Azomethine derivatives. Part I. Reactions between diphenylketimine and trimethylborane, triethylborane, and triphenylborane

Abstract

Diphenylketimine reacts reversibly with trimethylborane below 20° to give the solid adduct Ph₂C:NH,BMe₃ which at 160–200° slowly forms methane and the azomethine derivative Ph₂C:N·BMe₂. Dissociation vapour-pressure measurements and infrared and proton magnetic resonance spectroscopy of the adduct show diphenylketimine to be intermediate in donor power between nitriles and amines. Mass spectroscopy of Ph₂C:N·BMe₂ reveals this compound to exist unassociated in the vapour phase at 200°, providing the first example of a boron–nitrogen analogue of an allene, although the B–N bond order appears to be appreciably lower than the CN bond order. No evidence of adducts was obtained in studies of the systems Ph₂C:NH–BR₃(R = Et or Ph). Diphenylketimine and triethylborane at 155° gave ethylene and Ph₂C:NCHPh₂. Features of the mass, infrared, and proton magnetic resonance spectra of the products of these reactions are discussed.