SYNTHESIS AND COORDINATION CHEMISTRY OF H EMILABILE P,N-HYBRID LIGANDS WITH TERMINAL 2-PYRIDYL DONOR GROUPS

P,N-hybride ligands 1-7 containing terminal 2-pyridyl donor groups hav e been obtained by base-catalyzed addition of diphenylvinylphosphane o r 2-vinylpyridine to primary or secondary phosphanes [2-Py-(CH2)(2)-PR 'H (R' = H, Ph), HMeP-(CH2)(3)-PMeH] or by alkylation of organolithium phosphides, R(2)P - (CH2)(3) -PMeLi or 2-Py-(CH2)(2) - PR'Li (R = Ph, iPr; R' = H, Ph), with 2-(2-chloroethyl)pyridine or di-tert-butylphos phetanium bromide. Upon reaction with NiBr2 3 H2O or K(2)MCl(4) (M = P d, Pt) the phosphanes (L) of type 2-py-(CH2)(2)-P(R')-(CH2)(m)-PR(2) ( 1, 3, 6) form square planar Ni(II), Pd(II), and Pt(II) complexes of co mposition MX(2)(L) (10-14). With NiBr2 and K(2)MX(4) the tripod type p hosphane 2 forms square pyramidal complexes [MX(2)]X (M = Ni, Pd;X = C l, Br; 15, 16). An X-ray structural analysis of [NiBr(2)]Br-+(-) (15) reveals a distorted square pyramidal coordination geometry at Ni(II), the 2-Py donor being in apical position with a long Ni-N bond [2.270(1 5) Angstrom]. The tetradentate ligand 7 forms Ni(II), Pd(II), and Pt(I I) complexes MX(2)(7) which for M = Pd, Pt show dynamic behaviour by e xchange of the terminal Py donor groups. With [RhCl(COD)](2) the tride ntate ligands L (1 and 3) yield complexes of composition RhCl(L) (20, 21). The structure of 20 has been determinated by X-ray diffraction. T he ligand 3, acting in a tridentate manner, is coordinated to Rh(I) in a distorted square-planar arrangement with a normal Rh-N distance [2. 145(3) Angstrom].