New bis(pyranodithiolene) tungsten(IV) and (VI) complexes as chemical analogues of the active sites of tungsten enzymes

First examples of tungsten complexes, (Et4N)2[WO(L0)2]((Et4N)2 [1a]) and (Et4N)2[WO2(L0)2]((Et4N)2 [1b]), containing pyranodithiolene were synthesized as new models of reaction center of tungsten enzymes. The complexes were characterized by IR, UV–Vis, Raman spectroscopies, and cyclic voltammogram (CV). The crystal structures were determined by X-ray crystallography. The pyrane ring affected the Wdouble bond; length as m-dashO bond stretchings in 1a and 1b, the redox potential of 1a, and LMCT bands of 1b.