Synthesis, Structure and Bonding in Triorganogermyl-alanes and Triphenylgermyl-aluminates

Triphenylgermyl-lithium in diethyl ether/THF did not react with Al2Me6 to form [(Ph3Ge)AlMe3]Li(THF)n. Addition of TMEDA to this solution yielded crystalline Ph3GeLi(THF)TMEDA. The reaction of Ph3GeLi in diethyl ether/hexane solution with H3Al-NMe3 in diethyl ether/THF generated [Ph3GeAlH3]Li(THF)4 while the reaction with Me2AlCl led to Ph3GeAlMe2(OEt2) and the trigermyl-aluminate [(Ph3Ge)3AlMe]Li. The analogous aluminate [(Ph3Ge)3AlH]Li(THF)3 was obtained by reacting LiGePh3 with AlH2Cl(OEt2) in the presence of THF. It was expected that the bulky bis(tetramethylpiperidino)chloroalane would react with Ph3GeLi to give the germyl-alane tmp2AlGePh3 which was observed when only diethyl ether was used as a solvent, but in an Et2O/toluene mixture only Ph8Ge3 could be isolated. Increasing the steric requirement of the germyllithium compound by using the bulky (tBu3Si)Me2Ge group instead of the Ph3Ge group led to a straightforward reaction generating the first structurally characterized germyl-alane (tBu3Si)Me2GeAl(tmp)2 with a planar tri-coordinated Al center. The X-ray structure determinations showed that the germyl-aluminates have shorter Ge–Al bonds than the germyl-alane inspite of the lower coordination number.