A new polymeric [Cu(SO3(CH2)3S–S(CH2)3SO3)(H2O)4]n complex molecule produced from constituents of a super-conformational copper plating bath: Crystal structure,infrared and Raman spectra and thermal behaviour

The formation and characterisation of a polymeric copper complex produced by chemical reaction between copper (II) ions and 3-mercapto-1-propanesulphonate sodium salt (MPSA) were studied. The formation of this complex, followed by sequential UV–visible spectroscopic measurements, involves the reduction of Cu(II) ions to Cu(I) by MPSA, the latter being oxidised to bis-(3-sulphopropyl)-disulphide (SPS), a dimer of MPSA. In the presence of oxygen, the re-oxidation of Cu(I) to Cu(II) results in the formation of polymeric complex species consisting of Cu(SO₃(CH₂)₃S–S(CH₂)₃SO₃)(H₂O)₄] units. Single crystal X-ray diffraction shows that this polymeric copper complex crystallizes in the monoclinic C2/c space group. The Cu(II) ion in the complex structure lies on an inversion centre in an elongated octahedral environment, equatorially coordinated to four water molecules and axially to two MPSA ligands through one of their sulphonic oxygen atoms. The complex units are arranged in the lattice as polymeric Cu(SPS)(H₂O)₄]_n molecules extending along the crystal 101] direction. The IR and Raman spectra as well as TGA and DTA data are reported. The stepwise thermal decomposition from room temperature up to 1000 °C begins with the loss of water molecules and ends with the formation of copper sulphide species.