STRUCTURAL DETERMINATION OF [(C5H5)2MO(H)CO][(C5H5)MO(CO)3]

On the basis of an X-ray diffraction study at -125 °C, [Cp2Mo(H)CO] [CpMo(CO)3] has been established to crystallize in space group P21/c with a = 6.370 (2) Å, b = 10.226 (3) Å, c = 27.233 (11) Å, and β = 84.58 (1)°. Refinement of 3931 nonzero reflections leads to R(F) = 0.040 and Rw(F) = 0.064; all hydrogen atoms were refined. The anion CpMo(CO)3-suffers only minor distortion from a symmetric “piano stool” configuration with average distances from Mo to cyclopentadienyl and carbonyl carbons of 2.381 and 1.930 Å; the MoCO groups are within 3σ of being linear. In the cation Cp2Mo(H)CO+, the corresponding distances are 2.291 and 1.991 Å. Comparison of these parameters, as well as the C-O distances, supports the idea that back-bonding is enhanced in low oxidation states. Comparison of the structural data for Cp2Mo(H)CO+ with the corresponding values in Cp2MoH2 indicates minimal π donation from CO to Mo(IV) in the cation. © 1979, American Chemical Society. All rights reserved.