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)A, 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.