Electronic communications mediated by metal clusters

Two model systems [CuI3(dppm)3(μ3-η1-C≡CFc)2] ·PF6(1·PF6) and [PtI2(dppm)2(C≡CFc)2] (2) were devised to probe the ability of metal clusters in mediating electronic communications. The complexes were characterized by using single-crystal X-ray diffraction, UV-vis spectroscopy, and voltammetry (dppm = bis(diphenylphosphino)methane; Fc = ferrocenyl). The complex is composed a of trimetallic CuI3core bridged by three dppm and capped with one and two ferrocenylacetylides, respectively. Cyclic and differential pulse voltammograms of 1·PF6show two reversible Fc oxidations separated by 110 ± 14 mV, giving a comproportionation constant Kcof 77 ± 30. The stability of the mixed-valence complex 12+arises mainly from the reduction of electrostatic repulsion and statistical distribution. On the other hand, the Pt-Pt σ-bond enhances electronic interactions between the terminal Fc-groups in compound 2. The CV of the complex shows two reversible Fc-centered oxidations which are separated by 267 ± 14 mV and the Kcis 3.3 × 104± 1.5 × 104. Addition of a d10AuCl/Br fragment to the Pt-Pt bond gives rise to complexes [Pt2(μ-AuX)(dppm)2(C≡CFc)2] [X = Cl (3) and Br (4)]. The two Fc-oxidations are not resolved in the CV of the complexes, indicating that the electronic communication is shut down.