1,2-DIMETHYL-1,2-DISILA-CLOSO-DODECABORANE(12), A SILICON ANALOG OF AN O-CARBORANE - SYNTHESIS - X-RAY CRYSTAL-STRUCTURE - NMR, VIBRATIONAL, AND PHOTOELECTRON-SPECTRA - BONDING

The reaction of (CH3)2Si(NMe2)2 with B10H14 yields a polymer, -[B10H12 .Me2NSi(CH3)2NMe2-]n, whose pyrolysis in a stream of ammonia gives hex agonal boron nitride containing a small amount of silicon nitride. In contrast, CH3(H)Si(NMe2)2 reacts with B10H14 to give 1,2-dimethyl-1,2- disila-closo-dodecaborane(12) (DMSB), an air-sensitive solid, the stru cture of whose 1:1 benzene solvate was determined by X-ray diffraction . This compound crystallizes in the space group Pccn (#56) with a = 10 .081 (1) angstrom, b = 10.666(8) angstrom, c = 16.130(5) angstrom, V = 1734(2) angstrom3, and Z = 4. Final R = 0.044 and R(w) = 0.058. The H -1, C-13, Si-29, and B-11 NMR spectra and mass spectrum of DSMB are re ported. Its vibrational spectrum (Raman, 5-3600 cm-1; IR, 200-3600 cm- 1) has been measured and compared with that of o-carborane. A study of its He(I) photoelectron spectrum led to the conclusion that DMSB is t he most electron-rich cluster of type XYB10H10 with two adjacent main group element centers known.