Oxidation of phosphine by sulfur or selenium involving a catalytic cycle in the interconversion of monomer and tetramer forms of copper-maleonitriledithiolate complexes

Abstract

The addition of triphenylphosphine (PPh₃), into [Et₄N]₄[Cu₄(mnt)₄] shifted its characteristic electronic spectral band at 377 nm to 372 nm which is identical to that of the monomeric species, [Et₄N][Cu(mnt)(PPh₃)]. This reaction was followed by electrochemical study and also by ³¹P NMR spectroscopy. Such interconversion with the participation of breaking of bridging copper-μ₃-sulfur bond with the formation of new copper-phosphorous bond led to the development of a catalytic cycle using excess PPh₃ and S or Se as the reacting substrates. The turnover number for the oxidation of PPh₃ by S was found to be 0·8 × 10^-2 s^-1 and that with Se was 0·6 × 10^-2 s^-1 using this catalytic system.