SYNTHESIS AND X-RAY STRUCTURE OF PENTACARBONYL(7-η1-CYCLOHEPTA-1,3,5-TRIENYL)RHENIUM(I)

Article abstract of DOI:10.1016/S0022-328X(00)89214-1

Synthesis by two routes of (7-η¹-C7H7)Re(CO)5 (2), the first monohaptocycloheptatrienyl derivative of a transition metal, is described.The first involves ultraviolet irradiation of the acyl C7H7(CO)Re(CO)5 (1) in acetone at -78 deg C.The second and preferred route involves reaction of NaRe(CO)5 with in THF to form orange crystalline 2 in 90percent yield.Activation enthalpy for thermal decomposition of 2 to form ditropyl and Re2(CO)10 is 30.4 +/- 0.3 kcal mole^-1, a value close to the estimated strength of the C7H7-Re(CO)5 bond.A single crystal X-ray diffraction study of 2 shows a nearly octahedral Re(CO)5 group bonded in the quasi-axial position to the methylene carbon atom of the seven-membered ring, which has a boat conformation.NMR spectra are consistent with a similar structure as the exclusive or dominant form in solution.