PREPARATION, B-11, C-13, SI-29 NMR AND VI BRATIONAL-SPECTRA OF TRIMETHYLSILYLMETHYL-HEXAHYDRO-CLOSO-HEXABORATE, [B6H6(CH2SI(CH3)(3))](-) AND THE CRYSTAL-STRUCTURE OF [P(C6H5)(4)][B6H6(CH2SI(CH3)(3))]

By reaction of [N(C4H9)(4)](2)[B6H6] with iodomethyl-trimethylsilane i n acetonitrile a solution with trimethylsilymethyl-closo-hexaborate(1- )anions, [B6H6(CH2Si(CH3)(3))](-), is formed. The crystal structure of [P(C6H5)(4)][B6H6(CH2Si(CH3)(3))] has been determined by single cryst al X-ray diffraction analysis; monoclinic, space group P2(1)/n with a = 16.140(2), b = 11.646(8), c = 16.731(3) Angstrom, beta = 109.664(11) degrees. The B-11 NMR spectrum reveals features of a mono hetero subst ituted octahedral B-6 cage. The C-13 NMR spectrum exhibits a quartet a t +0.18 ppm with (1)J(C,H) = 118 Hz for the three methyl groups and a weak multiplet at -0.65 ppm for the methylene bridge due to quadrupole coupling with the boron atoms. In the Si-29 NMR spectrum a decet at 2.25 ppm with (2)J(C,H) = 6.9 Hz is observed. The B-C stretching vibra tion is observed at 1155 cm(-1) in the IR and Raman spectrum.