Chloridotris[μ2-2-(dimethyl­amino)­ethano­lato]-μ3-hydroxido-tri-μ2-trifluoro­acetato-tetra­copper(II) tetra­hydro­furan solvate

S Tajammul Hussain; Shahzad Abu Bakar; Mohammad Mazhar; Matthias Zeller

doi:10.1107/S1600536810022877

. 2010 Jun 18;66(Pt 7):m814–m815. doi: 10.1107/S1600536810022877

Chloridotris[μ₂-2-(dimethylamino)ethanolato]-μ₃-hydroxido-tri-μ₂-trifluoroacetato-tetracopper(II) tetrahydrofuran solvate

S Tajammul Hussain ^a,^*, Shahzad Abu Bakar ^a, Mohammad Mazhar ^b, Matthias Zeller ^c,^*

PMCID: PMC3006744 PMID: 21587732

Abstract

The title compound, [Cu₄(C₂F₃O₂)₃(C₄H₁₀NO)₃Cl(OH)]·C₄H₈O or [Cu₄(TFA)₃(dmae)₃Cl(OH)]·THF (dmae is dimethylaminoethanolate, TFA is trifluoroacetate and THF is tetrahydrofuran), has an approximate molecular threefold symmetry with three equivalent {Cu(dmae)(TFA)} units bridging between a Cu—Cl and a hydroxide unit, with the latter two lying on the molecular threefold axis. However, in the solid state, the tetranuclear complex has C_i symmetry. The Cu atom bonded to the Cl atom has a distorted tetrahedral geometry. The other three Cu atoms have distorted square-pyramidal geometries with an NO₄ coordination environment. The bonds within the CuNO₃ base of the pyramid range from 1.953 (2) to 2.033 (3) Å, while the apical Cu—O bonds are significantly longer, ranging from 2.286 (2) to 2.377 (2) Å. The square-pyramidal geometries are augmented by weak interactions towards a sixth O atom, forming a highly distorted octahedral coordination environment [long Cu—O distances = 2.712 (2)–2.824 (2) Å]. The hydroxide group is hydrogen bonded to the tetrahydrofuran solvent molecule. One of the –CF₃ groups shows minor disorder over two positions, with a refined occupancy ratio of 0.894 (4):0.106 (5).

Related literature

For the synthesis of [Cu(dmae)Cl]₄, used as starting material for title compound, see: Anwander et al. (1997 ▶). For general background to copper(II) complexes, see: Coastamagna et al. (1992 ▶). For related structures, see: Tahir et al. (2008 ▶); Shahid et al. (2009 ▶).

Experimental

Crystal data

[Cu₄(C₂F₃O₂)₃(C₄H₁₀NO)₃Cl(OH)]·C₄H₈O
M _r = 982.21
Monoclinic,
a = 16.4353 (14) Å
b = 12.1893 (12) Å
c = 35.547 (3) Å
β = 94.678 (2)°
V = 7097.7 (11) Å³
Z = 8
Mo Kα radiation
μ = 2.54 mm⁻¹
T = 100 K
0.41 × 0.38 × 0.28 mm

Data collection

Bruker SMART APEX CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2008 ▶) T _min = 0.673, T _max = 0.746
20465 measured reflections
10267 independent reflections
7515 reflections with I > 2σ(I)
R _int = 0.035

Refinement

R[F ² > 2σ(F ²)] = 0.043
wR(F ²) = 0.103
S = 1.01
10267 reflections
467 parameters
15 restraints
H-atom parameters constrained
Δρ_max = 0.92 e Å⁻³
Δρ_min = −0.69 e Å⁻³

Data collection: APEX2 (Bruker, 2008 ▶); cell refinement: SAINT (Bruker, 2008 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: Mercury (Macrae et al., 2008 ▶); software used to prepare material for publication: SHELXTL and publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810022877/fj2302sup1.cif

e-66-0m814-sup1.cif^{(35.3KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810022877/fj2302Isup2.hkl

e-66-0m814-Isup2.hkl^{(502.2KB, hkl)}

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

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O10—H10⋯O11	1.00	1.73	2.723 (3)	174

Open in a new tab

Acknowledgments

The authors are grateful to the Higher Education Commission of Pakistan for financial support. The diffractometer was funded by NSF grant 0087210, by Ohio Board of Regents grant CAP-491, and by YSU.

supplementary crystallographic information

Comment

In recent years, there has been a considerable interest towards the synthesis of copper complexes; these complexes are extensively used in catalysis, enzymatic reactions, magnetism and molecular architecture (Coastamagna, Vargas et al., 1992). The present work is a continuation of earlier studies for the preparation and structure eludication of copper (II) complexes (Shahid et al., 2009). The motivation behind the synthesis of the title compound was to use it as a starting material for the synthesis of single source precursors for the deposition of thin films of copper oxides using aerosol assisted chemical vapor deposition (AACVD). We present here the synthesis and crystal structure of the title compound, [Cu₄((CH₃)₂NCH₂CH₂O)₃(F₃CCOO)₃(OH)Cl] or [Cu₄(dmae)₃(TFA)₃(OH)Cl] (dmae = dimethylaminoethanolate, TFA = trifluoroacetate), which crystallized from THF as the mono solvate with the THF molecule tightly hydrogen bonded to the hydroxyl group.

The title compound has a slightly distorted molecular three fold symmetry with three equivalent Cu(dmae)(TFA) units bridging via their alcoholate oxygen atoms between a Cu—Cl and an hydroxyl unit with the latter two lying on a molecular pseudo threefold axis. The Cu atom bonded to the chlorine has a distorted tetrahedral geometry. The other three copper atoms have distorted square pyramidal geometries with a CNO₄ coordination environment from the dmae O and N atoms, the hydroxyl O atom and two TFA anions. The TFA anions are bridging between two neighboring copper ions with one of the oxygen atoms being part of the base of the pyramid of one copper ion, and the other being in the apical position of the neighboring copper ion. The bonds within the CuNO₃ bases of the pyramids are strong and quite similar in length with distances between 1.953 (2) and 2.033 (3) Å. The apical Cu—O bonds are significantly longer and between 2.286 (2) and 2.377 (2) Å, thus rendering the µ₂-bridge of the TFA ions asymmetric. The square pyramidal geometries are augmented by weak interactions towards a fifth oxygen atom to form a highly distorted octahedral coordination environment (Cu—O distances: O3—Cu3 = 2.712 (2), O2—Cu2 = 2.780 (2), O1—Cu4 = 2.8240 (2) Å).

A similar motif as in the title compound was previously observed for two mixed metal copper-titanium complexes (Tahir et al., 2008). In these complexes the TFA anions were replaced by benzoate or 2-methyl-benzoate ligands, and the Cu—Cl unit was replaced by a titanium atom, which in turn was bonded to another larger Cu—Ti cluster. The [Cu₃(dmae)₃(TFA)₃(OH)] unit in the title compound and the [Cu₃((CH₃)₂NCH₂CH₂O)₃(O₂C—C₆H₅R)₃(OH)] units in the Cu—Ti complexes (R = H, Me) are quite similar. In the 2-methyl-benzoate complexes the [Cu₃((CH₃)₂NCH₂CH₂O)₃(O₂C—C₆H₅Me)₃(OH)] unit is located on an actual crystallographic three fold axis. The carboxylate anions show coordination modes differing slightly from those observed in the title compound with some of the oxygen atoms being detached from the copper ions and interactions to the fifth oxygen atom, which are very weak in the title compound, being strengthened instead. The overall coordination environment - distorted square pyramidal CNO₄geometries with an additional weak interaction towards a fifth oxygen atom - is however the same in all three compounds, which shows the idiosyncracy commonly observed for copper(II) to form strongly distorted and highly flexible octahedral geometries with a set of four strong bonds in a square planar arrangement and two apical ligands at variable distances. Individual ligand atoms in these kinds of complexes can easily switch from tightly bound to only weakly coordinated as long as the overall coordination environment of the metal center is retained, and energy differences and activation barriers between the different arrangements that can be achieved that way are quite small. The difference in bonding arrangement in the three complexes in the solid state does thus probably not translate into a different chemical nature for the three complexes as the bonding environment around Cu(II) is very flexible and it can be assumed that in solution (i.e. upon release of packing effects) all complexes will attain the same connectivity pattern.

In the title compound the hydroxyl group is O—H···O hydrogen bonded to a tetrahydrofuran molecule (Table 1), which is embedded in a bowl shaped cleft of the complex formed by the three TFA ligands. No such host–guest behavior was observed for the other two related compounds (Tahir et al., 2008).

Experimental

Tetrameric N,N-dimethylaminoethanolato copper(II) chloride, [Cu(dmae)Cl]₄ was prepared according to a literature method (Anwander et al., 1997). The title compound was prepared as follows: 1.25 g (1.67 mmole) of [Cu(dmae)Cl]₄ in 20 ml THF were combined with 1.77 g (6.66 mmole) of Cu(F₃CCOO)₂ in 10 ml THF followed by the addition of 0.297 g (3.33 mmole) N,N-dimethylaminoethanol. The reaction mixture was stirred for 3 h and filtered through a cannula to remove any undissolved species. The filtrate was evaporated to dryness under vacuum, the solid was re-dissolved in 5 ml THF and placed in a vial with rubber seal at room temperature for one week to give blue crystals suitable for single-crystal X-ray diffraction analysis. Yield: 86% m.p. 393–394 K. Elemental Analysis for Cu₄((CH₃)₂NCH₂CH₂O)₃(F₃CCOO)₃(OH)Cl % calc: C, 21.99 H, 3.97 N, 4.27, % found: C, 22.10 H, 3.90 N, 4.53.