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Acta Cryst. (2007). E63, m2998-m2999    [ doi:10.1107/S1600536807056437 ]

Racemic dipotassium di-[mu]2-hydroxido-bis{[N,N-bis(carboxylatomethyl)leucinato-[kappa]4N,O,O',O'']cobaltate(III)} tetrahydrate

H. G. Visser, W. Purcell, A. Muller, J. M. Janse van Rensburg and P. Molosia

Abstract top

The racemic title compound, K2[Co2(C10H13NO6)2(OH)2]·4H2O, exhibits a slightly distorted octahedral coordination of the Co atoms, possibly because of constraints imposed by the tetradentate ligand. The ten-coordinate potassium cation provides a link between the ligating anions of the dinuclear dianion via the carbonyl O atoms of the N,N-bis(carboxylatomethyl)leucinate ligands, forming a polymeric three-dimensional network. The complex crystallizes in the orthorombic space group, Cmca, resulting in Co dimers situated around special positions in the unit cell, which leads to a 50% disorder of the bridging hydroxido H atoms and the isopropyl substituents.

Comment top

Tripod type ligands like nitrilotriacetic acid (nta) and the very similar N,N-bis(carboxymethyl) d,l-leucinate (d,l-lda) are of special interest to us in terms of its applicability as chelation agents of heavy metal ions in industrial effluents (Novitchi et al., 2005; Choi et al., 2003). Also, the fact that these ligands imitate simple biological systems make the investigation into the coordination chemistry and kinetic behaviour of complexes with metal ions like chromium(III) and cobalt(III) quite interesting (Bocarsley et al., 1990; Visser et al., 2002; Visser et al., 2006).

The title compound (I, see Fig. 1) crystallizes in the orthorhombic space group Cmca (Z=8), resulting in Co-dimers situated around special positions in the unit cell. The two cobalt centres are octahedrally surrounded by the nitrogen and three carboxylate O atoms of the lda ligand plus the two bridging hydroxo oxygen atoms. The lda ligand forms three glycinate rings around the central metal ion. These rings can be classified into one R ring, Co—N—C(2)—C(1)—O(1) and two G rings, Co—N—C(4)—C(3)—O(2) and Co—N—C(4)i—C(3)i—O(2)i according to the notations used by Weakliem et al. (1959) (Symmetry code i = −x,y,z).

The octahedral environment around the Co(III) atoms are substantially distorted. The Co—O bond distances vary between 1.897 (4) and 1.913 (3) Å, while the Co—N bond distance is 1.930 (4) Å. All the N—Co—O bond angles deviate from 90° and range between 85.88 (8) and 99.03 (18)°.

The Co—N and Co—O bond distances correspond well with that found for [Co(nta)(µ-OH)]22− [Visser et al., 1997] The N—C, C—C and C—O bonding distances within the lda ligand correspond well with those obtained for Ca(nta)·2H2O (Whitlow, 1972) and Hnta (Skrzypczak-Jankun et al., 1994). The nitrogen tetrahedron is slightly distorted with angles varying between 111.3 (3) and 114.9 (5)°.

Each potassium cation interacts with ten oxygen atoms (two water molecules and eight carboxylate O atoms from three different anions), serving as a link between the anions and generating a polymeric network. The K+ to oxygen interatomic distances vary between 2.827 (3) and 3.077 (4) Å. Further links between the anions are provided by an extensive network of hydrogen bonds (see Table 2).

Related literature top

For crystal structures of related compounds, see Bocarsley et al. (1990); Choi et al. (2003); Kato et al. (2006); Kumita et al. (1998); Novitchi et al. (2005); Skrzypczak-Jankun et al. (1994); Visser et al. (1997, 2001, 2005); Whitlow (1972). For the ring notation, see: Weakliem & Hoard (1959). For solution studies and kinetics, see Visser et al. (2002, 2003, 2006).

Experimental top

K2[Co(d,l-lda)(µ-OH)]2·2H2O, was prepared by the method similar to that used for Cs2[Co(nta)(µ-OH)]2·2H2O [Visser et al., 1997]. CoCl2·6H2O (2 g, 0.008 mol) and N,N-bis(carboxymethyl) d,l-leucinate (2.08 g, 0.008 mol) was added to a KHCO3 solution (5 g, 0.05 mol) and heated on a water bath. The pH of the solution was adjusted to 6 − 7 and this solution was placed on an ice bath. H2O2 (1 cm3, 30%) was added to the solution and after a few hours a bluish violate precipitate separated out from the solution. The precipitate was filtered and dried. Re-crystallization was carried out in water and blue/purple crystals, suitable for X-ray crystallography, were obtained after a few days. yield: 63.9%. IR ν(COOH 1625 cm−1. UV-Vis λmax304, 400, 565 nm. 1H NMR (D2O, p.p.m.): 0.95 (d, 6H), 1.65 (m, 1H), 1.90 (m, 2H), 3.56 (d, 1H), 3.85 (d, 1H), 3.82(d, 1H), 4.44 (d, 1H), 4.44 (t, 1H).

Refinement top

The methine, methylene and methyl H atoms were placed in geometrically idealized positions (C—H = 0.93–0.98) and constrained to ride on their parent atoms with Uiso(H) = 1.2Ueq(C) for methine and methylene, and Uiso(H) = 1.5Ueq(C) for methyl respectively. Methyl torsion angles were refined from electron density. Bridging hydroxo H atoms were located from a Fourier difference map and constrained to ride on their parent atoms with Uiso(H) = 1.2Ueq(O). These show a 50% disorder due to molecules being situated on special positions in the unit cell. The isopropyl substituents are also 50% disordered for the same reason and also show high thermal vibrations on the periphery. Possible hydogen coordinates from the Fourier difference map could not be refined satisfactory for the water solvate.

Computing details top

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT-Plus (Bruker, 2004); data reduction: SAINT-Plus and XPREP (Bruker, 2004); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. View of (I) (50% probability displacement ellipsoids). Hydrogen atoms have been omitted for clarity. Atoms labels containing superscripts indicates atoms generated by symmetry (symmetry codes i = −x,y,z; ii = x,-y,1 − z; iii = −x,-y,1 − z)
dipotassium di-µ2-hydroxido-bis{[N,N- bis(carboxylatomethyl)leucinato- κ4N,O,O',O'']cobaltate(III)} tetrahydrate top
Crystal data top
K2[Co2(C10H13NO6)2(OH)2]F000 = 1624
Mr = 788.56Dx = 1.69 Mg m−3
Orthorhombic, CmcaMo Kα radiation
λ = 0.71073 Å
Hall symbol: -C 2bc 2Cell parameters from 1747 reflections
a = 12.968 (5) Åθ = 2.7–28.1º
b = 25.868 (5) ŵ = 1.42 mm−1
c = 9.240 (5) ÅT = 293 (2) K
V = 3100 (2) Å3Plate, purple
Z = 40.25 × 0.19 × 0.02 mm
Data collection top
Bruker Kappa APEXII
diffractometer		2015 independent reflections
Monochromator: graphite1700 reflections with I > 2σ(I)
Detector resolution: 512 pixels mm-1Rint = 0.060
T = 100(2) Kθmax = 28.4º
φ and ω scansθmin = 2.8º
Absorption correction: multi-scan
(SADABS; Bruker, 2004)		h = −15→17
Tmin = 0.722, Tmax = 0.969k = −30→34
8534 measured reflectionsl = −10→12
Refinement top
Refinement on F233 restraints
Least-squares matrix: fullH atoms treated by a mixture of
independent and constrained refinement
R[F2 > 2σ(F2)] = 0.054  w = 1/[σ2(Fo2) + (0.0203P)2 + 25.1765P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.133(Δ/σ)max < 0.001
S = 1.24Δρmax = 0.63 e Å−3
2015 reflectionsΔρmin = −0.66 e Å−3
134 parametersExtinction correction: none
Crystal data top
K2[Co2(C10H13NO6)2(OH)2]V = 3100 (2) Å3
Mr = 788.56Z = 4
Orthorhombic, CmcaMo Kα
a = 12.968 (5) ŵ = 1.42 mm−1
b = 25.868 (5) ÅT = 293 (2) K
c = 9.240 (5) Å0.25 × 0.19 × 0.02 mm
Data collection top
Bruker Kappa APEXII
diffractometer		2015 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2004)		1700 reflections with I > 2σ(I)
Tmin = 0.722, Tmax = 0.969Rint = 0.060
8534 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.05433 restraints
wR(F2) = 0.133H atoms treated by a mixture of
independent and constrained refinement
S = 1.24  w = 1/[σ2(Fo2) + (0.0203P)2 + 25.1765P]
where P = (Fo2 + 2Fc2)/3
2015 reflectionsΔρmax = 0.63 e Å−3
134 parametersΔρmin = −0.66 e Å−3
Special details top

Experimental. The intensity data was collected on a Bruker X8 Apex II 4 K Kappa CCD diffractometer using an exposure time of 20 s/frame. A total of 620 frames were collected with a frame width of 0.5° covering up to θ = 28.4° with 98.8% completeness accomplished.

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
Co00.03898 (3)0.61246 (8)0.00824 (19)
C100.0787 (2)0.8831 (6)0.0122 (10)
C200.1258 (2)0.7900 (6)0.0165 (11)
H2A−0.06040.14640.81230.02*0.5
H2B0.06040.14640.81230.02*0.5
C3−0.1807 (3)0.09039 (14)0.5868 (4)0.0129 (8)
C4−0.0971 (3)0.13099 (14)0.5611 (5)0.0174 (8)
H4−0.08170.12710.45790.021*
C5−0.1206 (6)0.1870 (3)0.5748 (10)0.0187 (14)0.5
H5A−0.05840.20470.60580.022*0.5
H5B−0.17170.19140.65050.022*0.5
C6−0.1607 (8)0.2135 (4)0.4365 (12)0.0320 (18)0.5
H6−0.21660.19270.3950.038*0.5
C7−0.0754 (10)0.2203 (4)0.3234 (14)0.047 (3)0.5
H7A−0.02260.24250.36150.07*0.5
H7B−0.10390.23550.23750.07*0.5
H7C−0.04610.18720.30040.07*0.5
C8−0.2027 (10)0.2676 (4)0.4777 (17)0.054 (3)0.5
H8A−0.26320.26380.53650.081*0.5
H8B−0.21980.28630.39130.081*0.5
H8C−0.1510.28620.53070.081*0.5
N00.11323 (16)0.6325 (5)0.0097 (9)
O100.03494 (14)0.8175 (4)0.0113 (8)
O2−0.1472 (2)0.04429 (10)0.6132 (3)0.0124 (5)
O300.08247 (15)1.0160 (4)0.0156 (8)
O4−0.2731 (2)0.10165 (11)0.5758 (3)0.0187 (6)
O500.03447 (14)0.4072 (4)0.0129 (8)
O6−0.3530 (2)−0.08192 (14)0.7397 (4)0.0329 (8)
K−0.33220 (9)00.50.0170 (3)
H5−0.057 (4)0.043 (4)0.373 (10)0.02*0.5
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Co0.0076 (4)0.0083 (3)0.0088 (4)000.0003 (3)
C10.005 (2)0.017 (2)0.015 (3)00−0.002 (2)
C20.023 (3)0.013 (3)0.013 (3)00−0.002 (2)
C30.0126 (19)0.0149 (17)0.0113 (18)−0.0007 (14)−0.0036 (15)−0.0022 (13)
C40.014 (2)0.0114 (16)0.027 (2)0.0023 (13)−0.0090 (17)0.0012 (15)
C50.011 (3)0.014 (2)0.031 (3)0.005 (2)−0.006 (3)−0.004 (3)
C60.025 (4)0.024 (3)0.048 (4)0.010 (3)−0.008 (3)0.013 (3)
C70.055 (7)0.031 (5)0.054 (6)0.006 (5)0.008 (5)0.025 (5)
C80.053 (7)0.025 (4)0.083 (9)0.021 (4)0.001 (6)0.019 (5)
N0.007 (2)0.0090 (19)0.013 (2)000.0007 (16)
O10.0124 (19)0.0118 (17)0.0096 (19)000.0002 (14)
O20.0092 (13)0.0119 (12)0.0160 (14)−0.0005 (9)−0.0022 (11)−0.0003 (11)
O30.013 (2)0.023 (2)0.0110 (19)00−0.0016 (16)
O40.0105 (14)0.0187 (14)0.0268 (17)0.0053 (10)−0.0044 (13)−0.0020 (12)
O50.015 (2)0.0105 (17)0.013 (2)000.0004 (14)
O60.0193 (17)0.055 (2)0.0243 (18)0.0144 (15)−0.0040 (14)−0.0127 (16)
K0.0101 (6)0.0144 (5)0.0265 (7)00−0.0036 (5)
Geometric parameters (Å, °) top
Co—O11.897 (4)C4—N1.494 (4)
Co—O51.900 (4)C4—H40.98
Co—O5i1.909 (4)C5—C61.540 (13)
Co—O21.913 (3)C5—H5A0.97
Co—O2ii1.913 (3)C5—H5B0.97
Co—N1.930 (4)C6—C71.532 (16)
Co—Coi2.8959 (16)C6—C81.550 (14)
C1—O31.232 (7)C6—H60.98
C1—O11.283 (6)C7—H7A0.96
C1—C21.491 (8)C7—H7B0.96
C2—N1.491 (7)C7—H7C0.96
C2—H2A0.97C8—H8A0.96
C2—H2B0.97C8—H8B0.96
C3—O41.237 (5)C8—H8C0.96
C3—O21.293 (4)N—C4ii1.494 (4)
C3—C41.528 (5)O5—Coi1.909 (4)
C4—C51.485 (8)O5—H50.83 (2)
O1—Co—O5173.32 (16)N—C4—H4103
O1—Co—O5i92.31 (17)C3—C4—H4103
O5—Co—O5i81.01 (18)C4—C5—C6115.6 (7)
O1—Co—O290.02 (9)C4—C5—H5A108.4
O5—Co—O290.46 (9)C6—C5—H5A108.4
O5i—Co—O294.12 (8)C4—C5—H5B108.4
O1—Co—O2ii90.02 (9)C6—C5—H5B108.4
O5—Co—O2ii90.46 (9)H5A—C5—H5B107.4
O5i—Co—O2ii94.12 (8)C7—C6—C5111.9 (8)
O2—Co—O2ii171.76 (16)C7—C6—C8108.5 (9)
O1—Co—N87.65 (18)C5—C6—C8108.5 (9)
O5—Co—N99.03 (18)C7—C6—H6109.3
O5i—Co—N179.96 (19)C5—C6—H6109.3
O2—Co—N85.88 (8)C8—C6—H6109.3
O2ii—Co—N85.88 (8)C6—C7—H7A109.5
O1—Co—Coi132.70 (12)C6—C7—H7B109.5
O5—Co—Coi40.62 (11)H7A—C7—H7B109.5
O5i—Co—Coi40.39 (12)C6—C7—H7C109.5
O2—Co—Coi93.01 (8)H7A—C7—H7C109.5
O2ii—Co—Coi93.01 (8)H7B—C7—H7C109.5
N—Co—Coi139.65 (14)C6—C8—H8A109.5
O3—C1—O1122.8 (5)C6—C8—H8B109.5
O3—C1—C2120.6 (5)H8A—C8—H8B109.5
O1—C1—C2116.6 (5)C6—C8—H8C109.5
N—C2—C1112.7 (4)H8A—C8—H8C109.5
N—C2—H2A109.1H8B—C8—H8C109.5
C1—C2—H2A109.1C2—N—C4111.3 (3)
N—C2—H2B109.1C2—N—C4ii111.3 (3)
C1—C2—H2B109.1C4—N—C4ii114.9 (5)
H2A—C2—H2B107.8C2—N—Co108.1 (3)
O4—C3—O2124.0 (4)C4—N—Co105.3 (2)
O4—C3—C4120.8 (3)C4ii—N—Co105.3 (2)
O2—C3—C4115.1 (3)C1—O1—Co115.0 (3)
C5—C4—N115.8 (5)C3—O2—Co113.7 (2)
C5—C4—C3120.8 (5)Co—O5—Coi98.99 (18)
N—C4—C3108.6 (3)Co—O5—H5111 (7)
C5—C4—H4103Coi—O5—H5103 (7)
O3—C1—C2—N180.000 (2)O2—Co—N—C4−28.9 (3)
O1—C1—C2—N0.000 (2)O2ii—Co—N—C4150.7 (3)
O4—C3—C4—C522.2 (7)Coi—Co—N—C460.9 (3)
O2—C3—C4—C5−160.9 (5)O1—Co—N—C4ii119.1 (3)
O4—C3—C4—N159.4 (4)O5—Co—N—C4ii−60.9 (3)
O2—C3—C4—N−23.7 (5)O2—Co—N—C4ii−150.7 (3)
N—C4—C5—C6137.6 (7)O2ii—Co—N—C4ii28.9 (3)
C3—C4—C5—C6−88.1 (8)Coi—Co—N—C4ii−60.9 (3)
C4—C5—C6—C7−72.3 (10)O3—C1—O1—Co180.0000 (10)
C4—C5—C6—C8168.1 (8)C2—C1—O1—Co0.0000 (10)
C1—C2—N—C4115.2 (3)O2—Co—O1—C1−85.88 (8)
C1—C2—N—C4ii−115.2 (3)O2ii—Co—O1—C185.88 (8)
C1—C2—N—Co0.0000 (10)N—Co—O1—C10.0000 (10)
C5—C4—N—C257.3 (6)Coi—Co—O1—C1180.0000 (10)
C3—C4—N—C2−82.3 (4)O4—C3—O2—Co176.6 (3)
C5—C4—N—C4ii−70.5 (7)C4—C3—O2—Co−0.2 (4)
C3—C4—N—C4ii149.9 (3)O1—Co—O2—C3105.1 (3)
C5—C4—N—Co174.2 (5)O5—Co—O2—C3−81.5 (3)
C3—C4—N—Co34.5 (4)O5i—Co—O2—C3−162.5 (3)
O1—Co—N—C20N—Co—O2—C317.5 (3)
O5—Co—N—C2180Coi—Co—O2—C3−122.1 (3)
O2—Co—N—C290.19 (9)O5i—Co—O5—Coi0
O2ii—Co—N—C2−90.19 (9)O2—Co—O5—Coi−94.10 (8)
Coi—Co—N—C2180.0000 (10)O2ii—Co—O5—Coi94.10 (8)
O1—Co—N—C4−119.1 (3)N—Co—O5—Coi180
O5—Co—N—C460.9 (3)
Symmetry codes: (i) −x, −y, −z+1; (ii) −x, y, z.
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O5—H5···O6iii0.83 (2)1.98 (5)2.745 (4)153 (9)
C4—H4···O6iii0.982.483.294 (6)140
Symmetry codes: (iii) −x−1/2, −y, z−1/2.
Table 1
Selected geometric parameters (Å, °) top
Co—O11.897 (4)Co—O2ii1.913 (3)
Co—O51.900 (4)Co—N1.930 (4)
Co—O5i1.909 (4)Co—Coi2.8959 (16)
Co—O21.913 (3)
O1—Co—O5173.32 (16)O5i—Co—O2ii94.12 (8)
O1—Co—O5i92.31 (17)O2—Co—O2ii171.76 (16)
O5—Co—O5i81.01 (18)O1—Co—N87.65 (18)
O1—Co—O290.02 (9)O5—Co—N99.03 (18)
O5—Co—O290.46 (9)O5i—Co—N179.96 (19)
O5i—Co—O294.12 (8)O2—Co—N85.88 (8)
O1—Co—O2ii90.02 (9)O2ii—Co—N85.88 (8)
O5—Co—O2ii90.46 (9)
Symmetry codes: (i) −x, −y, −z+1; (ii) −x, y, z.
Acknowledgements top

Financial assistance from the research funds of UFS and NRF is gratefully acknowledged. Part of this material is based on work supported by the South African National Research Foundation under grant number GUN 2067416. Opinions, findings, conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NRF.

references
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