Synthesis, structure and reactivity of fluorovinyl nickel complexes: formation of a phosphonioethenyl complexDedicated to Professor Dieter Naumann on the occasion of his 60th birthday.

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)(CNtBu)(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)}(CNtBu)(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.