Synthesis, spectral and structural characterization of three zinc(II) azide complexes with aminopyrazine

The reaction between zinc(II) azide, Zn(N-3)(2) and aminopyrazine (ampyz) afforded the complexes: [Zn(N-3)(2)(ampyz)(2)] (1), [Zn(N-3)(2)(ampyz)](n) (2) and [Zn-3(N-3)(6)(ampyz)(2)](n) (3). These complexes are characterized by spectroscopic and crystallographic methods. The IR spectra of these compounds are measured and discussed. The structure of I consists of isolated tetrahedral zinc atom surrounded by two mono-dentate N-ampyz and two terminal azido ligands. Complex 2 features a zigzag chain of zinc centers in which each zinc is surrounded by alternate di-EO (end-on) and di-EE (end-to-end) azide bridges, the chain thus contains alternate four-membered Zn2N2 and eight-membered Zn-2(NNN)(2) rings. The two ampyz ligands are located in cis-arrangement and each of them further binds another zinc atom giving rise to a 3D network. Complex 3 contains two structurally different zinc atoms; the six-coordinate Zn(1) center links two di-EO azido bridges and two trans ampyz, thus having ZnN6 chromophore. The five-coordinate Zn(2) center binds two di-EO bridging azido groups and the fifth position is occupied by an N atom from a bridging ampyz molecule. Both zinc centers, therefore participate in the formation of a 1D chain of cyclic Zn2N2 units. Each ampyz ligand binds another zinc atom via the second pyrazinic N atom giving another cross-chain and thus the structure consists of 2D sheets. In these three complexes the azido ligands of all types are asymmetric and linear within the experimental error. (C) 2007 Elsevier B.V. All rights reserved.