Preparation and structure of chloro-copper(II) complexes of 7-azaindole

Abstract

The light green trans-CuCl 2 (Haza) 2 adduct precipitates immediately from mixtures of CuCl 2 •2H 2 O with excess 7-azaindole (Haza) in methanol. Upon standing in azaindole-rich solution, this solid is replaced by a deep green Cu 2 Cl 4 (Haza) 6 compound, whose crystal structure (orthorbombic, Fdd2, a = 26.558, b = 23.750, c = 12.727 Ǻ, Z = 8, R = 0.068, R w = 0.066) shows the presence of square-planar [Cu(Haza) 4 ] 2+ and trans-[CuCl 2 (Haza) 2 ] units connected by bridging Cl − ions, making each Cu atom (4 + 2)-coordinated. Azaindole is bonded to the metal via the pyridine N7 site, whereas the five-membered ring retains its N1—H proton. The azaindole ligands are disordered over two orientations in the [CuCl 2 (Haza) 2 ] unit. The square-planar Cu species and apical Cl − ions lie on a twofold axis and define along c an infinite chain based on the [Formula: see text] pattern. Equimolar mixtures of azaindole and CuCl 2 •2H 2 O yield a brown Cu 4 OCl 6 (Haza) 4 compound. The crystal structure of its ethyl acetate solvate (monoclinic, P2 1 /c, a = 11.661, b = 22.415, c = 15.077 Ǻ, β = 109.85°, Z = 4, R = 0.048, R w = 0.054) shows the presence of a tetranuclear cluster consisting of a μ 4 -oxide ion surrounded by a tetrahedron of Cu(II) atoms bridged in pairs by chlorine atoms. The trigonal-bipyramidal coordination of each copper atom is completed by a monodentate N7-bonded azaindole molecule hydrogen bonded to bridging chlorines via N1—H. The influence of complexation on the infrared spectrum of azaindole is discussed.