THE ADDITION OF CARBONYL-COMPOUNDS TO TETRAMESITYLGERMASILENE AND DIMESITYLGERMYLENE

Hexamesitylsiladigermirane, 1, has been photolyzed/thermolyzed in the presence of three representative carbonyl compounds: acetone, pivalaldehyde, and benzaldehyde. In each case, a [2 + 2] adduct between the carbonyl compound and MeS2Ge = SiMes2 was forme.d regioselectively to give a 2,3-silagermaoxetane. The 2,3-silagermaoxetanes have been fully characterized by IR and NMR (H-1, C-13, and Si-29) spectroscopy and mass spectrometry. In two cases, the structures have been confirmed by X-ray crystallography: 4,4-dimethyl-2,2,3,3-tetramesityl-2,3-silagermaoxetane, 2a; crystals are triclinic, space group P1BAR with Z = 2 in a unit cell 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)-degrees, and gamma = 89.97(2)-degrees. The structure was solved by direct methods and refined by least squares on the basis of 2955 observed reflections to R1 and wR2 values of 0.0600 and 0.1363, respectively. The structure of 4-tert-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) angstrom, c = 16.524(2) angstrom, and beta = 106.83(1)-degrees. The structure was determined by direct methods and refined by full-matrix least squares on the basis of 1817 observed reflections to R1 and wR2 values of 0.0621 and 0.1681, respectively. An adduct between dimesitylgermylene and the carbonyl compound was also isolated in each reaction. The structure of the adduct appears to depend upon the steric bulk of the group attached to the carbonyl carbon.