Synthesis and Structures of Amino(triphenylgermyl) Boranes and Trihydro(triphenylgermyl) Borates

The B-(triphenylgermyl)borazines 4 a and 4 b, the 1,2-bis(dimethylamino)-1,2-bis(triphenylgermyl)-diborane(4), 5, and the (2,2,6,6-tetramethylpiperidino)(triphenylgermyl)-boranes 6 and 7 were prepared by allowing LiGePh3 to react with the corresponding B-bromoborazines and aminochloroboranes, respectively. BH3 dissolved in thf readily adds to LiGePh3 generating Li(H3BGePh3), 8 a, in thf solution. Addition of N-bases to the solution of 8 a produced (tmen · thf)Li(H3BGePh3), 8 b, and dimeric (py)2Li(H3BGePh3), 8 c. The borazine ring in 4 b is distorted into a boat shape. In 5 the NBGe planes are twisted against each other by 85°. Comparison with analogous (triphenylstannyl)boranes points to a more pronounced steric effect of the Ph3Ge group over the Ph3Sn group due to the shorter B–Ge bond. A fairly short B–Ge bond is found for the (triphenylgermyl)trihydroborates. The molecular structure of (Et2O)3LiGePh3 shows compressed C–Ge–C bond angles. Its molecular parameters fit well into the series LnLiEPh3 (E = Si, Sn, Pb).