C-H VERSUS C-C ACTIVATION OF BIPHENYLENE IN ITS REACTIONS WITH IRON-GROUP CARBONYL CLUSTERS

Co-thermolysis of biphenylene ((C6H4)(2)) with Fe-3(CO)(12) or Fe-2(CO )(9) leads to activation of a biphenylene C-C bond to generate Fe-2(CO )(5)(mu-CO)(mu-eta(2),eta(4)-(C6H4)(2)) (1). Similar reaction with RU3 (CO)(12) affords Ru-2(CO)(5)(mu-CO)(mu-eta(2),eta(4)-(C6H4)(2)) (2) an d RU6(CO)(17)(mu(6)-C) (3), and the reaction with Os-3(CO)(12) affords Os-2(CO)(6)(mu-eta(2),eta(4)-(C(6)H(4)2)) (4) and Os-4(CO)(12)(mu(4)- eta(2)-(C6H3)Ph) (5). In contrast, treating biphenylene with Os-3(CO)( 10)(NCMe)(2) leads to C-H bond activation to give (mu-H)(2)Os-3(CO)(9) (mu(3)-eta(2)-C6H2(C6H4)) (6). The new compounds have been characteriz ed by elemental analyses and mass, IR, and NMR spectroscopy. The struc tures of a, 4, and 5 were determined by an X-ray diffraction study. Co mpound 2 and 4 can be viewed to contain a metallacyclopentadienyl unit which binds the other metal, atom in an eta(5)-fashion. Compound 5 is the first butterfly cluster of the type Os-4(CO)(12)(aryne).