The azide-bridged mixed-valent cobalt(II,III) compound [(CH3)3NH]2[CoIICo2 III(N3)10]

Yan-Ju Liu; Yu-Xian Li; Min Xu; Xia Wang

doi:10.1107/S1600536810049421

. 2010 Dec 4;67(Pt 1):m27. doi: 10.1107/S1600536810049421

The azide-bridged mixed-valent cobalt(II,III) compound [(CH₃)₃NH]₂[Co^IICo₂ ^III(N₃)₁₀]

Yan-Ju Liu ^a,^*, Yu-Xian Li ^a, Min Xu ^a, Xia Wang ^a

PMCID: PMC3050209 PMID: 21522551

Abstract

The crystal structure of the title compound, poly[bis(trimethylammonium) hexa-μ_1,1-azido-tetraazidotricobaltate(II,III)], [(CH₃)₃NH]₂[Co^IICo^III ₂(N₃)₁₀], consists of anionic chains [Co^IICo^III ₂(N₃)₁₀]²⁻ extending parallel to the c axis and [(CH₃)₃NH]⁺ counter-cations situated between the chains. In the anionic chain, one tetrahedrally coordinated Co^II atom (site symmetry 2) and two octahedrally coordinated Co^III atoms are arranged alternately and are linked by μ_1,1-azide bridges. The anionic chains and cations are connected via N—H⋯N hydrogen bonding into a three-dimensional structure.

Related literature

For background to transition-metal azido-complexes templated by counter-cations of various sizes, see: Liu et al. (2006 ▶, 2008 ▶). For related cobalt complexes, see: Zhang et al. (2010 ▶).

Experimental

Crystal data

(C₃H₁₀N)₂[Co₃(N₃)₁₀]
M _r = 717.33
Monoclinic,
a = 21.7200 (6) Å
b = 11.3812 (4) Å
c = 12.1628 (4) Å
β = 115.524 (2)°
V = 2713.21 (15) Å³
Z = 4
Mo Kα radiation
μ = 1.88 mm⁻¹
T = 293 K
0.10 × 0.06 × 0.05 mm

Data collection

Rigaku Saturn diffractometer
Absorption correction: multi-scan (REQAB; Jacobson, 1998 ▶) T _min = 0.708, T _max = 0.823
22049 measured reflections
2389 independent reflections
1481 reflections with I > 2σ(I)
R _int = 0.103

Refinement

R[F ² > 2σ(F ²)] = 0.032
wR(F ²) = 0.061
S = 0.98
2389 reflections
190 parameters
24 restraints
H-atom parameters constrained
Δρ_max = 0.31 e Å⁻³
Δρ_min = −0.35 e Å⁻³

Data collection: CrystalClear (Rigaku/MSC, 2006 ▶); cell refinement: CrystalClear; data reduction: CrystalClear; 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: publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810049421/wm2430sup1.cif

e-67-00m27-sup1.cif^{(20.9KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810049421/wm2430Isup2.hkl

e-67-00m27-Isup2.hkl^{(117.5KB, hkl)}

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

Table 1. Selected bond lengths (Å).

Co1—N7	1.944 (3)
Co1—N4	1.948 (3)
Co1—N10	1.964 (3)
Co1—N1	1.979 (3)
Co1—N13ⁱ	2.008 (3)
Co1—N13	2.008 (3)
Co2—N1ⁱⁱ	1.968 (3)
Co2—N1	1.968 (3)
Co2—N10ⁱ	2.014 (3)
Co2—N10ⁱⁱⁱ	2.014 (3)

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

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

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N16—H16⋯N7	0.91	2.02	2.890	159

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Acknowledgments

This study was supported by the Doctoral Research Fund of Henan Chinese Medicine (BSJJ2009–38).

supplementary crystallographic information

Comment

Azido-bridged complexes have attracted a lot of attention in recent times because of their importance in diverse fields, encompassing condensed matter physics, materials chemistry, biological chemistry, etc. Having diverse coordination modes and being an efficient magnetic coupler, the azide anion is a versatile ligand in bridging different transition metals, generating rich and fascinating architectures ranging from discrete polynuclears to extended three-dimensional networks with interesting magnetic properties (antiferromagnetic, ferromagnetic, ferrimagnetic, canted and alternating systems). In fact, remarkable structural variations of azido-bridged complexes have been reported by using various ancillary ligands, with different number of coordination sites and steric hindrance, to control over the dimensions of complexes and bridging modes of the azide anions, thus leading to the control over their magnetic properties. However, only a few metal-azido systems devoid of ancillary ligands have been obtained by varying the size of the coutercations (Liu et al., 2006, 2008). A small coutercation such as (CH₃)₄N⁺ produced the one-dimensional ferromagnetic complex [(CH₃)₄N][Cu(N₃)₃], in which the Cu(II) ions are connected by a triple azido-bridge, including two µ_1,3-N₃ and one µ_1,1-N₃ anions. When more bulky coutercations were employed, the mononuclear paramagnetic complex [(CH₃CH₂)₄N]₂[Cu(N₃)₄], the dinuclear antiferromagnetic complex [(CH₃CH₂CH₂CH₂)₄N]₂[Cu₂(N₃)₆] and the one-dimensional ferromagnetic complex [(CH₃CH₂CH₂)₄N]₂[Cu₃(N₃)₈] were obtained separately. For magnese(II)-azido complexes, use of small coutercations like (CH₃)₄N⁺ and Cs⁺ produced compounds with interesting three-dimensional structures [(CH₃)₄N][Mn(N₃)₃] and Cs[Mn(N₃)₃], where the cations are situated in the voids the anionic Mn^II-azido network. When using the more bulky cation (CH₃CH₂)₄N⁺, the one-dimensional ferromagnetic complex [(CH₃CH₂)₄N][Mn(N₃)₃] was obtained. Despite the results obtained above, azido-bridged complexes with mixed-valent metal ions have not been reported. In this work, we report on a mixed-valence cobalt(II,III) complex, [(CH₃)₃NH]₂[Co^IICo^III₂(N₃)₁₀], (I).

The structure of (I) consists of anionic chains [Co^IICo^III₂(N₃)₁₀]^2- extending parallel to the c-axis. The [(CH₃)₃NH]⁺ countercations are situated between the chains (Fig. 1). In the [Co^IICo^III₂(N₃)₁₀]^2- anionic chain, the Co^II atom (Co2, site symmetry 2) is tetrahedrally coordinated by N atoms, whereas the Co^III atom (Co1) is octahedrally coordinated. Co^II and Co^III atoms are linked by µ_1,1-azido ligands and are alternatively arranged along the chain direction. The Co1—N distances range between 1.944 (3)–2.008 (3) Å, slightly longer than those expected for Co^III. The Co2—N distances range between 1.968 (3)–2.014 (3) Å, slightly shorter than those expected for Co^II (Zhang et al., 2010). The anionic chain and the cations are connected via N—H···N hydrogen bonding between the donating N—H function of the cation and non-bridging azido groups of the anion (Fig 2).

Experimental

In a test tube a 5 ml methanol solution of 0.10M Co(ClO₄)₂^.6H₂O was layered carefully with 3 ml methanol and then with 10 ml methanol solution of 0.20M HCl, 0.20M NaN₃, and 0.10M trimethylamine. The tube was sealed and kept undisturbed. Tiny red columnar crystals appeared overnight. Crystallization time of one week produced crystals in a yield of 25% based on the metal salt.