Nuclear magnetic resonance studies of π-bonding in aminoboranes. Part I. Ambient temperature spectra

Abstract

The ¹H n.m.r. spectra at ambient temperatures of a number of aminoboranes with general formula ArB(X¹)NMe₂(I) or PhB(X²)N(R¹)R²(II) are reported both for pure liquids and for a variety of solutions. Positive evidence is presented for restricted rotation about the boron–nitrogen bond for the compounds (a) of type (I) with Ar = Ph, X¹= Br, Cl, NCO, Me or with Ar =p-MeOC₆H₄, X = Cl and (b) of type (II) with X²= Cl, R = Et, R²= Me or with X²= Cl, R¹= Prⁱ, R²= Me. The effects of varying the boron-substituent and the solvent upon chemical shifts are considered.