Synthesis and Characterization of Ethylbis(2-pyridylethyl)amineruthenium Complexes and Two Different Types of C–H Bond Cleavage at an Ethylene Arm

Ruthenium complexes bearing ethylbis(2-pyridylethyl)amine (ebpea), which has flexible −C2H4– arms between the amine and the pyridyl groups and coordinates to a metal center in facial and meridional modes, have been synthesized and characterized. Three trichloro complexes, fac-[RuIIICl3(ebpea)] (fac-[1]), mer-[RuIIICl3(ebpea)] (mer-[1]), and mer-[RuIICl3{η2-N(C2H5)(C2H4py)CH–CH2py}] (mer-[2]), were synthesized using the Ru blue solution. Formation of mer-[2] proceeded via a C–H activation of the CH2 group next to the amine nitrogen atom of the ethylene arm. Reduction reactions of fac- and mer-[1] afforded a triacetonitrile complex mer-[RuII(CH3CN)3(ebpea)](PF6)2 (mer-[3](PF6)2). Five nitrosyl complexes fac-[RuX2(NO)(ebpea)]PF6 (X = Cl for fac-[4]PF6; X = ONO2 for fac-[5]PF6) and mer-[RuXY(NO)(ebpea)]PF6 (X = Cl, Y = Cl for mer-[4]PF6; X = Cl, Y = CH3O for mer-[6]PF6; X = Cl, Y = OH for mer-[7]PF6) were synthesized and characterized by X-ray crystallography. A reaction of mer-[2] in H2O–C2H5OH at room temperature afforded mer-[1]. Oxidation of C2H5OH in H2O–C2H5OH and i-C3H7OH in H2O–i-C3H7OH to acetaldehyde and acetone by mer-[2] under stirring at room temperature occurred with formation of mer-[1]. Alternative C–H activation of the CH2 group occurred next to the pyridyl group, and formation of a C–N bond between the CH moiety and the nitrosyl ligand afforded a nitroso complex [RuII(N3)2{N(O)CH(py)CH2N(C2H5)C2H4py}] ([8]) in reactions of nitrosyl complexes with sodium azide in methanol, and reaction of [8] with hydrochloric acid afforded a corresponding chloronitroso complex [RuIICl2{N(O)CH(py)CH2N(C2H5)C2H4py}] ([9]).