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.