THE ADDITION OF CARBONYL-COMPOUNDS TO TETRAMESITYLGERMASILENE AND DIMESITYLGERMYLENE

Hexamesitylsiladigermirane, 1, has been photolyzed/thermolyzed in the presence of three representative carbonyl compounds: acetone, pivalald ehyde, and benzaldehyde. In each case, a [2 + 2] adduct between the ca rbonyl compound and MeS2Ge = SiMes2 was forme.d regioselectively to gi ve a 2,3-silagermaoxetane. The 2,3-silagermaoxetanes have been fully c haracterized by IR and NMR (H-1, C-13, and Si-29) spectroscopy and mas s spectrometry. In two cases, the structures have been confirmed by X- ray crystallography: imethyl-2,2,3,3-tetramesityl-2,3-silagermaoxetane , 2a; crystals are triclinic, space group P1BAR with Z = 2 in a unit c ell of dimensions a = 12.318(3) angstrom, b = 12.436(2) angstrom, c = 11.884(2) angstrom, alpha = 100.13(1)-degrees, beta = 103.80(2)-degree s, and gamma = 89.97(2)-degrees. The structure was solved by direct me thods and refined by least squares on the basis of 2955 observed refle ctions to R1 and wR2 values of 0.0600 and 0.1363, respectively. The st ructure of -butyl-2,2,3,3-tet-ramesityl-2,3-silagermaoxetane, 2b, was also determined, crystals are monoclinic, space group Cc with Z = 4 in a unit cell of dimensions a = 11.306(2) angstrom, b = 21.292(4) angst rom, c = 16.524(2) angstrom, and beta = 106.83(1)-degrees. The structu re was determined by direct methods and refined by full-matrix least s quares on the basis of 1817 observed reflections to R1 and wR2 values of 0.0621 and 0.1681, respectively. An adduct between dimesitylgermyle ne and the carbonyl compound was also isolated in each reaction. The s tructure of the adduct appears to depend upon the steric bulk of the g roup attached to the carbonyl carbon.