IN-SITU IR AND NMR-STUDY OF THE INTERACTIONS BETWEEN PROTON DONORS AND THE RE(I) HYDRIDE COMPLEX [(MEC(CH2PPH2)3)RE(CO)(2)H] - REH-CENTER-DOT-CENTER-DOT-CENTER-DOT-H BONDING AND PROTON-TRANSFER PATHWAYS

The reactions of various proton donors (phenol, hexafluoro-2-propanol, perfluoro-2-methyl-2-propanol, monochloroacetic acid, and telrafluoro boric acid) with the rhenium(I) hydride complex [(triphos)Re(CO)(2)H] (1) have been studied in dichloromethane solution by in situ IR and NM R spectroscopy. The proton donors form [ (triphos)Re( CO)(2)H ... HOR] adducts exhibiting rather strong H ... H interactions. The enthalpy v ariations associated with the formation of the II-bonds ( -Delta H= 4. 4-6.0 kcal mol(-1)) have been determined by IR spectroscopy, while the H ... H distance in the adduct [(triphos)Re(CO)(2)H ... HOC(CF3)(3)] (1.83 Angstrom) has been calculated by NMR spectroscopy through the de termination of the T-1min relaxation time of the Re-H proton. It has b een shown that the [ (triphos)Re( CO)(2)H ... HOR] adducts are in equi librium with the dihydrogen complex [(triphos)Re(CO)(2)( eta(2)-H-2)]( +), which is thermodynamically more stable than any I-I-bond adduct. ( C) 1998 Elsevier Science S.A. Ail rights reserved.