Architecture of framework copper(I) halide π-complexes with N-allyl-N,N,N′,N′-tetramethyl-ethylenediaminium and N,N′-diallyl-N,N,N′,N′-tetramethylethylenediaminium: Synthesis and crystal structure of [{C2H4N2(H+)×(CH3)4(C3H5)} Cu4Cl6] and [{C2H4N2(CH3)4(C3H5)2}0.5Cu2Cl1.67Br1.33

Abstract

N,N,N′,N′-tetramethylethylenediamine is obtained by the reaction of ethylenediamine with formaldehyde and formic acid (the Eschweiler-Clarke reaction) and then alkylated with allyl chloride (or bromide) in a ratio of 1:1 or 1:2 to obtain N-allyl-N,N,N′,N′-tetramethylethylenediaminium and N,N′-diallyl-N,N,N′,N′-tetramethylethylenediaminium bromide respectively. [{C2H4N2(H+)(CH3)4(C3H5)}Cu4Cl6] (1) and [{C2H4N2(CH3)4(C3H5)2}0.5Cu2Cl1.67Br1.33] (2) π-complexes are obtained from alcohol solutions containing an ethylenediamine derivative and copper(II) chloride by ac-electrochemical synthesis on copper wire electrodes. An XRD study of the complexes is carried out. The crystals are monoclinic; 1: P21/n space group, a = 9.0081(6) A, b = 12.5608(7) A, c = 16.8610(10) A, β = 102.061(3)°, V = 1865.7(2) A3, Z = 4; 2: C2/c space group, a = 14.462(2) A, b = 12.519(1) A, c = 12.762(2) A, β = 107.861(5)°, V = 2199.1(4) A3, Z = 8. The structure of 1 consists of infinite copper halide networks with four crystallographically independent copper atoms, one of which coordinates the double bond of the allyl group of the ligand. The [C2H4N2(H)(CH3)4(C3H5)]2+ cations are attached above and below the plane of the network. The individual fragments are bonded via an extensive system of (N)H…Cl and (C)H…Cl hydrogen bonds. The structure of 2 contains a three-dimensional copper halide framework whose cavities contain the [C2H4N2(CH3)4(C3H5)2]2+ cations that are π-coordinated with copper(I) atoms. In both structures, the Cu(I) atom that coordinates the C=C bond has a trigonal-pyramidal coordination environment consisting of the double C=C bond of the corresponding ligand and three halogen atoms. The other Cu(I) atoms have a tetrahedral environment consisting solely of halogen atoms. The Cu-(C=C) distance is 1.958(1) A, (1) and 1.974(1) A (2).