Proton and C-13 NMR spectroscopic studies of possible interactions of the copper electroplating accelerant disodium bis(3-sulfopropyl)disulfide(SPS) and its reduced form sodium 3-mercaptopropylsulfonate (MPS) with both cuprous chloride and cupric chloride were carried out in 0.25 M D2SO4/D2O with reagent concentrations between millimolar and 0.1 M under anaerobic conditions. It was confirmed that MPS reacted with CuCl to yield Cu(I)-thiolate products. No evidence for formation of a solution Cu(I)-SPS complex from CuCl and SPS was found. Instead, a redox reaction yielded a Cu(I)-thiolate along with Cu(II) with an estimated equilibrium constant of 5.2 x 10(-3) M-1. The previously reported reaction of aqueous cupric chloride with MPS was investigated further under anaerobic conditions. In addition to SPS, Cu(I)-thiolate products similar to those from the CuCl/MPS reaction were identified. The reaction was found to be complete only upon addition of over 2 equiv of MPS. No evidence for any interaction between CuCl2 and SPS was observed. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3529937] All rights reserved.