Intramolecularly stabilised group 10 metal stannyl and stannylene complexes: Multi-pathway synthesis and observation of platinum-to-tin alkyl transfer

Reaction of [PdClMe(P∧N)₂] with SnCl₂ followed by Cl-abstraction leads to apparent Pd-C bond activation, resulting in methylstannylene species trans-[PdCl{(P∧N)₂SnClMe}][BF₄] (P∧N = diaryl phosphino-N-heterocycle). In contrast, reaction of Pt analogues with SnCl₂ leads to Pt-Cl bond activation, resulting in methylplatinum species trans-[PtMe{(P∧N)₂SnCl2}][BF₄]. Over time, they isomerise to methylstannylene species, indicating that both kinetic and thermodynamic products can be isolated for Pt, whereas for Pd only methylstannylene complexes are isolated. Oxidative addition of RSnCl₃ (R = Me, Bu, Ph) to M0 precursors (M = Pd or Pt) in the presence of P∧N ligands results in diphosphinostannylene pincer complexes trans-[MCl{(P∧N)₂SnCl(R)}][SnCl₄R], which are structurally similar to the products from SnCl₂ insertion. This showed that addition of RSnCl₃ to M0 results in formal Sn-Cl bond oxidative addition. A probable pathway of activation of the tin reagents and formation of different products is proposed and the relevancy of the findings for Pd and Pt catalysed processes that use SnCl₂ as a co-catalyst is discussed.