Solid-state NMR and EXAFS spectroscopic characterization of polycrystalline copper(I) O,O′-dialkyldithiophosphate cluster compounds:: Formation of copper(I) O,O′-diisobutyldithiophosphate compounds on the surface of synthetic chalcocite

A number of polycrystalline copper(I) O,O'-dialkyldithiophosphate cluster compounds with Cu-4, Cu-6, and Cu-8 cores were synthesized and characterized by using extended X-ray absorption fine-structure (EXAFS) spectroscopy. The structural relationship of these compounds is discussed. The polycrystalline copper(i) O,O'-diisobutyldithiophosphate cluster compounds, [Cu-8{S2P(OiBu)(2),}(6)(S)] and [CU6{S2P(OiBU)(2)}(6)], were also characterized by using P-31 CP/MAS NMR (CP = cross polarization, MAS = magic-angle spinning) and static Cu-65 NMR spectroscopies (at different magnetic fields) and powder X-ray diffraction (XRD) analysis. Comparative analyses of the P-31 chemical-shift tensor, and the Cu-65 chemical shift and quadrupolar-splitting parameters, estimated from the experimental NMR spectra of the polycrystalline copper(I) cluster compounds, are presented. The adsorption mechanism of the potassium O,O'-diisobutyldithiophosphate collector, K[S2P(OiBu)(2)], at the surface of synthetic chalcocite (Cu2S) was studied by means of solid-state P-31 CP/MAS NMR spectroscopy and scanning electron microscopy (SEM). P-31 NMR resonance lines from collector-treated chalcocite surfaces were assigned to a mixture of [Cu-8{S2P(OiBu)(2)}(6)(S)] and [Cu-6- {S2P(OiBu)(2)}(6)] compounds.