Copper complexes of Picloram: The crystal and molecular structures of Bis(4-amino-3,5,6-trichloropyridine-2-carboxylato)aquacopper(II) dihydrate and Bis(4-amino-3,5,6-trichloropyridine-2-carboxylato)bis(pyrimidin-2-amine)copper(II)

Abstract

The crystal structures of two copper(II) complexes of the herbicide Picloram (4-amino-3,5,6-trichloro- pyridine-2-carboxylic acid) have been determined by single-crystal X-ray diffractometry. Bis(4-amino- 3,5,6-trichloropyridine-2-carboxylato)aquacopper(II) dihydrate (1) is monoclinic, space group C2/c, with Z 4 in a cell of dimensions a 15.593(6), b 7.940(6), c 16.983(6) Å, β 107.58(3)º. The structure was refined to a residual R 0.046 for 905 'observed' reflections. Complex (1) is trigonal bipyramidal with the trigonal plane consisting of oxygens from two picolinate ligands [Cu-O 1.995(5) Å] and a water molecule [Cu-O 2.080(5) Å]. The apical positions are occupied by pyridine ring nitrogens from the Picloram ligands [Cu-N 2.021(5) Å]. Bis(4-amino-3,5,6-trichloropyridine- 2-carboxylato)bis(pyrimidin-2-amine)copper(II) (2) is monoclinic, space group P2,/c, with Z 4 in a cell of dimensions a 12.3 11(5), b 15.435(5), c 15.320(6) Å, β 115.95(3)º, and gave a final R 0.059 for 2429 'observed' reflections. In complex (2), the copper(II) atom has a tetragonally distorted octahedral stereochemistry with the Picloram ring nitrogens once again occupying the two axial positions [Cu-N 2.586(7) and 2.611(7) Å]. The square plane consists of two carboxylato oxygens [Cu-O 1.941(6) and 1.960(7) Å] and two hetero-nitrogens from pyrimidin-2-amine ligands [Cu-N 2.048(6) and 2.054(6) Å].