Investigating the reactivity of neutral water-soluble Ru(ii)–PTA carbonyls towards the model imine ligands pyridine and 2,2′-bipyridine

Abstract

As a continuation of our strategy for preparing new Ru(II) precursors to be exploited as building blocks in the construction of metal-mediated supramolecular assemblies with improved solubility in water, here we describe the reactivity of selected neutral Ru(II)–PTA carbonyls (PTA = 1,3,5-triaza-7-phosphaadamantane) towards the model imine ligands pyridine (py) and 2,2′-bipyridine (bpy) and the preparation and characterization of several neutral and cationic water-soluble derivatives: trans,trans,trans-[RuCl₂(CO)(py)(PTA)₂] (7), cis,cis,trans-[RuCl₂(CO)₂(py)(PTA)] (9), cis,trans-[Ru(bpy)Cl(CO)(PTA)₂]Cl (10), mer-[Ru(bpy)(CO)(PTA)₃](Cl)₂ (12), cis,trans-[Ru(bpy)(CO)₂Cl(PTA)]Cl (13), cis,trans-[Ru(bpy)(CO)₂(PTA)₂](NO₃)₂ (14NO₃). In addition, we found that light-induced isomerization in some bpy compounds could be induced. The following species, either side-products isolated in low yield or compounds obtained exclusively in solution, were also unambiguously identified: cis,cis,trans-[RuCl₂(CO)(py)(PTA)₂] (8), trans-[RuCl₂(bpy)(CO)(PTA)] (11), cis,cis-[Ru(bpy)Cl(CO)(PTA)₂]Cl (15) and cis,cis-[Ru(bpy)(CO)₂Cl(PTA)]Cl (16). The X-ray structures of 7, 11·H₂O, and 12·7H₂O are also reported. All compounds are new and – with few exceptions – show a good solubility in water.