Diastereoselective Synthesis of the First Enantiomerically Pure (Triazolinylidene)ruthenium(ii) and ‐rhodium(iii) Chelate Complexes

The chloro bridges of the dinuclear complexes [(.65‐cymene)‐RuCl2]2 and [(.5‐C5Me5)RhCl2]2 can be cleaved by reaction wht an N‐phenyltriazolium perchlorate (1) and a base, resulting in the formation of (carbene)metal complexes. In this manner, abstraction of one ortho‐proton of the phenyl group and elimination of HCl leads to pseudo‐tetrahedral ruthenium (2) and rhodium (3) complexes, thereby creating a stereogenic center at the transition metal. By using enantiomerically pure triazolium perchlorates, the diastereoselective synthesis of these complexes with diastereomeric excesses of up to 95% can be achieved, with the possibility of separating the two diastereomers by column chromatography. The relative, and therefore also the absolute configuration of the ruthenium complex (RRu)‐2b could be determined by X‐ray structure analysis. A stereospecific substitution of chlorine by iodine or acetonitrile to form the diastereomerically pure complexes 4, 5 and 6 (the latter as cationic ruthenium complexes) allows a further variation of the ligands.