Synthesis and reactivity of trinuclear complexes of platinum containing the single bridging ligand SC4H8. Molecular structure of [NBu4]2[trans-PtCl2{(µ-SC4H8)Pt(C6F5)3}2]

Abstract

Trinuclear complexes of the type [NBu₄]₂[trans-PtX₂{(µ-SC₄H₈)Pt(C₆F₅)₃}₂](X = Cl,Br,I, or C₆F₅;SC₄H₈= tetrahydrothiphene)(1)–(4) have been prepared form trans-[PtX₂(SC₄H₈)₂] and NBu₄[Pt(C₆H₅)₃(OCMe₂)](molar ratio 1:2). The SC₄H₈ ligands act as the single bridge between the central platinum atom and the two terminal ones. Attemps to prepare similar trinuclear complexes with singly bridging halide ligands failed since the reaction between trans-[PtCl₂(py)₂](py = pyridine) and NBu₄[Pt(C₆F₅)₃(OCMe₂)](molar ratio 1:2) does not take place, while trans-[Ptl₂(py)₂] or [PtBr₂(cod)](cod = cyclo-octa-1,5-diene), under similar conditions, yield cis-[Pt(C₆F₅)₂(py)₂] and [NBu₄]₂[Pt₂(µ-I)₂(C₆F₅)₄] or [Pt(C₆F₅)₂(cod)] and [NBu₄]₂[Pt₂(µ-Br)₂(C₆F₅)₄] respectively. The trinuclear derivatives (1) and (3) react with neutral ligands L to give different mononuclear complexes, depending on the ligand L: when L = PPh₃, NBu₄[Pt(C₆F₅)₃(SC₄H₈)] and cis-[PtX₂(PPh3)2]; when L = CO, NBu₄[Pt(C₆F₅)₃(CO)] and trans-[PtCl₂(SC₄H₈)₂]. The molecular structure of [NBu₄]₂[trans-PtCl₂{(µ-SC₄H₈)Pt(C₆F₅)₃}₂] has been established by a single-crystal X-ray diffraction study. The compound forms triclinic cryctals in the space group P, with Z= 1 and unit-cell dimensions a= 12.463(3), b= 12.487(3), c= 15.137(3)Å, α= 85.68(15), β= 66.04(2), and γ= 87.04(1)°. The structure was refined to R= 0.048 and R′= 0.048. The central platinum atom in the trinuclear anion [trans-PtCl₂{(µ-SC₄H₈)Pt(C₆F₅)₃}₂]^2– lies on a crystallographic centre of symmetry and is bonded to two Cl atoms and two S atoms (from two SC₄H₈ ligands), the latter acting as bridging ligands between the central and the terminal Pt atoms.