Ru2M(dpa)4Cl2 (M = Cu, Ni): Synthesis, Characterization, and Theoretical Analysis of Asymmetric Heterometal String Complexes of the Dipyridylamide Family

Abstract

AbstractFour heterotrinuclear strings of metal atoms stabilized by dipyridylamide (dpa–) ligands were synthesized and characterized. The metal frameworks of Ru2Cu(dpa)4Cl2 (1), its monooxidized counterpart [Ru2Cu(dpa)4Cl2]PF6 (2), and their nickel homologues, Ru2Ni(dpa)4Cl2 (3) and [Ru2Ni(dpa)4Cl2]PF6 (4), were shown by X‐ray diffraction to be nonsymmetric, in spite of a severe disorder affecting the metal positions. The metal string is composed of a Ru dimer with a short Ru–Ru bond that is completed with the heterometal at a longer distance from the central ruthenium atom. This nonsymmetric structure was confirmed from NMR spectroscopy. The [Ru2M]6+ framework of 1 and 3 was shown from spectroelectrochemical analysis and DFT calculations to exist in the form of a mixed‐valent [Ru2]5+ moiety coupled to a formally M+ heterometal. The temperature‐dependant magnetic susceptibility of these compounds is reported and interpreted by means of a model previously applied to [Ru2]5+ complexes. The redox chemistry of 1 and 3 was investigated by cyclic voltammetry, and the electronic structure of the mono‐ and dioxidized species was assigned from the observed changes in the UV/Vis spectra and from DFT calculations.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)