BIS(4-AMINOPYRIDINIUM) HEXABROMODICUPRATE(II) DIAQUATETRABROMODICOPPER(II)

The structure of (C5H7N2)2[Cu2Br6].[Cu2Br4(H2O)2] consists of stacks o f altemating Cu2Br62- anions and neutral Cu2Br4(H2O)2 molecules with t he cations separating the stacks. The two chemically distinct species within the stack are both centrosymmetric quasi-planar bibridged dimer s. The water molecules in the neutral dimers are located in trans posi tions. Cu-Br distances within the two dimers are essentially identical with Cu-Br(terminal) = 2.401 (average) and Cu-Br(bridging) = 2.443 an gstrom (average). The bridging Cu-Br-Cu angle is substantially smaller in the neutral dimer [92.3 (1) versus 95.6 (1)-degrees]. The dimers a re linked by longer semi-coordinate Cu ... Br bonds [range 2.940 (2)-3 .200 (2) angstrom] to form stacks (represented by an envelope diagram) .