Studies of molybdenum compounds. 6. Diaryl(2,2′-bipyridyl)dioxomolybdenum(VI) and related compounds

Article abstract of DOI:10.1021/om00092a007

The first σ-diaryl derivatives of the type R₂Mo(O)₂(bpy) (R = C₆H₅, 4-CH₃OC₆H₄, 4-CH₃C₆H₄, 4-ClC₆H₄, or 2-CH₃C₆H₄; bpy = 2,2′-bipyridyl) are described. The Mo-C bonds in these compounds are labilized through a combination of steric and electronic effects arising from interactions of the Mo=O moieties with the aromatic π-electron systems and overcrowding due to the presence of the coordinated bpy. In the complex with R = 4-CH₃OC₆H₄, the observed mean Mo-C_sp2 bond lengths of 2.202 (3) A? are similar to the mean Mo-C_sp3 bond lengths in the corresponding complex with R = C₂H₅. The aryl substituents adopt a conformation maximizing π-orbital overlap with one Mo=O moiety. This is possible only with distortions of the Mo-C-C bond angles. The π-orbital interactions affect the energies of first low-energy absorptions in the UV-vis spectra and of the IR ν_Mo=O absorptions. Crystal data for (4-CH₃OC₆H₄)₂Mo(O)₂(bpy): space group P1, a = 8.492 (2) A?, b = 11.340 (2) A?, c = 13.076 (2) A?, α = 65.8 (1)°, β = 78.9 (1)°, γ = 71.4 (1)°, Z = 2. The structure was solved and refined (2397 independent reflections above 2σ) to the final values of residual R(F_o) = 0.025 and R_w(F_o) = 0.032.