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

Abstract

The neutral, homoleptic pyridylphosphininenickel(0) complex 6-Ph 2 -PC 5 H 2 ) 2 ] (1) has been obtained by reaction of the formal Ni(0) source [(IPr)Ni(H 2 CCHSiMe 3 ) 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]BF 4 , [1(THF)]PF 6 , and [1 2 ](BAr F 4 ) 2 . The structures of these salts reveal an interesting dependence on the nature of the anion. While [1]BF 4 and [1(THF)]PF 6 show trigonal-bipyramidal coordination of Ni in the solid state, [1 2 ](BAr F 4 ) 2 exists as a dinuclear Ni(I) complex and possesses a bridging phosphinine moiety in a rare μ 2 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 λ 5 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.

The case of a μ2-P aromatic phosphinine as a 4-electron donor forming σ- and π-three–center-two-electron bonds

“…An intriguing coordination mode involves bridging of two metal centers. 4 Although Venanzi and co-workers crystallographically characterized a μ 2 -P bridging phosphinine ( A , Fig. 1a) over three decades ago, 5 profound insight into the electronic structures of such μ 2 -P bridging phosphinines remains limited.…”

A dinuclear Rh(−i)/Rh(i) complex bridged by biphilic phosphinine ligands

“…[22][23][24][25][26] Phosphinine can exhibit all three bridging modes illustrated in Fig. 1c; 27 Type I with a lone pair on the phosphorus atom, [28][29][30][31][32][33][34] Type II with a phosphide-like resonance structure 28,[35][36][37] or 8e donor character where both the lone pair on the P atom and p-electrons of the phosphinine ring are donated, [38][39][40] and Type III utilizing the lone pair and the low-lying p* orbital. 40,41 Mathey, Le Floch, and coworkers reported that a dinuclear ruthenium complex with bisphosphinine ligands showed Type III bridging mode (Fig.…”