Synthesis and characterization of ruthenium(II) complexes bearing the bis(2-pyridylmethyl)amine ligand

The reaction of [Ru(CO)2Cl2]n with bis(2-pyridylmethyl)amine (bpma) in refluxing ethanol followed by anion exchange yields two products: cis,fac-[Ru(bpma)(CO)2Cl]PF6 (1a, 71%) and trans,fac-[Ru(bpma)(CO)2Cl]PF6 (1b, 29%). Reaction of 1a with AgBF4 in acetone, followed by acetonitrile and then anion exchange gave cis,fac-[Ru(bpma)(CO)2(CH3CN)](PF6)2 (2a). In the same way, 1b afforded trans,fac-[Ru(bpma)(CO)2(CH3CN)](PF6)2 (2b). Reaction of depolymerized [Ru(CO)2Cl2]n with bpma in ethanol at room temperature afforded cis,cis-[Ru(η2-bpma)(CO)2Cl2] (3). In refluxing ethanol, 3 was converted to cis,fac-[Ru(bpma)(CO)2Cl]Cl (1a-Cl). Heating 3 in chlorobenzene afforded 1b-Cl, exclusively; heating 3 in ethylene glycol gave mainly 1a-Cl. Heating 1a-Cl in ethanol resulted in no isomerization, but heating in chlorobenzene gave a mixture of 3 and 1b-Cl. Anion exchange for PF6 with 1a-Cl and 1b-Cl afforded 1a and 1b, respectively, whereas anion exchange for BPh4 afforded 1a-BPh4. Compounds 1a, 1b, 2a and 3 have been structurally characterized.