Bis[μ-2-(2-pyridylmethyl­amino­meth­yl)phenolato]-κ4 N,N′,O:O;κ4 O:N,N′,O-bis­[(thio­cyanato-κN)copper(II)]

Gervas E Assey; Yohannes Tesema; Teshome Yisgedu; Yilma Gultneh; Ray J Butcher

doi:10.1107/S1600536809031742

. 2009 Aug 22;65(Pt 9):m1121–m1122. doi: 10.1107/S1600536809031742

Bis[μ-2-(2-pyridylmethylaminomethyl)phenolato]-κ⁴ N,N′,O:O;κ⁴ O:N,N′,O-bis[(thiocyanato-κN)copper(II)]

Gervas E Assey ^a, Yohannes Tesema ^a, Teshome Yisgedu ^a, Yilma Gultneh ^a, Ray J Butcher ^a,^*

PMCID: PMC2970067 PMID: 21577463

Abstract

The centrosymmetric binuclear complex, [Cu₂(C₁₃H₁₃N₂O)₂(NCS)₂], formed via phenolate oxygen bridges, involves the Cu^II atoms in a distorted square-pyramidal coordination [τ = 0.197 (1)]. A Cu⋯Cu separation of 3.2281 (3) Å is observed. The in-plane Cu—O_phenolate distance [1.9342 (8) Å] is shorter than the axial distance [2.252 (8) Å]. The Cu—N_amine and Cu—N_py distances are similar [2.0095 (10) and 2.0192 (10) Å, respectively]. The Cu—N_thiocyanate distance [1.9678 (11) Å] is in the range found for Cu—N distances in previously determined structures containing coordinated thiocyanate anions. There is an intermolecular hydrogen bond between the amine H atom and the S atom of a coordinated thiocyanate anion.

Related literature

For the chemical properties, ligand binding properties and the synthesis of related copper complexes: Kuzmic et al. (1992 ▶); Lim et al. (2006 ▶); Rogers & Wolf (2002 ▶); Sharma et al. (2008 ▶); Yisgedu (2001 ▶). For related structures, see: Assey et al. (2009 ▶); Biswas et al. (2005 ▶); Sarkar et al. (2006 ▶); Shakya et al. (2006 ▶); Wang & Li (2005 ▶); You & Zhu (2004 ▶, 2005 ▶); You (2005 ▶). For the τ parameter, see: Addison et al. (1984 ▶).

Experimental

Crystal data

[Cu₂(C₁₃H₁₃N₂O)₂(NCS)₂]
M _r = 669.75
Monoclinic,
a = 7.4747 (1) Å
b = 16.9237 (3) Å
c = 11.0714 (2) Å
β = 91.1317 (18)°
V = 1400.25 (4) Å³
Z = 2
Mo Kα radiation
μ = 1.71 mm⁻¹
T = 200 K
0.44 × 0.37 × 0.28 mm

Data collection

Oxford Diffraction Gemini R diffractometer
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2008 ▶) T _min = 0.944, T _max = 1.000 (expected range = 0.586–0.620)
18586 measured reflections
7024 independent reflections
4611 reflections with I > 2σ(I)
R _int = 0.026

Refinement

R[F ² > 2σ(F ²)] = 0.029
wR(F ²) = 0.071
S = 0.89
7024 reflections
181 parameters
H-atom parameters constrained
Δρ_max = 0.44 e Å⁻³
Δρ_min = −0.49 e Å⁻³

Data collection: CrysAlis CCD (Oxford Diffraction, 2008 ▶); cell refinement: CrysAlis RED (Oxford Diffraction, 2008 ▶); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809031742/kp2227sup1.cif

e-65-m1121-sup1.cif^{(19.9KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809031742/kp2227Isup2.hkl

e-65-m1121-Isup2.hkl^{(343.7KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected geometric parameters (Å, °).

Cu—O	1.9342 (8)
Cu—N	1.9678 (11)
Cu—N1	2.0095 (10)
Cu—N2	2.0192 (10)
Cu—Oⁱ	2.2526 (8)

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O—Cu—N	95.37 (4)
O—Cu—N1	92.66 (3)
N—Cu—N1	153.23 (5)
O—Cu—N2	165.03 (4)
N—Cu—N2	97.14 (4)
N1—Cu—N2	79.76 (4)
O—Cu—Oⁱ	79.39 (3)
N—Cu—Oⁱ	102.22 (4)
N1—Cu—Oⁱ	104.35 (3)
N2—Cu—Oⁱ	89.94 (3)

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Symmetry code: (i) Inline graphic .

Table 2. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1A⋯Sⁱⁱ	0.93	2.48	3.3866 (10)	164

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Symmetry code: (ii) Inline graphic .

Acknowledgments

RJB acknowledges the NSF–MRI program (grant CHE-0619278) for funds to purchase the diffractometer.

supplementary crystallographic information

Comment

The synthesis and structure determination of copper complexes containing potentially bridging or ambidentate ligands, such as the thiocyanate anion, is of wide interest. The different possible coordination modes of the thiocyanate anion can involve bridging or ambidentate functions. A major obstacle to a more comprehensive study of thiocyanate polynuclear complexes is the lack of rational synthetic procedures. One convenient synthetic strategy is use displacement of weakly coordinated anions such as perchlorate of trifluoromethanesulfonate. In this instance some control over resulting stereochemistry can be achieved.

The present complex was synthesized by displacement of weakly coordinated perchlorate anions from a structurally determined complex (Assey et al., 2009) The crystal structure of the resulting complex, bis{µ-O-[2-((pyridin-2-ylmethylamino)methyl)phenolato]thiocyanatocopper(II)} has been determined. In this instance, two thiocyanate ligands were ligated to the copper(II) complex as a result of displacement of weakly coordinated perchlorate ligands. This method of ligand substitution has been used in the area of chemical sensors such as: competitive assay method involving the displacement of an indicator ligand (Sharma et al., 2008), fluorescence displacement method involving determination of receptor-ligand binding constants (Kuzmic et al., 1992), luminescence molecular sensing based on analyte coordination to the transition metal complexes (Rogers & Wolf, 2002), and the use of ligand substitution for fluorescence sensing in detection of NO in biological aqueous solution (Lim et al., 2006).

The complex contains a reduced Schiff base, 2-{[(pyridine-2-ylmethyl)amino]methyl}phenolato and thiocyanate coordinated to copper. The phenolate O atoms bridge the two copper centres and the two thiocyanate anions are terminally coordinated to each copper through their N donors (Fig. 1 and Table 1). The resulting complex reveals a centre of inversion. The coordination geometry about each Cu^II is distorted square pyramidal (τ = 0.197 (1), Addison et al., 1984) with the bridging O, N_amine, N_pyridine and N_thiocyanate forming the base and a bridging O forming the apex. The Cu—O_base and Cu—O_apex distances are 1.9342 (8) and 2.2526 (8) Å respectively. The Cu—N_thiocyanate distance [1.9678 (11) Å] is in the range observed for other copper(II) complexes containing coordinated thiocyanate (Wang & Li, 2005; You & Zhu, 2004; You, 2005; You & Zhu, 2005). The bond distances to the central copper [Cu—N(1) 2.0095 (10) Å, Cu—N(2) 2.0292 (10) Å, Cu—O 1.9342 (8) Å] are comparable to those observed for related complexes (Shakya et al., 2005) and (Biswas et al., 2005).

Experimental

The complex was synthesized in a three-step process. 1. The ligand (2-pyridylmethyl)(2-hydroxybenzyl)amine (L¹H) was synthesized as described below (Yisgedu, 2001). To 5.4 g (50 mmol) of 2-(2-aminomethyl)pyridine in 10 ml of ethanol was added 6.1 g (50 mmol) of salicylaldehyde in 15 ml of ethanol which resulted in a deep yellow colour. The solution was left to stir for 30 m. A sodium borohydride solution (3 g NaBH₄, 0.4 g NaOH, and 40.0 ml of H₂O) were added dropwise. The solution changed to colourless and was left to stir for 1 h after adding all the NaBH₄ solution. The volume of the solution was reduced to 20 ml after extracting three times with chloroform (3 x 40 ml). The extracts were combined and dried in anhydrous Na₂SO₄ overnight. The Na₂SO₄ was filtered and the filtrate concentrated to give a colourless oil (9.3 g, 87%).

2. Copper(II) perchlorate precursor complex was synthesized as follows (Yisgedu, 2001): 1.64 g (7.7 mmol) of L¹H was mixed with 2.86 g (7.7 mmol) of Cu(ClO₄)₂.6H₂O in 25 ml MeOH and 1.75 ml NaOCH₃. The solution mixture was stirred overnight and a green filtrate of precipitate (2.7 g) was obtained. This was washed with EtOH/MeOH (2:1), then crystallized from CH₃CN/CH₃NO₂.

3. Cu(II) thiocyanate complex was synthesized as follows: 0.1 mmol (0.0835 g) of the dinuclear Cu^II perchlorate complex was dissolved in 15 ml s of EtOH and reacted with 0.25 mmol (0.0203 g) of NaSCN dissolved in 10 ml s EtOH. The mixture was stirred for 18.5 h. A mixture of solids and supernatant were obtained at the end of the reaction. The supernatant was decanted and the solids were re-dissolved in 7.5 ml of DMF, filtered and layered with diethyl ether and left to crystallize. Dark-green crystals suitable for X-ray diffraction were obtained and used for X-ray structure determination.