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

A polycrystalline copper(1) O,O'-di-n-butyldithiophosphate cluster compound, Cu-8[S2P(O-n-Bu)(2)](6)(mu(8)-S), was synthesized and characterized by P-31 CP/MAS NMR at 8.46 T and static Cu-65 NMR at multiple magnetic field strengths (7.05, 9.4 and 14.1 T). The principal values of the P-31 chemical shift tensor and the Cu-65 chemical shift and quadrupolar splitting parameters are presented. The data are compared to those for the analogous octa-nuclear cluster compounds [Cu-8(S2P(OEt)(2))6(mu(8)-S)], [Cu-8(S2P(O-n-Pr)(2))(6)(mu(8)-S)] and [Cu-8(S2P(O-i-Bu)(2))(6)(mu(8)-S)]. The transverse relaxation time constant, T-2, for the [Cu-8(S2P(O-n-Bu)(2))(6)(mu(8)-S)] cluster compound was found to be 160 +/- 8 ps. 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 Cu-65 NMR responses of the systems. (c) 2006 Elsevier B.V. All rights reserved.