Spectroscopic characterization of the polycrystalline copper(I) di-n-butyldithiophosphate cluster – Cu8[S2P(O-n-Bu)2]6(μ8-S): Solid-state 31P CP/MAS and static 65Cu NMR studies

A polycrystalline copper(I) O,O′-di-n-butyldithiophosphate cluster compound, Cu8[S2P(O-n-Bu)2]6(μ8-S), was synthesized and characterized by 31P CP/MAS NMR at 8.46 T and static 65Cu NMR at multiple magnetic field strengths (7.05, 9.4 and 14.1 T). The principal values of the 31P chemical shift tensor and the 65Cu chemical shift and quadrupolar splitting parameters are presented. The data are compared to those for the analogous octa-nuclear cluster compounds [Cu8(S2P(OEt)2)6(μ8-S)], [Cu8(S2P(O-n-Pr)2)6(μ8-S)] and [Cu8(S2P(O-i-Bu)2)6(μ8-S)]. The transverse relaxation time constant, T2, for the [Cu8(S2P(O-n-Bu)2)6(μ8-S)] cluster compound was found to be 160 ± 8 μs. Possible intra-molecular motions in the cluster structures in terms of size and branching of the hydrocarbon chains are discussed as reasons for the different 65Cu NMR responses of the systems.