Synthesis and structure of a dmpe-substituted dinuclear complex bridged by a substituent-free gallium atom: Electronic effect of metal fragment on the iron–gallium bonding

A dinuclear complex bridged by a substituent-free gallium atom, Cp∗(dmpe)Fe–Ga–Fe(CO)4 (1b: Cp∗ = η-C5Me5, dmpe = Me2PCH2CH2PMe2), was synthesized by the reaction of Cp∗Fe(dmpe)GaCl2 with K2[Fe(CO)4]. Crystal structure analysis of complex 1b showed that the geometry around the gallium atom is essentially linear and the two Fe–Ga bonds are significantly shorter than those of usual single bonds, indicating the multiple bonding character of the Fe–Ga bonds. Comparison of the structure and IR data of 1b and those of Cp∗(dppe)Fe–Ga–Fe(CO)4 (1a: dppe = Ph2PCH2CH2PPh2) revealed that the Fe–Ga bond is sensitive to the electronic character of the metal fragment. The Fe–Ga bond is shortened upon introducing a more π-basic metal fragment.