Oxidative Coordination versus C -C(O)Me Bond Cleavage in Acetylacetonate Iridium Complexes.

Iridabicycles [Ir{κ -N,C,O-(pyC(H)=C(C(O)Me) }(Cl)(L-L)](L-L=cod (cod=1,5-cyclooctadiene), 1 a; bipy (bipy=2,2'-bipyridine), 1 b) have been obtained by oxidative coordination of 3-(pyridine-2-yl-methylene)pentane-2,4-dione L1, to the complexes [{Ir(μ-Cl)(cod)} ] and [{Ir(μ-Cl)(coe) } ] (coe=cis-cyclooctene), the latter in the presence of bipy. Remarkably, cleavage of the C -C(O)Me bond of L1 has instead been achieved in the reaction with [Ir(Cl)(dmb) ] (dmb=2,3-dimethylbutadiene), yielding a compound formulated as [Ir{κ -N,C-(pyC(H)C(C(O)Me))}(CO)(μ-Cl)(Me)] , 2. Treatment of dimer 2 with DMSO or PMe produced the complexes[Ir{κ -N,C-(pyC(H)C(C(O)Me)}(CO)Cl(Me)L] (L=DMSO, 3 a; PMe , 3 b). Plausible mechanisms for the reactions leading to complexes 1 and 2 are proposed by means of DFT calculations.