Polycrystalline octa-miclear copper(l) O,O'-di-i-propyl- and O,O'-di-i-amyldithiophosphate cluster compounds, {Cu-8[S2P(OR)(2)](6)(mu(8)-S)} where R=Pr-i and Am-i, were 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 symmetries of the electronic environments around the P sites were estimated from the (31)p chemical shift anisotropy (CSA) parameters, delta(aniso) and eta. Analyses of the Cu-65 chemical shift and quadrupolar splitting parameters for these compounds are presented with the data being compared to those for the analogous octa-miclear cluster compounds with R = "Bu and Bu-i. The Cu-65 transverse relaxation for the copper sites in {Cu-8[S2P((OPr)-Pr-i)(2)](6)(mu(8)-S)} and {CU8[S2P((OAm)-Am-i)(2)](6)(mu(8)-S) I was found to be very different, with a relaxation time, T-2, of 590 mu s (Gaussian) and 90 mu s (exponential), respectively. The structures of {Cu-4[S2P((OPr)-Pr-i)(2)](4)} and {Cu-8[S2P((OPr)-Pr-i)(2)](6)(mu(8)-S)} cluster compounds in the liquid- and the solid-state were studied by Cu K-edge EXAFS. The disulfide, [S2P((OAm)-Am-i)(2)](2), was obtained and characterized by P-31 {H-1} 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 3 T NMR spectroscopy and only the presence of copper(I) dithiophosphate species with the {Cu-8[S2P((OAm)-Am-i)(2)](6)(mu(8)-S)} structure was observed. (c) 2006 Elsevier Ltd. All rights reserved.