Bis(μ-5-diisopropyl­amino-1,2,3,4-tetra­zolido-κ2 N 2:N 3)bis­[(triisopropyl­phosphane)copper(I)]

Issam Kobrsi; Ghada Bassioni

doi:10.1107/S1600536811022719

. 2011 Jun 25;67(Pt 7):m975–m976. doi: 10.1107/S1600536811022719

Bis(μ-5-diisopropylamino-1,2,3,4-tetrazolido-κ² N ²:N ³)bis[(triisopropylphosphane)copper(I)]

Issam Kobrsi ^a,^*, Ghada Bassioni ^b,^‡

PMCID: PMC3151938 PMID: 21836950

Abstract

In the binuclear centrosymmetric crystal structure of the title compound, [Cu₂(C₇H₁₄N₅)₂(C₉H₂₁P)₂], all atoms except those of the isopropyl groups are approximately co-planar. The Cu(II) atom is in a distorted trigonal–planar CuN₂P coordination. Bond angles around the amino N atom suggest sp ² hybridization. Several intramolecular C—H⋯N interactions are present involving tetrazolate N atoms.

Related literature

For background to the coordination chemistry of anionic five-membered nitrogen-containing heterocyclic ligands, see: Nief (2001 ▶); Rottger et al. (1994 ▶); Hitzbleck et al. (2004 ▶); Gust et al. (2001 ▶, 2002 ▶); Dezelah et al. (2004 ▶); Sebe et al. (2005 ▶); Vela et al. (2006 ▶). Complexes containing these ligands have a strong tendency to form oligomeric and polymeric structures, see: Haasnoot (2000 ▶); Zhang et al. (2006 ▶); Dinca et al. (2006 ▶). η¹ Coordination is the most commonly observed binding mode in monomeric complexes containing 1,2,4-triazolato and tetrazolato ligands, see: Hunyh et al. (2003 ▶); Jiang et al. (2004 ▶). Theoretical predictions regarding the high stability of the pentazolate (N₅ ⁻) ion suggest that metal complexes containing this ligand might be stable enough to allow isolation, see: Frunzke et al. (2002 ▶); Lein et al. (2001 ▶); Burke et al. (2001 ▶). For our work on the synthesis, structures and molecular orbital calculations of a series of Ba(alkyltetrazolate)₂(18-crown-6), K(alkyltetrazolate)(18-crown-6), Ba(pentazolate)₂(18-crown-6) and K(pentazolate)(18-crown-6) complexes, which exhibited highly distorted tetrazolato and pentazolato ligand bonding, see: Kobrsi et al. (2005 ▶, 2006 ▶). For van der Waals radii, see: Allinger et al. (1968 ▶); Bondi (1964 ▶). graphic file with name e-67-0m975-scheme1.jpg

Experimental

Crystal data

[Cu₂(C₇H₁₄N₅)₂(C₉H₂₁P)₂]
M _r = 784.02
Triclinic,
a = 7.3573 (6) Å
b = 10.8987 (8) Å
c = 12.7134 (9) Å
α = 94.273 (2)°
β = 96.993 (2)°
γ = 93.548 (2)°
V = 1006.43 (13) Å³
Z = 1
Mo Kα radiation
μ = 1.17 mm⁻¹
T = 100 K
0.37 × 0.28 × 0.21 mm

Data collection

Bruker APEXII diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2005 ▶) T _min = 0.675, T _max = 0.791
17280 measured reflections
4689 independent reflections
4336 reflections with I > 2σ(I)
R _int = 0.042

Refinement

R[F ² > 2σ(F ²)] = 0.029
wR(F ²) = 0.079
S = 1.05
4689 reflections
218 parameters
H-atom parameters constrained
Δρ_max = 0.70 e Å⁻³
Δρ_min = −0.42 e Å⁻³

Data collection: APEX2 (Bruker, 2005 ▶); cell refinement: SAINT-Plus (Bruker, 2005 ▶); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL-Plus (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL-Plus (Sheldrick, 2008 ▶).

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536811022719/hp2003sup1.cif

e-67-0m975-sup1.cif^{(27.3KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811022719/hp2003Isup2.hkl

e-67-0m975-Isup2.hkl^{(229.7KB, hkl)}

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

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

Cu1—P1	2.1957 (5)
Cu1—N2	1.9919 (14)
Cu1—N3	1.9938 (13)

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P1—Cu1—N2	126.53 (4)
P1—Cu1—N3	126.52 (4)
N2—Cu1—N3	106.96 (5)

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

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C3—H3A⋯N4ⁱ	0.98	2.58	3.182 (2)	119
C4—H4B⋯N4ⁱ	0.98	2.48	3.082 (2)	120
C5—H5⋯N1	1.00	2.32	2.784 (2)	107

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Symmetry code: (i) Inline graphic .

Acknowledgments

The authors would like to acknowledge Professor Charles H. Winter for his support.

supplementary crystallographic information

Comment

The coordination chemistry of anionic five-membered nitrogen heterocyclic ligands has generated considerable recent interest from several different perspectives (Nief 2001, Rottger et al. 1994, Hitzbleck et al. 2004, Gust et al. 2001, Dezelah et al. 2004, Sebe et al. 2005, Gust et al. 2002, Vela et al. 2006). Due to the presence of many nitrogen atoms in 1,2,4-triazolato and tetrazolato ligands, complexes containing these ligands have a strong tendency to form oligomeric and polymeric compounds through bridging ligand coordination modes (Haasnoot 2000, Zhang et al. 2006, Dinca et al. 2006). Furthermore, η¹-coordination is the most commonly observed binding mode in monomeric complexes containing 1,2,4-triazolato and tetrazolato ligands (Jiang et al. 2004, Hunyh et al. 2003). Theoretical predictions regarding the high stability of the pentazolate (N₅^-) ion suggest that metal complexes containing this ligand might be stable enough to allow isolation (Frunzke et al. 2002, Lein et al. 2001, Burke et al. 2001).

Since complexes containing N₅^- ligands may be at the edge of isolability due to facile loss of dinitrogen, it is important to develop a knowledge base that allows the synthesis of soluble, tractable 1,2,4-triazolato and tetrazolato complexes. Presumably, the basic coordination chemistry of pentazolato ligands will share similarities with that of tetrazolato ligands.

Several years ago, we reported the synthesis, structure, and molecular orbital calculations of a series of barium complexes of the formula Ba(alkyltetrazolate)₂(18-crown-6), potassium complexes of formula K(alkyltetrazolate)(18-crown-6), as well as calculations of Ba(pentazolate)₂(18-crown-6) and K(pentazolate)(18-crown-6). These complexes contained highly distorted tetrazolato and pentazolato ligand bonding (Kobrsi et al. 2005, Kobrsi et al. 2006).

The present work demonstrates the stabilization of copper tetrazolate complexes using a 2-electron donor phosphane ligand. The copper complex crystallizes as a dimer having all nuclei except the isopropyl groups' in the same plane. The phosphane ligands are terminal, while each tetrazolate ligand bridges two Cu(I) centers.

While the work aimed for a monomeric complex, it can be concluded that the combination of isopropyl groups in the phosphane ligand and the tetrazolate ligand does not provide the necessary steric repulsion. However, enough steric hindrance is provided for the tetrazolate to coordinate in an N2—N3 bridging mode as opposed to the normally observed N1—N2 bridging mode.

The C1—N5—C5 angle of 120.30 (13)° and the C2—N5—C5 angle of 118.89 (13)° suggest that the N-atom of the amino group is sp²-hybridized, having its electrons donated to the aromatic ring, thus providing stability to the electron-deficient heterocycle.

Several intramolecular CH—N interactions exist between the tetrazolate's N1 and N4, and the hydrogen atoms on C9, C10, C13, C16. The CH—N distances range from 2.64 to 2.77 Å, whereas the sum of the van der Waals radii for N and H is about 2.7–3.0 Å (Bondi 1964, Allinger et al. 1968), which supports weak, attractive CH—N interactions. These types of interactions have been previously observed, where calculations have shown that these interactions provide stability to the heterocycle (Kobrsi et al. 2005, Kobrsi et al. 2006).

Experimental

A 100 ml Schlenk flask was charged with copper(I) chloride (0.300 g, 3.06 mmol), 40 ml of THF, and a stir bar under an inert atmosphere of argon. Triisopropylphosphane (0.491 g, 3.06 mmol) was added to the mixture while stirring. After 2 h, lithium 5-diisopropylamino-1,2,3,4-tetrazolate (0.536 g, 3.06 mmol) was added, and the reaction mixture was allowed to stir for 18 h at room temperature. The solvent was then removed under vacuum, the products extracted in 30 ml of hexane, and the resulting mixture filtered through a pad of celite. Single crystals were grown from a supersaturated solution at 0°C in the form of white needles. Crystalline samples were mounted in sealed thin wall capillaries under nitrogen atmosphere for X-ray data collection.