Hydrogen bonding of the undecahydro-thiocyanato-closo-dodecaborate anion with proton donors

Abstract

The interaction of (Bu₄N)₂[B₁₂H₁₁SCN] (1) with various proton donors (MeOH, indole, pyrazole, imidazole, PhOH, 4-NO₂C₆H₄OH, CF₃CH₂OH, (CF₃)₂CHOH and (CF₃)₃COH) was investigated by IR spectroscopy at 190 – 290 K in dichloromethane. Both the hydride hydrogen and the nitrogen atom of the SCN group of 1 acted as proton-accepting sites. IR spectral evidence of BH ···· HO and N ···· HO hydrogen-bond formation was obtained by changes in the acid ν_XH stretches as well as in the ν_BH and ν_CN bands of the hydride. Spectral and thermodynamic characteristics of the H-complexes were determined. Interaction with NH-acids was also examined. The electronic effects of the SCN group and the boron cage on the proton-accepting properties of both sites in 1 were analyzed by comparison with previously studied hydrogen bonding to (Bu₄N)₂[B₁₂H₁₂] and (Bu₄N)[SCN]. Both types of hydrogen bonds in the model complexes of [B₁₂H₁₁SCN]²⁻ HOCF₃ were studied using the B3LYP/6-31G(d,p) approximation.