Crystal and molecular structure of dibromobis(benzimidazole)copper(II)

The reaction of CuBr₂ with benzimidazole and HBr in aqueous solution leads to the formation of Cu(C₇H₆N₂)₂Br₂ as dark-brown, stable monoclinic crystals. Space groupP2₁/c witha=13.794(5),b=7.875(2),c=14.510(6) Å;=105.82(5)°;V _c =1516(5) ų;D _x =2.010(3) Mg m^–3. The structure was refined by a full-matrix least-squares procedure to giveR=R _w =0.045 for 1932 intensities above 3(I). The copper (II) ions are four coordinates in the form of a distorted flattened tetrahedron CuN₂Br₂, with the bond lengths Cu-Br(1)=2.402(1), Cu-Br(2)=2.446(1), Cu-N(1)=1.976(7), and Cu-N(11)=1.946(7) Å. The flattened angles are Br-Cu-Br=139.0(1) and N-Cu-N=154.6(3)°. The geometry of intermolecular and intramolecular hydrogen bonds is discussed.