An infrared study of co-ordinated BH3 and BH2 groups as proton acceptors in hydrogen bonding

Abstract

Boron co-ordination compounds of the type L,BH₃(L = Me₃N, Et₃N, Py, and Et₃P) and Me₃N,BH₂X (X = Cl, Br, and I) are shown to form hydrogen-bonded complexes with OH (MeOH, PhOH, and p-F·C₆H₄·OH) in carbon tetrachloride solution. These complexes appear to be formed via OH ⋯ BH₃ and OH ⋯ BH₂ interactions and are readily detected by the appearance of a low-frequency i.r. OH stretch. Formation of similar complexes with the more extensively halogenated amine–boranes Me₃N,BHX₂(X = Cl, Br, and I) and Me₃N,BX₃(X = F, Cl, and Br) could not be observed. Cyclotriborazanes (RNH·BH₂)₃ are shown to undergo self-association in solution and this is attributed to a related NH ⋯ BH₂ interaction.