Pendant Ancillary Ligand Switches Off Auto-Oxidation of Group 13 Metal Alkyl Compounds Bearing Non-Bulky Alkyl Groups

The reaction of 3,5-di-2-pyridyl-1,2,4-triazole with excess Al(CH(3))(3) and Ga(CH(3))(3) afforded (3,5-di-2-pyridyl-1,2,4-triazolate)Al(CH(3))(2)•3Al(CH(3))(3) (1) and (3,5-di-2-pyridyl-1,2,4-triazolate) Ga(CH(3))(2)•3Ga(CH(3))(3) (2) respectively. 1 and 2 reacted with oxygen gas to produce (CH(3))(2)M(µ-3,5-di-2-pyridyl-1,2,4-triazolate)(µ-OCH(3))M(CH(3))(2) (M = Al, 3; M = Ga, 4). 3 and 4 contain the non-bulky dimethylalumino moiety, yet they are indefinitely stable in the presence of oxygen gas. This increased stability towards oxygen is due to ancillary 2-pyridyl groups bonding to the metal centers producing a pseudo-trigonal pyramidal Al and Ga environments. This environment blocks oxygen from further inserting into the M–C bond. The Al–N(pyridine) and Ga–N(pyridine) bonds reported herein are extremely elongated yet inactive towards dissociation due to the chelate effect.