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...H bonding and proton-transfer pathways

The reactions of various proton donors (phenol, hexafluoro-2-propanol, perfluoro-2-methyl-2-propanol, monochloroacetic acid, and tetrafluoroboric acid) with the rhenium(I) hydride complex [(triphos)Re(CO)2H] (1) have been studied in dichloromethane solution by in situ IR and NMR spectroscopy. The proton donors form [(triphos)Re(CO)2H⋯HOR] adducts exhibiting rather strong H⋯H interactions. The enthalpy variations associated with the formation of the H-bonds (-ΔH=4.4-6.0 kcal mol-1) have been determined by IR spectroscopy, while the H⋯H distance in the adduct [(triphos)Re(CO)2H⋯HOC(CF3)3] (1.83 Å) has been calculated by NMR spectroscopy through the determination of the T1 min relaxation time of the Re-H proton. It has been shown that the [(triphos)Re(CO)2H⋯HOR] adducts are in equilibrium with the dihydrogen complex [(triphos)Re(CO)2(η2-H2)]+, which is thermodynamically more stable than any H-bond adduct. © 1998 Elsevier Science S.A. All rights reserved.