Unprecedented Reactivity of 1-Alkynes with 2-Chloroethanol Promoted by Cationic Solvento(trifluoromethyl)platinum(II) Complexes. Synthesis of β-Alkoxyalkenyl Derivatives and X-ray Structure of trans-[Pt{C(H)C(Ph)OCH2CH2Cl}(CO)(PPh3)2][BF4]·Et2O

Abstract

Reactions at ambient temperature of the solvento cationic trifluoromethyl complex trans-[Pt(CF3)(PPh3)2(solv)][BF4] with 1.5 equiv of 1-alkynes RC⋮CH (R = Ph, p-tolyl) and 2-chloroethanol afford in high yield the β-alkoxyalkenyl complexes trans-[Pt{C(H)C(R)OCH2CH2Cl}(CO)(PPh3)2][BF4] (R = Ph (1), p-tolyl (2)). In these reactions the CF3 group is also converted to a CO ligand. Complexes 1 and 2 were characterized by spectroscopic techniques and 1 also by an X-ray diffraction analysis. Reaction of the alkynyl complex trans-[Pt(CF3)(C⋮C-p-tolyl)(PPh3)2] with 2-chloroethanol and 1 equiv of HBF4 gives the acetylide-carbonyl derivative trans-[Pt(C⋮C-p-tolyl)(CO)(PPh3)2][BF4] (3), which was also formed by reaction of trans-[Pt(CF3)(C⋮C-p-tolyl)(PPh3)2] with aqueous HBF4. Possible mechanisms of these reactions are discussed.