Bis(1-methyl-piperazine-1,4-diium) tetra-bromidocuprate(II).

The title compound, (C(5)H(14)N(2))[CuBr(4)], was synthesized by hydro-thermal reaction of CuBr(2) with 1-methyl-piperazine in an HBr/water solution. Both amine N atoms are protonated. The Cu-Br distances in the tetrahedral anion are in the range 2.3809 (11)-2.4131 (11) Å. In the crystal, moderately strong and weak inter-molecular N-H⋯Br hydrogen bonds link the anion and cation units into an infinite two-dimensional network parallel to the ab plane.

Bis(1-methyl-piperazine-1,4-diium) tetra-chloridocuprate(II).

The title compound, (C(5)H(14)N(2))[CuCl(4)], was synthesized by hydro-thermal reaction of CuCl(2) with 1-methyl-piperazine in an HCl/water solution. Both amine N atoms are protonated. The piperazine ring adopts a chair conformation. The Cu-Cl distances in the tetrahedral anion are in the range 2.2360 (7)-2.2732 (7) Å. In the crystal, moderately strong and weak inter-molecular N-H⋯Cl hydrogen bonds link the anion and cation units into an infinite two-dimensional network parallel to the ab plane.

Bis(4-methyl-morpholin-4-ium) tetra-bromidozincate(II).

The title compound, (C(5)H(12)NO)(2)[ZnBr(4)], was synthesized by hydro-thermal reaction of ZnBr(2) with 4-methyl-morpholine in a HBr/distilled water solution. Each of the two independent cations exhibits a chair conformation; the anion deviates slightly from an tetrahedral configuration. The Zn-Br distances in the anion are in the range of 2.3996 (9)-2.4247 (9) Å. All of the amine H atoms are involved in bifurcated inter-molecular N-H⋯Br hydrogen bonds, building up a trimer.

(±)-2-Methyl-piperazin-1-ium perchlorate.

In the title compound, C(5)H(13)N(2) (+)·ClO(4) (-), the monoprotonated piperazine ring adopts a chair conformation. In the crystal structure, cations and anions are linked by inter-molecular N-H⋯O and N-H⋯N hydrogen bonds into layers parallel to (01).

Piperazine-1,4-diium bis-(perchlorate) dihydrate.

The asymmetric unit of the title compound, C(4)H(12)N(2) (2+)·2ClO(4) (-)·2H(2)O, contains half of a piperazinediium cation, one perchlorate anion and one water mol-ecule. The diprotonated piperazine ring, which is completed by crystallographic inversion symmetry, adopts a chair conformation. In the crystal structure, the cations and anions are linked by inter-molecular N-H⋯O and O-H⋯O hydrogen bonds into a three-dimensional network.

(R)-2-Methyl-piperazine-1,4-diium diaqua-tetra-chloridoferrate(II).

In the title salt, (C(5)H(14)N(2))[FeCl(4)(H(2)O)(2)], the Fe(II) cation is coordinated by four Cl(-) anions and two water mol-ecules in a distorted octa-hedral geometry. The piperazine ring adopts a normal chair conformation. Inter-molecular N-H⋯Cl, N-H⋯(Cl,Cl) and O-H⋯Cl hydrogen bonding is present in the crystal structure.