trans-Tetraaqua(dibromo)nickel(II) 4,7,13,16,21,24-hexaoxa-1,10-diazoniabicyclo[8.8.8]hexacosane dibromide:: Synthesis and crystal structure

A new complex, trans-tetraaqua(dibromo)nickel(II) 4,7,13,16,21,24-hexaoxa-1,10-diazoniabicyclo[8.8.8]hexacosane dibromide, [NiBr2(H2O)(4)][H-2(Crypt-222)]Br-2 (I), was synthesized and its crystal sructure was studied by X-ray diffraction analysis: space group P2(1)/c, a = 13.573, b = 8.328, c = 14.523 angstrom, beta = 111.08 degrees, Z = 2. Structure I was solved by a direct method and refined by full-matrix least-squares method in anisotropic approximation to R = 0.067 on 2684 independent reflections (CAD-4 autodiffractometer, lambda MoK alpha). The octahedral complex molecule [NiBr2(H2O)(4)] and the [H-2(Crypt-222)](2+) dication (with two protonated N atoms) are located around the inversion center; the latter is statistically disordered. The dication contains trifurcate hydrogen bonds N-H(O-...)(3)- Crystal I also contains intermolecular hydrogen bonds O(w)-(HBr-)-Br-..., which join the complex molecules [NiBr2(H2O)(4)] and the Br- anions into infinite "thick" layers parallel to the plane yz.