Structure and bonding properties of the complex (eta(5)-diphenylfulvene)Mn(CO)(3)(+)

Reaction of cymantrene (6) with n-butyl-lithium followed by benzophenone an d subsequent hydrolysis yielded 1-(diphenylhydroxymethyl)(eta (5)-cyclopent adienyl)(tricarbonyl)manganese (7). Treatment of 7 with HBArF . 2Et(2)O in methylene chloride affords the blue cation 2b. Investigations of single cry stals of 2b by means of the X-ray technique showed a displacement of the ex o carbon by 6.6 degrees toward the metal and a pronounced bond alternation of the C-C bonds of the fulvene moiety. DFT calculations on the parent syst em 2a and on a system with a planar fulvene moiety (2a') yielded an energy difference of 23 kJ/mol in favor of 2a. As a result of the bending of the e xo methylene group the positive charge at the metal is increased and at C9 decreased.