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

Pt(IV)-mediated addition of the sulfimide Ph 2 S=NH and the mixed sulfide/sulfimides o- and p-{PhS(=NH)}(PhS)-C 6 H 4 by the S=NH group to the metal-bound nitriles in the platinum(IV) complexes [PtCl 4 (RCN) 2 ] proceeds smoothly at room temperature in CH 2 Cl 2 and results in the formation of the heterodiazadiene compounds [PtCl 4 {NH= C(R)N=SR'Ph} 2 ] (R' = Ph, R = Me, Et, CH 2 Ph, Ph; R' = o- and p-(PhS)C 6 H 4 ; R = Et). While trans-[PtCl 4 -(RCN) 2 ] (R = Et, CH 2 Ph, Ph) reacting with Ph 2 S=NH leads exclusively to trans-[PtCl{NH=C(R)N=SPh 2 } 2 ], cis/trans-[PtCl 4 (MeCN) 2 ] leads to cis/trans mixtures of [PtCl 4 {NH=C(Me)N=SPh 2 } 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 [PtCl 4 {NH=C(Me)N=SMe 2 } 2 ] indicate a higher stability for the latter. Compounds trans-[PtCl 4 -{E-NH=C(R)N=SPh 2 } 2 ] (R = Me, Et) and cis-[PtCl 4 {E-NH=C(Me)N=SPh 2 }{Z-NH=C(Me)N=SPh 2 }] have been characterized by X-ray crystallography. The complexes [PtCl 4 {NH=C(R)N=SPh 2 } 2 ] undergo hydrolysis when treated with HCI in nondried CH 2 Cl 2 to achieve the amidines [PtCl 4 {NH=C(NH 2 )R} 2 ] (the compound with R = Et has been structurally characterized) and Ph 2 SO. The heterodiazadiene ligands, formed upon Pt(IV)-mediated RCN/ sulfimide coupling, can be liberated from their platinum(IV) complexes [PtCl 4 {NH=C(R)N=SR'Ph} 2 ] by reaction with Ph 2 PCH 2 CH 2 PPh 2 (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)C 6 H 4 also react with the Pt(II) nitrile complex [PtCl 2 (MeCN) 2 ] but the coupling-in contrast to the Pt(IV) species-gives the chelates [PtCl 2 {NH=C(Me)N=S(Ph)C 6 H 4 SPh}]. The X-ray crystal structure of [PtCl 2 {NH=C(Me)N=S(Ph)C 6 H 4 SPh-o}] reveals the bond parameters within the metallacycle and shows an unusual close interaction of the sulfide sulfur atom with the platinum.