Electronic communications mediated by metal clusters

摘要

Two model systems [Cu-3(1)(dppm)(3)(mu(3)-eta(1)-C=-CFC)(2)].PF6 (1.PF6) and [Pt-2(1)(dppm)(2)(Cequivalent toCFC)(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 Cu-3(1) core bridged by three dppm and capped with one and two ferrocenylacetylides, respectively. Cyclic and differential pulse voltammograms of 1.PF6 show two reversible Fc oxidations separated by 110 +/- 14 mV, giving a comproportionation constant K-c of 77 +/- 30. The stability of the mixed-valence complex 1(2+) arises mainly from the reduction of electrostatic repulsion and statistical distribution. On the other hand, the Pt-Pt a-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 K-c is 3.3 x 10(4) +/- 1.5 x 10(4). Addition of a d(10) AuCl/Br fragment to the Pt-Pt bond gives rise to complexes [Pt-2(mu-AuX)(dppm)(2)(Cequivalent toCFC)(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.