Cu(I) and Cu(II) complexes of a pyridine-based pincer ligand

The pincer ligands 2,6-H3C5N(CH2NR2)(2), L-R, have been studied in their reaction towards CuCl2 and CuCl. For CuCl2, the case R = Et gives square-pyramidal (eta(3)-L-ET)CUCL2 with an apical Cu-Cl distance 0.27 Angstrom longer than the equatorial one. For R = Pr-1, the chloride-loss product (eta(3)-(LPr)-Pr-1)CuCl+ is established as its CuCl42- salt. The mer geometry of the ligand in these two compounds is intolerable for Cu(I), and a ligand-redistribution product from CuCl is (eta(2)-L-Me)(2)Cu+, together with linear CuCl2. Density functional theory (DFT) calculations of monomeric (L-Me)Cu(I)L-9 with L = MeCN, C2H4 or Cl- show a distinct tendency for one or both NMe2 arms to dissociate from Cu(I), while the Cu(II) analogs adopt planar geometry, (0 2002 Published by Elsevier Science B.V.