C−H versus C−C Activation of Biphenylene in Its Reactions with Iron Group Carbonyl Clusters

Co-thermolysis of biphenylene ((C6H4)2) with Fe3(CO)12 or Fe2(CO)9 leads to activation of a biphenylene C-C bond to generate Fe2(CO)5(μ-CO)(μ-η,η-(C6H4)2) (1). Similar reaction with Ru3(CO)12 affords Ru2(CO)5(μ-CO)(μ-η,η-(C6H4)2) (2) and Ru6(CO)17(μ6-C) (3), and the reaction with Os3(CO)12 affords Os2(CO)6(μ-η,η-(C6H4)2) (4) and Os4(CO)12(μ4-η-(C6H3)Ph) (5). In contrast, treating biphenylene with Os3(CO)10(NCMe)2 leads to C-H bond activation to give (μ-H)2Os3(CO)9(μ3-η-C6H2(C6H4)) (6). The new compounds have been characterized by elemental analyses and mass, IR, and NMR spectroscopy. The structures of 2, 4, and 5 were determined by an X-ray diffraction study. Compound 2 and 4 can be viewed to contain a metallacyclopentadienyl unit which binds the other metal atom in an η5-fashion. Compound 5 is the first butterfly cluster of the type Os4(CO)12(aryne).