Reactivity of some cuprous salts towards tenmembered macrocyclic disulphides: a new route to the synthesis of Cu(II)-thiolates

Abstract

Cuprous ion is found to be quite reactive towards disulphide present in a macrocycle. Thus, when [Cu(MeCN)₄] BF₄ or [Cu(MeCN)₄]ClO₄ is allowed to reflux in acetonitrile with a ten-membered macrocycle containing two amino nitrogens and one disulphide donor in an atmosphere of nitrogen, electron transfer takes place from the metal centre to the disulphide group. As a result, copper is oxidised to the +2 state and the disulphide reduced to thiolates. The thiolates then bind the Cu(II) and form discrete and neutral CuN₂S₂ complexes. Syntheses of two new CuN₂ S₂ complexes have been achieved following this route. The reactions take place smoothly and give the desired product in excess of 25% yield with respect to the macrocycle. Electronic absorption spectral results are consistent with a nearly square planar geometry. Each of the two complexes isolated exhibits quasireversible Cu(II)/Cu(I) couple with Ef near - 0.3 V vs SCE. Both the complexes are further characterised by room temperature magnetic susceptibility, EPR spectroscopy at 298 and 77 K and elemental analyses.