Lantern-type dinuclear Cr(III)Pt-II and V(IV)Pt-II complexes bridged by pyridine-2-thiolate. Synthesis and characterization

Reaction of complex [Pt(4-Hmpyt)(4)]Cl-2 with Na[CrO(hmp)(2)] in toluene gave the lantern-type binuclear [ClCr(4-mpyt)(4)Pt] 1 (4-Hmpyt = 4-methylpyridine-2-thiol; H(2)hmp = 2-hydroxy-2-methylpropionic acid). The Cl- ligand of 1 was readily replaced by OH- to give [(HO)Cr(4-mpyt)(4)Pt] 2. [OV(L)(4)Pt] type complexes (L = 4-mpyt 3a; L = pyt 3b) were obtained from the reaction of [Pt(LH)(4)]Cl-2 with [VO(acac)(2)] (Hpyt = pyridine-2-thiol; acac = acetylacetonato) in toluene at 160 degrees C in the presence of KHCO3. Compounds 1, 2.2CH(3)CN and 3a were characterized by single-crystal X-ray crystallography. These complexes have a common XM(4-mpyt)(4)Pt core (M = Cr, X = Cl (1), OH (2); M = V, X = O (3a)) in which the 4-mpyt ligands bridge the Pt and M atoms to give a square-planar PtS4 and a square-pyramidal MN4X co-ordination sphere. The core has a crystallographically imposed 4-fold axis (2.2CH(3)CN, 3a) or an approximate one (1). In the crystal structure of 1 a pair of [ClCr(4-mpyt)(4)Pt] units are combined to form a dimer through two Pt ... S interactions (2.89(1) and 3.30(1) Angstrom) between the PtS4 planes of the respective monomers. The M ... Pt distances range from 2.497(2) to 2.604(7) Angstrom. The cyclic voltammogram (CV) of 1 in CH3CN shows a reversible wave for [ClCr(4-mpyt)(4)Pt](0/-1) with E-1/2 = -1.12 V vs. Ag/Ag+, whereas 2 gives an irreversible reduction peak at -1.90 V and reoxidation peaks at -1.12 V. Addition of hydrochloric acid, however, results in a dramatic change of the CV pattern to exhibit a reversible wave at E-1/2 = -1.12 V, the shape and potential are similar to those of 1 indicating the generation of [ClCr(4-mpyt)(4)Pt] by replacement of OH ligand by HCl.