(Nitrato-κ2 O,O′)bis(1,10-phenanthroline-κ2 N,N′)copper(II) tricyanomethanide

The title compound, [Cu(NO3)(C12H8N2)2][C(CN)3], is formed of discrete [Cu(NO3)(phen)2]+ complex cations (phen is 1,10-phenanthroline) and C(CN)3 − counter-anions. The CuII atom has an asymmetric tetragonal–bipyramidal (4 + 1+1) stereochemistry with a pseudo-C 2 symmetry axis bisecting the nitrate ligand and passing through the CuII atom between the two phen ligands. The four N atoms of the phen ligands coordinate to the CuII atom with Cu—N distances in the range 1.974 (2)–2.126 (2) Å, while the two O atoms coordinate at substantially different distances [2.154 (2) and 2.586 (2) Å]. The structure is stabilized by C—H⋯O hydrogen bonds and weak π–π interactions between nearly parallel benzene and pyridine rings of two adjacent phen molecules, with centroid–centroid distances of 3.684 (2) and 3.6111 (2) Å, and between π-electrons of the tricyanomethanide anion and the pyridine or benzene rings [N⋯(ring centroid) distances = 3.553 (3)–3.875 (3) Å].


Katarína Lacková and Ivan Potočňák Comment
The shape of coordination polyhedra (SCP) in the case of five-coordination is one of the current problems in coordination chemistry. With the aim of establishing possible reasons for different SCP in related compounds, our research group has previously prepared and studied the structures of five-coordinate copper(II) complexes of the general formula [Cu(L) 2 X]Y, where L is 1,10-phenanthroline (phen) or 2,2′-bipyridine (bpy), X is N(CN) 2or ONC(CN) 2and Y is 1-anion (Potočňák et al., 2005(Potočňák et al., , 2008. The obtained results showed that the preferred SCP for compounds with phen is close to trigonal bipyramid, whereas SCP for bpy compounds is close to tetragonal pyramid. It is known that tricyanomethanide anion (tcm, C(CN) 3 -) can coordinate similarly as N(CN) 2and ONC(CN) 2anions (Golub et al., 1986). Thus, to verify the findings about SCP, we have attempted to prepare compounds with X = tcm and Y = Clor Brand checked their SCP.
However, X-ray structure analysis of four prepared complexes has shown that their formulae are [Cu(L) 2 Y]tcm, thus smaller Cland Branions were coordinated while larger tcm anion remained out of coordination sphere (Lacková, 2012). Therefore, we have decided to replace smaller Clor Branions by larger NO 3anion with the hope that it remains uncoordinated. Nevertheless, the title compound, [Cu(NO 3 )(phen) 2 ]tcm with coordinated NO 3and uncoordinated tcm anions has been prepared during our attempts and we present its structure here.
Each of the two phen molecules in the title compound possesses one nitrogen atom (N20 and N40) occupying an equatorial position and one nitrogen atom (N10 and N30) coordinated in an axial position (corresponding bond lengths are reported in Table of geometric parameters), two remaining equatorial positions are occupied by O1 and O2 atoms from the nitrato ligand. Aromatic rings of phen molecules are nearly planar; the largest deviation of atoms from their mean planes is 0.060 (3) Å for C13 atom and bond distances and angles are normal (van Meerssche et al., 1981;Marsh, 1997;Chen et al., 2005;Ovens et al., 2010). The positive charge of the [Cu(NO 3 )(phen) 2 ] + cation is balanced by an uncoordinated tcm anion, which is settled under the "umbrella" of the copper atom and the two phen molecules. The N≡C as well as the C-C distances (Table of geometric  bonds (Golub et al., 1986). The bond angles around methanide and cyanide carbon atoms are, as expected, nearly 120 and 180° confirming sp 2 and sp hybridization states of the corresponding carbon atoms (Table of geometric

Experimental
The title compound was prepared by chance during our attempts to prepare [Cu(phen) 2 (tcm)]NO 3 compound with a fivecoordinated Cu II atom. Crystals of the title compound were prepared by mixing a 0.1 M aqueous solution of Cu(NO 3 ) 2 (5 ml, 0.5 mmol) with a 0.1 M methanol solution of 1,10-phenanthroline (10 ml, 1 mmol). To the resulting green solution, a 0.1 M aqueous solution of KC(CN) 3 (5 ml, 0.5 mmol) was added (all solutions were heated almost to boiling before mixing). After 15 days, green crystals were filtered off and dried in air.

Refinement
H-atoms were positioned geometrically and refined as riding atoms, with C-H = 0.93 Å and U iso (H) = 1.2U eq (C).

Computing details
Data collection: CrysAlis CCD (Oxford Diffraction, 2007); cell refinement: CrysAlis RED (Oxford Diffraction, 2007); data reduction: CrysAlis RED (Oxford Diffraction, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2001); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).    π-π interactions (dashed lines) between tcm, benzene and pyridine rings in the title compound (symmetry codes: (i) = 1 - x, -y, 1 -z; (ii) = -x, 1 -y, 1 -z). 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.