CHELATE COMPLEXES LM N OF TRANSITION-META LS WITH PHOSPHINOIMIDIC AMIDATO LIGANDS R2P(NR')(2)(-) (= L)/

Reaction of LLi with metal halides or metal halide complexes affords c helate complexes LM/n (L = R2P(NR')(2)(-); M=Cr+++, Co++, Ni++, Zn++). With the bulky ligand r-Bu2P(NSiMe3)(2) and Ni(PPh3)(2)Cl-2 or Ni(dme )Br-2 (dme = dimethoxyethane) only halide bridged chelates [LNiHal](2) (Hal = Cl, Pr) containing tetrahedral chromophors NiN(2)Hal(2) were o btained. Main objects of investigation were the bischelates L2Ni 2. 2a (R = i-Pr, R' = Me) and 2c (R = Ph, R' = Et) are planar, 2b (R = i-Pr , R' = Et) and 2d-g (R, R' = i-Pr, i-Pr; Ph, i-Pr; Et, SiMe3; Ph, SiMe 3) tetrahedral. In solutions of 2b and 2c a conformational equilibrium planar (diamagnetic) reversible arrow tetrahedral (paramagnetic) exis ts that is shifted to the right with increasing temperature and is dom inated by the tetrahedral (2b) or planar conformer (2c) at room temper ature. As is the case with the isovalence electronic compounds [R2P(S) NR'](2)Ni small substituents R' apparently favour the planar state and in contrast to some complexes [R2P(O)NR'](2)Ni no paramagnetic planar species 2 have yet been observed. These findings that are derived fro m the results of magnetic measurements and of UV/VIS as well as NMR sp ectroscopy are confirmed by crystal structure determinations: 2a was f ound to be planar (orthorhombic; a = 3382.8(11), b = 1124.0(4), c = 88 74(3); P2(1)2(1)2; Z = 6), and 2g to be tetrahedral (monocline; a = 12 68.4(2), b = 1806.8(2), c = 1971.6(2), P2(1)/n; Z = 4). The bite angle NNiN of the chelate ligand in 2a (ca. 77 degrees) is similar to those in paramagnetic planar complexes [R2P(O)NR'](2)Ni (NNiO 74-77 degrees ) and shows that a small chelate bite does not necessarily imply param agnetism of planar Ni(II) complexes.