In situ IR and NMR study of the interactions between proton donors and the Re(I) hydride complex [{MeC(CH 2PPh 2) 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(CF 3) 3] (1.83 Å) 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) 2H…HOR] adducts are in equilibrium with the dihydrogen complex [(triphos)Re(CO) 2( η 2-H 2)] +, which is thermodynamically more stable than any H-bond adduct.