In situ IR and NMR study of the interactions between proton donors and the Re(I) hydride complex [{MeC(CH2PPh2)3}Re(CO)2H].: ReH•••H bonding and proton-transfer pathways

The reactions of various proton donors (phenol, hexafluoro-2-propanol, perfluoro-2-methyl-2-propanol, monochloroacetic acid, and telrafluoroboric acid) with the rhenium(I) hydride complex [(triphos)Re(CO)(2)H] (1) have been studied in dichloromethane solution by in situ IR and NMR spectroscopy. The proton donors form [ (triphos)Re( CO)(2)H ... HOR] adducts exhibiting rather strong H ... H interactions. The enthalpy variations 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 determination of the T-1min relaxation time of the Re-H proton. It has been shown that the [ (triphos)Re( CO)(2)H ... HOR] adducts are in equilibrium 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.