(tert‐Butoxy)aluminium and ‐gallium Hydrides

The crystal structures obtained by X‐ray methods of ( tert ‐ butoxy)alane and ‐gallane ( t BuOMH 2 ) are isotypic and are composed of discrete centrosymmetric dimers. The dimers arise from almost symmetrical AlOAl [1.810(3), 1.815( 3 ) Å] and GaOGa [1.902(9), 1.908(9) Å] bridges forming a central rhombohedral four membered M 2 O 2 cycle [OAlO 81.0(2)°, OGaO 78.6(5)°] with the metallic atoms in a distorted tetrahedral environment. When one of the hydride ligands on the metals is further substituted by tert ‐butoxy, the formation of ( t BuO) 2 AlH and ( t BuO) 2 GaH is observed. These two compounds crystallize in different lattices and space groups, but they are nevertheless very similar in their structure: the centrosymmetric M 2 O 2 cycle is maintained [AlO 1.817(3), 1.817(3) Å; GaO 1.904(4), 1.907(4) Å] As expected, the terminal Al–O [1.675(3) Å] and GaO [1.783(4) Å] distances are considerably shorter than the bridging ones.