Synthesis and reactivity of Ir(CO)(eta(2)-C2R2)(eta(5)-C9H7) (R=Ph, Tol). Alkyne coupling and arene C-H bond activation forming a substituted butadiene ligand

The reaction of Ir(CO)(eta(2)-C8H14)(eta(5)-C9H7) with excess C2R2 (R = Ph, Toll in benzene at reflux leads to a mixture containing Ir(CO)(eta(2)-C2R2)(eta(5)-C9H7) (1a, R = Ph; 1b, R = Tall, Ir-2(CO)(2)(mu-C2R2)(eta(5)-C9H7)(2) (2a, R = Ph; 2b; R = Tol), and Ir(eta(4)-HC4R4R')(eta(5)-C9H7) (3a, R = Ph, R' = Ph; 3b, R = Tol, R' = Ph). Conducting the reaction in benzene-d(6), toluene, or m-xylene leads to 1 and 2 and Ir(eta(4)-DC4R4R')(eta(5)-C9H7) (3c, R = Tol, R' = C6D5) or Ir(eta(4)-HC4R4R')(eta(5)-C9H7) (3d, R = Ph, R' = C6H4Me; 3e, R = Ph, R' = C6H3Me2; 3f, R = Tol, R' = C6H4Me). The structures of compounds 2a and 3b have been determined by X-ray diffraction. Compound 2a contains a dimetallacyclobutene framework with the CO Ligands adopting a trans orientation with. respect to the Ir2C2 mean plane. The indenyl Ligands take positions opposite the carbonyls at each Ir center. Compound 3b contains a 1-phenyl-1,2,3,4-tetratolyl-1,3-butadiene ligand formed through both alkyne coupling and CH bond activation of the solvent benzene, The direct reactions of 1 with excess Ir(CO)(eta(2)-C8H14)(eta(5)-C9H7) or C2R2 lead to higher yields of 2 or 3, respectively.