rac-Dichlorido[3-eth­oxy-3-(1-ethyl-1H-benzimidazol-2-yl)-2,3-dihydro-1H-pyrrolo­[1,2-a]benzimidazole]­copper(II)

Robert T Stibrany; Joseph A Potenza

doi:10.1107/S1600536812051641

. 2013 Jan 9;69(Pt 2):m92–m93. doi: 10.1107/S1600536812051641

rac-Dichlorido[3-ethoxy-3-(1-ethyl-1H-benzimidazol-2-yl)-2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole]copper(II)

Robert T Stibrany ^a,^*, Joseph A Potenza ^a

PMCID: PMC3569191 PMID: 23424435

Abstract

The title complex, [CuCl₂(C₂₁H₂₂N₄O)], contains a bis(benzimidazole) unit with a chiral bridgehead C atom that forms part of a tetrahydropyrrole ring fused to one of the benzimidazoles. The chelate angle is 90.45 (9)° and the dihedral angle between the essentially planar benzimidazole fragments is 26.68 (9)°. The Cu^II coordination geometry lies approximately midway between tetrahedral and square planar. Overall, each chiral molecule contains six fused rings, and a racemic mixture is formed with symmetry-related enantiomers. In the crystal, C—H⋯π and C—H⋯Cl interactions link molecules into a supramolecular chain along the a-axis direction.

Related literature

For ¹⁹F NMR studies of related compounds, see: Stibrany (2003 ▶). For polymerization studies, see: Stibrany et al. (2003 ▶). For their use as agents to study electron transfer, see: Knapp et al. (1990 ▶). For related structures, see: Baugh et al. (2006 ▶); Stibrany (2009 ▶); Stibrany et al. (2002 ▶, 2004 ▶); Stibrany & Potenza (2006 ▶, 2008 ▶). For calculation of the four-coordination geometry, see: Yang et al. (2007 ▶).

Experimental

Crystal data

[CuCl₂(C₂₁H₂₂N₄O)]
M _r = 480.87
Triclinic,
a = 8.9409 (17) Å
b = 9.5209 (18) Å
c = 14.323 (3) Å
α = 106.973 (4)°
β = 92.373 (4)°
γ = 113.778 (4)°
V = 1049.3 (3) Å³
Z = 2
Mo Kα radiation
μ = 1.32 mm⁻¹
T = 294 K
0.43 × 0.23 × 0.06 mm

Data collection

Bruker SMART CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2000; ▶ Blessing, 1995 ▶) T _min = 0.771, T _max = 1.00
10062 measured reflections
4126 independent reflections
3380 reflections with I > 2σ(I)
R _int = 0.027

Refinement

R[F ² > 2σ(F ²)] = 0.044
wR(F ²) = 0.124
S = 1.00
4126 reflections
264 parameters
1 restraint
H-atom parameters constrained
Δρ_max = 0.90 e Å⁻³
Δρ_min = −0.29 e Å⁻³

Data collection: SMART (Bruker, 2000 ▶); cell refinement: SAINT (Bruker, 2000 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEPIII (Burnett & Johnson, 1996 ▶), ORTEP-3 for Windows (Farrugia, 2012 ▶); software used to prepare material for publication: SHELXTL (Sheldrick, 2008 ▶).

Supplementary Material

Click here for additional data file.^{(23.5KB, cif)}

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812051641/tk5184sup1.cif

e-69-00m92-sup1.cif^{(23.5KB, cif)}

Click here for additional data file.^{(202.2KB, hkl)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812051641/tk5184Isup2.hkl

e-69-00m92-Isup2.hkl^{(202.2KB, hkl)}

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

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

Cu—N23	1.993 (2)
Cu—N13	2.005 (2)
Cu—Cl1	2.2169 (9)
Cu—Cl2	2.2198 (9)

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N23—Cu—N13	90.45 (9)
N23—Cu—Cl1	141.12 (8)
N13—Cu—Cl1	94.14 (7)
N23—Cu—Cl2	100.17 (7)
N13—Cu—Cl2	143.67 (8)
Cl1—Cu—Cl2	98.64 (4)

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

Cg1 is the centroid of the C11/C13–C17 phenyl ring.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C4—H4B⋯Cg1ⁱ	0.96	2.99	3.910 (5)	160
C17—H17⋯Cl1ⁱⁱ	0.93	2.78	3.694 (4)	169

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Symmetry codes: (i) Inline graphic ; (ii) .

supplementary crystallographic information

Comment

The title complex (I), Fig. 1, was prepared as part of our long-term interest in the chemistry of bis(imidazoles), bis(benzimidazoles), and their complexes with metal ions. These species have demonstrated their usefulness as proton sponges (Stibrany et al., 2002), geometrically constraining ligands (Stibrany et al., 2004), agents to study electron transfer (Knapp et al., 1990), polymerization catalysts (Stibrany et al., 2003), ¹⁹F NMR polymerization catalyst probes (Stibrany, 2003), and in the formation of metal-organic copolymers (Stibrany & Potenza, 2008). In this study we extend the ring system with the addition of a fused tetrahydropyyrole.

Only two bis(benzimidazole) ligands containing quaternary bridgehead carbon atoms have been structurally characterized (Fig. 2) II (Stibrany, 2009) and III (Stibrany et al., 2003; Stibrany & Potenza, 2006). Several structures containing bis(benzimidazole) ligands with a single bridgehead carbon atom of the form Cu^IIN₂X₂, where X is a halogen, have previously been reported (Baugh et al., 2006; Stibrany, 2009; Stibrany et al., 2003; Stibrany & Potenza, 2006; Stibrany & Potenza, 2008). Of those structures, several contain tertiary bridgehead carbon atoms (3') and the remaining contain quaternary bridgehead carbon atoms (4'). The "bite" angle of the bis(benzimidazole) ligands, which is defined as the N—Cu—N angle and is constrained by the ligand structure. The previously reported average for structures containing (4') carbon bridgehead atoms was reported as 90.4 (8)° (Stibrany, 2009). This compares favorably with the title structure which is 90.45 (9)° for the N23—Cu—N13 bond angle. The essentially planar benzimidazole fragments are twisted by 26.68 (9)°. A τ₄ value of 0.53 indicates the coordination geometry is approximately midway between a perfect tetrahedral coordination geometry (τ₄ = 1) and a perfect square-planar geometry (τ₄ = 0) (Yang et al., 2007).

Experimental

In a 50 ml Erlenmeyer flask containing acetonitrile (10 ml), CuCl₂^.2H₂O (20 mg) was dissolved. Then rac-[3-ethoxy-3-(1-ethylbenzimidazol-2-yl)-4,5- dihydro-pyrrolo[1,2-a]benzimidazole] (41 mg) was added to the flask to give a green solution. The flask was sealed in a jar containing diethyl ether designed to allow slow vapor diffusion of diethyl ether. After 3 days, yellow-green plates of the title complex formed.