Ava M Park1, Duyen N K Pham2, James A Golen2, David R Manke2. 1. Portsmouth Abbey School, 285 Cory's Lane, Portsmouth, RI, 02871, USA. 2. University of Massachusetts Dartmouth, 285 Old Westport Rd., North Dartmouth, MA, 02747, USA.
The synthesis of metal–pyrdine–sulfates has been reported since the 19th century, when Jørgensen’s chain theory was still the prevailing hypothesis (Reitzenstein, 1894 ▸; Howe, 1898 ▸). Since that time, the structural understanding of metal complexes has greatly increased, first with the acceptance of Werner’s coordination theory (Werner, 1893 ▸), with crystal field theory from Bethe in 1929 (Bethe, 1929 ▸), and the modifications of theory in the ninety years since. Despite the long history of these compounds, their crystallographic study is rather limited. Before we began a crystallographic examination of metal–pyridine–sulfates in 2018, there were only two examples of such complexes without other ligands or components reported in the literature (Cotton & Reid, 1984 ▸; Memon et al., 2006 ▸).Since we began studying the structural chemistry of metal–pyridine–sulfates, we have observed many different structural motifs in the complexes. The coordination environment of each compound can usually be predicted with crystal field theory, although the exact nature is dependent upon the number of pyridines bound and the binding mode of the sulfate anion. The sulfate anion can have a number of different coordination modes, including μ-sulfato-κ2-O:O, μ-sulfato-κ2-O:O′ and μ-sulfato-κ3-O:O′:O". Herein we report two new structures of cobalt–pyridine–sulfates formed by altering the growth conditions and compare these structures with the previously reported structure of a cobalt–pyridine–sulfate and the structures of related complexes.
Structural commentary
The asymmetric unit of the pink crystals of (1) consists of two pyridine molecules and one half of a sulfate anion coordinated to a cobalt atom sitting on an inversion center (Fig. 1 ▸
a). When grown out, the cobalt ion shows an octahedral coordination environment (Fig. 1 ▸
b). The equatorial positions of the octahedron are occupied by four pyridine ligands in a square-planar arrangement. The CoN4 unit exhibits planarity enforced by symmetry, with cis N—Co—N angles of 86.45 (6) and 93.55 (6)°. To complete the octahedron, the axial positions are occupied by two sulfate ions, with an inversion enforced O—Co—O angle of 180° and cis O—Co—N angles of 88.87 (6) and 91.67 (6)°. The pyridine rings are rotated from the CoN4 plane by dihedral angles of 47.30 (10) and 78.33 (9)°. The 78.33 (9)° angles are constrained by two C—H⋯O interactions between the ortho hydrogen atoms and the two trans sulfates (Table 1 ▸).
Figure 1
The molecular structure of compound (1), including (a) the asymmetric unit and (b) the coordination environment around Co1. Displacement ellipsoids are drawn at the 50% probability level. H atoms are drawn as spheres of arbitrary radius. C—H⋯O interactions (Table 1 ▸) are shown as dashed lines. [Symmetry codes: (i) 1 − x, 1 − y, 1 − z; (ii) x, 1 − y, − + z; (iii) 1 − x, y, − z].
Table 1
Hydrogen-bond geometry (Å, °) for (1)
D—H⋯A
D—H
H⋯A
D⋯A
D—H⋯A
C6—H6A⋯O1i
0.93
2.51
3.106 (2)
122
C6—H6A⋯O2i
0.93
2.51
3.429 (3)
171
C10—H10A⋯O1
0.93
2.48
3.046 (2)
120
C10—H10A⋯O2ii
0.93
2.43
3.353 (3)
171
Symmetry codes: (i) ; (ii) .
The asymmetric unit of the purple crystals of (2) consists of two cobalt atoms, six coordinated pyridines and two sulfate anions (Fig. 2 ▸
a). There are two crystallographically unique cobalt atoms, with Co1 (Fig. 2 ▸
b) displaying an octahedral N4O2 coordination environment and Co2 (Fig. 2 ▸
c) exhibiting an octahedral N2O4 coordination geometry.
Figure 2
The molecular structure of compound (2), including (a) the asymmetric unit, (b) the coordination environment around Co1, and (c) the coordination environment around Co2. Displacement ellipsoids are drawn at the 50% probability level. H atoms are drawn as spheres of arbitrary radius. C—H⋯O interactions (Table 2 ▸) are shown as dashed lines. [Symmetry code: (i) −1 + x, −1 + y, −1 + z].
Co1 has four pyridine ligands occupying the equatorial positions of an octahedron, with the CoN4 plane showing a maximum deviation from planarity of 0.018 Å. Two sulfate anions occupy the axial positions to complete the octahedral coordination. The cis N—Co—N angles have values ranging from 87.48 (13) to 93.18 (12)°, and the trans O—Co—O angle is 173.43 (12)°. The planes of the four pyridine rings are rotated from the equatorial CoN4 plane by dihedral angles of 58.6 (2), 64.6 (2), 65.6 (2), and 73.1 (2)°. Two of the rings show one C—H⋯O interaction with an ortho hydrogen atom, one ring shows two C—H⋯O interactions with two ortho hydrogen atoms, and the fourth ring shows no C—H⋯O interactions (Table 2 ▸).
Table 2
Hydrogen-bond geometry (Å, °) for (2)
D—H⋯A
D—H
H⋯A
D⋯A
D—H⋯A
C1—H1A⋯O6
0.95
2.63
3.563 (6)
167
C2—H2A⋯O2i
0.95
2.52
3.219 (5)
131
C5—H5A⋯O4
0.95
2.42
3.009 (5)
120
C6—H6A⋯O5
0.95
2.56
3.054 (5)
112
C6—H6A⋯O7
0.95
2.47
3.322 (6)
149
C10—H10A⋯O4
0.95
2.53
3.010 (5)
112
C12—H12A⋯O7ii
0.95
2.60
3.271 (5)
128
C15—H15A⋯O5
0.95
2.45
3.017 (5)
118
C16—H16A⋯O2
0.95
2.19
3.139 (6)
176
C20—H20A⋯O5
0.95
2.51
3.091 (5)
119
C20—H20A⋯O6
0.95
2.32
3.272 (5)
175
C25—H25A⋯O8
0.95
2.55
3.162 (5)
123
C30—H30A⋯O7
0.95
2.54
3.116 (5)
119
Symmetry codes: (i) ; (ii) .
Co2 is bound by two pyridine ligands and two chelating sulfate anions to give an octahedral coordination environment. The pyridine rings adopt a cis configuration, with an N—Co—N angle of 93.63 (13)°. The two sulfate ligands exhibit O—Co—O bite angles of 65.90 (10) and 66.37 (10)°. The other cis O—Co—O angles are 86.87 (11), 98.98 (11), and 102.84 (11)°, and the six cis N—Co—O angles range from 92.49 (12) to 98.33 (13)°. Each pyridine ring is involved in ortho C—H⋯O interactions (Table 2 ▸).
Supramolecular features
The CoII atoms in compound (1) are linked together into infinite chains along the [001] direction through sulfate anions with O—S—O bridges (Figs. 3 ▸
a, 4 ▸
a). Between each successive tetrapyridinecobalt unit, there are parallel slipped π–π interactions [inter-centroid distance: 3.637 (1) Å, inter-planar distance: 3.611 (1) Å, slippage: 0.435 (1) Å].
Figure 3
The infinite chains of (a) compound (1) along [001], (b) compound (2) along [111], and (c) the previously reported cobalt–pyridine-sulfate complex [Co3(SO4)3(C5H5N)11] along [001] (Pham et al., 2019 ▸). Displacement ellipsoids are drawn at the 50% probability level. H atoms are omitted for clarity. The π–π interactions in (1) are shown as dashed lines.
Figure 4
The packing of (a) compound (1) along the c-axis and (b) compound (2) along the b-axis. Displacement ellipsoids are drawn at the 50% probability level. H atoms are omitted for clarity.
The CoII atoms in compound (2) are linked together into infinite chains along the [111] direction through the sulfate anions (Figs. 3 ▸
b, 4 ▸
b). The chain alternates between tetrapyridinecobalt units and dipyridinecobalt units. No π–π interactions are observed in the crystal.
Database survey
In a prior publication, we reported the structure of another cobalt–pyridine–sulfate [Co3(SO4)3(C5H5N)11)], which was grown at a lower concentration of cobalt. This structure shows two successive octahedral cobalt atoms with N4O2 coordination, where each atom is coordinated to four pyridines and two bridging sulfates. The third cobalt atom in the chain shows N3O3 coordination where three pyridines are bound and there are two sulfates bound, one of which is chelating to the cobalt (Pham et al., 2018 ▸). Fig. 3 ▸ compares the chain structure of this complex with those of compounds (1) and (2). In compound (1), every cobalt atom possesses an octahedral N4O2 coordination. This complex is isostructural with the structure observed for the iron and nickelpyridine–sulfate complexes (Roy et al., 2018 ▸). This structural motif is also consistent with that observed for the 4-picoline–sulfate structures of iron, cobalt, nickel and cadmium (Pham et al., 2019 ▸). In compound (2), the cobalt atoms alternate between N4O2 coordination and N2O4 coordination. This tetrapyridine/bipyridine alternation is similar to what is observed in the zinc–pyridine–sulfate structure, which alternates between octahedral and tetrahedral zinc centers. In the case of cobalt, the bis(pyridine) cobalt center is still octahedral because the two coordinated sulfates both chelate to the cobalt. The end result is an infinite chain of octahedral cobalt atoms, which is true in compound (1) and the previously reported cobalt–pyridine–sulfate complex. The methanesulfato complexes of cobalt (II) have also been reported as octahedral tetrakis(pyridine), [Co(SO3CH3)2(py)4], and octahedral bis(pyridine), [Co(SO3CH3)2(py)2], compounds, consistent with the two independent cobalt centers observed in (2) (Johnson et al., 1977 ▸).
Synthesis and crystallization
For compound (1), 40 mg of cobaltsulfate heptahydrate (J. T. Baker) was dissolved in pyridine (2 mL, Fischer Chemical) and distilled water (100 µL) in a 20 mL vial. The vial was heated to 338 K for 48 h, after which single crystals suitable for X-ray diffraction studies were isolated from the reaction mixture.For compound (2), 48 mg of cobaltsulfate heptahydrate (J. T. Baker) was dissolved in pyridine (2 mL, Fischer Chemical) and distilled water (30 µL) in a 20 mL vial. The vial was heated to 358 K for 48 h, after which single crystals suitable for X-ray diffraction studies were isolated from the reaction mixture.
Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3 ▸. All structure solutions were obtained by intrinsic phasing. All non-hydrogen atoms were refined anisotropically (SHELXL) by full-matrix least squares on F
2. Hydrogen atoms were placed in calculated positions and then refined with a riding model with C—H bond lengths of 0.95 Å and with isotropic displacement parameters set to 1.20 U
eq of the parent C atom. The structre of (2) was refined as a two-component inversion twin, BASF = 0.165 (13).
Table 3
Experimental details
(1)
(2)
Crystal data
Chemical formula
[Co(SO4)(C5H5N)4]
[Co2(SO4)2(C5H5N)6]
Mr
471.39
784.58
Crystal system, space group
Monoclinic, C2/c
Triclinic, P1
Temperature (K)
295
200
a, b, c (Å)
18.6323 (18), 10.0803 (9), 11.9403 (11)
9.5795 (6), 9.7612 (5), 10.7219 (6)
α, β, γ (°)
90, 115.945 (3), 90
98.488 (2), 107.697 (2), 115.948 (2)
V (Å3)
2016.6 (3)
811.46 (8)
Z
4
1
Radiation type
Mo Kα
Mo Kα
μ (mm−1)
0.99
1.21
Crystal size (mm)
0.28 × 0.13 × 0.06
0.25 × 0.20 × 0.02
Data collection
Diffractometer
Bruker APEXIII CMOS
Bruker APEXIII photon2
Absorption correction
Multi-scan (SADABS; Bruker, 2016 ▸)
Multi-scan (SADABS; Bruker, 2016 ▸)
Tmin, Tmax
0.667, 0.745
0.661, 0.745
No. of measured, independent and observed [I > 2σ(I)] reflections
20212, 1854, 1572
22679, 6013, 5906
Rint
0.071
0.026
(sin θ/λ)max (Å−1)
0.604
0.610
Refinement
R[F2 > 2σ(F2)], wR(F2), S
0.027, 0.063, 1.02
0.026, 0.072, 1.03
No. of reflections
1854
6013
No. of parameters
139
434
No. of restraints
0
3
H-atom treatment
H-atom parameters constrained
H-atom parameters constrained
Δρmax, Δρmin (e Å−3)
0.24, −0.24
0.79, −0.30
Absolute structure
–
Refined as an inversion twin
Absolute structure parameter
–
0.165 (13)
Computer programs: APEX3 and SAINT (Bruker, 2016 ▸), SHELXT (Sheldrick, 2015a
▸), SHELXL2014 (Sheldrick, 2015b
▸), OLEX2 (Dolomanov et al., 2009 ▸), SHELXTL (Sheldrick, 2008 ▸), and publCIF (Westrip, 2010 ▸).
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell esds are taken
into account individually in the estimation of esds in distances, angles
and torsion angles; correlations between esds in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell esds is used for estimating esds involving l.s. planes.
Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full
H-atom parameters constrained
R[F2 > 2σ(F2)] = 0.026
w = 1/[σ2(Fo2) + (0.0524P)2 + 0.1142P] where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.072
(Δ/σ)max < 0.001
S = 1.03
Δρmax = 0.79 e Å−3
6013 reflections
Δρmin = −0.29 e Å−3
434 parameters
Absolute structure: Refined as an inversion twin
3 restraints
Absolute structure parameter: 0.165 (13)
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell esds are taken
into account individually in the estimation of esds in distances, angles
and torsion angles; correlations between esds in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refined as a 2-component inversion twin. BASF 0.16482
Authors: Duyen N K Pham; Mrittika Roy; Ava Kreider-Mueller; James A Golen; David R Manke Journal: Acta Crystallogr C Struct Chem Date: 2019-04-15 Impact factor: 1.172
Authors: Ashfaq A Memon; Mohammad Afzaal; Mohammad A Malik; Chinh Q Nguyen; Paul O'Brien; Jim Raftery Journal: Dalton Trans Date: 2006-07-24 Impact factor: 4.390
Authors: Mrittika Roy; Duyen N K Pham; Ava Kreider-Mueller; James A Golen; David R Manke Journal: Acta Crystallogr C Struct Chem Date: 2018-02-05 Impact factor: 1.172