Reactions of (SiMe2)(GeMe2) doubly bridged biscyclopentadiene with iron carbonyl and tungsten carbonyl

Thermal treatment of (SiMe2)(GeMe2)(C5H4)2 (1) with Fe(CO)5 in refluxing xylene provided the normal doubly bridged biscyclopentadienyl diiron tetracarbonyl complex (SiMe2)(GeMe2)[(η5-C5H3)Fe(CO)]2(μ-CO)2 (2) and the degermylated product (SiMe2)[(η5-C5H4)Fe(CO)]2(μ-CO)2 (4), together with a novel complex (SiMe2)(η5-C5H3)(η5:η1-C5H3)[(GeMe2)Fe(CO)2][Fe(CO)2)] (3) containing an Fe–Ge bond, whose formation was accompanied by migration of bridging GeMe2 group from the ligand to iron atom. Similar treatment of 1 with W(CO)6 afforded the tungsten analogue of compound 4, (SiMe2)(η5-C5H3)(η5:η1-C5H3)[(GeMe2)W(CO)3][W(CO)3)] (6) and the degermylated product (SiMe2)[(η5-C5H4)W(CO)3]2 (7). A plausible mechanism for formation of 3, and 6 was proposed. The crystal structures of 3, and 6 were determined by X-ray crystallography.

Reactions of double-bridged biscyclopentadiene (SiMe2)(GeMe2)(C5H4)2 with Fe(CO)5, and W(CO)6 were studied. The bridging group GeMe2 in the ligand generally migrated to give compounds containing an M–Ge bond (M = Fe, or W), together with the corresponding degermylated products. A plausible mechanism for formation of the former was proposed.Figure optionsDownload as PowerPoint slideHighlights
► GeMe2 in ligand migrates from one Cp ring to an Fe atom in reaction with Fe(CO)5.
► SiMe2 in ligand does not migrate in reaction with Fe(CO)5.
► Reaction of (SiMe2)(GeMe2)(C5H4)2 with W(CO)6 affords the similar results.
► Complexes containing an M–Ge bond (M = Fe, or W) were obtained by GeMe2 migration.
► A plausible mechanism for the reaction was proposed.