorganischer Verbindungen, 47. Die Kristall- und MolekülStruktur von 1,3,5,7- Tetramethyl-tetrasila-adamantan

Formation of organosilicon compounds. 47. The crystal land molecular structure of 1,3,5,7-tetramethyl-tetrasila-adamantan 1,3,5,7- Tetramethyl-tetrasila-adamantan, Si₄C₁₀H₂₄, is a pyrolysis product of Si(CH₃)₄. It crystallizes in the monoclinic space group P2₁/c with a = 8.859 Å, b = 9.844 Å, c = 18.316 Å, β = 91.04°, Z = 4. The molecule exhibits T_d-symmetry within the experimental error. The mean bond lengths Si? C are 1.889 Å and 1.866 Å for the Si? CH₃ and Si? CH₂ bonds respectively.     

Bildung siliciumorganischer Verbindungen. 67. Untersuchungen zur metallorganischen Synthese Si-methylierter und C-chlorierter Carbosilane über Chlorcarbenoide

Formation of Organosilicon Compounds. 67. Studies of Metallorganic Synthesis of Si-methylated and C-chlorinated Carbosilanes Using Chlorocarbenoids Synthesis and reactions of C₆H₅me₂Si? CCl₂H (A), (H₅C₆me₂Si)₂CCl₂ (B), and me₂Si(CCl₂H)₂ (C) were investigated in order to find conditions for the synthesis of C-functional carbosilanes via chlorocarbenoids. (A) and (B) react with n-butyl-Li(buLi) (?100°C/THF/ether/pentane) yielding H₅C₆me₂Si? CCl₂Li and (H₅C₆me₂Si)CClLi, respectively. These lithium reagents form (B) and(H₅C₆me₂Si)₃CCl with H₅C₆me₂SiCl. In the reaction of (H₅C₆me₂Si)₃CCl with lithium (H₅C₆me₂Si)₃CLi (D) is obtained. (D) forms with H₂O/HCl the compound (H₅C₆me₂Si)₃CH which is cleaved by HBr yielding (Brme₂Si)₃CH. (C) gives LiCCl₂? Sime₂(CCl₂H) with buLi (molar ratio 1:1) in a low temperature reaction. Clme₂Si? CCl₂? Sime₂(CCl₂H) is formed in the reaction of LiCCl₂? Sime₂? CCl₂H with Sime₂CCl₂ (yield >90%). Reacting (C) and buLi (1:3) and treating this solution with Sime₂CI₂ gives (ClSime₂)₂C?CH Sime₂Cl (>85%) via a monosilacyclopropane intermediate. In the inverse reaction, if (C) is added to buLi, (HCCl₂)me₂SiC?Sime₂(CCl₂H) is one of the isolated reaction products. If buLi is added to (C) (2:l) and this solution is treated with Sime₃Cl, compounds me₃Si? CCL₂? Sime₂? CCL₂H, me₃Si? CClH? Sime₂(CCl₂H), (me₃Si? CC1₂)₂Sime₂, me₃Si? CHCI? Sime₂? CC1₂? Sime₃ are isolated. The same products were obtained in the reaction of me₃Si? CCl₂? Sime₂? CCl₂H with buLi and me₃SiCl.     

Bildung siliciumorganischer Verbindungen. XXXXIV. Synthese und Reaktionen Si-funktioneller 1, 3, 5, 7-Tetrasila-cyclo-octane

The synthesis of the HSi?resp. BrSi? containing 1,3,5,7-tetrasila-cyclooctanes (a) and (b) is described. (a) can be prepared from meH₂Si? CH₂? Sime₂? CH₂? SiHme? CH₂? Sime₂? CH₂Br resp. from meBrHSi? CH₂? Sime₂? CH₂? SiHme? CH₂? Sime₂? CH₂Br with Li and converted to (b) with Br₂. The siloxane (c) (m.p. 37–39°C) is formed by hydrolysis of (b) and also during the reaction of (b) with CH₂Br₂ and Li in (C₂H₅)₂O because of a cleavage of the ether.     

Bildung siliciumorganischer Verbindungen. 73. Reaktionen C-chlorierter 1,3-Disilapropane mit CH3MgCl

Formation of Organosilicon Compounds. 73. Reactions of C-chlorinated 1,3-Disilapropanes with CH₃MgCl (Cl₃Si)₂CCl₂ reacts with an excess of meMgCl (me = CH₃) in Et₂O (diethylether) forming (me₃Si)₂₂C?CH₂ mainly besides Si-methylated 1,3-disilapropanes with CmeCl, CHCl, CH₂ groups [6]. For investigating the mechanism of formation of the methylidengroup reactions were carried out with differently Si-methylated and Si-chlorinated 2-methyl-1-2-chloro-1,3-disilapropanes and 2,2-dichloro-1,3-disilapropanes. Whereas (me₃Si)₂CmeCl reacts neither with meMgCl nor with Lime. it forms (me₃Si)₂C?CH₂ and (me₃Si)₂CmeH with Li or Mg resp. The reaction starts with the metallation to (me₃Si)₂CmeLi and (me₃Si)₂Cme(MgCl) resp., followed by elimination of LiH and HMgCl resp. with formation of (me₃Si)₂C?CH₂. LiH and HMgCl resp. reduces (me₃Si)₂CmeCl to (me₃Si)₂CmeH. This mechanism is supported by the reactions of (me₃Si)₂CCl(CD₃). The Si-chlorination increases the reactivity of the CmeCl group and the created C?CH₂ group favours Si-methylation. The CCl₂ group is more reactive than the CmeCl group; (me₃Si)₂CCl₂ already forms the methyliden group with meMgCl in Et₂O via the not isolated intermediate (me₃Si)₂CCl(MgCl). which prefers the methylation to (me₃Si)₂Cme(MgCl). The n.m.r. data of the investigated compounds are given.     

Bildung siliciumorganischer Verbindungen. 96. Bildung und Struktur von P-Yliden des 1,3,5-Trisilacyclohexans (Einfluß der Substituenten)

Formation of Organosilicon Compounds. 96. Preparation and Structure of P-Ylides of the 1,3,5-Trisilahexanes (Influence of the Substituents) The influence of the substituents at the silicon atoms on formation and structure of ylides of 1,3,5-trisilacyclohexanesis investigated. The reactions of 1 , 2 , 3 with Me₃Si? PMe₂ lead via cleavage of the Si? P bond and subsequent rearrangement to the ylides 4 , 5 and 6 . The x-ray structure determination reveals, that the atoms of the ylid part of 4 are in a plane with the shortened bond distances d(C? P) = 168.6 pm and d(Si? C) = 180.1 pm, whereas the other endocyclic Si? C distances remain nearly unaffected by the ylid formation. Only the endocyclic bond angles C? Si? C of the Si atoms of the ylid are enlarged (116°). In the molecule 6 d(C? P) = 164.6 pm is much shorter, but d(P? Br) = 236.6 pm is enlarged. This enlargement is coupled with a deviation of 17 pm for the ylidic C atom from the ylid plane. Distances and angles are normal in the methylated trisilnhexane. The ring in 6 has boat conformation, in 4 a flat chair conformation.     

Bildung siliciumorganischer Verbindungen. 99. Zur Trennung von Carbosilan- und Silylphosphan-Gemischen mit Hilfe der Hochdruckflüssigkeitschromatographie

Formation of Organosilicon Compounds. 99. Separation of Carbosilane and Silylphosphane Mixtures by Means of HPLC Test mixtures of Si-methylated carbosilanes were separated by means of reversedphase HPLC (nucleosil 5-C₁₈; CH₃OH:hexane = 90:10). The corresponding SiCl-containing mixtures were successfully separated only after reductin of the SiCl groups by means of LiAlH₄ (CH₃OH: C₆H₆ + H₂O = 92.5:7.5 + 4—8%). A model separation of the silylphosphanes Me₃SiPH₂, (Me₃Si)₂PH and (Me₃Si)₃P using the same material but acetonitrile: toluene = 85:15 is also reported.     

Bildung siliciumorganischer Verbindungen. 88. Zur SiH-Addition von 1,3,5-Trisilacyclohexanen an silylierte Alkine

Formation of Organosilicon Compounds. 88. SiH-Addition of 1,3,5-Trisilacyclohexanes to Silylalkynes Catalyzed by means of H₂PtCl₆ the SiH addition of 1,1,3,3,5-pentamethyl-1,3,5-trisilacyclohexane to HC?C? Sime₂CH₂Cl, and of 1,1,3,3,5-pentaphenyl-1,3,5-trisilacyclohexane to HC?C? Sime₂CH₂Br yields a and b , or c and d , resp. (Formulae see Inhaltsübersicht), whereas 1,3,5-trisilacyclohexanes with more SiH groups preferrably yield polymers. The c/d ratio is strongly governed by the solvent: 38% c in n-hexane, 72% c in CCl₄/cyclohexane. Treatment of c and d with HCl/AlCl₃ under cleavage of all of the phenyl groups, addition of HCl to the vinyl group and subsequent β-elimination leads to (Cl₂Si? CH₂)₃ ClSime₂? CH₂Br and compound e , whereas HBr at ?78°C only cleaves one phenyl group per Si atom.