SYNTHESIS OF CARBONYL-OLEFIN COMPLEXES OF PLATINUM(II), PTX2(CO)(OLEFIN), AND THE CATALYTIC HYDROCHLORINATION OF OLEFINS

The mixed olefin-carbonyl complexes of platinum(II), PtX2(CO)(C6H10), X = Cl, Br, have been prepared by the reaction of PtX2(CO)2 with cyclohexene or, better, from Pt2Cl4(CO)2 and the olefin. Spectroscopic evidence has been gathered for the existence in solution of the mixed olefin-carbonyl species of platinum(II) with cyclopentene, ethylene, and propylene. Spectroscopic data are in agreement with the cis geometry of the complexes. The olefin ligand is promptly displaced by carbon monoxide. The chloro-carbonyl complex PtCl2(CO)(C6H10) reacts with dry HCl to yield cyclohexyl chloride and Pt2Cl4(CO)2. The mixed carbonyl-cyclohexene complex, or PtCl2(CO)2 or Pt2Cl4(CO)2 were found to be effective catalyst precursors for the hydrochlorination with dry HCl of a number of symmetrical (cyclohexene, norbornene), terminal (1-decene, propylene, styrene), and internal olefins (cis-2-decene, trans-2-decene, trans-5-decene), in hydrocarbon or chlorinated solvents. Hydrochlorination of cyclohexene-1,3,3-d3 gives the syn addition product, no anti product being observed, in contrast with the results of the hydrochlorination of the same substrate in glacial acetic acid with anhydrous hydrogen chloride. With terminal olefins, Markovnikov hydrochlorination was observed.