Rhodium complexes sulfur-containing

Azoles containing an acidic NH-group, e.g. 3,5-dimethylpyrazole, react with various alcohols in the presence of a catalytic amount of ruthenium-, rhodium-, and iridium-trialkylphosphite complexes to afford the corresponding A-alkyl derivatives with excellent yields (92CL575). Regioselective A-alkylation was achieved using alkenes and sulfuric acid (89JHC3). 

The dimeric Rh11 complex [Rh2(MeCOS)4(MeCOSH)2] contains four bridging thioacetate groups the two thioacetic acid ligands are in the thione form and are each bound via the sulfur atom to one of the rhodium atoms.133 The Ru" complex [Ru(MeCOS)2(CO)(Ph3 P)2] is known in two isomeric forms.134... 

Apart from anion exchange reactions the complexes are inert. One of the few reagents to bring about a change in the coordination sphere is sulfur dioxide which coordinates to rhodium without displacement of a bidentate ligand. However, the product is not well characterized and the crystals contain clathrated sulfur dioxide.250... 

Efforts to optimize rhodium-based systems for methanol carbonylation led to the development of new supporting ligands containing phosphorus and sulfur donor atoms, both thiolates and thioethers, such as those used in the preparation of complexes (20) and (21). Ligands such as 2-diphenylphosphinothiolate have been shown to give rise to complexes that exhibit higher activities, up to four times faster, for the carbonylation of methanol compared to [Rh(CO)2l2] . ... 

---