Preparation and reactivity of η-cyclopentadienyl(thiocarbonyl)(triphenylphosphine)-rhodium(I) and -iridium(I): formation of methyl(methylthio)methylene complexes

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Abstract
The complexes [M(η-C5H5)(CS)(PPh3)][M = Rh (1) or Ir (2)] have been synthesized from [MCl(CS)(PPh3)2] and sodium cyclopentadienide. The behaviour of the new thiocarbonyl complexes in their reactions with halogens or dry hydrogen chloride is similar to that observed for analogous carbonyl derivatives. The complexes [Rh(η-C5H5)X(CS)(PPh3)]X (X = Cl, Br, or I) have been obtained by treating (1) with halogens at liquid-nitrogen temperature; on increasing the temperature these rearrange to [Rh(η-C5H5)X2(PPh3)]. The analogous cationic iridium(III) complexes are more stable and can be obtained at room temperature. Complex (1) reacts with dry HCl giving probably [{RhCl(CS)(PPh3)}2]; in the same reaction (2) gives the cationic hydride [Ir(η-C5H5)H(CS)(PPh3)]Cl. The reactions of (1) and (2) with Mel afford the thiocarbene species [M(η-C5H5){CMe(SMe)}I(PPh3)]I which has been isolated analytically pure only for the iridium derivative. The reactions of the complexes [MCl(CS)(PPh3)2](M = Rh or Ir) with Mel have also been investigated. A possible mechanism of formation of the carbene species is proposed, and the influence of the metal–methyl σ-bond strength in the oxidative-addition product formed in the first step of this reaction is discussed. Complexes (1) and (2) react with HgCl2 giving the adducts [M(η-C5H5)(CS)(HgCl2)(PPh3)]. The i.r. and 1H n.m.r. spectra of the complexes prepared are discussed.

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