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

Treatment of [Ni(COD)(2)] with trifluoroiodoethene or 1,1-dibromodifluoroethene in the presence of PEt3 effects the formation of the complexes trans-[NiI(CF=CF2)(PEt3)(2)] (1) and trans-[NiBr(CBr=CF2)(PEt3)(2)] (2), respectively. Reaction of 1 with NaBAr'(4) and acetonitrile gives trans-[Ni(CF=CF2)(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(CF=CF2)(CO)(PEt3)(2)]BAr'(4) (5), which is only stable in a CH2Cl2 solution. The reaction of 1 with NaBAr'(4) and (BuNC)-Bu-t affords the compound trans-[Ni(CF=CF2)((CNBu)-Bu-t)(PEt3)(2)]BAr'(4) (6). On treatment with NaBAr'(4) and PEt3 complex 6 can be converted into the dicationic phosphonioethenyl compound trans-[Ni{CF=CF(PEt3)}((CNBu)-Bu-t)(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) Angstrom. The C=C and the CF-P bond lengths are 1.309(6) Angstrom and 1.794(5) Angstrom, respectively.