Synthesis of Chiral Cationic (Diimino- and diaminodiphosphane)ruthenium Complexes and Their Applications in Catalytic Oxidation (see abstract)

Halide abstraction of trans-[RuCl₂{κ ⁴-(1R,2R)-PNNP}] {(1R,2R)-PNNP = (1R,2R)-N,N′ -bis[2-(diphenylphosphanyl)-benzylidene]-1,2-diiminocyclohexane} and trans-[RuCl₂{κ⁴-(1R,2R)-P(NH)(NH)P}] {(1R,2R)-P(NH)(NH)P = (1R,2R)-N,N′ -bis[2-(diphenylphosphanyl)benzylidene]-1,2-diaminocyclohexane} with AgBF ₄ in acetonitrile at ambient temperature gave cis-[RuCl(CH ₃CN){κ⁴-(1R,2R)-PNNP}][BF₄] (1) and cis-[RuCl(CH₃CN){κ⁴-(1R,2R)-P(NH)(NH)P}][BF ₄] (2), respectively. When I was refluxed in pyridine (py), the coordinated CH₃CN was replaced by pyridine to form cis-[RuCl(py){κ⁴-(1R,2R)-PNNP}][BF₄] (3). However, when 2 was refluxed in pyridine, one of the amino moieties (-CH ₂-NH-)was oxidized to an imino moiety (-CH=N-) with concomitant displacement of the coordinated CH₃CN by pyridine to produce cis-RuCl(py){κ⁴-(1R,2R)-P(N)(NH)P}][BF₄] (4). The structures of 3 and 4 were ascertained by X-ray crystallography. Compounds 1-4 are effective catalysts for the epoxidation of various olefins with air. A turnover frequency of up to 733 h^-1 and an enantiomeric excess of up to 24% were obtained for the epoxidation of styrene catalysed by 2. Compound 2 can also catalyse the epoxidation, dehydrogenation and C-H activation of various olefins, alcohols and alkanes by tert-butyl hydroperoxide with high chemical selectivity.