Redetermination of the crystal structure of bis[ N , N ′ -ethylenebis(acetylacetoniminato) nickel(II)] sodium perchlorate, C 24 H 36 ClN 4 NaNi 2 O 8


 C24H36ClN4NaNi2O8, monoclinic, C2/c (no. 15), a = 19.5909(11) Å, b = 10.8023(6) Å, c = 14.5722(8) Å, β = 112.032(1)°, V = 2858.7(3) Å3, Z = 4, R
 
 gt
 (F) = 0.0260, wR
 
 ref
 (F
 2) = 0.0701, T = 93(2) K.


Source of material
Preparation of 5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-4,6,11,13-tetraene (LH 2 ): Ethylenediamine (6.7 mL, 0.1 mmol) was added to acetylacetone (10.29 mL, 0.1 mmol) in methanol (50 mL) taken in a 100 mL volumetric flask. The solution was stirred on a magnetic stirrer while 70% perchloric acid (8.9 mL, 0.1 mmol) was added slowly from a dropping funnel. The temperature of the reaction mixture was maintained at 333-338 K, at which stage the solution turned yellow. The resulting mixture was refluxed for 15 h. The reaction mixture was then allowed to stand for 2-3 days at room temperature, after which the solid product was filtered off, washed with methanol and finally with diethyl ether. The white crystalline product, LH 2 , was dried in vacuo.
Preparation of nickel(II) complex of L: Nickel acetate tetrahydrate (0.25 g, 1.0 mmol) and LH 2 (0.449 g, 1.0 mmol) were dissolved separately in 30 mL hot methanol and mixed. After heating on a water bath for a few minutes, the solution immediately turned brown. The solution was then heated for 30 min to reduce the volume to 20 mL. Sodium perchlorate (0.368 g, 3.0 mmol) was added to the cooled solution. After standing overnight, a deep-brown precipitate, anticipated to be [NiL](ClO 4 ) 2 , was separated by filtration, washed with methanol followed by diethyl ether and stored in a vacuum desiccator.
Preparation of crystals: Crystals were grown by the slow crystallization from its acetonitrile/n-hexane (1:1, v/v) solution. X-ray crystallography proved to the formulation to be [NiL] 2 Na(ClO 4 ), a known species [6], so no further characterisation was performed. The melting point of the sample was not determined as perchlorates are explosive at elevated temperatures.

Experimental details
The C-bound H atoms were geometrically placed (C-H = 0.95-0.99 Å) and refined as riding with U iso (H) = 1.2-1.5U eq (C). Owing to poor agreement, one reflection, i.e. (−1 1 6), was omitted from the final cycles of refinement.

Comment
In continuation of recent and on-going studies of N 4donor macrocycles and their transition metal complexes [7,8], an attempt was made to synthesise the nickel (II) complex derived from 5,7,12,14-tetramethyl-1,4,8,11tetraazacyclotetradeca-4,6,11,13-tetraene, prepared from the 1:1 condensation reaction of ethylenediamine and acetylacetone. However, under the reaction conditions employed, cyclisation did not occur/persist and the title complex [NiL] 2 Na(ClO 4 ), hereafter (I), was obtained. While the crystal structure of (I) has been reported previously [6], the new data enables a more detailed discussion of geometric parameters and the absence of disorder facilitates the discussion of supramolecular association in the crystal.  The molecular structure of two-fold symmetric (I) is shown in the figure (70% probably displacement ellipsoids); the Na1 and Cl1 atoms lie on the two-fold axis of symmetry. The nickel(II) centre lies within a square-planar geometry defined by a N 2 O 2 donor set with the r.m.s. deviation for the five atoms being 0.0175 Å; the maximum deviation from the least-squares plane being 0.0208 (5)  The structure of (I) is not the only example where a second residue links two NiL complexes. In another example, Zn(NCS) 2 mediates the formation of a threemolecule aggregate, with the zinc centre attaining a N 2 O 4 donor set [10]. With each of Cd(NCS) 2 and Cd(N 3 ) 2 , NiL 2 is an ancillary ligand in one-dimensional coordination polymers formulated as {Cd(NCS) 2 NiL 2 } n and {Cd(N 3 ) 2 NiL 2 } n , respectively [11].
An analysis of the calculated Hirshfeld surfaces and of the full and delineated two-dimensional fingerprint plots was also conducted, being calculated with Crystal Explorer 17 [13] employing literature methods [14].