Xanthate complexes of {Nb2S4}4+

Alkyl xanthate complexes [Nb2S4(S2COR)4] (R = Et (I), iso-Pr (II), n-Bu (III), and iso-Am (IV)) are synthesized by the ligand exchange reaction in solutions from (Et4N)4[Nb2S4(NCS)8] and the corresponding potassium salts in satisfactory yields. The X-ray diffraction analyses are carried out for the isopropyl xanthate (II) and butyl xanthate (III) complexes. From the view point of mutual arrangement of chelate cycles, complexes II and III exist in crystals as ΛΔ isomers. The niobium-niobium distances are 2.8789(4) A in complex II and 2.8856(3) A in complex III. The first example for the formation of short S...S contacts between the disulfide ligands of the {Nb2S4}4+ fragments in the crystal structure of III is found (3.146 A).