Di-μ-oxido-bis­[(1,4,8,11-tetra­aza­cyclo­tetra­decane-κ4 N,N′,N′′,N′′′)dimangan­ese(III,IV)] bis­(tetra­phenyl­borate) chloride acetonitrile disolvate

Marilyn M Olmstead; David W Boyce; Lauren E Bria

doi:10.1107/S1600536811019829

. 2011 Jun 4;67(Pt 7):m824–m825. doi: 10.1107/S1600536811019829

Di-μ-oxido-bis[(1,4,8,11-tetraazacyclotetradecane-κ⁴ N,N′,N′′,N′′′)dimanganese(III,IV)] bis(tetraphenylborate) chloride acetonitrile disolvate

Marilyn M Olmstead ^a,^*, David W Boyce ^a, Lauren E Bria ^a

PMCID: PMC3151985 PMID: 21836836

Abstract

The title compound, [Mn₂O₂(C₁₀H₂₄N₄)₂](C₂₄H₂₀B)₂Cl·2CH₃CN, is a mixed-valent Mn^III/Mn^IV oxide-bridged manganese dimer with one chloride and two tetraphenylborate counter-anions. There are two non-coordinated molecules of acetonitrile in the formula unit. A center of inversion is present between the two metal atoms, and, consequently, there is no distinction between Mn^III and Mn^IV metal centers. In the Mn₂O₂ core, the Mn—O distances are 1.817 (3) and 1.821 (3) Å. The cyclam ligand is in the cis configuration. The chloride counter-anion resides on a center of symmetry, whereas the tetraphenylborate counter-anion is in a general position. The cyclam ligand is hydrogen bonded to the acetonitrile as well as to the chloride anion. One of the phenyl rings of the anion and the acetonitrile solvent molecule are each disordered over two sets of sites.

Related literature

For structures of different salts containing the disordered mixed-valent {[(cyclam)MnO]₂}³⁺ cation, see: Goodson et al. (1990 ▶); Lu et al. (2001 ▶). For structures of the non-disordered Mn^III—Mn^IVO₂ core, see: Brewer et al. (1989 ▶); Levaton & Olmstead (2010 ▶). For cyclam configurations, see: Bosnich et al. (1965 ▶).

Experimental

Crystal data

[Mn₂O₂(C₁₀H₂₄N₄)₂](C₂₄H₂₀B)₂Cl·2C₂H₃N
M _r = 1298.52
Triclinic,
a = 11.437 (2) Å
b = 11.713 (2) Å
c = 13.967 (3) Å
α = 104.136 (3)°
β = 97.697 (3)°
γ = 107.627 (3)°
V = 1684.9 (6) Å³
Z = 1
Mo Kα radiation
μ = 0.47 mm⁻¹
T = 90 K
0.15 × 0.11 × 0.08 mm

Data collection

Bruker SMART APEXII diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.952, T _max = 0.972
17931 measured reflections
6092 independent reflections
4083 reflections with I > 2σ(I)
R _int = 0.064

Refinement

R[F ² > 2σ(F ²)] = 0.061
wR(F ²) = 0.173
S = 1.03
6092 reflections
433 parameters
258 restraints
H-atom parameters constrained
Δρ_max = 0.54 e Å⁻³
Δρ_min = −0.81 e Å⁻³

Data collection: APEX2 (Bruker, 2007 ▶); cell refinement: SAINT (Bruker, 2007 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: XP in SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536811019829/hg5039sup1.cif

e-67-0m824-sup1.cif^{(29.1KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811019829/hg5039Isup2.hkl

e-67-0m824-Isup2.hkl^{(298.2KB, hkl)}

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

Table 1. Selected bond lengths (Å).

Mn1—O1	1.817 (3)
Mn1—O1ⁱ	1.821 (3)
Mn1—N1	2.187 (5)
Mn1—N2	2.092 (3)
Mn1—N3	2.178 (3)
Mn1—N4	2.116 (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—H1⋯N5	0.93	2.42	3.313 (11)	160
N1—H1⋯N5B	0.93	1.98	2.832 (10)	151
N2—H2⋯Cl1	0.93	2.37	3.289 (4)	169
N3—H3⋯N5ⁱ	0.93	2.22	3.034 (9)	146
N3—H3⋯N5Bⁱ	0.93	2.23	3.120 (9)	160
N4—H4⋯Cl1	0.93	2.42	3.330 (4)	168

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Symmetry code: (i) Inline graphic .

Acknowledgments

The authors thank the University of California, Davis, for acquisition of the Bruker SMART APEXII diffractometer and the support of the Summer Undergraduate Research Program of the University of California, Davis.

supplementary crystallographic information

Comment

In the title compound (Fig. 1), the Mn^III—Mn^IV centrosymmetric, dinuclear cation is bridged by two oxo ligands. Each manganese atom also binds to a tetradentate cyclam (cyclam = 1,4,8,11-tetraazacyclotetradecane) to achieve a distorted octahedral coordination environment. Due to the center of inversion, there is no distinction between the two different oxidation states in the structure, and it is disordered mixed valent. The dinuclear cation bears a +3 charge, and the charge is balanced by a chloride anion and two tetraphenylborate anions. The chloride resides on a center of symmetry. The configuration of the cyclam ligand is cis-V, in which the N—H bonds alternate above and below the N₄ plane (Bosnich et al., 1965).

The structures of similar disordered mixed valent (III/IV) µ-oxo bridged manganese cyclam complexes are reported in Lu, et al., 2001, with two perchlorate and one nitrate anions; Goodson, et al., 1990, with dithionate and thiosulfate anions, and a second structure with three bromides. In the title compound, the Mn₂O₂ core has Mn—O distances of 1.817 (3) and 1.821 (3) Å. All of the above referenced structures show similar coordination geometry, and the mean Mn—O bond distances in the Mn₂O₂ core for these complexes is 1.824 Å. A trifluoromethanesulfonate salt (Brewer, et al., 1989) crystallized with discrete Mn^III and Mn^IV metal centers, and these mean Mn—O distances are characteristic of the oxidation states of Mn: Mn^III—O, 1.861 Å and Mn^IV—O, 1.788 Å. Related values were also seen in the structure of a large Mn₁₂ cluster with three units of Mn₂O₂ core geometry. Average values with average deviations from the mean were Mn^III—O, 1.879 (7) Å and Mn^IV—O, 1.787 (6) Å (Levaton & Olmstead, 2010). Thus, the disordered distances agree well with the average III/IV values.

In the structure of the title compound, all of the available hydrogen atoms bonded to the N atoms in the cyclam ligand participate in hydrogen bonding (Fig. 2 and Table 2). The hydrogen atoms bonded to N atoms N2 and N4 are hydrogen bonded to chloride atom. The hydrogen atoms on N atoms N1 and N3 hydrogen bond to the acetonitrile N atoms.

Experimental

The title compound was obtained while attempting to prepare an azido derivative. To a stirred solution of 1,4,8,11-tetraazacyclotetradecane (cyclam), (200 mg, 1 mmol) in 5 ml of methanol was added a solution of MnCl₂^.4H₂O (200 mg, 1 mmol) in 25 ml of methanol. Over the one hour course of the addition, the reaction color progressed from red to dark green. After stirring for 1 hr an excess of NaN₃ (200 mg, 2.5 mmol) was added to the reaction mixture in a solution of 9 ml me thanol and 1 ml H₂O. No color change was observed upon addition of the azide. After 20 min of stirring NaBPh₄ (350 mg, 1 mmol) was added. Addition of the tetraphenylborate salt caused a precipitate to form and the solution turned red-brown. Subsequently, 18 ml of a 5:1 acetonitrile:water and 10 ml of 0.1 M HClO₄ were added. The orange-brown solid was collected by filtration. Dichroic, red-green crystals of the product were obtained by slow evaporation of a toluene solution.