The preparation and properties of [Cu(chelate)X2] complexes. Crystal structure and electronic properties of [bis(2-pyridyl)amine]dibromocopper(II)

Abstract

The preparation and properties of a series of [Cu(chelate)X₂] complexes are reported, where ‘chelate’= 1,10-phenanthroline (phen) and bis(2-pyridyl)amine (bipyam) and X = Cl^– and Br^–. The crystal structure of [Cu-(bipyam)Br₂] has been determined; the crystals are monoclinic, space group C2, with a= 14.44(5), b= 7.92(3), c= 5.26(3)Å, β= 94.7(5)°, and Z= 2. The structure has been solved using microdensitometer estimated photographic data using 509 reflections and refined to R 0.1022. The structure involves a distorted CuN₂Br₂ chromophore, with two-fold symmetry, and CU–N = 1.96, Cu–Br = 2.40 Å, which from a consideration of the e.s.r. spectrum is best described as compressed, rather than elongated, tetrahedral. The electronic spectra of the [Cu(phen)X₂] complexes are considered to involve an elongated rhombic octahedral CuN₂X₂X′₂ chromophore stereochemistry.