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 {S 2 P(O i Bu) 2 } 6 (S)] and [Cu 6 {S 2 P(O i Bu) 2 } 6 ], were also characterized by using 31 P CP/MAS NMR (CP = cross polarization, MAS = magic‐angle spinning) and static 65 Cu NMR spectroscopies (at different magnetic fields) and powder X‐ray diffraction (XRD) analysis. Comparative analyses of the 31 P chemical‐shift tensor, and the 65 Cu 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[S 2 P(O i Bu) 2 ], at the surface of synthetic chalcocite (Cu 2 S) was studied by means of solid‐state 31 P CP/MAS NMR spectroscopy and scanning electron microscopy (SEM). 31 P NMR resonance lines from collector‐treated chalcocite surfaces were assigned to a mixture of [Cu 8 {S 2 P(O i Bu) 2 } 6 (S)] and [Cu 6 {S 2 P(O i Bu) 2 } 6 ] compounds.