Tetra­kis(μ-2-phen­oxy­propionato)-κ3 O,O′:O′;κ3 O:O,O′;κ4 O:O′-bis­[(1,10-phenanthroline-κ2 N,N′)(2-phen­oxy­propionato-κ2 O,O′)holmium(III)]

Jin-Bei Shen; Jia-Lu Liu; Guo-Liang Zhao

doi:10.1107/S160053681103738X

. 2011 Sep 20;67(Pt 10):m1401. doi: 10.1107/S160053681103738X

Tetrakis(μ-2-phenoxypropionato)-κ³ O,O′:O′;κ³ O:O,O′;κ⁴ O:O′-bis[(1,10-phenanthroline-κ² N,N′)(2-phenoxypropionato-κ² O,O′)holmium(III)]

Jin-Bei Shen ^a, Jia-Lu Liu ^a, Guo-Liang Zhao ^a,^b,^*

PMCID: PMC3201487 PMID: 22058704

Abstract

The title compound, [Ho₂(C₉H₉O₃)₆(C₁₂H₈N₂)₂], lies about a centre of symmetry and is comprised of six 2-phenoxypropionate (POPA) anions and two 1,10-phenanthroline (phen) ligands. The two Ho^III ions are linked by four POPA groups utilizing both bi- and tridentate bridging modes to form an inversion-symmetric dimer. Each Ho^III ion is nine-coordinate, with a chelating 1,10-phenanthroline molecule, one bidentate chelating carboxylate group, two bidentate bridging carboxylate groups and two tridentate bridging carboxylate groups in a distorted mono-capped square antiprism geometry. There are weak π–π aromatic interactions between the phen groups and aromatic rings of the POPA ligands [centroid–centroid distance = 3.829 (1) Å].

Related literature

For phenoxyalkanoic acids, see: Markus & Buser (1997 ▶). For holmium complexes, see: Hu et al. (2006 ▶); Zhao et al. (2010 ▶). For isotypic complexes, see: Shen et al. (2011a ▶,b ▶,c ▶,d ▶).

Experimental

Crystal data

[Ho₂(C₉H₉O₃)₆(C₁₂H₈N₂)₂]
M _r = 1681.24
Monoclinic,
a = 11.4657 (2) Å
b = 25.7960 (3) Å
c = 13.8366 (2) Å
β = 120.687 (1)°
V = 3519.37 (9) Å³
Z = 2
Mo Kα radiation
μ = 2.31 mm⁻¹
T = 296 K
0.25 × 0.16 × 0.06 mm

Data collection

Bruker APEXII area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.656, T _max = 0.877
24604 measured reflections
6189 independent reflections
4266 reflections with I > 2σ(I)
R _int = 0.053

Refinement

R[F ² > 2σ(F ²)] = 0.033
wR(F ²) = 0.062
S = 1.00
6189 reflections
464 parameters
H-atom parameters constrained
Δρ_max = 0.67 e Å⁻³
Δρ_min = −0.55 e Å⁻³

Data collection: APEX2 (Bruker, 2006 ▶); cell refinement: SAINT (Bruker, 2006 ▶); data reduction: SAINT; 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: SHELXL97.

Supplementary Material

Crystal structure: contains datablock(s) global. DOI: 10.1107/S160053681103738X/pk2341sup1.cif

e-67-m1401-sup1.cif^{(37.4KB, cif)}

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

supplementary crystallographic information

Comment

The group of phenoxyalkanoic acids includes a considerable number of important herbicides. The desired biological activity is largely dependent on the length of the carbon chain of the alkanoic acid, the nature of the phenoxy group, and the position of its attachment to the carbon chain (Markus & Buser, 1997). The fascinating structures of 2-phenoxypropionic acid complexes coupled with their special functionality catch our interests. Recently, we have reported our partial research results (Shen et al., 2011a,b,c,d). Here we describe a new Ho^III complex.

The structure of the complex is shown in Fig. 1 and the coordination environment of Ho^III is shown in Fig. 2. The dimeric title compound is centrosymmetric and is comprised of six L and two phen ligands. The two Ho^III ions are linked together by four L groups by bi- and tridentate bridging modes to form a dimeric unit with crystallographic inversion symmetry. The distance between two Ho^III ions is 3.9769 (4) Å, which is similar to analogous complexes (Hu et al., 2006; Zhao et al., 2010). Each Ho^III ion is coordinated to nine atoms, of which five are oxygen atoms from bridging carboxylates, two are oxygen atoms from the bidentate chelating carboxylate groups, and two are nitrogen atoms from a 1,10-phenanthroline molecule. The analysis of structural features indicates that the central Ho^III ion adopts a distorted mono-capped square antiprism geometry (Fig. 2). The Ho—O distances are all within the range 2.312 (3)–2.618 (3) Å, and the Ho—N distances are 2.500 (3) and 2.594 (3) Å. There are weak π–π aromatic interactions from phen molecules and aromatic rings of the L ligands.

Experimental

Reagents and solvents were of commercially available quality and were used without further purification. 2-phenoxypropionic acid (1.5 mmol), Ho(NO₃)₃.6H₂O (0.5 mmol) and 1,10-phenanthroline (0.5 mmol) were dissolved in 20 ml ethanol, then 10 ml water was added. The mixed solution was stirred for 12 h at room temperature. Solid deposits were removed by filtration, and the colourless solution allowed to slowly evaporate in air. Colourless crystals were obtained after several days.