A COPPER(II) AZIDE COMPOUND OF PYRAZINIC ACID-CONTAINING A NEW DINUCLEAR COMPLEX ANION [CU-2(N-3)(6)](2-) - SYNTHESIS, SPECTRAL AND STRUCTURAL STUDY OF KCU2(PYRAZINATO)(N-3)(4)

A new complex of copper(II) azide with pyrazinic acid, of general form ula KCu2(pyrazinato)(N-3)(4) has been synthesized and characterized by spectroscopic and crystallographic methods. The structure of the comp lex consists of a new dinuclear complex anion [Cu-2(N-3)(6)](2-), pota ssium cations and neutral polymeric complex [Cu(pyrazinato)(N-3)]. Eac h distorted square-planar copper centre [Cu(l)] in the complex anion i s coordinated to four nitrogen atoms from two terminal and two mu-(1,1 ) bridging azido ligands [Cu-N distances 1.940(6)-2.011(5) Angstrom]. In the polymeric complex, each copper atom, Cu(2), is coordinated to N (41) of a terminal azido group and N(61), N(62) and O(31) from pyrazin ato anions to form infinite, ''neutral'' chains of polyhedra with orie ntations along [010]. The potassium cations are located in broad chann els which are a consequence of stacking of the copper complexes. The I R spectrum confirms the presence of different asymmetric azido ligands . The absorption frequencies of diagnostic values are given and discus sed. The electronic spectrum displays three absorption bands associate d with N-3-Cu-II charge transfer transitions. The EPR spectrum of the solid complex suggests an axial structure with non-coupled copper(II) atoms. Copyright (C) 1996 Elsevier Science Ltd