Coordination and activation of the NS bond in sulfurdiimines RNSNR and sulfinylanilines RNSO by metal atoms

A survey is given of the coordination chemistry of sulfurdiimines RNSNR and sulfinylanilines RNSO towards metal atoms. It is shown that these pseudoallene ligands which are isostructural and isoelectronic with SO 2 may coordinate via N, S or via the π‐NS double bond. Nitrogen coordination is favoured by metals in the higher oxidation states e.g. Pt II , Pd II , but may also occur for Rh 1 and If and even for zerovalent metals such as Cr°, Mo° and W°. Sulfur coordination probably occurs for Cr°, Mo° and W°, but has been observed for Rh 1 and Ir 1 . Finally, metal‐π‐N=S bonding is clearly favoured by electron‐rich metal atoms like Ni°, Pd°, Pt°, Rh 1 and Ir 1 . In the case of metal‐ π 2 ‐N=S coordination of the RNSNR ligands further reactions may occur which lead to NS bond rupture. Such bond rupture may result in a large number of reactions varying from simple insertion of a metal atom into an N‐S bond to the formation of RNS, S and NR fragments which are captured in metal cluster complexes. Other ways of converting the RNSNR ligand involve the reactions with LiR′, R′MgX and trialkylaluminium compounds. The anionic RNS(R′)NR ligand so formed may behave as a bridging ligand but, more interestingly, as a pseudoallylic chelate group. It is shown that RNS(R′)NR − bonded as a chelate to transition metal atoms decomposes stereospecifically into azo compounds and SR − fragments.