Platinum(IV) Complexes: C−H Activation at Low Temperatures

Abstract

The oxidation of square-planar cyclometalated Pt(II) phenylpyridine species using the electrophilic chlorine based oxidant PhICl2 has been studied. Rapid oxidations are observed in chloroform solvent at −40 °C leading to single products. In acetone solvent isomeric forms of the product are formed, and these are observed to isomerize at around −10 °C. The oxidation of a complex with an uncyclometalated pendant arm resulted in the very rapid cyclometalation of that arm by the resulting electrophilic Pt(IV) species.

Platinum(ii) N-heterocyclic carbene complexes: coordination and cyclometallation.

“…R ≠ R') two signals (each of relative integral three) are seen for the DMSO protons at room temperature, consistent with the plane of the NHC ligand being perpendicular to the coordination plane of the platinum, together with restricted rotation about the NHC-Pt bond. 25,27 Gentle heating of the new complexes 5a-c results in a C-H activation reaction of the phenyl ring, similar to that seen before. 26,28,29 Cyclometallated products 6a-c are now seen, presumably accompanied by the elimination of methane, Scheme 4.…”

Luminescent Platinum(IV) Complexes Bearing Cyclometalated 1,2,3‐Triazolylidene and Bi‐ or Terdentate 2,6‐Diarylpyridine Ligands

“…To obtain Pt IV complexes with a cyclometalated trz ligand, we treated the Pt II complexes trans ‐ C , C* ‐ 3 and 4 with PhICl 2 in a 1:1 molar ratio in CH 2 Cl 2 . On the basis of related precedents, these reactions were expected to proceed by formal oxidative addition of a Cl + ion to form a pentacoordinated cationic Pt IV intermediate, followed by electrophilic metalation of the pendant phenyl ring of the trzH ligand with the release of a proton. In the case of trans ‐ C , C* ‐ 3 , however, this reaction did not lead to cyclometalation of the trzH ligand, but to the complex [PtCl 3 (dtpyH)(trzH)] ( 5 ), in which the trzH ligand is oriented cis to both the nitrogen atom and metalated carbon atom of the dtpyH ligand (Scheme ).…”

“…To obtain Pt IV complexes with ac yclometalated trz ligand, we treated the Pt II complexes trans-C,C*-3 and 4 with PhICl 2 in a1 :1 molar ratio in CH 2 Cl 2 .O nthe basis of relatedp recedents, [22,27,28,63] these reactions were expectedt op roceed by formal oxidative addition of aC l + ion to form ap entacoordinated cationic Pt IV intermediate, followed by electrophilicm etalation of the pendantp henylr ing of the trzH ligand with the releaseo faproton.I nt he case of trans-C,C*-3,h owever,t his reactiond id not lead to cyclometalation of the trzH ligand,b ut to the complex [PtCl 3 (dtpyH)(trzH)] (5), in which the trzH ligand is oriented cis to both the nitrogen atom and metalated carbon atom of the dtpyH ligand (Scheme1). Reasonably,t he cationic Pt IV intermediate resulting from addition of aC l + ion to complex trans-C,C*-3 is very unstable, either because of the mutually trans arrangement of the metalated carbon atom of the dtpyH ligand and the carbenic carbon atom or the steric crowding caused by the nonmetalated tolyl group of the dtpyH ligand, and therefore isomerizes before metalation of the pendant phenylr ing of the trzH ligand can take place;t he Cl À ion liberated by the PhICl 2 reagent then combinesw ith the metal center to give 5 (Scheme 2).…”

Synthesis, structures and spectroscopic properties of platinum complexes containing orthometalated 2-phenylpyridine

“…Recently orthometalated palladium(III) and platinum(IV) complexes have been described [42][43][44]. The palladium(III) complex [Pd 2 X 2 (l-OAc) 2 (benz) 2 ] (benz = metalated benzoquinoline) undergo bimetallic reductive elimination of halogenated benzoquinoline [44].…”