Post-coordination functionalisation of pyrazolyl-based ligands as a route to polynuclear complexes based on an inert RuIIN6core

Abstract

The simple mononuclear complex [Ru(H2bpp)2][PF6]2 [H2bpp = 2,6-bis(pyrazol-3-yl)pyridine] contains four coordinated pyrazolyl ligands which each have a reactive NH site at the position adjacent to the coordinated N atom. Alkylation of these with either 2-[1-{4-(bromomethyl)benzyl}-1H-pyrazol-3-yl]pyridine or 4′-[(4-bromomethyl)phenyl]terpyridine allows attachment of four additional chelating groups, either bidentate pyrazolyl–pyridine and terdentate terpyridyl units, respectively, which are pendant from the central kinetically inert RuIIN6 complex core. These functionalised mononuclear complexes [Ru(L1)2][PF6]2 (with four pendant pyrazolyl–pyridine bidentate sites) and [Ru(L2)2][PF6]2 (with four pendant terpyridyl sites) can be used as the starting point for polynuclear assemblies by attachment of additional labile metal ions as the secondary sites. As examples of this we prepared and structurally characterised the trinuclear complex [RuAg2(L1)2][ClO4]4, an unusual example of a polynuclear helicate containing a kinetically inert metal centre, and the pentanuclear complex [RuCu4(MeCN)5(H2O)1.5(L2)2](SbF6)6(BF4)4 in which each of the pendant terpyridyl sites of the [Ru(L2)2]2+ core is coordinated to a Cu(II) ion.