New unexpected coordination modes of azide and picolinato anions acting as bridging ligands between copper(II) and sodium or potassium ions. Synthesis, crystal structures and spectral characterizations of [MCu(picolinato)(N 3) 2] n (M = Na or K) complexes

Abstract

The polymeric complexes [NaCu(picolinato)(N 3) 2] n ( 1) and [KCu-(picolinato)(N 3) 2] n ( 2) have been synthesized and characterized by spectroscopic methods and X-ray crystallography. The overall spectral results indicate that the complexes contain different asymmetric azido ligands and axial five-coordinate copper(II) environments. In the structure of complex 1, each copper atom, which is chelated by 0(1) and N(1) of the picolinato anion, links N(11), N(21) and N(21a) of the azido groups [ Cu O = 1.997(5) A ̊ and Cu N = 1.957(6)–2.488(6) A ̊ ]. Each sodium atom is six-coordinated to oxygen atoms O(1), O(2c) and O(2d) [ Na O = 2.299(6)–2.470(6) A ̊ ] picolinato ligand and nitrogen atoms N(11), N(11a), N(13e) [ Na N = 2.454(7)–2.686(7) A ̊ ] of azide groups. Both μ(1,1) and μ(1,1,1,3) bridging azido ligands are linear and asymmetric [ N(11) N(12) = 1.204(8), N(12) N = 1.137(8), N(21) N(22) = 1.204(8), N(22) N(23) = 1.152(10 A ̊ ] . The structure of polymeric complex 2 features five-coordinate copper(II), eigth-coordinate potassium μ(1,3) and μ(1,1,1,3,3) bridging azido ligands and O, O, O′, O′, O′, N-hexadentate picolinato anions. The CuO bond length is 1.990(3) Å, CuN distances from 1.903(3) to 2.649(4) Å, whereas the KO distances are 2.729(3)–3.081(3) Å and KN 2.845(4)–3.289(5) Å.