The Structure of 1,3-Enaminoketonatoboron Difluorides in Solution and in the Solid State

Abstract

Nuclear magnetic resonance, infrared, and ultraviolet spectra and X-ray analysis of three 1,3-enaminoketonatoboron difluorides (BF₂ complexes, (2a)–(2c)) both in solution and in the solid state have been recorded. Their structures are discussed in relation to the electron distribution in their chelate rings and in comparison with those of their parent compounds (1a)–(1c) and 1,3-diketonatoboron difluorides. C1 and C3 chemical shifts in the ¹³C NMR spectra indicated that the ketoamine and enolimine tautomeric forms may be present in equal amounts. Additionally, the phenyl groups participate in the delocalized π-electron system of the chelate ring. On the other hand, in the solid state, a comparison of the bond lengths by X-ray analysis provides information on processes occurring as contribution of the enolimine form increases. The information found may offer valuable suggestions for the reactivity and the structure of the products for the reactions of the BF₂ complexes.