C−C Activation in Biphenylene. Synthesis, Structure, and Reactivity of (C5Me5)2M2(2,2‘-biphenyl) (M = Rh, Co)

• DOI: 10.1021/om961059a
• Publication Date: 2002-07-26T05:17:11Z
• Authors: Christophe Perthu...; Brian L. Edelbach; Deanna L. Zubris; William D. Jones
• Keywords: Biphenyl; Biphenylene; Bimetallic strip; Reactivity; Bond cleavage; Carbon fibers

Carbon−carbon bond cleavage of biphenylene was achieved with (C5Me5)M(C2H4)2 (M = Rh, Co) to give the bimetallic species (C5Me5)2M2(2,2'-biphenyl). The isomorphous solid state X-ray structures these complexes showed biphenyl substrate be σ-coordinated one metal and η4-bound other. These display dynamic behavior, interchanging σ- π-bonding. Variable-temperature NMR studies were performed on both binuclear species, energy barrier for interconversion two (C5Me5) fragments calculated ΔG⧧ (350 K) 16.8 kcal/mol (248 11.4 rhodium cobalt complexes, respectively. (C5Me5)2Rh2(2,2'-biphenyl) reacted CO (C5Me5)Rh(CO)2 (C5Me5)Rh(CO)(2,2'-biphenyl), while analog gave (C5Me5)Co(CO)2 fluorenone. (C5Me5)2Co2(2,2'-biphenyl) (C5Me5)Co(PMe3)2 (C5Me5)Co(PMe3)(2,2'-biphenyl) when PMe3, as determined by crystallography latter complex. Both found resistant hydrogenation.