{2,2′-[N,N′-Bis(pyridin-2-ylmethyl)propane-1,3-diyldi(nitrilo)]diacetato}cobalt(III) hexafluoridophosphate acetonitrile 0.064-solvate

In the title compound, [Co(C19H22N4O4)]PF6·0.064CH3CN, commonly known as [Co(bppd)]PF6·0.064CH3CN, where bppd represents the historical ligand name N,N′-bis(2-pyridylmethyl)-1,3-diaminopropane-N,N′-diacetate, the CoIII atom is coordinated in a distorted octahedral geometry with an N4O2 donor atom set. The acetate O atoms, which exhibit monodentate coordination, are oriented in a trans configuration with respect to each other, whereas the pyridyl N atoms are coordinated in a cis configuration. The compound crystallizes with two crystallographically unique cations and two anions per asymmetric unit along with a disordered, partially occupied (occupancy = 0.128) acetonitrile solvent molecule. Crystals of the title complex were found to be twinned by pseudomerohedry with a 180° rotation around [10-1] and a refined contribution of 90.5 (3)% of the major twin component.

In the title compound, [Co(C 19 H 22 N 4 O 4 )]PF 6 Á0.064CH 3 CN, commonly known as [Co(bppd)]PF 6 Á0.064CH 3 CN, where bppd represents the historical ligand name N,N 0 -bis(2pyridylmethyl)-1,3-diaminopropane-N,N 0 -diacetate, the Co III atom is coordinated in a distorted octahedral geometry with an N 4 O 2 donor atom set. The acetate O atoms, which exhibit monodentate coordination, are oriented in a trans configuration with respect to each other, whereas the pyridyl N atoms are coordinated in a cis configuration. The compound crystallizes with two crystallographically unique cations and two anions per asymmetric unit along with a disordered, partially occupied (occupancy = 0.128) acetonitrile solvent molecule. Crystals of the title complex were found to be twinned by pseudomerohedry with a 180 rotation around [101] and a refined contribution of 90.5 (3)% of the major twin component.

Experimental
Crystal data [Co(C 19 Table 1 Selected bond lengths (Å ).  et al. (1997) for Co(bped) + , but with a somewhat less distorted octahedral coordination geometry in the present case.

Experimental
The H 2 bppd ligand was prepared by a three step synthetic procedure (Kissel et al., 2013) using simple starting materials, which produced higher yields than previously reported methods (Kanamori et al., 2001

Refinement
The structure of the title complex can be solved and refined in P2 1 /n routinely with R 1 of ca 0.11. Analysis of the data confirms that the crystals are likely a case of twinning by pseudomerohedry with a 180° rotation around [101] in this setting. With inclusion of the twin law, the batch scale factor refines to 0.905 (3) and R 1 values go below 0.03. Although quite satisfactory, residual electron density approximating an acetonitrile, the solvent of cyrstallization, is clearly present and can be further modelled. The occupancy of the CH 3 CN molecule was allowed to vary and refined to a nonchemically meaningful 11%, or 5.5% per cation/anion pair. Upon inspection, the refined bond lengths within the solvent were unreasonable, though, notably the C-C distance, and the molecule was then re-refined with isotropic displacement parameters and H atoms removed resulting in a slightly higher occupancy of 6.4 (5)% per cation/anion pair. As a comparison, another crystal isolated using the same crystallization method refined to an occupancy of 4.5% per cation/anion pair. Efforts to further model both the disorder and the partial occupancy were unfruitful and the overall effort involved does little to improve on the intial R 1 value with no CH 3 CN modelled at all, and makes no significant difference to the cation and anion models of (I).
All H atoms were geometrically placed (C-H = 0.93-0.97 Å) and refined as riding with the exception of the H atoms on the disordered, partially occupied CH 3 CN, which were not modelled, but included in the overall formulation.  View of the molecular structure of one cation of the title compound down the non-crystallographic 2-fold axis (approximate unit vector -0.290 0.896 0.332). H atoms have been removed for clarity.