Tetraammine(carbonato-κ2 O,O′)cobalt(III) perchlorate

In the title complex, [Co(CO3)(NH3)4]ClO4, both the cation and anion lie on a mirror plane. The CoIII ion is coordinated by two NH3 ligands and a chelating carbonato ligand in the equatorial sites and by two NH3 groups in the axial sites, forming a distorted octahedral geometry. In the crystal, N—H⋯O hydrogen bonds connect the anions and cations, forming a three-dimensional network.

In the title complex, [Co(CO 3 )(NH 3 ) 4 ]ClO 4 , both the cation and anion lie on a mirror plane. The Co III ion is coordinated by two NH 3 ligands and a chelating carbonato ligand in the equatorial sites and by two NH 3 groups in the axial sites, forming a distorted octahedral geometry. In the crystal, N-HÁ Á ÁO hydrogen bonds connect the anions and cations, forming a three-dimensional network.
Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: POV-RAY (Persistence of Vision Team, 2004) and PLATON (Spek, 2009); software used to prepare material for publication: PLATON (Spek, 2009 Cobalt(III) ammine complexes are well known and were widely studied by Werner (1908). In aqueous medium, the chelated ring of a bicarbonate complex is opened and protonation occurs due to hydrolysis which leads to instability. The less stability of a carbonato complex in acidic aqueous medium not only leads to protonation but also makes a site for metallation (McClintock et al., 2008;Cavigliasso et al., 2008). The carbanato complex also plays a vital role in photocleavage of proteins with high preference and it assists the new models of transition metal complexes for the photocleavage (Kumar & Thota, 2005). The P-O bonds present in the phosphodiester of DNA have been cleaved hydrolytically by the imitative of chelated carbonato complexes (Xu et al., 2009). Recently the carbonate radical generation by photochemical reaction of carbonatopentaamminecobalt(III) complex was also reported (Busset et al., 2007). The photochemical reactions of carboxylatopentamminecobalt(III) complexes lead to the reduction of metal centre and the formation of oxidized ligands, which may lead to the synthesis of value added products (Palaniappan et al., 2001;Jothivenkatachalam et al., 2013).
The crystal structure of the title complex is composed of one [CoCO 3 (NH 3 ) 4 ] + cation and a ClO 4anion in a 1:1 molar ratio. A mirror plane bisects the cation as well as the perchlorate anion, hence half a cation and an anion form the asymmetric unit. The molecular structure of the title complex is shown in Fig. 1. The Co III ion is coordinated by two NH 3 ligands and a chelating carbanato ligand equatorially, by two NH 3 groups axially. Unlike other d 6 octahedral Co(II) complexes the title complex shows a distortion from ideal octahedral geometry. This can be noted by the deviation of O1 -Co-O1 i bond angle of 68.41 (7)° from the ideal octahedral bond angle of 90°. This is due to the steric restriction of the carbanato ligand in the formation of four membered chelate ring. The observed O-Co-O bond angle is similar to those observed in related [Co(CO 3 )(N) 4 ]+ species (Kim et al., 1998;Massoud et al., 2000). The chelating CO 3 2has a slight influence on the N1-Co-N1 i bond angle trans to the O1-Co-O1 i angle. The N1-Co-N1 i bond angle is 94.22 (8)°. The Co-N bond distances observed for the complex under investigation is similar to those reported earlier (Massoud et al., 2000;Sharma et al., 2004a,b;Sharma et al., 2005a,b). In the crystal, N-H···O hydrogen bonds connect anions and cations to form a three-dimensional network ( purple crystals of X-ray quality separated out after one week. These were filtered, washed with ethanol, acetone and airdried.

Refinement
The H atoms attached to N3 and N4 were located from a difference Fourier map and were refined freely. The H atoms attached to N1 were placed in geometrically idealized positions and constrained to ride on their parent atom, with N-H distance of 0.89 Å, and with U iso (H) set at 1.5U eq (N).

Figure 1
The molecular structure of the title compound, with anisotropic displacement ellipsoids drawn at 50% probability level  The packing of the complex viewed along the c axis, showing N-H···O hydrogen bonds as dashed lines.

Special details
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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.