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Phosphorus Analogues of [Ni(bpy)2]: Synthesis and Application in Carbon–Halogen Bond Activation

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journal contribution
posted on 02.07.2020, 17:35 by J. Leitl, P. Coburger, D. J. Scott, C. G. P. Ziegler, G. Hierlmeier, R. Wolf, N. P. van Leest, B. de Bruin, G. Hörner, C. Müller
The neutral, homoleptic pyridylphosphininenickel(0) complex [Ni­(2-Py-4,6-Ph2-PC5H2)2] (1) has been obtained by reaction of the formal Ni(0) source [(IPr)­Ni­(H2CCHSiMe3)2] with 2 equiv of 2-(2′-pyridyl)-4,6-diphenylphosphinine (L). Compound 1 can be oxidized both electrochemically and through the use of ferrocenium salts, to afford the corresponding Ni­(I) complexes [1]­BF4, [1(THF)]­PF6, and [12]­(BArF4)2. The structures of these salts reveal an interesting dependence on the nature of the anion. While [1]­BF4 and [1(THF)]­PF6 show trigonal-bipyramidal coordination of Ni in the solid state, [12]­(BArF4)2 exists as a dinuclear Ni­(I) complex and possesses a bridging phosphinine moiety in a rare μ2 mode. Reactions of 1 with halobenzenes highlight the noninnocent behavior of the aromatic phosphinine ligand, leading to the formation of oxidized Ni complexes but not to classical oxidative addition products. The reaction of 1 with bromobenzene affords the λ5 phosphinine 2 and the bipyramidal Ni­(I) complex [1]­Br, whereas a more unconventional oxidation product 3 is formed from the reaction of 1 and iodobenzene.