The crystal and molecular structure of π-cycloheptatrienyliumtricarbonylmolybdenum(0) tetrafluoroborate

Abstract

The crystal and molecular structure of π-cycloheptatrienyliumtricarbonylmolybdenum(0) tetrafluoroborate has been determined using X-ray diffraction techniques. The orange crystals are orthorhombic, space group Pbca. The unit cell dimensions are a = 16.297(2), b = 12.955(2) and c = 11.749(2) Å and with eight molecules per cell, the calculated density is 1.91 g/cm 3 versus 1.90 g/cm 3 measured by flotation. The structure was solved by the heavy atom method and refined by full-matrix least-squares method to a final R of 0.049 for the 1383 observed reflections used in the analysis. The cation has a 'piano stool' arrangement, with the planar cycloheptatrienylium ring as a 'seat' and the three carbonyl groups as 'legs'. While the average CC distance in the C 7H 7 + ring of 1.400 Å is similar to that found in other C 7H 7 + ring systems, the average MoC(carbonyl) distance of 2.032 Å is longer than that found in other molybdenum tricarbonyl complexes.