Synthesis and characterization of Bis(imino)phosphine [NPN] ligands and their copper(I) halide complexes

A series of four new bis(imino)phosphine [NPN] ligands PhP(C6H4-2-HC=NAr)2 (Ar = 4-OMeC6H4 (L1, 1 ), 4ClC6H4 (L2, 2 ), 4-BrC6H4 (L3, 3 ), 2,6-iPr2C6H3 (L4, 4 )) were synthesized and structurally characterized. Their reactions with Cu(I) halides CuX (X = Cl, Br, I) were explored for the assembly of coordination complexes LnCuX, and the effects of substituent (Ar) and anion (X) were also investigated in a comparative manner. It was found that the reaction of methoxy substituted L1 (Ar = 4-OMeC6H4) with CuX gave the mononuclear Cu(I) complexes L1CuX (X = Cl (1a), Br (1b), I (1c)) with isostructural feature. In contrast, when halogen-substituted ligands L 2-3 (4-ClC6H4, 4-BrC6H4) were applied, their reactions with CuCl afforded the formation of tetranuclear dimer [Ln(CuCl)2]2 (n = 2 (2a), 3 (3a)) bridged by the Cu2Cl2 square, regardless of the composition of the reactants. On the other hand, reactions of L 2-3 with CuBr and CuI generated the mononuclear Cu(I) complexes LnCuX (n = 2, X = Br (2b), I (2c); n = 3, X = Br (3b), I (3c)) again. In all these cases above, L 1-3 ligands played the tridentate role by biting the copper(I) centers through NPN sites. When the bulky L4 (Ar = 2,6-iPr2C6H3) was involved, the binuclear dimer (L4CuI)2 (4c) bridged by iodide anions was obtained, where each L4 ligand coordinated the copper center using the bidentate P"N mode with another imino arm pendant. In further exploration, 1,10-o- phenanthroline (denoted as phen) was introduced to produce the heteroleptic complex L1CuCl(phen) (1d), where both imino arms in L1 were pendent. The obtained ligand (L1-4) and Cu(I) complexes were characterized by melting point, elemental analysis, FT-IR, UV-Vis, NMR, and single crystal X-ray diffraction.