Trimetallic complexes featuring Group 10 tetracyanometallate dianions as bridging ligands

Abstract

The trimetallic complexes {Ru(PPh 3) 2Cp} 2{μ-M(CN) 4} and {Ru(dppe)Cp*} 2{μ-M(CN) 4} (M = Ni, Pd, Pt) have been prepared from reactions of RuCl(PPh 3) 2Cp or RuCl(dppe)Cp* with the appropriate tetracyanometallate salt, and structurally characterised. While a similar reaction of FeCl(dppe)Cp with K 2[Pt(CN) 4] afforded {Fe(dppe)Cp} 2{μ-Pt(CN) 4}, the iron cyanide complex Fe(CN)(dppe)Cp was isolated as the only iron containing product from reaction of FeCl(dppe)Cp with K 2[Ni(CN) 4]. The trimetallic complexes can be oxidised in two sequential one-electron steps. Spectroelectrochemical experiments reveal weak NIR absorption bands in the mono-oxidised complexes which are not present in the binuclear complex K[Ru(dppe)Cp*{Pt(CN) 4}], and are therefore attributed to Ru II → Ru III charge transfer processes. The coupling parameter, V ab, extracted using Hush-style analysis falls in the range 250 ± 50 cm −1, consistent with the weak interaction between the Group 8 metal centres. The energy of the IVCT process is dominated by reorganisation energy of the Group 8 metal–ligand fragment.