Di-μ-chlorido-bis­[chlorido(1,4,6-trimethyl-6-nitro-1,4-diazepine)copper(II)]

Adailton J Bortoluzzi; Ademir Neves; Rosely A Peralta; Tiago P Camargo; Vitor C Weiss

doi:10.1107/S1600536808043390

. 2009 Jan 8;65(Pt 2):m144–m145. doi: 10.1107/S1600536808043390

Di-μ-chlorido-bis[chlorido(1,4,6-trimethyl-6-nitro-1,4-diazepine)copper(II)]

Adailton J Bortoluzzi ^a,^*, Ademir Neves ^a, Rosely A Peralta ^a, Tiago P Camargo ^a, Vitor C Weiss ^a

PMCID: PMC2968152 PMID: 21581759

Abstract

The title neutral copper complex, [Cu₂Cl₄(C₈H₁₇N₃O₂)₂], shows a binuclear center with a Cu—(μ-Cl)₂—Cu core, in which each copper ion is coordinated by the N,N,O donor atoms of the tridentate ligand 1,4,6-trimethyl-6-nitro-1,4-diazepine (meaaz-NO₂) and three chloride exogenous ligands. Each metal ion is facially coordinated by meaaz-NO₂ through N,N,O donor atoms, whereas two bridging and one terminal chloride ions occupy the other face of the highly Jahn–Teller-distorted octahedron. Two N atoms from tertiary amine groups of the meaaz-NO₂ ligand and two exogenous Cl atoms with short Cu—N and Cu—Cl distances define the equatorial plane. The coordination around each Cu^II ion is completed by another Cl atom and an O atom from the NO₂ group, in the axial positions. The binuclear complex exhibits a centrosymmetric structure with point symmetry Inline graphic .

Related literature

For related literature, see: Belousoff et al. (2006 ▶); Deal & Burstyn (1996 ▶); Fry et al. (2005 ▶); Hegg & Burstyn (1998 ▶); Peralta et al. (2005 ▶); Rodriguez, et al. (1999 ▶); Romba et al. (2006 ▶). For the synthesis of the meaaz-NO₂ ligand see Ge et al. (2006 ▶). For related structures, see: Astner et al. (2008 ▶); Schwindinger et al. (1980 ▶); Steed et al. (2007 ▶).

Experimental

Crystal data

[Cu₂Cl₄(C₈H₁₇N₃O₂)₂]
M _r = 643.37
Monoclinic,
a = 10.5478 (2) Å
b = 10.9251 (2) Å
c = 11.4430 (2) Å
β = 102.297 (1)°
V = 1288.39 (4) Å³
Z = 2
Mo Kα radiation
μ = 2.10 mm⁻¹
T = 296 (2) K
0.31 × 0.14 × 0.09 mm

Data collection

Bruker APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2006 ▶) T _min = 0.562, T _max = 0.833
25284 measured reflections
2528 independent reflections
2080 reflections with I > 2σ(I)
R _int = 0.036

Refinement

R[F ² > 2σ(F ²)] = 0.030
wR(F ²) = 0.083
S = 1.07
2528 reflections
148 parameters
H-atom parameters constrained
Δρ_max = 0.76 e Å⁻³
Δρ_min = −0.37 e Å⁻³

Data collection: APEX2, BIS and COSMO (Bruker, 2006 ▶); cell refinement: SAINT (Bruker, 2006 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: PLATON (Spek, 2003 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808043390/pk2138sup1.cif

e-65-0m144-sup1.cif^{(15.5KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808043390/pk2138Isup2.hkl

e-65-0m144-Isup2.hkl^{(121.7KB, hkl)}

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

Acknowledgments

The authors thank the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and the Financiadora de Estudos e Projetos (FINEP) for financial support. The authors also thank to Dr Manfredo Hörner and Dr Robert A. Burrow at Universidade Federal de Santa Maria for the crystallographic facilities.

supplementary crystallographic information

Comment

Tridentate ligands that are able to force facial geometry, such as 1,4,7-tacn (1,4,7-triazacyclononane), daza (1,4-diazepan-6-amine) (Romba, et al., 2006), tach (cis,cis-1,3,5-triaminocyclohexane) (Hegg & Burstyn, 1998), play an important role in the stabilization of a great number of structural motifs in coordination compounds and in biological systems (Peralta et al., 2005). Copper complexes with this kind of ligand have been reported over the past few years with a view to the study of the hydrolysis of phosphate esters, proteins and DNA (Deal & Burstyn, 1996; Fry et al., 2005). Indeed such copper(II) complexes exhibit high catalytic reactivity in the hydrolysis of DNA model diesters as bis(4-nitrophenyl)phosphate with rate constants of ≈ 10 ^-4 s^-1 (Belousoff et al., 2006). In this context we report herein the synthesis and X-ray analysis of a new dinuclear copper complex with the tridentate ligand meaaz-NO₂.

This neutral copper complex exhibits a centrosymmetric structure (Fig. 1) with a highly distorted octahedral environment around the copper center. Each metal ion is facially coordinated by meaaz-NO₂ through N₂O donors atoms, whereas two bridged and one terminal coordinated chlorines occupy the other face of the distorted octahedron. Two amine nitrogen atoms (N3 and N6) of the ligand and two exogenous chlorines (Cl1, Cl2) lie in the equatorial plane. The coordination sphere of Cu1 is completed by another chlorine (Cl2') and an oxygen atom (O2) from the NO₂ group, in the axial positions. In the equatorial plane, the Cu—N and Cu—Cl bond lengths are Cu1—N6 2.064 (2) Å, Cu1—N3 2.122 (2) Å, Cu1—Cl2 2.2686 (7) Å and Cu1—Cl1 2.2694 (7) Å), respectively. The longer bond lengths Cu1—Cl2' (2.7611 (8) Å) and Cu1—O2 (2.845 (2) Å) are associated with the two apical positions, as expected for a (4 + 2) distorted geometry, as is common for Cu^II. The Cu—N and the Cu—Cl bond lengths in the equatorial plane are comparable to those found for other copper complexes [Cu(tacn)Cl₂] (Cu—N2 2.063 (4) Å, Cu—N3 2.038 (4) Å, CU—Cl1 2.268 (1) Å and Cu—Cl2 2.312 (1) Å) (Schwindinger, et al., 1980), [Cu₂(µ-Cl)₂(Me-bpa)₂(ClO₄)₂] (Me-bpa = N-methyl-bis(2-pyridylmethyl)amine) (Cu1—N36 1.983 (2) Å, Cu1—N10 2.036 (2) Å, Cu1—N26 1.989 (2) Å and Cu1—Cl1 2.2587 (6) Å) (Astner et al., 2008) and [Cu(me₃tacn)Cl₂] (Cu1—N1 2.100 (2) Å, Cu1—N2 2.111 (2) Å, Cu1—Cl2 2.2558 (9) Å and Cu1—Cl1 2.3050 (8) Å) (Steed et al., 2007). The seven-membered chelate ring of the meaaz-NO₂ ligand restricts the N—Cu—N angle to 77.35 (8)°, which is about 6° smaller than the respective angles formed by nine-membered ring in the Cu-tacn complexes.

As described in Rodriguez, et al. (1999), there are three kinds of configurations for copper complex containing the Cu-(µ-Cl)₂—Cu core: Type I, in which two square pyramids share one base-to-apex edge with the two bases nearly perpendicular to one another; Type II, square pyramids sharing one base-to-apex edge but with parallel basal planes and Type III, square pyramids sharing a basal edge with coplanar basal planes. The configuration of the Cu centers reported here are Type II given that the axial positions of one copper(II) center is directed toward the top and the same axis of the adjacent center is in the anti position. Although the Cu centers in the complex are hexacoordinate, it can be considered as type II, because the sixth coordination bond is very long (Cu—O2 = 2.845 (2)Å).

The packing is mainly governed by weak C—H···O and C—H···Cl interactions with average D···A distances of 2.99 Å and 3.74 Å, respectively. In addition, the packing analysis reveals that the molecules are accomodated in layers parallel to the (001) plane and are stacked along crystallographic a axis (Fig. 2).

Experimental

The ligand 6-nitro-1,4,7-trimethyl-1,4-diazepine (meaaz-NO₂) was prepared as reported in the literature (Ge et al., 2006). The ligand was obtained with good yeld and was characterized by ¹H NMR [δ (p.p.m.) (CDCl3) 400 MHz: 1.46 (s, 3H); 2.36 (s, 6H); 2.48 (m, 2H); 2.56 (m, 2H); 2.66 and 3.36 (AB system, 4H)].

Copper complex was synthesized by adding 187 mg of the ligand meaaz-NO₂ (1.0 mmol) to a CH₃CN solution containing CuCl₂.2H₂O (171 mg, 1.0 mmol). The solution was then concentrated under magnetic stirring and was allowed to stand at room temperature for a few days, yielding a small number of dark green crystals which were suitable for the single-crystal X-ray analysis.