Aluminum-Boron Bond Formation by Boron Ester Oxidative Addition at an Alumanyl Anion.

The potassium diamidoalumanyl, [K{Al(SiN Dipp )}] 2 (SiN Dipp = {CH 2 SiMe 2 NDipp} 2 ), reacts with the terminal B-O bonds of pinacolato boron esters, ROBpin (R = Me, i -Pr), and B(OMe) 3 to provide potsassium (alkoxy)borylaluminate derivatives, [K{Al(SiN Dipp )(OR)(Bpin)}] n (R = Me, n = 2; R = i -Pr, n = ∞) and [K{Al(SiN Dipp )(OMe)(B(OMe) 2 )}] ∞ , comprising Al-B σ bonds. An initial assay of the reactivity of these species with the heteroallene molecules, N , N '-diisopropylcarbodiimide and CO 2 , highlights the kinetic inaccessibility of their Al-B bonds; only decomposition at high temperature is observed with the carbodiimide, whereas CO 2 preferentially inserts into the Al-O bond of [K{Al(SiN Dipp )(OMe)(Bpin)}] 2 to provide a dimeric methyl carbonate species. Treatment of the acyclic dimethoxyboryl species, however, successfully liberates a terminal alumaboronic ester featuring trigonal N 2 Al-BO 2 coordination environments at both boron and aluminum.