Coordination behaviour of an unsymmetrical dithiolate with transition metals. Syntheses and properties of propane-1,2-dithiolate complexes and structures of [Ph4As]2[Mn2(1,2-pdt)4] and [Ph4P]2[Ni3(1,2-pdt)4]·2MeCN

Compounds (C)2[Mn2(1,2-pdt)4], where C = Ph4As+ (1a) or Et4N+ (1b), (Et4N)2[Fe2(1,2-pdt)4] (2) and (Ph4P)2[Ni3(1,2-pdt)4]·2MeCN (3), where 1,2-pdt = propane-1,2-dithiolate, were prepared by reaction of disodium 1,2-propanedithiolate with metal chlorides. Compound (1a) crystallizes in the orthorhombic space group Pbca with a = 10.854(2), b = 22.562(4), c = 24.545(6) A, V = 6010.8 A3, Z = 4. The structure was solved from 3003 reflections with I≥3σ(I) and refined to R(Rw) = 0.038(0.045). The two identical fragments [Mn(1,2-pdt)2]− dimerize by bridging through sulfur atoms, on from each of the monomers, to form a rectangular Mn2(μ-S)2 unit. Compound (3) crystallizes in the monoclinic space group P21/c with a = 10.802(2), b = 30.111(7), c = 9.907(3) A, β = 93.60(3)°, V = 3216.0 A3, Z = 2. The structure was refined to R(Rw) = 0.063(0.068) from 2256 reflection with I≥3σ(I). The anion of (3) is formed by chelation of two [Ni(1,2-pdt)2]2− units to a central NiII atom. The three NiS4 planes form a chair with a crystallographic centre of symmetry. Complexes (1) and (2) are paramagnetic and dissociate into monomers in solution while (3) is diamagnetic and may not dissociate. Solid state magnetic susceptibility measurements showed the ground state spins of the MnIII and FeIII ions in (1) and (2) to be S = 2 and S = 3/2, respectively, and the two metal atoms in both molecules exhibit antiferromagnetic interactions. The unsymmetrical 1,2-pdt2− ligand chelates to the metal such that the methyl substituent on the terminal carbon atom is remote from the bridging sulfur.