The First Structurally Characterized Metal (κ^<i>2</i><i>N</i>,<i>P</i>)-Phosphinohydrazides: The Key to Understanding the Intramolecular Rearrangement R₂P−NR′−NR′−M → R′N═PR₂−NR′−M. Metalloderivatives of Diisopropylphosphinohydrazines: Synthesis and Properties

Abstract

A number of novel phosphinohydrazines, iPr(2)P-NPh-NPh-H (1), iPr(2)P-NH-NH-PiPr(2) (2), iPr(2)P-NMe-NH-PiPr(2) (3), and H-NMe-NH-PiPr(2) (4), were prepared and characterized. The interaction of 1 with 1 equiv of n-BuLi afforded a complex compound [Li(DME)(3)][Li{(NPh-NPh-PiPr(2))-kappaN}(2)] (5). The reaction of 5 with NiBr(2) resulted in the formation of the first stable transition metal phosphinohydrazide [Ni{(NPh-NPh-PiPr(2))-kappa(2)N,P}(2)] (6). Similarly, the cobalt(II) derivative [Co{(NPh-NPh-PiPr(2))-kappa(2)N,P}(2)] (7) was prepared by the reaction of 1 with Co[N(SiMe(3))(2)](2). An X-ray study reveals formation of the complexes containing elongated N-N bonds (1.443(1), 1.466(2), and 1.470(2) A for 5, 6, and 7, respectively) as compared with the starting material 1 (1.407(1) A). Nickel phosphinohydrazide 6 has a square-planar cis configuration; the cobalt complex 7 possesses a square-planar centrosymmetric trans configuration. The half-sandwich nickel(II) complex [CpNi{(NPh-NPh-PiPr(2))-kappa(2)N,P}] (8) was prepared by prolonged heating of phosphinohydrazine 1 with NiCp(2) in toluene. The lithiation of 3 with n-BuLi resulted in the formation of an iminophosphoranate [LiN=PiPr(2)-NMe-PiPr(2)] (13) (in situ), which is the product of insertion of a PiPr(2) group into the nitrogen-nitrogen bond. The hydrolysis of 13 followed by the addition of CoCl(2) gave the phosphino-iminophosphoranato complex [CoCl(2){(HN=PiPr(2)-NMe-PiPr(2))-kappa(2)N,P}] (15) according to X-ray investigation. The phosphinohydrazine 3 reacted with FeX(2) in toluene to form adducts (1:1) [FeX(2){(PiPr(2)-NMe-NH-PiPr(2))-kappa(2)P,P'}] (X = Cl (9), Br (10)), while CoCl(2) gave the complex salt [{Co(PiPr(2)-NMe-NH-PiPr(2))-kappa(2)P,P'}(2)(mu-Cl)(3)][CoCl(3)(THF)] (11). A THF solution of complex 11 shows thermochromic behavior.