Tetraammine(selenito-O,O′)cobaltate(III) nitrate monohydrate

The title compound crystallizes as the mono­hydrate, [Co(SeO₃)(NH₃)₄]NO₃·H₂O. The crystallographic mirror symmetry coincides with the molecular symmetry; the mirror plane passes through the cation, anion and water mol­ecule. The CoN₄O₂ octahedron is distorted, with the selenito group acting as a bidentate ligand through two bridging O atoms to the cobalt. The coordinated Se—O distance is 1.742 (2) Å, whereas the uncoordinated Se—O distance is 1.646 (3) Å. A three-dimensional hydrogen-bonded network exists between [Co(SeO₃)(NH₃)₄]NO₃ and the water mol­ecule. The nitrate anion and water mol­ecule form open pores in the structure when hydrogen bonded to two neighboring [Co(SeO₃)(NH₃)₄]⁺ cations. Selenium participates in two types of relatively close intermolecular interactions with neighboring charged species (Se...N1 and Se...O3), but does not participate in an interaction with a neighboring O2 atom, the nearest contact distance being 4.638 (3) Å.

S1. Comment

As part of studies directed towards the synthesis of selenatoammine cobaltate(III) complexes, the reaction of carbonatotetrammine cobaltate(III) nitrate (Schlessinger, 1960) with selenous acid (H₂SeO₃) gave the title compound, (I) (Salib et al., 1988). X-ray diffraction analysis of (I) was undertaken in order to deduce the stereochemistry of this complex. \sch

The molecular structure of (I) (Fig. 1) is similar to that of carbonatotetrammine-cobaltate(III) bromide (Barclay & Hoskins, 1962). The geometry about the cobalt is distorted, with ammine groups occupying four sites with Co—N bonds ranging from 1.946 (3)–1.957 (2) Å and angles approximating that of an octahedron [89.1 (1)–94.8 (2), 179.7 (2)°]. The SeO₃ moiety acts as a bidentate ligand, forming a four-membered ring through the O atoms with the cobalt. A Co—O distance of 1.942 (2) Å is observed. A non-bonded distance of 2.735 (1) Å separates the selenium and cobalt atoms. Typical Se-first row transition metal single-bond distances are observed ranging from 2.40–2.56 Å (Day et al., 1982; Fischer et al., 1981; Hermann et al., 1983; Rott et al., 1982).

The coordinated Se—O distance is 1.742 (2) Å whereas the uncoordinated Se—O distance is 1.646 (3) Å, these distances are consistent with single and double bonded Se—O character, respectively. Similar distances are reported by Hughes et al. (1986) for (selenito-O,O')-bis(triphenylphosphine)platinum(II) where Se—O_bridged = 1.726 (5)–1.746 (5) Å and Se—O_terminal = 1.602 (7) Å. In (I) the geometry about Se is a pyramidal, O1—Se—O2 angle [104.6 (1)°], with the fourth coordination site occupied by the Se lone pair of electrons.

As with [Co(NH₃)₄CO₃]Br (Barclay & Hoskins, 1962), significant strain is involved in the formation of the four-membered ring in (I). The O1—Co—O1' angle of 78.6 (1)° deviates markedly from the expected angle of 90°. The Co—O1—Se [95.72 (9)°] and O1—Se—O1' [89.9 (1)°] angles are also compressed. Some strain relief may be observed in the angles N2—Co—N2' [94.8 (2)°] and O1—Co—N2 [93.28 (9)°] which are somewhat relaxed.

A slight folding towards N3 [3.1 (2)°] is observed in the equatorial plane of the molecule comprised of O1—O1'-N2—N2' and the selenato fragment, Se—O1—O1'. Barclay & Hoskins (1962) found a similar but more pronounced folding (7°) in the carbonato complex.

An extensive network of N—H.·O and O—H.·O hydrogen bonding (Fig. 2) is observed for (I) and the water molecule. The extensive hydrogen bonding for (I) is expected due to the ability of the SeO₃ moiety to attract the hydrogen from water molecules to form hydrogen selenite or selenous acid. Prior to this work, this behavior was discussed by thermal dehydration of Cu^II, Ni^II, Co^II selenite dihydrates. It was found that the water molecules persist until 523 K and the SeO₃ is transformed into HSeO₃ (Emara et al., 1996). Similarly, the related compound [Co(NH₃)₅SeO₃]Cl is very hygroscopic (Salib et al., 1988). In (I), the nitrate anion and water molecule form open pores in the structure when hydrogen bonded to two neighboring [Co(NH₃)₄SeO₃]⁺ cations. Selenium participates in two types of close intermolecular interactions with neighboring charged species, cation-anion [Se···O3=3.15 (2) Å]; symmetry code: x + 1/2, y, -z + 3/2), and cation-cation [Se···N1 = 3.595 (3) Å]; symmetry code: x + 1/2, y, -z + 3/2). Additional nearest neighbor contacts with Se are Se···N3 = 3.930 (2) Å (symmetry code: -x + z, -y, -z + 1) and Se···O5 = 4.005 (2) Å (symmetry code: -x + 3/2, -y, z + 1/2). Se essentially does not participate in an interaction with a neighboring O2, the nearest contact distance being 4.64 Å.

S2. Experimental

The carbonato complex was initially prepared from an aqueous solution of cobalt(II) nitrate and ammonium carbonate, to which concentrated ammonia solution was added. Oxidation to Co^III was affected by H₂O₂ to form the carbonato complex, [Co(NH₃)₄CO₃]NO₃ (Schlessinger, 1960). The carbonate group was replaced by an SeO₃ group upon reacting the carbonato complex with an equimolar amount of selenous acid. The resulting red-purple solution was heated to 343 K for several minutes, methanol (200 ml) was added and a red-purple precipitate was obtained. The precipitate was collected by filtration, washed with methanol and filtered (63% yield). Crystals of (I) were obtained by dissolving the crude product in a minimum volume of water to which methanol was added. The crystals were dried over H₂SO₄ in a desiccator. The product was characterized by elemental analysis, UV-vis and infrared spectroscopy. M.p. 458 K C (dec). Elemental analysis: CoH₁₂N₅O₆·H₂O (mol. wt = 334.05), calculated; Se 25.0, H 3.8, N 22.2%: found; Se 25.1, H 4.0, N 22.0% IR (deuterated sample of 1): ν(SeO₃): 832 (s), 690–790 (s,b) cm^-1. UV-vis: 18700 (¹A_{1 g} → ¹T_{1 g}), 25800 (¹A_{1 g} → ¹T_{2 g}) cm^-1.

S3. Refinement

H atoms were located directly from the difference map and fixed where located in subsequent refinement cycles. H-atom isotropic temperature factors were defined as U(H) = 1.5*U(N,O). A final difference Fourier map showed a relatively large electron density peak of 1.15 e Å^-3 with distances of 0.9 and 1.7 Å from H3B and N3, respectively. However this peak is not located in a position in terms of reasonable bonding geometry.

Computing details

Data collection: SMART (Siemens, 1995); cell refinement: SMART; data reduction: SAINT (Siemens, 1995); program(s) used to solve structure: SHELXTL (Sheldrick, 1994); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. Structure of (I) showing 50% probability displacement ellipsoids and atomic numbering scheme.
	Fig. 2. Packing diagram of (I) showing hydrogen-bonding interactions (view of ac plane).

selenitotetrammine cobaltate(III) nitrate, monohydrate

Crystal data

[Co(Se)3)(NH3)4]NO3·H2O	Dx = 2.243 Mg m^−3
Mr = 334.05	Melting point: 185° C (dec) K
Orthorhombic, Pnma	Mo Kα radiation, λ = 0.71073 Å
a = 11.327 (1) Å	Cell parameters from 6242 reflections
b = 7.054 (1) Å	θ = 2.4–28.3°
c = 12.381 (1) Å	µ = 5.44 mm^−1
V = 989.3 (2) Å^3	T = 293 K
Z = 4	Rod, dark purple
F(000) = 664	0.30 × 0.08 × 0.05 mm

Data collection

SMART 1K CCD diffractometer	1327 independent reflections
Radiation source: sealed tube	1180 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.041
Detector resolution: 0.75 pixels mm^-1	θmax = 28.3°, θmin = 2.4°
ω scans	h = −15→15
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	k = −9→9
Tmin = 0.561, Tmax = 0.762	l = −16→16
10448 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.030	Hydrogen site location: difference Fourier map
wR(F^2) = 0.065	H-atom parameters not refined
S = 1.12	w = 1/[σ^2(Fo^2) + (0.0264P)^2 + 1.4436P] where P = (Fo^2 + 2Fc^2)/3
1327 reflections	(Δ/σ)max = −0.001
76 parameters	Δρmax = 1.15 e Å^−3
0 restraints	Δρmin = −0.53 e Å^−3

Special details

Experimental. The decay correction is carried out by repeating the first 100 frames of the data collection and comparing the metrical details for those reflections. The decay correction was applied simultaneously with the absorption correction in SADABS (Sheldrick, 1996). No formal measure of the extent of decay is printed out by this program.

The final unit cell is obtained from the refinement of the XYZ weighted centroids of reflections above 20 σ(I).

Note that the absorption correction parameters Tmin and Tmax also reflect beam corrections, etc. As a result, the numberical values for Tmin and Tmax may differ from expected values based solely on absorption effects and crystal size.

Unit cell and intensity data were collected at 293 K with a detector distance of 4.959 cm. Unit-cell dimensions were calculated from reflections collected using 20-sec frames measured at 0.3° intervals of ω. For data collection, a sphere of data was measured using 20-sec frames (0.3° intervals of ω) out to a maximum θ of 28.29°. Crystal decay was monitored by repeating the initial 100 frames at the conclusion of the data collection. Analysis of the duplicated reflections indicated no decay. The data was corrected for Lorentz and polarization effects as well as absorption. The structure was solved by a combination of direct methods and the difference Fourier technique and refined by full-matrix least squares on F².

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.

Refinement. Refinement on F² for ALL reflections except for 0 with very negative F² or flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

A final difference Fourier map showed a showed a relatively large electron density peak of 1.15 e Å^-3 with distances of 0.9 and 1.7 Å from H3B and N3, respectively. However this peak is not located in a position in terms of reasonable bonding geometry.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Se	0.95043 (3)	0.2500	0.68317 (3)	0.02225 (11)
Co	0.80254 (4)	0.2500	0.50858 (4)	0.01820 (13)
O1	0.8818 (2)	0.0756 (3)	0.60588 (15)	0.0243 (4)
O2	1.0885 (2)	0.2500	0.6418 (3)	0.0322 (7)
N1	0.6632 (3)	0.2500	0.6013 (3)	0.0288 (7)
H1A	0.6503	0.1636	0.6427	0.043*
H1B	0.5828	0.2500	0.5772	0.043*
N2	0.7355 (2)	0.0458 (4)	0.4209 (2)	0.0289 (5)
H2A	0.7039	0.0833	0.3593	0.043*
H2B	0.6808	−0.0408	0.4550	0.043*
H2C	0.7970	−0.0269	0.4013	0.043*
N3	0.9410 (3)	0.2500	0.4155 (3)	0.0241 (7)
H3A	0.9814	0.1390	0.4188	0.036*
H3B	0.9108	0.2500	0.3481	0.036*
N4	0.5415 (3)	−0.2500	0.6261 (3)	0.0257 (7)
O3	0.5285 (2)	−0.0979 (4)	0.6741 (2)	0.0494 (7)
O4	0.5711 (3)	−0.2500	0.5279 (3)	0.0512 (10)
O5	0.7155 (3)	0.2500	0.2036 (3)	0.0362 (7)
H5	0.7022	0.1494	0.1645	0.054*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Se	0.0247 (2)	0.0207 (2)	0.0214 (2)	0.000	−0.00105 (15)	0.000
Co	0.0192 (2)	0.0149 (2)	0.0205 (2)	0.000	0.0010 (2)	0.000
O1	0.0306 (10)	0.0147 (9)	0.0277 (9)	−0.0013 (7)	−0.0046 (8)	0.0011 (7)
O2	0.0207 (13)	0.031 (2)	0.045 (2)	0.000	0.0009 (13)	0.000
N1	0.023 (2)	0.030 (2)	0.033 (2)	0.000	0.0107 (14)	0.000
N2	0.0298 (12)	0.0238 (13)	0.0331 (13)	−0.0010 (10)	−0.0060 (10)	−0.0041 (10)
N3	0.027 (2)	0.019 (2)	0.026 (2)	0.000	0.0056 (13)	0.000
N4	0.020 (2)	0.025 (2)	0.032 (2)	0.000	−0.0037 (14)	0.000
O3	0.059 (2)	0.0263 (12)	0.063 (2)	0.0056 (11)	0.0176 (13)	−0.0063 (11)
O4	0.055 (2)	0.067 (3)	0.032 (2)	0.000	0.000 (2)	0.000
O5	0.035 (2)	0.033 (2)	0.040 (2)	0.000	−0.0061 (14)	0.000

Geometric parameters (Å, º)

Se—O2	1.646 (3)	Co—N1	1.952 (3)
Se—O1	1.742 (2)	Co—N2	1.957 (2)
Se—O1^i	1.742 (2)	Co—N2^i	1.957 (2)
Se—Co	2.735 (1)	N4—O3	1.236 (3)
Co—O1^i	1.942 (2)	N4—O3^ii	1.236 (3)
Co—O1	1.942 (2)	N4—O4	1.260 (5)
Co—N3	1.946 (3)
O2—Se—O1	104.6 (1)	O1^i—Co—N2^i	93.28 (9)
O2—Se—O1^i	104.6 (1)	O1—Co—N2^i	171.81 (9)
O1—Se—O1^i	89.9 (1)	N3—Co—N2^i	89.1 (1)
O2—Se—Co	109.6 (1)	N1—Co—N2^i	90.7 (1)
O1—Se—Co	44.96 (6)	N2—Co—N2^i	94.8 (2)
O1^i—Se—Co	44.96 (6)	O1^i—Co—Se	39.32 (5)
O1^i—Co—O1	78.6 (1)	O1—Co—Se	39.32 (5)
O1^i—Co—N3	89.7 (1)	N3—Co—Se	88.5 (1)
O1—Co—N3	89.7 (1)	N1—Co—Se	91.7 (1)
O1^i—Co—N1	90.5 (1)	N2—Co—Se	132.54 (7)
O1—Co—N1	90.5 (1)	N2^i—Co—Se	132.54 (7)
N3—Co—N1	179.7 (2)	Se—O1—Co	95.72 (9)
O1^i—Co—N2	171.81 (9)	O3—N4—O3^ii	120.5 (4)
O1—Co—N2	93.28 (9)	O3—N4—O4	119.7 (2)
N3—Co—N2	89.1 (1)	O3^ii—N4—O4	119.7 (2)
N1—Co—N2	90.7 (1)
O2—Se—Co—O1^i	−91.30 (9)	O1^i—Se—Co—N2	178.74 (14)
O1—Se—Co—O1^i	177.4 (2)	O2—Se—Co—N2^i	−87.44 (10)
O2—Se—Co—O1	91.30 (9)	O1—Se—Co—N2^i	−178.74 (14)
O1^i—Se—Co—O1	−177.4 (2)	O1^i—Se—Co—N2^i	3.86 (13)
O1—Se—Co—N3	−91.30 (9)	O2—Se—O1—Co	−103.28 (10)
O1^i—Se—Co—N3	91.30 (9)	O1^i—Se—O1—Co	1.84 (12)
O2—Se—Co—N1	180.0	O1^i—Co—O1—Se	−1.68 (11)
O1—Se—Co—N1	88.70 (9)	N3—Co—O1—Se	88.06 (9)
O1^i—Se—Co—N1	−88.70 (9)	N1—Co—O1—Se	−92.11 (10)
O2—Se—Co—N2	87.44 (10)	N2—Co—O1—Se	177.15 (10)
O1—Se—Co—N2	−3.86 (13)	N2^i—Co—O1—Se	6.5 (7)

Symmetry codes: (i) x, −y+1/2, z; (ii) x, −y−1/2, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O3	0.81	2.34	3.027 (3)	143.7
N1—H1B···O4^iii	0.96	2.18	3.098 (5)	161
N2—H2A···O5	0.88	2.26	3.060 (4)	150.2
N2—H2B···O4	0.97	2.13	3.095 (4)	175.2
N2—H2C···O2^iv	0.90	2.11	2.989 (3)	166.3
N3—H3A···O1^iv	0.91	2.19	3.062 (3)	161.4
N3—H3B···O3^v	0.90	2.50	3.195 (4)	134
O5—H5···O1^v	0.87	1.99	2.821 (3)	159.2

Symmetry codes: (iii) −x+1, −y, −z+1; (iv) −x+2, −y, −z+1; (v) −x+3/2, −y, z−1/2.