Competition studies on the activation of the C_H bond of diazines by the unsaturated triangular cluster anion [Re3(μ-H)4(CO)10]−

Abstract

The reactions of the unsaturated cluster anion [Re 3 ( -H) 4 ]1 with 1,3-diazine at room temperature gives two orthometallated isomers 6, corresponding to the metallation of carbon C2 (6a) and C6 (6b), respectively (6b/6a ratio ca. 1.2). Differently from what previously found for the analogous cluster anion containing orthometallated pyridine, the metallation reaction of diazines showed little reversibility, and poor conversion of 5 and 6 to the starting anion 1 was observed after several days under 100 atm of H 2 . Competition experiments, performed by dissolving [NEt 4 ]1 in equimolar mixtures of pyridine/pyrazine or pyridine/pyrimidine, showed that the anion with metallated pyridine was the kinetically preferred product and that at longer times it slowly converted to the derivatives with metallated diazines (5 or 6).