Three-Dimensional Coordination Polymers of Ruthenium(2+) with 1,4-Diisocyanobenzene ligands and Their Catalytic Activity

Organometallic compounds have been playing an increasingly important role in a variety of technologically relevant fields such as catalytic processes and solid-state devices. Of special technological interest are organometallic materials which contain several metal sites, e.g., clusters. Multiple metal centers in a single complex may be achieved by utilizing multifunctional, nonchelating, rigid ligands such as aryldiisocyanides, which when coordinated to metal atoms, would act as bridges and would give rise to template polymerization. There are no studies to date concerning the coordination chemistry of the d⁶ transition elements, e.g., Ru(II), Os(II), and Rh(III) with diisocyanide ligands. Since most of the complexes of these transition metals in these oxidation states exhibit octahedral geometry, template polymerization may be obtained, resulting in three-dimensional coordination polymers. In this paper we shall examine the polymerization process of Ru(II) with 1,4-diisocyanobenzene, the physical and spectral properties of the polymers formed, and their potential catalytic activity. Depending on the starting ruthenium carbonyl complex, it is possible to obtain two distinctly different materials, both in their structure and in their catalytic properties. The first compound, polymer A, has a three-dimensional structure with a tetragonal geometry, having Ru-Ru stacking interactions in the z direction, while the second compound, polymer B, has a cubic geometry, having all the Ru atoms separated by the 1,4-diisocyanobenzene ligands. Polymer A is the catalytically active compound, in spite of exhibiting an induction period, and its activity is enhanced by UV irradiation prior to the catalytic reaction, accompanied by the elimination of the induction period.