Syntheses and Structural Characterizations of Mononuclear and Dinuclear Platinum(II) Terpyridyl Acetylide Complexes

Abstract

Six mononuclear and dinuclear platinum(II) terpyridyl acetylide complexes were synthesized and structurally characterized by using single crystal X-ray diffraction. They are [(tpy)Pt−C≡C-SiMe3]PF6 (1, tpy=terpyridine), [(tpy)Pt−C≡CH]PF6 (2), [(tpy)Pt−C≡C–C10H7]PF6 (3, C10H7=1-naphthyl), [(tpy)Pt−C≡C–C14H9]PF6 (4, C14H9=9-anthryl), [(tpy)Pt−C≡C–C10H6-C≡C−Pt(tpy)](CuICl2I) (5, C10H6=1,8-naphthyl), and [(tpy)Pt−C≡C–C14H8-C≡C−Pt(tpy)](PF6)2 (6, C14H8=1,8-anthryl). As catalyzed by copper(I) iodide, reactions of Pt(II) terpyridyl complex [Pt(tpy)Cl]PF6 and corresponding alkynes gave mononuclear complexes 1 (with trimethylsilylacetylene), 3 (with 1-ethynylnaphthalene), 4 (with 9-ethynylanthracene), and gave dinuclear complexes 5 (with 1,8-diethynylnaphthalene) and 6 (with 1,8-diethynylanthracene), respectively. Complex 2, which contains the simplest −C≡CH acetylide ligand, was obtained by removing the trimethylsilyl group in complex 1 through deprotection with tetrabutylammonium fluoride. In all these complexes, the Pt(II) centers are coordinated by a tpy ligand through three N atoms and by an acetylide ligand through a C atom to give a distorted square-planar geometry. In mononuclear complexes 1–4, with Pt⋅⋅⋅Pt and π–π interactions, these square-planar Pt(II) terpyridyl molecules stack with a head-to-tail arrangement to give one-dimensional chains in the solid state. Structural analysis showed that the packing of these Pt(II) terpyridyl molecules in the solid state is largely controlled by the acetylide group through steric effects and π–π interactions. In dinuclear complexes 5–6, the two square-planar Pt(II) terpyridyl units in the same molecule have a face-to-face arrangement, although molecules of 5–6 also stack with a head-to-tail arrangement to give one-dimensional chains in the solid state. The rarely observed face-to-face arrangement of two square-planar Pt(II) terpyridyl units is realized by using pre-organized and rigid dinucleating ligands 1,8-diethynylnaphthalene and 1,8-diethynylanthracene.