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

Abstract

The pincer ligands 2,6-H 3C 5N(CH 2NR 2) 2, L R, have been studied in their reaction towards CuCl 2 and CuCl. For CuCl 2, the case R=Et gives square-pyramidal (η 3-L Et)CuCl 2 with an apical CuCl distance 0.27 Å longer than the equatorial one. For R= iPr, the chloride-loss product (η 3-L iPr)CuCl + is established as its CuCl 4 2− salt. The mer geometry of the ligand in these two compounds is intolerable for Cu(I), and a ligand-redistribution product from CuCl is (η 2-L Me) 2Cu +, together with linear CuCl 2 − . Density functional theory (DFT) calculations of monomeric (L Me)Cu(I)L q with L=MeCN, C 2H 4 or Cl − show a distinct tendency for one or both NMe 2 arms to dissociate from Cu(I), while the Cu(II) analogs adopt planar geometry.