PROBLEMS OF UNUSUAL HYDROGEN-BONDS BETWEEN PROTON DONORS AND TRANSITION-METAL HYDRIDES AND BOROHYDRIDES

The results of experimental and theoretical studies of intermolecular MH...HX and BH...HX hydrogen bonds with the hydride hydrogen atom acti ng as a proton accepting site are analyzed. Spectral (IR and NMR) crit eria for their formation are presented. The spectral, structural, and thermodynamic characteristics of these unusual hydrogen bonds obey the regularities found for classical hydrogen bonds. It was shown that th e MH...HX bonds participate in the proton transfer with the formation of nonclassical cationic hydrides and the [M(eta(2)-H-2)](+)...A(-) hy drogen bonds are formed in low-polarity media. Problems arising in thi s new line of investigations are discussed.