Displacement reactions of cis-[PtIICl(R'SCSO)(PR3)2] (R = Ph, C6H11; R' = aryl) with nucleophiles. Formation with R'S- of an h2-CS coordinated sulphine (R'S)2CSO by reductive coupling,

Abstract

A cyclic process to synthesize sulphines in the coordination sphere of platinum has been tested by stepwise reactions. Step i: The Cl atoms in the metallo-sulphines cis-[Pt}I{}I{Cl(R'SCSO)(PR{3}){2}] (R = Ph, C{6}H{1}{1}; R' =p-MeC{6}H{4}) were displaced by R''S}-{ (R'' = p-MeC{6}H]4, p-MeOC{6}H{4}) leading to the metallo-sulphines cis-[Pt}I{}I{(SR'')(R'SCSO)(PR{3}){2}], with only (E)-(Z) isomerization being found and no scrambling between R'S and R''S groups. Step ii: These metallo-sulphines in the case of R = C{6}H{1}{1} were not detected, they are unstable because of the steric interaction between the bulky co-ligands and undergo immediate C@?S reductive coupling forming the @h}2{-CS coordinated sulphine compounds [Pt}0{{P(C{6}H{1}{1}){3}}{2}{(R''S)(R'S)CSO}]. Step iii:These latter @h}2{-CS coordinated sulphines could be displaced by (E)-(R'S)ClC@?S@?O forming the highly unstable @h}2{-CS compound [Pt{0}{P(C{6}H{1}{1}){3}}{2}{(E)-(R'S)-ClCSO}] which undergoes an immediate C@?Cl oxidative addition and reforms the starting metallo-sulphine cis-[Pt}I{}I{Cl(R'SCSO){P(C{6}H{1}{1}){3}}{2}] (Step iv).Two complications prevent this cyclic process becoming a catalytic cycle: (i) slow cis-to-trans isomerization of the metallo-sulphines cis-[Pt}I{}I{Cl(R'SCSO){P(C{6}H{1}{1}){3}}{2}] and (ii) decomposition during the sulphine displacement (Step iii). Test reactions showed that the sulphine (R'S){2}C@?S@?O is formed faster via direct displacement in (E)-(R'S)ClC@?S@?O by R''S}-{ than by the cyclic process. When the bidentate ligand Et{2}NCS}-{{2} is used as displacing ligand dissociation of one PR{3} group is initiated instead of C@?S reductive coupling, forming the metallo-sulphines [Pt}I{}I{}I{(S{2}CNEt{2})(R'SCSO)(PR{3})].