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