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)21 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.