Metal complexes of sulphur ligands. Part VII. Reaction of mer-trichlorotris(dimethylphenylphosphine)rhodium(III) with NN-dimethyldithiocarbamate, dimethyl- and diphenyl-phosphinodithioate, and O-ethyl dithiocarbonate (xanthate) ligands
Reactions of the complex mer-[RhCl3(PMe2Ph)3], (I), with excess of (S–S)– ion [(S–S)–=–S2CNMe2, –S2PMe2, –S2PPh2, –S2COEt] have been thoroughly studied. On shaking in methanol for 10 min, the complexes mer-[RhCl2(S–S)(PMe2Ph)3], (IV), are formed which contain a unidentate dithio-acid group. Recrystallisation of complexes (IV) from non-polar solvents gives trans-[RhCl2(S–S)(PMe2Ph)2], (II). For (S–S)–=–S2PMe2 or –S2PPh2, further recrystallisation gives small amounts of the cis–cis–cis–isomers (VII). Conversely, for (S–S)–=–S2CNMe2 or –S2COEt, reaction of complexes (IV) with NaBPh4 in methanol gives some mer-[RhCl(S–S)(PMe2Ph)3]BPh4, (V), as well as (II). However, reaction of complex (I) with excess of (S–S)– heated under reflux in ethanol for 60 min, followed by addition of Y (Y = BPh4– or PF6–) to the filtrate, gives high yields of cis-[Rh(S–S)2(PMe2Ph)2]Y [III; (S–S)–=–S2CNMe2, –S2PMe2, or –S2PPh2]. Reaction of the complex mer-[RhCl3(PMePh2)3] with NaS2CNMe2,2H2O in ethanol gives both cis- and trans-[Rh(S2CNMe2)2(PMePh2)2]Y [(III) and (VI) respectively]. In contrast, reaction of complex (I) with KS2COEt gives mer-[RhCl(S2CO)(PMe2Ph)3](X), K[RhCl2(S2CO)(PMe2Ph)2](XI), and trans- and cis-[Rh(S2CO)(S2COEt)(PMe2Ph)2][(XII) and (XIII) respectively], which can be separated by chromatography. The complexes have been characterised by elemental analyses and i.r. and n.m.r. spectroscopy (1H and 31P), and a detailed mechanism for the overall reaction is postulated.