Syntheses, Characterization, and Catalytic Ability in Alkane Oxygenation of Chloro(dimethyl sulfoxide)ruthenium(II) Complexes with Tris(2-pyridylmethyl)amine and Its Derivatives^1,2

New ruthenium(II) complexes having a tetradentate ligand such as tris(2-pyridylmethyl)amine (TPA), tris[2-(5-methoxycarbonyl)pyridylmethyl]amine [5-(MeOCO)₃-TPA], tris(2-quinolylmethyl)amine (TQA), or bis(2-pyridylmethyl)glycinate (BPG) have been prepared. The reaction of the ligand with [RuCl₂(Me₂SO)₄] resulted in a mixture of trans and cis isomers of the chloro(dimethyl sulfoxide-κS)ruthenium(II) complexes containing a TPA or a BPG, whereas a trans(Cl,N_amino) isomer was selectively obtained for 5-(MeOCO)₃-TPA and TQA. The trans and cis isomers of the [RuCl(TPA)(Me₂SO)]⁺ complex were easily separated by fractional recrystallization. The molecular structures of trans- and cis(Cl,N_amino)-[RuCl(TPA)(Me₂SO)]⁺ complexes and the trans(Cl,N_amino)-[RuCl{5-(MeOCO)₃-TPA}(Me₂SO)]⁺ complex have been determined by X-ray structural analyses. The reaction of TPA with [RuCl₂(PhCN)₄] gave a single isomer of the chloro(benzonitrile)ruthenium(II) complex, whereas the bis(benzonitrile)ruthenium(II) complex was obtained with BPG. The cis(Cl,N_amino)-[RuCl(TPA)(Me₂SO)]⁺ complex is thermodynamically much less stable than the trans isomer and isomerizes in dimethyl sulfoxide at 65−100 °C. Oxygenation of alkanes catalyzed by these ruthenium(II) complexes has been examined. The chloro(dimethyl sulfoxide-κS)ruthenium(II) complexes with TPA and its derivatives using m-chloroperbenzoic acid as a cooxidant showed high catalytic ability. Adamantane was efficiently and selectively oxidized to give 1-adamantanol up to 88%. The chloro(dimethyl sulfoxide-κS)ruthenium(II) complex with 5-(MeOCO)₃-TPA was found to be the most active catalyst among the complexes examined.