Isolation of enantiomers of a range of tris(bidentate)ruthenium(II) species using chromatographic resolution and stereoretentive synthetic methods

A range of chiral building blocks of the type Δ- or Ʌ- [Ru(pp)2(CO)2]2+ {pp = bidentate ligands bpy (2,2'-bi-pyridine), phen (1,10-phenanthroline) and Me2bpy (4,4'-dimethyl-2,2'-bipyridine)} have been synthesized, and their enantiomeric purity and absolute configurations determined by CD and NMR studies. Decarbonylation using trimeth-ylamine oxide in the presence of the respective pp ligand at room temperature produced the corresponding tris-(bidentate) species [Ru(pp)3]2+ with retention of configuration at the ruthenium(II) centre. A general chromatographic technique for resolution of tris-homoleptic complexes of the type [Ru(pp)3]2+ was investigated, with the absolute configurations of the resolved complexes confirmed by CD studies, and the X-ray structural analyses of Δ-(-)-[Ru(Me2bpy)3]{(-)-O,O9-dibenzoyl-l-tartrate} and Ë-(+)-[Ru(phen)3]{(+)-O,O'-dibenzoyl-1-toluoyl-d-tartrate}. Resolution is also reported for the analogous species containing three potential bridging ligands, [Ru(bpm)3]2+ and [Ru(HAT)3]2+ (bpm = 2,2'-bipyrimidine; HAT = 1,4,5,8,9,12-hexaazaylamine triphenylene). The versatility of the chromatographic procedure was demonstrated by the resolution of a series of bis-heteroleptic complexes [Ru(pp)2(pp9)]2+ {pp9 = dpq (dipyrido[3,2-d:2,3'-f]quinoxaline), dpqc (dipyrido[3,2-a:2,3-d]-6,7,8,9-tetrahydrophenazine), and dppz {dipyrido[3,2-a:2,3'-d]phenazine)}.