Oxidative Coordination versus C3 -C(O)Me Bond Cleavage in Acetylacetonate Iridium Complexes

Abstract

Iridabicycles [Ir{κ³ -N,C,O-(pyC(H)=C(C(O)Me)₂ }(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)}₂ ] and [{Ir(μ-Cl)(coe)₂ }₂ ] (coe=cis-cyclooctene), the latter in the presence of bipy. Remarkably, cleavage of the C³ -C(O)Me bond of L1 has instead been achieved in the reaction with [Ir(Cl)(dmb)₂ ] (dmb=2,3-dimethylbutadiene), yielding a compound formulated as [Ir{κ² -N,C-(pyC(H)C(C(O)Me))}(CO)(μ-Cl)(Me)]₂ , 2. Treatment of dimer 2 with DMSO or PMe₃ produced the complexes[Ir{κ² -N,C-(pyC(H)C(C(O)Me)}(CO)Cl(Me)L] (L=DMSO, 3 a; PMe₃ , 3 b). Plausible mechanisms for the reactions leading to complexes 1 and 2 are proposed by means of DFT calculations.

Keywords: C−C bond cleavage; coordinative oxidation; iridabicycles.