The coordination chemistry and anticancer activity of organo-ruthenium(II), -iridium(III) and -rhodium(III) complexes with sulfonyl-substituted thiourea ligands.

Some half-sandwich compounds with a variety of ligands and metal centres have shown promising anticancer activity. Herein we report a series of reactions between the sulfonylthiourea ligands -TolSONHC(S)NHPh, EtSONHC(S)NHPh and CHSONHC(S)NHPh and [(η--cymene)RuCl], [(η-arene)RuCl(PR)] (arene = benzene or -cymene), [Cp*MCl(PR)] or [Cp*RhCl] (M = Ir(III), Rh(III)), Cp* = η-pentamethylcyclopentadienyl, PR = triphenylphosphine (PPh), tris(2-cyanoethyl)phosphine (tcep) and 1,3,5-triaza-7-phosphaadamantane (pta) and their corresponding piano stool complexes. Single crystal X-ray diffraction structure determinations indicated that the resulting linkage isomer of the complex, , (coordination S,N placing the sulfonyl group near the coordination sphere) or (coordination S,N, placing the sulfonyl group away from the coordination sphere), is directly related to the steric bulk around the metal centre. to isomerisation of the complex [(η--cymene)Ru{-TolSONC(S)N(PPh)}] (1aL1) was observed by H and P{H} NMR spectroscopy. DFT calculations suggested this to be the result of the conversion from the initially formed kinetically favourable to the thermodynamically favourable isomer. Computational investigation of non-covalent interactions using the reduced density gradient also revealed a chalcogen bond present between the thiourea sulfur and sulfonyl oxygen atoms of complex 1aLa. The antiproliferative activity of several complexes was determined against human cancer cells, which revealed a correlation between potency and lipophilic properties of the ancillary ligands for a series of Ru(II) -cymene complexes.