SYNTHESIS AND CRYSTAL-STRUCTURE OF [MO3(MU-3-S)(MU-SSE)3(DTC)3]SECN - AN EXAMPLE OF FORMATION OF UNUSUAL POLYMERIC CHAINS BY CATION AND ANION CHALCOGEN ATOMS

The interaction of [Mo3S7(dtc)3]dtc with KSeCN gives the [Mo3S4Se3(dtc)3] SeCN salt (1) in 74% yield. The X-ray structure of 1 was determined. The [Mo3S4Se3(dtc)3]+ cation has the usual geometry, selected distances being 2.72(1)-2.73(1) angstrom for Mo-Mo, 2.16(3)-2.23(3) angstsrom for S-Se. The characteristic feature of structure 1 is the formation of rather short (2.9-3.3 angstrom) cation-anion contacts between the sulphur and selenium atoms of the mu2-SSe ligand and the selenium atom of the SeCN- counter-ion. This results in the formation of practically linear polymeric chains, S-Se...Se...S-Se...Se...S-Se.... The treatment of the (Ph4P)2W3S7Br, cluster with KSeCN and NaSCN yields the complex (Ph4P)2W3S4Se3(NCS), in 39% yield.