Copper Zinc Thiolate Complexes as Potential Molecular Precursors for Copper Zinc Tin Sulfide (CZTS).

Five copper zinc thiolate complexes [(iPr3 PCu)2 (ZnEt2 )(edt)]2 (1-Et), [(iPr3 PCu)2 (Zn(iPr)2 )(edt)]2 (1-iPr), [(iPr3 PCu)4 (edt)2 (ZnMe2 )]2 (2), [(iPr3 PCu)3 (ZnPh2 )(ZnPh)(edt)2 ]2 (3), and [(iPr3 PCu)2 Zn2 (edt)3 ]6 (4) were prepared by the reaction of [(iPr3 PCu)2 (edt)]2 with ZnR2 (R=Me, Et, Ph, iPr) with or without addition of ethanedithiol (edt2- =ethane-1,2-dithiolate). The molecular structures of these complexes were determined by single crystal X-ray diffraction. The ethanedithiolate ligands coordinate in μ3 -η1 :η2 :η1 (2, 4), μ4 -η1 :η1 :η2 :η1 (1-R, 3), and μ5 -η1 :η1 :η2 :η1 :η1 (2) bridging modes, each sulfur atom binds to two or three metal atoms. Evidence for the presence of the weak Zn-S bonds in solution was provided by NMR spectroscopy. Mixtures of 1-Et, 1-iPr, or 3 with Sn(edt)2 were examined by thermogravimetry up to 600 °C, whereupon volatile thermolysis products were identified by mass spectrometry. In all thermolysis experiments, the formation of Cu2 ZnSnS4 as main product, besides small amounts of binary metal sulfides, was confirmed by X-ray powder diffraction (PXRD) and EDX (energy dispersive X-ray spectroscopy) analysis.