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

The pincer ligands 2,6-H3C5N(CH2NR2)2, LR, have been studied in their reaction towards CuCl2 and CuCl. For CuCl2, the case R=Et gives square-pyramidal (η3-LEt)CuCl2 with an apical CuCl distance 0.27 Å longer than the equatorial one. For R=iPr, the chloride-loss product (η3-LiPr)CuCl+ is established as its CuCl4 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 (η2-LMe)2Cu+, together with linear CuCl2 −. Density functional theory (DFT) calculations of monomeric (LMe)Cu(I)Lq 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.