Synthesis of carbonyl-olefin complexes of platinum(II), PtX2(CO)(olefin), and the catalytic hydrochlorination of olefins

Article abstract of DOI:10.1021/om00052a010

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.