Reactions of [(Me(3)Si)(3)CAlMe(2)] with substituted benzoic acids. Isolation of a rare organoalumoxane carboxylate

Abstract

The reactivity of bulky tris(trimethylsilyl) methyl group substituted aluminum trialkyl [(Me(3)Si)(3)CAlMe(2)center dot THF] (1) with a series of substituted benzoic acid derivatives has been investigated. An equimolar reaction of 4-methyl benzoic acid or 4-tert-butyl benzoic acid with 1 in toluene at 50 degrees C leads to the formation of cyclic dimeric aluminum carboxylates [(Me(3)Si)(3)CAl(Me)(mu-O(2)CC(6)H(4)R)](2) (R = Me 2; (t)Bu 3). Reaction of 3,5-di-iso- propylsalicylic acid (H(2)dipsa) with 1 leads to the exclusive isolation of a trimeric organoaluminum carboxylate [(Me(3)Si)(3)CAl(mu-ipsa)](3) (4), in which each aluminum is bound to two carboxylates, a phenoxide, and an alkyl group and produce a 12-membered macrocycle. Deliberate, but controlled, introduction of water in the form of 3,5-di-tert-butyl salicylic acid monohydrate (H(2)dtbsa center dot H(2)O) in the reaction with 1 in toluene leads to the isolation of carboxylate [(Me(3)Si)(3)CAl(mu-O)(mu-Hdtbsa)}(2)] (5) with a bicyclic structure. Compound 5 represents a rare example of an organoalumoxane carboxylate that simultaneously possesses alkyl, oxo, and carboxylate moieties on aluminum.