Synthesis and reactivity of group 6 and group 8 organometallic complexes with sulfur-containing ligands

Abstract

The reactions of the scorpionate salts, K[HB(mt)3], Na[H2B(mt)2] and Li[HB(mt)2(pz)] with the organometallic complexes, [Cp*CrBr2]2 (1), [(HMB)RuIICl2]2 (8), [Cp*RuIIICl2]2 (12) and [Cp*RuII(OMe)]2 (13) yielding Cp*CrIII, (HMB)RuII and Cp*RuII/III complexes containing poly(methimazolyl)borates are described. The coordination modes of these ligands to the metal centres were determined using X-ray structural, electrochemical or/and NMR spectroscopic studies.The one-electron electrochemical oxidation of [Cp*RuIVCl2(S2CR)] (21-22) give [Cp*RuVCl2(S2CR)]+ (21+-22+). These complexes contain Ru in the most highly oxidized state ever recorded in organometallic chemistry. On the other hand, the chemical oxidation of [Cp*RuIVCl2(S2CNMe2)] (21a) with NOPF6 and [(C6H4Br)3N](SbCl6) gave the Ru(IV) complexes, [Cp*RuIV(MeCN)2(S2CNMe)](PF6)2 (23) and [Cp*RuIV(S2CNMe2)]2(SbCl6)2 (24). The reactions of [Cpb Ru(CO)2] (Cpb =C5H5, 25a; Cpb =C5Me5, 25b) with the heterocyclic disulfides lead to the isolation of the complexes of the type, [Cpb Ru(CO)B,2(o +1-SR)] (26-29) in moderate to high yields. IR spectroscopic, electrochemical and crystallographic studies have shown that the electron donating ability of SPy>SBzt>SPyCOOH>SBzCOOH. Complexes 26 and 27 were found to exhibit antiproliferative activity against MDA-MB231 and MCF-7 breast cancer cell lines and it was observed that the toxicity increased in order of increasing electron-donating ability of the ligands. In addition, the reactivity of 25 towards henb s egg white lysozyme (HEWL) was investigated and 25a was found to cleave two out of the four disulfide bonds present in the protein, HEWL.