Synthesis, structure and reactivity of fluorovinyl nickel complexes: formation of a phosphonioethenyl complex

Abstract

Treatment of [Ni(COD)₂] with trifluoroiodoethene or 1,1-dibromodifluoroethene in the presence of PEt₃ effects the formation of the complexes trans-[NiI(CFCF₂)(PEt₃)₂] (1) and trans-[NiBr(CBrCF₂)(PEt₃)₂] (2), respectively. Reaction of 1 with NaBAr′₄ and acetonitrile gives trans-[Ni(CFCF₂)(NCMe)(PEt₃)₂]BAr′₄ (4) [Ar′ = 3,5-C₆H₃(CF₃)₂]. Treatment of 1 with NaBAr′₄ in the presence of CO yields the cationic complex trans-[Ni(CFCF₂)(CO)(PEt₃)₂]BAr′₄ (5), which is only stable in a CH₂Cl₂ solution. The reaction of 1 with NaBAr′₄ and ^tBuNC affords the compound trans-[Ni(CFCF₂)(CN^tBu)(PEt₃)₂]BAr′₄ (6). On treatment with NaBAr′₄ and PEt₃ complex 6 can be converted into the dicationic phosphonioethenyl compound trans-[Ni{CFCF(PEt₃)}(CN^tBu)(PEt₃)₂][BAr′₄]₂ (7). The structures of complexes 2 and 7 have been determined by X-ray crystallography. The phosphonioethenyl ligand in 7 is bound at nickel with a Ni–C distance of 1.893(5) Å. The CC and the CF–P bond lengths are 1.309(6) Å and 1.794(5) Å, respectively.