1,2-METHYL SHIFT BETWEEN Pt AND THE COORDINATED ARYL GROUP IN THE REACTION OF METHYL IODIDE WITH 2,6-BISPHENYL-N,N',C COMPLEXES OF PLATINUM(II). X-RAY CRYSTAL STRUCTURE OF THE ARENONIUM-PLATINUM COMPOUND

Article abstract of DOI:10.1021/ja00296a010

The ionic complexes OTf (X = Cl, Br, I) prepared from the reaction of with MeOTf possess a ?-metal-substituted arenonium ion with the Pt-C ?-bond trans to the halide.Synthetic investigations revealed that not only these species with X = Cl, Br, and I trans to the arenonium unit were isolable but also complexes with a more sterically demanding tolyl (ortho or para) group were formed in the reaction of with MeI.A single-crystal X-ray study has revealed the structure of the complex I (see Figure 3): triclinic, space group P1 with a = 7.295 (2) Angstroem, b = 9.832 (2) Angstroem, c = 15.044 (3) Angstroem, α = 87.47 (2) Deg, β = 86.24 (2) Deg, γ = 83.42 (2) Deg, and Z = ".The intensities of 3481 independent reflections were used to determine the structure.The structure was solved and refined using standard heavy-atom and least-squares techniques.The approximately square-planar complex has a ?-bonded o-tolyl group (Pt-C = 2.005 (9) Angstroem) twisted perpendicular to the coordination plane and trans to the ?bonded arenonium unit with Pt-C = 2.293 (9) Angstroem.These and other experimental findings provide new evidence regarding oxidative-addition reductive-elimination pathways.It is concluded that attack of the methyating reagent occurs at the metal center.Hereby a five-coordinate cationic Pt^IV-Me intermediate is formed that can consequently rearrange via two pathways, either (i) overall reductive elimination of MeX (in the case of X = Cl, Br, I) or (ii) 1,2-methyl shift across the Pt-C bond (Scheme I).Steric hindrance of the trans group and/or the presence of a nucleophile influence the available pathways which are discussed in detail.