Ru(II)/Ag(I) mixed-metal complexes based on kinetically inert Ru(II) complexes with pendant binding sites as subcomponents

Abstract

The mononuclear complexes [Ru(LoPh)2](PF6)2 and fac-[Ru(L3-Py)3](PF6)2 have been prepared which contain different types of pendant binding site. In [Ru(LoPh)2](PF6)2, one ligand acts as a tetradentate chelate but the other is only bidentate such that there is one bidentate pyrazolyl-pyridine site pendant from the Ru(II) complex core. In fac-[Ru(L3-Py)3](PF6)2 in contrast there are three monodentate 3-pyridyl units pendant from the same face of the Ru(II) core. Two [Ru(LoPh)2](PF6)2 units assemble around an Ag(I) ion to give trinuclear [{Ru(LoPh)2}2Ag](PF6)5 in which the Ag(I) ion is four coordinate. In the solid state three of these associate into a triangular trimeric array via π-stacking and CH⋯F hydrogen-bonding interactions to give an assembly which contains two cup-shaped cavities either side of a central Ag3 face and pointing in opposite directions; these cavities contain H-bonded hexafluorophosphate anions. In MeCN solution at high concentrations (11mM), according to 1H NMR DOSY measurements the trinuclear complex [{Ru(LoPh)2}2Ag](PF6)5 remains intact but there is no evidence for further aggregation into the trimer. Two fac-[Ru(L3-Py)3](PF6)2 units combine with two {Ag(NCMe)}+ units and an additional Ag(I) ion to give a complex coordination network [{Ru(L3-Py)3}2{Ag(MeCN)2}2Ag](PF6)7. In this structure two fac-[Ru(L3-Py)3](PF6)2 and two {Ag(NCMe)}+ units form tetranuclear Ru2Ag2 rings via Ag–N(pyridyl) interactions; these rings are crosslinked into a one-dimensional chain by additional Ag–N(pyridyl) interactions. Argentophilic Ag⋯Ag interactions then connect the resulting chains into two-dimensional sheets. Both mixed-metal networks are based on initial formation of kinetically inert Ru(II) complexes which then associate in a separate step with Ag(I) ions, via pendant N-donor binding sites. However [{Ru(LoPh)2}2Ag](PF6)5 exploits π–π stacking and hydrogen-bonding interactions to form in the solid state a trimeric assembly which encapsulates anions; in contrast [{Ru(L3-Py)3}2{Ag(MeCN)2}2Ag](PF6)7 exploits argentophilic interactions to complete formation of the network.