Hahn, Christine Miranda, Mayra Chittineni, Nagendra P. B. Pinion, Trent A. Perez, Ricardo Mechanistic Studies on Platinum(II) Catalyzed Hydroarylation of Alkynes The dicationic acetylene platinum­(II) complex [Pt­(PNP)­(C<sub>2</sub>H<sub>2</sub>)]­(BF<sub>4</sub>)<sub>2</sub> (PNP = 2,6-bis­(diphenylphosphinomethyl)­pyridine) was generated in situ by ligand substitution from the ethylene complex [Pt­(PNP)­(C<sub>2</sub>H<sub>4</sub>)]­(BF<sub>4</sub>)<sub>2</sub> and was reacted with a series of arenes at low temperature. Only electron-rich arenes added across the coordinated C–C triple bond and gave the corresponding arylalkenyl complexes (<i>E</i>)-[Pt­(PNP)­(CHCHAr)]­BF<sub>4</sub> (Ar = C<sub>6</sub>Me<sub>5</sub>, C<sub>6</sub>H<sub>2</sub>Me<sub>3</sub>-2,4,6, C<sub>6</sub>H<sub>3</sub>Me<sub>2</sub>-2,6, C<sub>6</sub>H<sub>3</sub>Me<sub>2</sub>-2,4). A slow <i>E</i>–<i>Z</i> isomerization of the arylalkenyl complexes was observed. Single-crystal X-ray structure analyses were obtained for both <i>E</i> and <i>Z</i> isomers of the pentamethylbenzene derivative. The <i>E</i> isomers of [Pt­(PNP)­(CHCHAr)]­BF<sub>4</sub> (Ar = C<sub>6</sub>Me<sub>5</sub>, C<sub>6</sub>H<sub>2</sub>Me<sub>3</sub>-2,4,6) reacted with excess HBF<sub>4</sub>·Et<sub>2</sub>O to give the corresponding arylalkene complexes [Pt­(PNP)­(CH<sub>2</sub>CHAr)]­(BF<sub>4</sub>)<sub>2</sub>, whereas the <i>Z</i> isomers did not undergo immediate protonolysis. Using (<i>E</i>)-[Pt­(PNP)­(CDCDC<sub>6</sub>Me<sub>5</sub>)]­BF<sub>4</sub> it was shown that the stereochemistry of the C–C double bond in the protonolysis product depends on the nature of the acid anion HX (X<sup>–</sup> = Cl<sup>–</sup>, BF<sub>4</sub><sup>–</sup>). The catalytic hydroarylation was studied in solution by NMR spectroscopy. The reaction studies provide a more refined view of the individual steps proposed for the Friedel–Crafts type mechanism of the Pt<sup>II</sup>-catalyzed intermolecular hydroarylation of alkynes. BF;HBF;C 6Me C 6H C 6H C 6H;bond;Pt;arene;Z isomers;hydroarylation;C 6Me C 6H;NMR;arylalkenyl complexes;protonolysi;acid anion HX;PNP;Ar 2014-06-23
    https://acs.figshare.com/articles/dataset/Mechanistic_Studies_on_Platinum_II_Catalyzed_Hydroarylation_of_Alkynes/2280793
10.1021/om5003123.s002