Cp ∗Ru(NO) (catecholate) compounds. Synthesis, redox behavior, extended Hückel molecular orbital calculations, and X-ray diffraction structure of the pentamethylcyclopentadienylruthenium complex Cp ∗Ru(NO) (2,3-naphthalenediolate)·CH 2Cl 2

Abstract

Eight new catecholate- and naphthalenediolate-substituted pentamethylcyclopentadienylruthenium, compounds have been prepared from the reaction between Cp ∗Ru(NO)Cl 2 and the appropriate aromatic diol in methanolic KOH. Each new compound has been isolated and fully characterized in solution by IR and NMR ( 1H and 13C) spectroscopy, in addition to X-ray diffraction analysis which has established the solid-state structure of the naphthalenediolate compound Cp ∗Ru(NO)(2,3-O 2C 10H 6). Cp ∗Ru(NO)(2,3-O 2C 10H 6) crystallizes, as the CH 2Cl 2 solvate, in the monoclinic space group P2 1/ n with a = 11.0176(8), b = 16.041(2), c = 13.0504(9) A ̊ , β = 112.024(6)° , V = 2138.1(3) A ̊ 3 and Z=4. Full-matrix least-squares refinement yielded R=0.0376 for 1893 ( l.3 ϱ( l)) reflections. Cyclic voltammetric studies have been carried out, and two redox responses were observed, assignable to the 0/1− and 0/1+ redox couples. Whereas the reduction wave in each of the compounds is essentially independent of the nature of the ancillary diolate ligand, the stability of the oxidation couple is modulated by the electronic properties of the diolate ligand. The molecular orbital properties of several model CpRu(NO)(diolate) compounds were explored by extended Hückel calculations. The calculated HOMO and LUMO energies of each compound displayed good agreement with the cyclic voltammetry data, allowing for generalizations to be made concerning the site of electron addition to and electron removal from the new Cp ∗Ru(NO)(diolate) compounds.