LINEAR AND CYCLIC PLATINUM SIGMA-ACETYLIDE COMPLEXES OF TETRAETHYNYLETHENE

The syntheses of the first organometallic mono- and dinuclear platinum complexes bearing the tetraethynylethene unit as an eta(1)-ligand are reported, Structural characterization of two of the trans sigma-bis(acetylide) derivatives by X-ray crystallography reveals coplanarity of the acetylenic pi-ligands and indicates possible electronic delocalization across the metal center. This notion is further supported by comparing the electronic absorption spectra of the platinum-containing compounds with those of related tetraethynylethene derivatives without metals. The solid-state structure of a dinuclear complex with two iodoplatinum fragments attached to one set of geminal acetylenes of tetraethynylethene was also investigated by X-ray diffraction. Hay coupling of a mononuclear species leads to the incorporation of the sigma-bis(acetylide) moiety into a diplatinated metallacycle. This macrocyclic compound represents a novel structural motif in the design of a transition metal linked carbon network based on tetraethynylethene.