THE CRYSTAL-STRUCTURE OF A MACROCYCLE CONTAINING PYRIDINE AND PIPERAZINE SUBUNITS, AND OF A CU(I) COMPLEX OF ITS DIPROTONATED CATION

The 2:2 macrocycle C22H30N6, containing pyridine and piperazine subuni ts, crystallizes in monoclinic space group C2/c with a = 17.614(3), b = 9.696(2), c = 12.662(2) Angstrom, beta = 111.65(2)degrees, V = 2010( 1) Angstrom(3), Z = 4. The structure was refined to R = 0.036 for 1863 observed reflections. The molecule lies on an inversion center, and t he piperazine subunits have the chair conformation. Surprisingly, this macrocycle becomes diprotonated, and the Cu(II) is reduced to Cu(I) u pon reaction with CuCl2 in methanol. The resulting Cu(I) complex of th e diprotonated macrocyclic dication, [CuCl(C22H32N6)]Cl-2 . 2H(2)O, cr ystallizes in monoclinic space group P2(1)/n with a = 10.745(1), b = 1 3.728(2), c = 17.774(2) Angstrom, beta = 98.08(1)degrees, V = 2596(1) Angstrom(3), Z = 4. The structure was refined to R = 0.058 for 3989 ob served reflections. The Cu atom coordinates approximately linearly to one of the pyridine N atoms and a chloro ligand with Cu-N distance 1.9 47(3) Angstrom, Cu-Cl distance 2.133(1) Angstrom, and N-Cu-Cl angle 16 4.5(1)degrees. While the piperazine subunits maintain their chair conf ormations, one N of each is protonated and turned outward. The unproto nated piperazine N atoms form long interactions of 2.488(4) and 2.508( 4) Angstrom distance to the Cu atom.