Electron-Rich Trichlorogermyl Complexes of Molybdenum and Tungsten Bearing a Cyclopentadienyl Ligand:  Synthesis, Crystal Structures, and Cyclic Voltammetric Studies

Oxidative decarbonylation of cis-(η⁵-C₅R₅)M(CO)₂(PMe₃)Cl (1a−1d) (a, R = H, M = Mo; b, R = H, M = W; c, R = Me, M = Mo; d, R = Me, M = W) with 1 equiv of PhICl₂ yields selectively the M(IV) complexes (η⁵-C₅R₅)M(CO)(PMe₃)Cl₃ (2a−2d). Complex 1c reacts with 1.5 equiv of PhICl₂ and complex 2d with 0.5 equiv of PhICl₂ to give respectively Cp*Mo(PMe₃)Cl₄ (3c) and Cp*W(PMe₃)Cl₄ (3d) (Cp* = C₅Me₅) in quantitative yield. Complex 2d can also be prepared from Cp*W(CO)₃Cl (4d) in two steps. The first step involves an oxidation of 4d with 1 equiv of PhICl₂ to yield selectively Cp*W(CO)₂Cl₃ (5d) followed by a CO ligand exchange reaction of 5d with PMe₃. Reduction of 2a−2d with Na/Hg affords in the presence of PMe₃ the M(II) chloro complexes trans-(η⁵-C₅R₅)M(CO)(PMe₃)₂Cl (6a−6d) in high yield. Complexes 6a−6d rapidly insert GeCl₂ into the metal−chlorine bond to give selectively the “electron-rich” trichlorogermyl complexes trans-(η⁵-C₅R₅)M(CO)(PMe₃)₂GeCl₃ (7a−7d). The crystal structures of CpW(CO)(PMe₃)Cl₃·MeCN (Cp = C₅H₅) (2b-1), CpW(CO)(PMe₃)Cl₃·0.5THF (2b-2), 6d, and 7b are presented, and the cyclic voltammetric data of the complexes 6b−6d and 7a−7d are compared.