Platinum Dithiolene Complexes of π-Coordinating and π-Interacting η⁴-Cyclobutadiene Ligands

Abstract

Five new organometallic platinum dithiolene complexes of the η4-cyclobutadiene ligand [(η4-C4Me4)Pt(dithiolene)] (dithiolene = mnt (2), dcmedt (3), tdt (4), dddt (5), dmit (6)) and one platinum diselenolene complex, [(η4-C4Me4)Pt(dsit)] (7), were prepared from [(η4-C4Me4)Pt(Cl)(μ-Cl)]2 (1) and Na2(mnt), OC(dcmedt), H2tdt, OC(dddt), (NBu4)2[Zn(dmit)2], or (NEt4)2[Zn(dsit)2], respectively. The (η4-C4Me4)Pt complexes 2−7 were characterized by NMR, UV−vis spectra, and CV. Those 1H and 13C NMR spectra showed 195Pt satellite coupling at the C4 Me 4 (J Pt−H = 13−15 Hz), at the C 4 Me4 (J Pt−C = ca. 100 Hz), and at the dithiolene carbons. The complexes having an electron-rich dichalcogenolene ligand (5−7) resulted in lower energy electronic absorption compared with the electron-poor series 2−4. The η4-C4Me4 ligand was replaced by the nucleophilic substitution of bis(diphenylphosphino)ethane (DPPE) to form the square-planar [Pt(dithiolene)(dppe)] complex. 2, 3, and 5−7 were structurally determined by X-ray diffraction studies. All the molecules were monomeric, had two-legged piano-stool geometries, and were formal 16-electron complexes with the PtII (d8) center. The crystal structure of 2 showed an inversion-centered dyad. 5 had η4-C4Me4···dithiolene plane-to-plane interaction in the crystal to form a zigzag chain. 6 and 7 were isostructural to each other and had intermolecular interactions through η4-C4Me4···trithiocarbonate contacts to form a zigzag chain. The η4-C4Me4 group behaves as a π-coordinating ligand and a π-interacting ligand as well. Dithiolene and diselenolene ligands used in this work were as follows: mnt = maleonitrile-1,2-dithiolate, dcmedt = 1,2-dimethoxycarbonylethylene-1,2-dithiolate, tdt = toluene-3,4-dithiolate, dddt = 5,6-dihydro-1,4-dithiine-2,3-dithiolate, dmit = 1,3-dithiol-2-thione-4,5-dithiolate, and dsit = 1,3-dithiol-2-thione-4,5-diselenolate.

Organometallic dithiolene complexes of the group 8–10 metals: Reactivities, structures and electrochemical behavior

“…6). 108 The [(h 4 -C 4 Me 4 )Pt(dsit)] complex also showed a similar interaction to the dmit complex because they are isostructural with each other (Table 2). We also reported dithiolene ◊ ◊ ◊ dithiolene dimeric interactions (e.g.…”