First Ruthenium Complex of Glyoxalbis(N-phenyl)osazone (LNHPhH2): Synthesis, X-ray Structure, Spectra, and Density Functional Theory Calculations of (LNHPhH2)Ru(PPh3)2Cl2

Abstract

The first ruthenium complex containing the parent osazone ligand, glyoxalbis(N-phenyl)osazone (LNHPhH2), is reported. The complex (LNHPhH2)Ru(PPh3)2Cl2 (1) was characterized with mass, IR, 1H NMR, and UV−vis spectroscopy as well as with theoretical calculations. Density functional theory calculations on the model compound (LNHPhH2)Ru(PMe3)2Cl2 (2) reproduce the geometrical features observed for 1 and verify that it formally contains a ruthenium(II) metal center coordinated by a neutral osazone. Subsequent bonding analyses identify π-interactions between the occupied orbitals of the metal fragment and the LUMO of the osazone, which results in transfer of approximately 0.3 electrons from the metal to the ligand. The complex 1 absorbs strongly at 405 nm, which is assigned to a ruthenium-to-ligand charge-transfer band on the basis of results of theoretical calculations. Complex 1 is also electroactive and displays a single one-electron oxidation wave at 0.39 V; coulometric oxidation gives the oxidized species [1]+ as a [PF6]- salt. Simulation of the EPR spectra of [1][PF6], a one-electron paramagnetic species, affords g-tensor parameters gx = 2.2649, gy = 2.0560, and gz = 1.9064 consistent with a ruthenium(III) description for [1]+, thereby confirming a metal-centered redox reaction.