Bromido(1,4,7,10,13-pentaazacyclohexadecane)cobalt(III) dibromide dihydrate

The title salt, [CoBr(C11H27N5)]Br2·2H2O, contains a complex cation with mirror symmetry and two Br− counter-anions that are likewise located on the mirror plane. The central CoIII atom of the complex cation has one Br− ion in an axial position, one N atom of the pentadentate macrocyclic ligand in the other axial position and four N atoms of the ligand in equatorial positions, defining a distorted octahedral coordination geometry. The macrocyclic ligand is coordinated to the CoIII atom within a 5, 6, 5 arrangement of chelate rings in the equatorial plane of the four N atoms. Due to symmetry, the configuration of the chiral N atoms is 1RS, 4SR, 10RS, 13SR. In the crystal, N—H⋯Br, O—H⋯Br and N—H⋯O hydrogen bonds between the complex cation, anions and lattice water molecules generate a three-dimensional network.

The title salt, [CoBr(C 11 H 27 N 5 )]Br 2 Á2H 2 O, contains a complex cation with mirror symmetry and two Br À counter-anions that are likewise located on the mirror plane. The central Co III atom of the complex cation has one Br À ion in an axial position, one N atom of the pentadentate macrocyclic ligand in the other axial position and four N atoms of the ligand in equatorial positions, defining a distorted octahedral coordination geometry. The macrocyclic ligand is coordinated to the Co III atom within a 5, 6, 5 arrangement of chelate rings in the equatorial plane of the four N atoms. Due to symmetry, the configuration of the chiral N atoms is 1RS, 4SR, 10RS, 13SR. In the crystal, N-HÁ Á ÁBr, O-HÁ Á ÁBr and N-HÁ Á ÁO hydrogen bonds between the complex cation, anions and lattice water molecules generate a three-dimensional network.
In the title complex, [CoBr(C 11 H 27 N 5 )]Br 2 . 2H 2 O, the Co III atom is surrounded by one Branion and N atoms of the macrocyclic ligand to form a distorted octahedral environment (Fig.1). The Co-N(axial) bond in the complex is longer than the Co-N(equatorial) bonds, presumably caused by the trans effect of the Br atom. The average Co-N(equatorial) distance of 1.967 Å is shorter than that in cobalt(III) complexes of 1,4,7,11,14-pentaazacycloheptadecane (Eigenbrot et al., 1988) and1,4,7,11,15-pentaazacyclooctadecane (Curtis et al., 1987a). The macrocyclic ligand adopts a stable conformation with the one six-membered chelate ring in chair form and four five-membered chelate rings in gauche forms. The macrocyclic ligand is coordinated in a configuration with five-, six-, and five-membered chelate rings in the equatorial plane. The deviation of the Co III atom from the equatorial plane is 0.03 A. The N3 and N3* atoms have opposite chirality giving the meso-syn diastereoisomer. The macrocyclic ligand coordinates in the meso-syn configuration with hydrogen atoms on N2, N2*, N3, and N3* on the same side of the equatorial plane relative to the axially coordinating bromide anion. Due to mirror symmetry of the entire complec cation, the configurations of the four chiral amine N atoms are 1RS, 4SR, 10RS, and 13SR. Hydrogen bonds between N atoms of the macrocyclic ligand, water molecules and bromide counter anions exists ( Fig. 2; Table 1), stabilizing the crystal packing within a three-dimensional network.

Refinement
All H atoms attached to C and N atoms were placed geometrically (C-H = 0.97 and N-H = 0.91 Å) and were refined as riding with U iso (H) = 1.2U eq (C,N). The water H atoms were located in difference Fourier maps and were refined initially with restrains O-H = 0.85 (2) Å. In the last cycles of refinement, they were eventually refined as riding, with U iso (H) = 1.5U eq (O).

Figure 1
The molecular structure of the title compound, with 50% probability displacement ellipsoids and the atom-numbering scheme.  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.89 e Å −3 Δρ min = −0.88 e Å −3 Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq