Hamao Watanabe

Reaction of disilanes with acetylenes : I. Stereoselective addition of methoxymethyldisilanes to phenylacetylene catalyzed by group-VIII metal phosphine complexes

Abstract Addition reactions of methoxymethyldisilanes to phenylacetylene in the presence of various triphenylphosphine complexes of Ni, Rh, Pd and Pt were investigated. Palladium and platinum complexes, Pd(PPh3)4, PdCl2(PPh3)2 and Pt(PPh3)4 were found to be effective catalysts for the double silylation, giving adducts, cis-α,β-disilylated styrene derivatives selectively. It also was shown that hexamethyldisilane reacted with the acetylene. A possible mechanism for the stereoselective and regioselective double silylation is proposed. The cis-adducts isomerized to the corresponding trans isomers in the presence of disilane and a palladium complex catalyst.

Reaction of disilanes with acetylenes : II. Double silylation of 1-hexyne, trimethylsilylacetylene and acetylene with methoxymethyldisilanes catalyzed by tetrakis(triphenylphosphine)palladium

Abstract In the presence of a palladium(0) complex catalyst, methoxymethyldisilanes, (MeO) n Me 3-n SiSiMe 3-m (OMe) m ( m , n  1, 2), added to 1-hexyne, trimethylsilyl-acetylene and acetylene to give double silylation products, 1,2-bis(methoxy-methylsilyl)olefins, in varying yields.

Conversion of disilanes to functional monosilanes : Preparation of some nitrophenyltrimethylsilanes by tetrakis(triphenylphosphine)palladium(O) catalyzed reactions of hexamethyldisilane with nitrohalobenzenes

Abstract o -, m - and p -Nitrophenyltrimethylsilanes and 2,4-dinitrophenyltrimethylsilane were conveniently prepared by the reactions of hexamethyldisilane with the corresponding nitrohalobenzenes catalyzed by tetrakis(triphenylphosphine)-palladium(O).

The stereoselective addition of phenyldimethylsilane to phenylacetylene catalyzed by rhodium triphenylphosphine complexes

Abstract Tris(triphenylphosphine)chlororhodium was found to be an effective catalyst for the hydrosilylation of phenylacetylene. Trans addition of phenyldimethylsilane gave cis products, but concomitant cis addition leading to trans products occurred to some extent. Under certain conditions, complete isomerization of the cis to the trans isomer of the product was also observed during the hydrosilylation. In the hydrosilylation employing bis(triphenylphosphine)carbonylchlororhodium as catalyst the stereoselective reaction proceeded at faster rates than those using the above rhodium complex and no isomerization occurred.

Preparation of dimethyltetramethoxydisilane from the disilane fraction

Abstract Reaction of sym-dimethyltetrachlorodisilane, obtained by chlorination with hydrogen chloride of the higher-boiling residue produced in the Direct Synthesis of methylchlorosilanes, with methyl orthoformate or methanol/methyl orthoformate gave rise to sym-dimethyltetramethoxydisilane.

Correlaiton of Hammett σ constants withNMR parameters for substituted phenylsilanes, phenylmethylsilanes and phenyldimethylsilanes

Abstract The 29 Si-H coupling constants and SiH chemical shifts have been determined for a series of substituted phenylsilanes, phenylmethylsilanes and phenyldimethylsilanes. Excellent correlations with almost identical ϱ values, were found to exist between the coupling constants and the Hammett σ constants of the ring substituents for the three series. Treatment of the couplings withing the framework of the Hammett-Taft equation gave new Taft σ * constants for six substituted phenyl groups. The SiH chemical shifts were found to be much less sensitive to change in structure than J -( 29 Si-H). The 13 C-H coupling constants and chemical shifts of the methyl groups of substituted phenylmethylsilanes and phenyldimethylsilanes have also been measured and correlated by the Hammett σ constants. The ϱ values obtained are compared with those of substituted phenyltrimethylsialnes reported by other workers.

Group VIII metal phosphine complexes-catalyzed addition of disilanes to allenic compounds: Formation of new organosilicon compounds containing both vinylsilane and allylsilane units

Abstract Addition of chloromethyl- and methoxymethyldisilanes, X3-mMemSiSiMen-X3-n (X - Cl and OMe;m, n - 0-2), as well as hexamethyldisilane, to allene and 1, 2-butadiene in the presence of Pd(PPh3)4 catalyst gave regioselectively new functionalized organosilicon compounds, 2, 3-bis(organosilyl)prop-1-enes and 2, 3-bis(organosilyl)but-1-enes, respectively. Other group VIII metal-phospine complexes also affected the reaction, but results were found to be less satisfactory. Also, the reaction of any unsymmetrical disilane with an allenic compound gave only a single product; e.g., the addition of chloropentamethyldisilane to 1, 2-butadiene in the presence of Pd(PPh3)4 gave CH2-C(SiMe3)CH(SiMe2Cl)Me in 93% yield.

Addition of chlorodisilanes to 1,3-butadienes in the presence of tetrakis(triphenylphosphine)palladium(0). A facile route to (Z)-1,4-bis(chlorosilyl)but-2-enes

Abstract In the presence of a catalytic amount of tetrakis(triphenylphosphine)palladium(0), chlorodisilanes of type MenSi2Cl6-n (n  0, 2, 3 and 4) add to 1,3-butadienes to give (Z)-1,4-bis(chlorosilyl)but-2-enes.

Peralkylcyclotrisilane: crystal and molecular structure of [(t-BuCH2)2Si[3

Abstract The crystal and molecular structure of the first peralkylcyclotrisilane, [(t-BuCH 2 Si] 3 , have been determined by X-ray diffraction. Crystal data: orthorhombic, space group Pnna , a 35.668(3), b 16.963(1), c 12.251(1) A, d calcd 0.9183 g cm −3 for Z = 8 and V 7392.8 A 3 . Final R factor, based on 851 reflections (| F o | > 3σ|( F o )|), 0.069. The SiSi bond length in the Si 3 ring is the longest among those of various peralkylcyclopolysilanes, [R 1 R 2 Si] n ( n = 3−6), and is comparable with that in the perarylcyclotrisilane [2,6-Me 2 C 6 H 3 ) 2 Si] 3 .

Convenient laboratory synthesis of vinylic silicon compounds via the reactions of acetylene with hydrosilanes catalyzed by group-VIII metal phosphine complexes

The hydrosilylation of acetylene (HCCH) with trichlorosilane, triethoxysilane, methyldichlorosilane, methyldiethoxysilane and n-hexyldichlorosilane in an inert solvent in the presence of various phosphine complexes of Group-VIII metals such as Ru, Rh, Pd and Pt, as well as chloroplatinic acid, was investigated. Among the complexes studied, RuCL2 (PPh3)3, PtCl2 (PPh3)2, RhCl (PPh3)3, RhH(PPh3)4 and Pt(PPh3)4 were found to be the catalysts of choice for the selective syntheses of vinyltrichlorosilane, vinyltriethoxysilane, methylvinyldichlorosilane, methylvinyldiethoxysilane and n-hexylvinyldichlorosilane, respectively.