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C–F Bond activation at Ni(0) and simple reactions of square planar Ni(ii) fluoride complexes

By Suzanne Burling, Paul I. Elliott, Naser A. Jasim, Richard J. Lindup, Jennifer McKenna, Robin N. Perutz, Stephen J. Archibald and Adrian C. Whitwood

Abstract

The reaction of Ni(COD)2(COD = 1,5-cyclooctadiene) with triethylphosphine and pentafluoropyridine in hexane has been shown previously to yield trans-[NiF(2-C5NF4)(PEt3)2]( 1a) with a preference for reaction at the 2-position of the heteroaromatic. The corresponding reaction with 2,3,5,6-tetrafluoropyridine was shown to yield trans-[NiF(2-C5NF3H)(PEt3)2]( 1b). In this paper, we show that reaction of Ni(COD)2 with triethylphosphine and pentafluoropyridine in THF yields a mixture of 1a and 1b. Competition reactions of Ni(COD)2 with triethylphosphine in the presence of mixtures of heteroaromatics in hexane reveal a kinetic preference of k(pentafluoropyridine) : k(2,3,5,6-tetrafluoropyridine)= 5.4 : 1. Treatment of 1a and 1b with Me3SiN3 affords trans-[Ni(N3)(2-C5NF4)(PEt3)2]( 2a) and trans-[Ni(N3)(2-C5NHF3)(PEt3)2]( 2b), respectively. The complex trans-[Ni(NCO)(2-C5NHF3)(PEt3)2]( 3b) is obtained on reaction of 1b with Me3SiNCO and by photolysis of 2b under CO, while trans-[Ni(1-CCPh)(2-C5NF4)(PEt3)2]( 4a) is obtained by reaction of phenylacetylene with 1a. Addition of KCN, KI and NaOAc to complex 1a affords trans-[Ni(X)(2-C5NF4)(PEt3)2]( 5a X = CN, 6a X = I, 7a X = OAc), respectively. The PEt3 groups of complex 1a are readily replaced by addition of 1,2-bis(dicyclohexylphosphino)ethane (dcpe) to produce [NiF(2-C5F4N)(dcpe)]( 8a). Addition of dcpe to trans-[Ni(OTf)(2-C5F4N)(PEt3)2]( 10a), however, yields the salt [Ni(2-C5F4N)(dcpe)(PEt3)](OTf)( 9a) by substitution of only one PEt3 and displacement of the triflate ligand. The structures of 2b, 4a, 7a and 8a were determined by X-ray crystallography. The influence of different ancillary ligands on the bond lengths and angles of square-planar nickel structures with polyfluoropyridyl ligands is analysed

Topics: Q1, QD
Publisher: Royal Society of Chemistry
Year: 2005
DOI identifier: 10.1039/b510052f
OAI identifier: oai:eprints.hud.ac.uk:4152
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