Platinum(IV)-Mediated Nitrile−Sulfimide Coupling:  A Route to Heterodiazadienes

Pt(IV)-mediated addition of the sulfimide Ph2SNH and the mixed sulfide/sulfimides o- and p-{PhS(NH)}(PhS)C6H4 by the SNH group to the metal-bound nitriles in the platinum(IV) complexes [PtCl4(RCN)2] proceeds smoothly at room temperature in CH2Cl2 and results in the formation of the heterodiazadiene compounds [PtCl4{NHC(R)NSR‘Ph}2] (R‘ = Ph, R = Me, Et, CH2Ph, Ph; R‘ = o- and p-(PhS)C6H4; R = Et). While trans-[PtCl4(RCN)2] (R = Et, CH2Ph, Ph) reacting with Ph2SNH leads exclusively to trans-[PtCl4{NHC(R)NSPh2}2], cis/trans-[PtCl4(MeCN)2] leads to cis/trans mixtures of [PtCl4{NHC(Me)NSPh2}2] and the latter have been separated by column chromatography. Theoretical calculations at both HF//HF and MP2//HF levels for the cis and trans isomers of [PtCl4{NHC(Me)NSMe2}2] indicate a higher stability for the latter. Compounds trans-[PtCl4{E-NHC(R)NSPh2}2] (R = Me, Et) and cis-[PtCl4{E-NHC(Me)NSPh2}{Z-NHC(Me)NSPh2}] have been characterized by X-ray crystallography. The complexes [PtCl4{NHC(R)NSPh2}2] undergo hydrolysis when treated with HCl in nondried CH2Cl2 to achieve the amidines [PtCl4{NHC(NH2)R}2] (the compound with R = Et has been structurally characterized) and Ph2SO. The heterodiazadiene ligands, formed upon Pt(IV)-mediated RCN/sulfimide coupling, can be liberated from their platinum(IV) complexes [PtCl4{NHC(R)NSR‘Ph}2] by reaction with Ph2PCH2CH2PPh2 (dppe) giving free NHC(R)SR‘Ph and the dppe oxides, which constitutes a novel route for such rare types of heterodiazadienes whose number has also been extended. The hybrid sulfide/sulfimide species o- and p-{PhS(NH)}(PhS)C6H4 also react with the Pt(II) nitrile complex [PtCl2(MeCN)2] but the couplingin contrast to the Pt(IV) speciesgives the chelates [PtCl2{NHC(Me)NS(Ph)C6H4SPh}]. The X-ray crystal structure of [PtCl2{NHC(Me)NS(Ph)C6H4SPh-o}] reveals the bond parameters within the metallacycle and shows an unusual close interaction of the sulfide sulfur atom with the platinum.