Pendant ancillary ligand switches off auto-oxidation of group 13 metal alkyl compounds bearing non-bulky alkyl groups

Abstract

The reaction of 3,5-di-2-pyridyl-1,2,4-triazole with excess Al(CH 3)3 and Ga(CH3)3 afforded (3,5-di-2-pyridyl-1,2,4-triazolate)Al(CH3)2· 3Al(CH3)3 (1) and (3,5-di-2-pyridyl-1,2,4-triazolate) Ga(CH3)2·3Ga(CH3)3 (2) respectively. 1 and 2 reacted with oxygen gas to produce (CH3) 2M(μ-3,5-di-2-pyridyl-1,2,4-triazolate)(μ-OCH 3)M(CH3)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 pseudotrigonal 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. © 2014 Issam Kobrsi.