Bis(1-carbamimidoyl-2-ethylisourea)copper(II) bis(perchlorate)

The title complex, [Cu(C4H10N4O)2](ClO4)2 or [Cu(L 1e)2](ClO4)2, where L 1e is 1-carbamimidoyl-2-ethylisourea, was obtained from the ethanolysis reaction of 2-cyanoguanidine and copper(II) perchlorate hexahydrate in a 2:1 molar ratio. The two bidentate L 1e ligands are coordinated to the CuII center through N-donor atoms, leading to the CuN4 chromophore. The CuII environment is slightly distorted square-planar, with a dihedral angle of 5.17 (6)° between the two six-membered chelate rings. One of the ClO4 − anions is disordered over two positions in a 0.6:0.4 ratio.


Data collection
Bruker SMART APEX CCD areadetector diffractometer Absorption correction: multi-scan (SADABS;Sheldrick, 1996) Table 1 Selected geometric parameters (Å , ). reveals that the mono-chelate complex is comprised solely of dinuclear [Cu(L 1e )Cl 2 ] 2 units (L 1e = 1-carbamimidoyl-2ethylisourea) in which each Cu II center is bridged by the neighboring chloride in the axial position to give a squarepyramidal geometry.
Herein, we present the structure of a copper(II) complex containing the same bidentate L 1e ligand but with the charge balance provided by two perchlorate anions instead of the chloride anions as described above. The [Cu(L 1e ) 2 ](ClO 4 ) 2 was obtained from the similar procedure as previously reported by Begley et al. (1986), but using a 2:1 molar ratio of 2cyanoguanidine to copper(II) perchlorate hexahydrate. Structure determination on the title product reveals a [Cu(L 1e ) 2 ] 2+ cation and two ClO 4counter anions. Fig. 1 shows the [Cu(L 1e ) 2 ] 2+ unit. The Cu II center is coordinated by two N,Nbidentate ligands, thus yielding a slightly distorted square-planar CuN 4 geometry ( Table 1) with Cu-N bond distances of 1.9376 (15)-1.9641 (15) Å. The bite angles of 89.00 (6)° for N1-Cu1-N4 and 89.27 (7) ° for N1-Cu1-N8 are slightly less than 90° with a dihedral angle of 5.17 (6) ° between the two six-membered chelate rings. Additionally, the intermolecular hydrogen bonds of the type N-H···O (perchlorate) also stabilize the [Cu(L 1e ) 2 ] 2+ cation to give a twodimentional layered structure (Fig.2)

S2. Experimental
Suitable single crystals of the title complex were raised from the initial product, which was obtained from the ethanolysis reaction of 2-cyanoguanidine precursor (0.1682 g, 2 mmol, Aldrich, 99%) in the presence of copper(II) perchlorate hexahydrate (0.3705 g, 1 mmol,Aldrich, 98%). The reaction was carried out in the refluxing condition for 24 h, then cooled down and filtered off to remove excess solid. The reddish-pink powder was obtained by reducing the solvent volume. The pink blocky single crystals were grown by slow vapor phase diffusion of diethylether into the methanolic solution of this product at room temperature over a few days.

Bis(1-carbamimidoyl-2-ethylisourea)copper(II) bis(perchlorate)
Crystal data [Cu(C 4   Hydrogen site location: inferred from neighbouring sites H-atom parameters constrained where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.003 Δρ max = 0.77 e Å −3 Δρ min = −0.30 e Å −3 Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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. Rfactors 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ.