Synthesis, chemistry, and catalytic activity of ruthenium diaminodiphosphane complexes

The interaction of [RuCl2(PPh3)3] with one equivalent of N,N′-bis[2-(diphenylphosphanyl)benzyl]-1R,2R-cyclohexanediamine [1R,2R-P(NH)(NH)P] in dichloromethane at room temperature gave trans-[RuCl2{κ3-1R,2R- P(NH)(NH)P}(PPh3) (1). When heated under reflux in toluene under a nitrogen atmosphere, 1 was converted into trans-[RuCl2{κ4-1R,2R-P(NH)(NH)P}] (2). However, when 1 was stirred at room temperature in air, it was oxidized to trans-[RuCl2{κ3-1R,2R-PN(NH)P}(PPh3)] (3). Depending on the reaction conditions, 3 was converted into trans-[RuCl2{κ3- 1R,2R-P(NH)(NH)P=O}(PPh3)] (4) when heated to 80 °C in toluene in air, to cis-[RuCl2{κ4-1R,2R-PN(NH)P}] (5) when stirred at room temperature in acetone in air, or to trans-[RuCl2{κ4-1R,2R-PN(NH)P}] (6) when heated under reflux in acetone under a nitrogen atmosphere. When heated under reflux in toluene under a nitrogen atmosphere, 5 isomerized to 6 quantitatively. When heated under reflux in mesitylene under a nitrogen atmosphere, 6 was slowly reduced to 2. The solid state structures of 3 and 5 were ascertained by X-ray crystallography. Catalytic studies showed that 1 could catalyze the oxidation of alkanes and alkenes with molecular oxygen.