LIGAND SUBSTITUTION-REACTIONS IN NEW SQUARE-PLANAR IRIDIUM, RHODIUM AND PLATINUM COMPLEXES CONTAINING A POTENTIALLY TERDENTATE C,N,N' LIGAND SYSTEM - CRYSTAL-STRUCTURE OF [IR(C6H4CH2N(ME)CH2CH2NME2-2-C,N,N')(COD)] (COD = CYCLOOCTA-1,5-DIENE)

Transmetallation reactions with the new dimeric compound [LiL]2 (L = C 6H4CH2N(Me)CH2CH2NMe2-2] have incorporated the potentially terdentate monoanionic C,N,N' ligand system L into the new complexes [M(I)L(cod)] (M = Rh or Ir, cod = cycloocta-1,5-diene) and [Pt(II)CI(L)] which hav e been characterized by H-1 and C-13 NMR spectroscopy. In solution the se complexes are square-planar with L co-ordinated as a C,N bidentate in [ML(cod)] and as a C,N,N' terdentate in [PtCl(L)]. However, the sol id-state molecular structure of [IrL(cod)] shows a C,N,N' terdentate c o-ordination mode of L; the square-pyramidal geometry reflects a situa tion in the direction of the reaction transition state of a nucleophil e (NMe2) attacking a d8 metal centre. Crystals of [IrL(cod)](C20H31IrN 2) are orthorhombic, space group P2(1)2(1)2(1), with a = 7.956(3), b = 14.090(l), c = 16.484(2) angstrom, Z = 4, final R = 0.0284 for 2078 r eflections with I greater-than-or-equal-to 2.5sigma(I) and 221 paramet ers. The neutral monodentate ligands CO and PPh3 replace the bidentate cod ligand in [ML(cod)] (M = Rh or Ir) to afford complexes which in s olution on the NMR time-scale are fluxional and in which L is either b i- or ter-dentate.