NMR Spectral Studies of Interactions Between the Accelerants SPS and MPS and Copper Chlorides

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 D 2 S O 4 ∕ D 2 O 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 × 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 Cu Cl 2 and SPS was observed.