Equilibria in scrambling reactions of some boron compounds

Abstract

Exchange of substituents on boron was investigated for the systems: B(OCH 3) 3 vs. B(C 6H 5) 3, B[N(CH 3) 2] 3 vs. B(C 6H 5) 3, and BCL 3 vs. B(OC 6H 5) 3. Data on the first two systems were obtained by proton nuclear magnetic resonance (n.m.r.); whereas 11B n.m.r. was used for the third system. The equilibrium distribution of the four molecular species obtained by exchanging phenyl with methoxyl groups was nearly random; but the exchange equilibrium of phenyl with dimethyl-amino groups was very nonrandom, with the compound B(C 6H 5) 2[N(CH 3) 2] being present in amounts much greater than those predicted for ideally random sorting of substituents. Because of considerable overlapping of the 11B n.m.r. resonance peaks, the equilibria for scrambling of chloro and phenoxyl groups on boron could only be estimated approximately.