Mono- and Di-t-Butylcyclopentadienyl Carbonyl Complexes of Iron and Molybdenum - Crystal Structure of [CpMo(CO)2]2 (Cp = n5-C5H3-t-Bu2-1,3)
Cothermolysis of M(CO)m (M = Fe, m = 5; M = Mo, m = 6) with t-Bu-substituted cyclopentadienyls constitutes a simple synthesis of complexes of the type [Cp*M(CO)n]2 (CP* = n5-C5H3 (t-Bu), R, R = H, t-Bu; M = Fe, Mo; n = 2, 3). Each synthesis has an optimal temperature. The yield of Fe complexes decreases at temperatures above 130°C because of decomposition of the product. Optimal yields of [Cp*Mo(CO)3]2 are obtained at 130-140°C, whereas at 160°C complexes of the type [Cp*Mo(CO)2]2 with formal MoMo triple bonds are obtained. The structure of the complexes is discussed on the basis of 1H-, 13C-NMR, IR, and mass spectrometry. The structure of [CpMo(CO)2]2 (Cp = n5-C5H3t-Bu2-1,3) was determined by X-ray crystallography at -95°C. It crystallises in the space group Pbca, with cell constants a = 1808.6(6), b = 1308.5(4), c = 2507.9(9) pm, Z = 8, R = 0.031 for 3794 reflections. The MoMo bond length of 253.3 pm is very long for a formal triple bond. The CpMoMoCp axis is non-linear.