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Migratory Insertion of the R2P Group into a Nitrogen−Nitrogen Bond − A Novel Type of Rearrangement in Phosphorus−Nitrogen Ligand Chemistry. 3. The Rearrangement of Triphosphinohydrazide Ligand −N(PPh2)−N(PPh2)2 to Triphosphazenide Anion {[(Ph2P−N]2PPh2} in the Coordination Sphere of Divalent Cobalt and Nickel

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posted on 07.04.2008, 00:00 by Vyacheslav V. Sushev, Natalia V. Belina, Georgy K. Fukin, Yuriy A. Kurskiy, Alexander N. Kornev, Gleb A. Abakumov
Hydrazine dihydrochloride reacts with 3 equiv of Ph2PCl in tetrahydrofuran in the presence of triethylamine to give tris(diphenylphosphino)hydrazine (1) in 70% yield. Each nitrogen atom in 1 has a trigonal-planar environment according to X-ray analysis. Thermolysis of 1 at 130 °C results in the formation of two products: bis(diphenylphosphino)amine and octaphenylcyclotetraphosphazene. The interaction of free ligand 1 with NiBr2 affords a simple adduct [(Ph2P)2N−NH−PPh2]NiBr2, while its anionic (hydrazide) form undergoes rearrangement in a coordination sphere of divalent cobalt and nickel involving migratory insertion of the Ph2P group into a nitrogen−nitrogen bond. The reaction of 1 with cobalt bis(trimethylsilyl)amide, [(Me3Si)2N]2Co, yields the complex of phosphazenide-type (Me3Si)2N−Co[(Ph2PN)2PPh2] (2) in 86% yield. A similar reaction of 1 with nikelocene proceeds with substitution of one Cp ring to form durable 18-electron complex CpNi[(Ph2PN)2PPh2] (3).