Synthesis and structural characterization of dicopper(II) and dipalladium(II)complexes of 1,1,2,2-tetrakis(carboxamido-2-methylpyridyl)ethane

摘要

The binucleating ligand, 1,1,2,2-tetrakis(carboxamido-2-methylpyridyl)ethane (H_4L~(py)) was prepared. Inneutral aqueous medium the H_4L~(py)binds two metal(II) ions and the dinuclear complexes [Cu2(LPY)(-H_2O)_2] 10H_2O(1) and [Pd_2(L~(py))] 4H_2) are formed. The complexes were structurally characterizedby X-ray crystallography. The two complexes crystallize in the triclinic system with space group P1. 1:a = 8.829(2), b = 9.080(2), and c= 12.414(3) A; α = 76.50(3),β= 79.12(3), and γ = 87.25(3)°;V=950.3(4) A~3andZ=1 and 2:a=8.638(2), b =10.009(andc=10.448(2)A; α=78.03(3), β = 69.66(and γ = 71.20(3)°; V= 797.2(3) A~3andZ=1. The coordination polyhedron in 1 may be described as axiallyelongated square pyramid where the Cu(II) centers are coordinated with the four N atoms of the LPY tet-raanion and an O(3) atom of the aqua ligand. In complex 2, each Pd(II) center displays a distorted squareplanar geometry achieved by the four N-donor atoms of L~(py).The intra-dimeric M(1)…1A) distances in1 and 2 are 6.9680(17) and 6.7345(18) A, respectively. Molecular mechanics (MM) calculations wereapplied on the two complexes to determine their molecular structures in the solid state. Fair agreementwas obtained between the structures predicted by MM calculations (M…M distances are 6.574 and5.890 A for 1 and 2, respectively) and X-ray crystal structures.