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

Co-thermolysis of biphenylene ((C 6 H 4 ) 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 (μ-CO)(μ-η 2,η 4 -(C 6 H 4 ) 2 ) ( 1 ). Similar reaction with Ru 3 (CO) 12 affords Ru 2 (CO) 5 (μ-CO)(μ-η 2,η 4 -(C 6 H 4 ) 2 ) ( 2 ) and Ru 6 (CO) 17 (μ 6 -C) ( 3 ), and the reaction with Os 3 (CO) 12 affords Os 2 (CO) 6 (μ-η 2,η 4 -(C 6 H 4)2 ) ( 4 ) and Os 4 (CO) 12 (μ 4 -η 2 -(C 6 H 3 )Ph) ( 5 ). In contrast, treating biphenylene with Os 3 (CO) 10 (NCMe) 2 leads to C−H bond activation to give (μ-H) 2 Os 3 (CO) 9 (μ 3 -η 2 -C 6 H 2 (C 6 H 4 )) ( 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 η 5 -fashion. Compound 5 is the first butterfly cluster of the type Os 4 (CO) 12 (aryne).