Sterically crowded diolates of group 13 metals

The dependence of the structure of complexes of sterically crowded 2,4-dimethylpentane-2,4-diol with group 13 metals trialkyls on the kind of metal, as well as steric bulk of the substituents on the metal atoms is reported. The reaction of tBu3Ga with 2,4-dimethylpentane-2,4-diol leads to the formation of an unstable dimeric product {tBu2Ga[(OC(CH3)2CH2C(CH3)2OH]}2 (1) possessing a four-membered Ga2O2 core and two unreacted hydroxyl groups. Compound 1 undergoes further intramolecular reaction to yield the unusual (monoalkyl)gallane O,O′-chelate complex {tBuGa[OC(CH3)2CH2C(CH3)2O]}2 (2). In contrast to tBu3Ga, tBu3In reacts with 2,4-dimethylpentane-2,4-diol to give the stable dimeric complex tBu4In2[OC(CH3)2CH2C(CH3)2OH]2 (4) stabilised by two intramolecular O–H⋯O bonds. At higher temperature compound 4 reacts with an excess of tBu3In to form the trinuclear complex tBu5In3[OC(CH3)2CH2C(CH3)2O]2 (5). The reactions of 2,4-dimethylpentane-2,4-diol with trialkylmetallane with small alkyl groups, i.e. Me3Ga and Me3In allow for the isolation of the trinuclear diolates {Me5M3[OC(CH3)2CH2C(CH3)2O]2} [M=Ga (3), M=In (6)]. The crystal structures of 2, 3 and 4 have been determined by single crystal X-ray diffraction. The reactions of tert-butylmetallane diolates with trimethyl metallanes have been studied. The interaction of the allane complex {tBuAl[OC(CH3)2CH2C(CH3)2O]}2 with Me3Al results in the formation of the trialuminium mixed-ligand product {Me3(tBu)2Al3[OC(CH3)2CH2C(CH3)2O]2} (7). Compounds 2 and 4 undergo a total transmetallation reaction in the presence of Me3M to yield [Me5M3(diol-(2H))2] [M=Al, Ga] products.