Tetra­kis(picolinato-κ2 N,O)zirconium(IV) dihydrate

Maryke Steyn; Hendrik G Visser; Andreas Roodt; T J Muller

doi:10.1107/S1600536811031710

. 2011 Aug 17;67(Pt 9):m1240–m1241. doi: 10.1107/S1600536811031710

Tetrakis(picolinato-κ² N,O)zirconium(IV) dihydrate

Maryke Steyn ^a,^*, Hendrik G Visser ^a, Andreas Roodt ^a, T J Muller ^a

PMCID: PMC3200838 PMID: 22065566

Abstract

In the title compound, [Zr(C₆H₄NO₂)₄]·2H₂O, the Zr^IV atom is located on a crystallographic fourfold rotoinversion axis ( Inline graphic ) and is coordinated by four picolinate anions with Zr—O and Zr—N distances of 2.120 (2) and 2.393 (2) Å, respectively. An approximate square-antiprismatic coordination polyhedron of the N,O-coordination ligand atoms is formed, with a distortion towards dodecahedral geometry. The crystal packing is stabilized by intermolecular π–π interactions between adjacent picolinate rings [centroid–centroid distances = 3.271 (1) and 3.640 (2) Å], as well as O—H⋯O hydrogen bonds between the solvent molecules and the coordinated ligands, thereby linking the molecules into a supramolecular three-dimensional network.

Related literature

For N,O- and O,O′-bidentate ligand complexes of zirconium and hafnium, see: Steyn et al. (2008 ▶); Viljoen et al. (2010a ▶,b ▶). For relevant studies of N,O- and O,O′-bidentate ligands with other transition metal atoms, see: Graham et al. (1991 ▶); Mtshali et al. (2006 ▶); Roodt et al. (2011 ▶); Schutte et al. (2008 ▶); Steyn et al. (1997 ▶); Van Aswegen et al. (1991 ▶); Van der Westhuizen et al. (2010 ▶).

Experimental

Crystal data

[Zr(C₆H₄NO₂)₄]·2H₂O
M _r = 615.66
Tetragonal,
a = 11.083 (5) Å
c = 9.548 (5) Å
V = 1172.8 (10) Å³
Z = 2
Mo Kα radiation
μ = 0.54 mm⁻¹
T = 100 K
0.12 × 0.09 × 0.04 mm

Data collection

Bruker X8 APEXII 4K Kappa CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2004 ▶) T _min = 0.942, T _max = 0.977
27234 measured reflections
1477 independent reflections
1271 reflections with I > 2σ(I)
R _int = 0.074

Refinement

R[F ² > 2σ(F ²)] = 0.037
wR(F ²) = 0.100
S = 1.10
1477 reflections
87 parameters
1 restraint
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.64 e Å⁻³
Δρ_min = −0.92 e Å⁻³

Data collection: APEX2 (Bruker, 2010 ▶); cell refinement: SAINT-Plus (Bruker, 2004 ▶); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg, 2006 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶).

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536811031710/zq2119sup1.cif

e-67-m1240-sup1.cif^{(13.7KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811031710/zq2119Isup2.hkl

e-67-m1240-Isup2.hkl^{(71.4KB, 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
O03—H03A⋯O2ⁱ	0.94 (2)	1.89 (2)	2.829 (3)	175 (5)

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Symmetry code: (i) Inline graphic .

Acknowledgments

Financial assistance from the Advanced Metals Initiative (AMI) and the Department of Science and Technology (DST) of South Africa, as well as the New Metals Development Network (NMDN) and the South African Nuclear Energy Corporation Limited (Necsa) is gratefully acknowledged.

supplementary crystallographic information

Comment

The introduction of N,O-bidentate ligands with the oxine or aminovinylketone backbones significantly influences both steric and electronic properties of transition metal centres as illustrated by literature examples (Graham et al., 1991; Mtshali et al., 2006; Roodt et al., 2011; Schutte et al., 2008; Steyn et al., 1997; Van Aswegen et al., 1991; Van der Westhuizen et al., 2010). This study is part of ongoing research initiatives investigating coordination behaviour of O,O'- and N, O,-bidentate ligands with zirconium(IV) and hafnium(IV) for possible separation of these two metals from base ore sources (Steyn et al., 2008; Viljoen et al., 2010a,b).

The title compound, [Zr(C₆H₄NO₂)₄].2H₂O, with C₆H₄NO₂ as picolinic acid, crystallizes in the form of colourless cubic crystals in the tetragonal P4₂/n space group. The Zr^IV atom, located on a crystallographic fourfold rotoinversion axis (4), is coordinated to four picolinic acid ligands (Fig. 1). The assymetric unit contains half a solvent molecule located on a twofold axis. The Zr—O and Zr—N bond lengths are 2.120 (2) Å and 2.393 (2) Å, respectively, with a N—Zr—O bite angle of 69.79 (7) °. The coordination polyhedron around the metal centre is an approximate square antiprism of the N,O-coordination ligand atoms, with a distortion towards dodecahedral geometry. The crystal packing is stabilized by intermolecular π-π interactions (Fig. 2), between adjacent picolinato rings, with interplanar and centroid-to-centroid distances of 3.271 (1) Å and 3.640 (2) Å, respectively. Further stabilization of the crystal structure is afforded by O—H···O hydrogen bonding (Fig. 3) between the carbonyl group of the picolinato ligands and the solvent water molecules. All of these interactions serve to link the molecules into a supramolecular three-dimensional network.

Experimental

Chemicals were purchased from Sigma-Aldrich and used as received. ZrCl₄ (103.3 mg, 0.463 mmol) and picolinic acid (PicA) (175.2 mg, 1.423 mmol) was separately dissolved in DMF (2.5 ml ea) and heated to 60 °C. The PicA solution was added drop-wise to the zirconium solution and stirred at 60 °C for 30 minutes. The reaction solution was removed from heating, covered and left to stand for crystallization. White cubic crystals, suitable for single-crystal X-ray diffraction, formed after 30 days (yield: 178 mg, 86%).