A new class of structure for selenium(II) dithiocomplexes. The trigonal molecular structure of bis(diethyldithiophosphinato)selenium(II), [Se(S2PEt2)(2)]

The crystal and molecular structure of bis(diethyldithiophosphinato)seleniu m(II), [Se(S2PEt2)(2)], has been determined by X-ray diffractometry. The co ordination sphere displays a planar trigonal geometry around the central se lenium atom, which is strongly bonded to two monodentate dithiophosphinate ligands and weakly to one sulfur atom from a neighboring molecule. The mole cular association through this intermolecular Se ... S interaction builds u p a polymeric network. This SeS3 arrangement has not been observed in analo gous divalent sulfur, selenium or tellurium systems, and thus it may be cla ssified as a new class of structures for related systems (class VI).