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

Abstract 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 from [(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 A) has been calculated by NMR spectroscopy through the determination of the T1min 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.