Crystal structures of (1,4,7,10-tetraazacyclododecane-κ4 N)bis(tricyanomethanido-κN)nickel and (1,4,7,10-tetraazacyclododecane-κ4 N)(tricyanomethanido-κN)copper tricyanomethanide

Two new nickel and copper tricyanomethanide (tcm−) complexes with 1,4,7,10-tetraazacyclododecane (cyclen) as a co-ligand have been synthesized and structurally characterized.


Structural commentary
In (I), the nickel cation binds to the four N atoms of the cyclen and two N atoms of two tcm À anions, forming a distorted octahedral geometry with the tcm À ligands mutually cis. The equatorial plane is therefore formed by two N atoms (N1, N3) of the cyclen unit and the N5 and N8 atoms of the coordinating tcm À anions. The apical sites are occupied by N2 and N4 from the cyclen ligand, Fig. 1.
In (II), the copper cation is also bound to the four N atoms (N1, N2, N3, N4) of a cyclen ligand but in the basal plane with the N5 atom of the tcm À ligand in an apical site, forming a fivecoordinate cation with a distorted square-pyramidal coordin-ation geometry. The second tcm À anion does not enter the inner coordination sphere of the metal (Fig. 2), but acts as a counter-anion that is linked to the cation in the asymmetric unit through an N1-H1Á Á ÁN9 hydrogen bond (Fig. 2).

Figure 4
The three-dimensional network of (II), formed by hydrogen-bonding interactions, viewed along the a axis. Hydrogen bonds are drawn as dashed lines. Each tcm À ligand is almost planar, with the mean deviations from the planes through all atoms of the coordinating tcm À anions being 0.0128 and 0.0322 Å , respectively in (I). For (II), the corresponding deviations from the planes of the coordinating tcm À anion and the tcm À counter-anion are 0.0211 and 0.0074 Å respectively. Bond lengths and angles within the anions are also in good agreement with those found in other tcm À complexes (Batten et al., 1999;Yuste et al., 2008).

Supramolecular features
In the crystal structure of (I), each complex molecule is linked to five others by a series of N-HÁ Á ÁN and C-HÁ Á ÁN hydrogen bonds. N1-H1Á Á ÁN10 and N2-H2Á Á ÁN6 hydrogen bonds each form inversion dimers, joining the complex molecule to two neighbouring molecules and generating R 2 2 (16) ring motifs (Bernstein et al., 1995). N3-H3Á Á ÁN7 and N4-H4Á Á ÁN6 hydrogen bonds link two additional complex molecules. A C4-H4BÁ Á ÁN9 contact involves the fifth complex. This array of contacts combines to generate an extensive three-dimensional network (Fig. 3, Table 3).
In the crystal structure of (II), N1-H1Á Á ÁN6 and N3-H3Á Á ÁN7 hydrogen bonds each form inversion dimers, also linking the complex cation to two neighbouring cations and generating R 2 2 (16) ring motifs. Each complex molecule is also linked via N-HÁ Á ÁN and C-HÁ Á ÁN hydrogen bonds to two adjacent complex cations and three tcm À anions, forming another extensive three-dimensional network (Fig. 4, Table 4).

Database survey
Structures of transition-metal complexes with two or more tcm À ligands are quite common with 47 unique compounds recorded in the Cambridge Crystallographic Database (Version 5.36, November 2014 with two updates; Groom & Allen, 2014). Of these the majority, 35, are polymeric or oligomeric systems. Five of these are Ni II complexes but only two of them [tris(2-aminoethyl)amine]bis(tricyanomethanide)nickel(II) (Luo et al., 2014) and cis-bis(tricyanomethanide- , 2007) are mononuclear, each with a distorted octahedral coordination environment and with the tcm À ligands mutually cis.
After stirring for another 5 min, the purple solution was filtered and the filtrate slowly evaporated in air. After two weeks, purple block-like crystals of (I) were isolated in 31% yield.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 5. In (I), the H1, H2, H3 and H4 atoms bound to the amine N atoms were found in a difference Fourier map and refined freely with isotropic displacement parameters. The N-H distances ranged from 0.90 (2) to 0.95 (2) Å . H atoms bound to carbon were constrained to an ideal geometry with C-H distances of 0.99 Å , and with U iso = 1.2U eq (C) for CH 2 . In (II), the amine H1, H2, H3 and H4 atoms and the H atoms linked to carbon were refined similarly. For both compounds, data collection: APEX2 (Bruker, 2010); cell refinement: SAINT (Bruker, 2010); data reduction: SAINT (Bruker, 2010); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2015); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).