Polymeric complexes of copper(II) azide and 2,5-dimethylpyridine without and with solvent molecules. Synthesis, spectral and structural characterization of [Cu(2,5-dimethylpyridine) (N 3) 2] n and [Cu(2,5-dimethylpyridine) (N 3) 2(H 2N-CHO)] 2

Abstract

Catina di-μ(1,1)-azido[di-μ(1,1)-azidobis(2,5-dimethylpyridine)dicopper(II)] ( 1) and di-μ(1,1)-azidobis[azido(2,5-dimethylpyridine)(formamide)]dicopper(II) ( 2) were synthesized and characterized by spectroscopic and crystallographic methods. In the triclinic complex 1 the copper(II) centres are penta-coordinated by four nitrogen atoms from the azido ligands [CuN distances = 1.980(3)-2.249(4) Å] and a fifth nitrogen from the organic molecule at a CuN bond length of 2.038(4) Å. Both azido ligands function as μ(1,1) bridges to form chains of polyhedra along the crystallographic a axis. The dimeric molecule 2, which possesses a crystallographic inversion centre, contains both terminal and μ(1,1) bridging azido ligands. Each copper(II) atom is further coordinated by a 2,5-dimethylpyridine molecule [ Cu O = 1.998(4) A ̊ ] and a formamide molecule via its carbonyl oxygen atom [ Cu O = 2.356(4) A ̊ ] to give a distorted square pyramid. The IR absorption spectra reveal asymmetric azido ligands in both complexes, O-bonded formamide and hydrogen bonds as well, in 2. The solid and solution electronic spectra of both complexes exhibit more than one strong N 3 − → Cu II charge-transfer transition band. The room-temperature EPR spectra of powdered samples and DMF solutions were recorded and discussed.