Solid-state 31P CP/MAS and static 65Cu NMR characterization of polycrystalline copper(I) dialkyldithiophosphate clusters

Luleå University of Technology, Division of Chemistry, SE 971 87 Luleå, Sweden.
Journal of Magnetic Resonance (Impact Factor: 2.51). 04/2006; 179(1):140-5. DOI: 10.1016/j.jmr.2005.10.013
Source: PubMed


Polycrystalline tetra-nuclear Cu4[S2P(O-i-C3H7)2]4, hexa-nuclear Cu6[S2P(OC2H5)2]6, and octa-nuclear Cu8[S2P(O-i-C4H9)2]6(S) complexes were synthesized and analyzed by means of solid-state 31P CP/MAS and 65Cu static NMR spectroscopy. The symmetries of the electronic environments around each P-site were estimated from the 31P chemical shift anisotropy (CSA) parameters, Deltaaniso and eta. The 65Cu chemical shift and quadrupolar splitting parameters obtained from the experimental 65Cu NMR spectra of the polycrystalline Cu(I)-complexes are presented. A solid-state NMR approach for the elucidation of the stereochemistry of poly-nuclear Cu(I) dithiophosphate complexes, when the structural analysis of the systems by single-crystal X-ray diffraction is not readily available, is proposed.

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    ABSTRACT: A number of polycrystalline copper(I) O,O'-dialkyldithiophosphate cluster compounds with Cu4, Cu6, and Cu8 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, [Cu8{S2P(OiBu)2}6(S)] and [Cu6{S2P(OiBu)2}6], were also characterized by using 31P CP/MAS NMR (CP = cross polarization, MAS = magic-angle spinning) and static 65Cu NMR spectroscopies (at different magnetic fields) and powder X-ray diffraction (XRD) analysis. Comparative analyses of the 31P chemical-shift tensor, and the 65Cu 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 31P CP/MAS NMR spectroscopy and scanning electron microscopy (SEM). 31P NMR resonance lines from collector-treated chalcocite surfaces were assigned to a mixture of [Cu8{S2P(OiBu)2}6(S)] and [Cu6{S2P(OiBu)2}6] compounds.
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    ABSTRACT: Polycrystalline octa-nuclear copper(I) O,O′-di-i-propyl- and O,O′-di-i-amyldithiophosphate cluster compounds, {Cu8[S2P(OR)2]6(μ8-S)} where R=iPr and iAm, were synthesized and characterized by 31P CP/MAS NMR at 8.46T and static 65Cu NMR at multiple magnetic field strengths (7.05, 9.4 and 14.1T). The symmetries of the electronic environments around the P sites were estimated from the 31P chemical shift anisotropy (CSA) parameters, δaniso and η. Analyses of the 65Cu chemical shift and quadrupolar splitting parameters for these compounds are presented with the data being compared to those for the analogous octa-nuclear cluster compounds with R=nBu and iBu. The 65Cu transverse relaxation for the copper sites in {Cu8[S2P(OiPr)2]6(μ8-S)} and {Cu8[S2P(OiAm)2]6(μ8-S)} was found to be very different, with a relaxation time, T2, of 590μs (Gaussian) and 90μs (exponential), respectively. The structures of {Cu4[S2P(OiPr)2]4} and {Cu8[S2P(OiPr)2]6(μ8-S)} cluster compounds in the liquid- and the solid-state were studied by Cu K-edge EXAFS. The disulfide, [S2P(OiAm)2]2, was obtained and characterized by 31P{1H} NMR. The interactions of the disulfide and of the potassium O,O′-di-i-amyldithiophosphate salt with the surfaces of synthetic chalcocite (Cu2S) were probed using solid-state 31P NMR spectroscopy and only the presence of copper(I) dithiophosphate species with the {Cu8[S2P(OiAm)2]6(μ8-S)} structure was observed.
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