Dihydrogen bonding of decahydro- closo-decaborate(2−) and dodecahydro- closo-dodecaborate(2−) anions with proton donors: experimental and theoretical investigation

Abstract

The interactions of [Bu 4N] 2[B 10H 10] and [Bu 4N] 2[B 12H 12] with various proton donors (MeOH, EtOH, Pr i OH, PhOH, 4-FC 6H 4OH, 4-NO 2C 6H 4OH, CF 3CH 2OH, (CF 3) 2CHOH, (CF 3) 3COH) in low polarity media were investigated. The site of coordination for [B 10H 10] 2− and [B 12H 12] 2− was found to be hydride hydrogen. Spectral (IR, NMR) evidences for the BH⋯HO hydrogen bonding between the boron hydrides and the OH proton donors in solution are presented. Spectral (Δ ν, Δ ν 1/2, ΔA) and thermodynamic (Δ H°, Δ S°) characteristics of the H-complexes were determined. The BH⋯HO bonding strength increases from [B 12H 12] 2− to [B 10H 10] 2− . The geometry, energy, as well as electron distribution in the [B 10H 10] 2−·HOCH 3, [B 10H 10] 2−·HOCF 3, [B 10H 10] 2−·HCN, and [B 12H 12] 2−·HOCH 3 complexes were studied using ab initio HF/6-31G approximation. It was shown that increase of the proton donor ability of acids leads to formation of bifurcate H-bonds.