Hydrogen bonding in coordination compounds containing homoconjugated bis-dimethylsulfoxide cation. Ab initio and IR studies

Abstract DFT calculations of vibrational spectra and structural parameters of dimethylsulfoxide (DMSO) molecule, its hydrogen bonded complex with HCl, mono- and bis-dimethylsulfoxide cations DMSOH + and DMSOHOSDM + have been performed at B3LYP/6-31G ∗∗ level. The results obtained for free DMSO and DMSO+HCl complex are in good agreement with the known experimental data. For free homoconjugated cation (DMSOHOSDM) + , an extremely short (R O ⋯ O =2.40 A ) and a practically linear hydrogen bond with nearly central position of the bridging proton have been found. The addition of a counterion leads to lengthening and bending of the hydrogen bond. A solid [(DMSO) 2 H] 2 [PtCl 6 ] compound has been synthesized and the IR spectrum of this salt has been investigated. The structural parameters and vibrational frequencies calculated for [(DMSO) 2 H] + X − complexes ( X = Cl , BF 4 ) were found to be in good agreement with experimental X-rays and IR data for solid [(DMSO) 2 H] 2 [PtCl 6 ]. The most important feature of vibrational spectrum of homoconjugated bis-dimethylsulfoxide cation is the essential involvement of proton stretching and bending coordinates in different normal modes, resulting in mixing of proton vibrations with vibrations of sulfoxide moiety, particularly with ν SO, ν CS, δ CH.