The structure of hexaamminecobalt(II) bis[tetracarbonylcobaltate(-I)] contains discrete octahedral [Co(NH3)6]2+ cations and [Co(CO)4]− anions held together by N—H⋯O hydrogen bonds.
Keywords: crystal structure, cobalt carbonyl, ammonia, hydrogen bonding
Abstract
Hexaamminecobalt(II) bis[tetracarbonylcobaltate(-I)], [Co(NH3)6][Co(CO)4]2, was synthesized by reaction of liquid ammonia with Co2(CO)8. The CoII atom is coordinated by six ammine ligands. The resulting polyhedron, the hexaamminecobalt(II) cation, exhibits point group symmetry -3. The Co-I atom is coordinated by four carbonyl ligands, leading to a tetracarbonylcobaltate(−I) anion in the shape of a slightly distorted tetrahedron, with point group symmetry 3. The crystal structure is related to that of high-pressure BaC2 (space group R-3m), with the [Co(NH3)6]2+ cations replacing the Ba sites and the [Co(CO)4]− anions replacing the C sites. N—H⋯O hydrogen bonds between cations and anions stabilize the structural set-up in the title compound.
Chemical context
The reaction of Co2(CO)8 with bases has already been described in the literature (Hieber et al., 1960 ▸). In addition, the reaction of dicobalt octacarbonyl with liquid ammonia has been known for several decades (Behrens & Wakamatsu, 1966 ▸). Thereby Co2(CO)8 forms with NH3 hexaamminecobalt(II) bis[tetracarbonylcobaltate(–I)], [Co(NH3)6][Co(CO)4]2, which is obtained as orange air-sensitive crystals. During this reaction, CO is released and reacts with ammonia to urea. However, structural data of of the title compound were missing and are presented in this communication.
Structural commentary
The cobalt atom Co1 of the hexaamminecobalt(II) cation occupies Wyckoff position 3a with site symmetry 
.. It is coordinated by six symmetry-related ammine ligands in form of a slightly distorted octahedron. The Co—N distance in the [Co(NH3)6] octahedron is 2.1876 (16) Å which compares well with those of other reported hexaamminecobalt(II) structures (Barnet et al., 1966 ▸).
The cobalt atom Co2 of the tetracarbonylcobaltate(–I) anion occupies Wyckoff position 6c and exhibits site symmetry 3.. It is coordinated by four carbonyl ligands in a shape close to an ideal tetrahedron. The distances between the Co2 atom and the carbon atoms C1 and C2 of the ligands are 1.7664 (18) and 1.779 (3) Å, respectively. In the literature, distances in the range from 1.77 (2) to 1.82 (2) Å are reported for Co—C in the compound Co2(CO)8 (Sumner et al., 1964 ▸). In the carbonyl ligands, the observed distances are in the expected range with 1.153 (2) and 1.140 (4) Å for C1—O1 and C2—O2, respectively. For the compound Co2(CO)8 distances from 1.14 (2) to 1.33 (2) Å were reported (Sumner et al., 1964 ▸).
The crystal structure of [Co(NH3)6][Co(CO)4]2 can be derived from the high-pressure rhombohedral phase of BaC2 (BaC2 -HP1, R
m) (Efthimiopoulos et al., 2012 ▸). Formally, the Ba sites on Wyckoff position 3a are replaced by the hexaammine cobalt(II) octahedra and the C site on position 6c is replaced by the tetracarbonylcobaltate(–I) tetrahedron.
The molecular components of the title compound are shown in Fig. 1 ▸. The unit cell of [Co(NH3)6][Co(CO)4]2 projected along [001] is shown in Fig. 2 ▸.
Figure 1.
The molecular structures of the tetracarbonylcobaltate(−I) anion and of the hexaamminecobalt(II) cation of the title compound. Displacement ellipsoids are shown at the 70% probability level. Labelling of symmetry-equivalent atoms has been omitted for clarity.
Figure 2.
The unit cell of [Co(NH3)6][Co(CO)4]2, viewed along [001]. Displacement ellipsoids are shown at the 70% probability level.
Supramolecular features
The arrangement of [Co(NH3)6]2+ octahedra and [Co(CO)4]− tetrahedra in the crystal structure is stabilized by N—H⋯O hydrogen bonds with the N1 atom as donor and the oxygen atoms O1 and O2 as acceptors atoms. One of the hydrogen bonds (N—H1C) is forked while, remarkably, in the neighbourhood of the hydrogen atom H1B no acceptor atom in the range of the sum of the van der Waals radii is present. Detailed information about hydrogen-bonding distances and angles are given in Table 1 ▸.
Table 1. Hydrogen-bond geometry (, ).
| DHA | DH | HA | D A | DHA |
|---|---|---|---|---|
| N1H1AO1i | 0.87(4) | 2.49(4) | 3.159(2) | 135(3) |
| N1H1CO1ii | 0.87(3) | 2.59(3) | 3.290(2) | 138(3) |
| N1H1CO2iii | 0.87(3) | 2.49(3) | 3.249(3) | 146(3) |
Symmetry codes: (i) 
; (ii) 
; (iii) 
.
Synthesis and crystallization
86 mg (29.4 mmol) of Co2(CO)8 were placed in a flame-dried bomb tube under argon. 0.2 ml of liquid ammonia were condensed to the bomb tube. The bomb tube, now containing an orange solution, was flame-sealed and stored at room temperature. The reaction equation is given in Fig. 3 ▸. After six months of crystallization time, moisture- and temperature-sensitive, orange single crystals of the title compound were obtained in almost quantitative yield from the still orange solution. After manual separation of the crystals under a light-optical microscope and evaporation of the solvent only a minute orange residue remained.
Figure 3.
Reaction equation for the preparation of the title compound.
Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2 ▸. All hydrogen atoms of the ammine ligands were located from a difference Fourier map and were refined isotropically without any further restraints.
Table 2. Experimental details.
| Crystal data | |
| Chemical formula | [Co(NH3)6][Co(CO)4]2 |
| M r | 503.07 |
| Crystal system, space group | Trigonal, R
|
| Temperature (K) | 100 |
| a, c () | 9.3679(4), 18.3089(18) |
| V (3) | 1391.48(18) |
| Z | 3 |
| Radiation type | Mo K |
| (mm1) | 2.70 |
| Crystal size (mm) | 0.16 0.12 0.08 |
| Data collection | |
| Diffractometer | Stoe IPDS2T |
| Absorption correction | Integration (X-RED32 and X-SHAPE; Stoe Cie, 2009 ▸) |
| T min, T max | 0.649, 0.907 |
| No. of measured, independent and observed [I > 2(I)] reflections | 7025, 994, 910 |
| R int | 0.087 |
| (sin /)max (1) | 0.724 |
| Refinement | |
| R[F 2 > 2(F 2)], wR(F 2), S | 0.034, 0.090, 1.08 |
| No. of reflections | 994 |
| No. of parameters | 52 |
| H-atom treatment | All H-atom parameters refined |
| max, min (e 3) | 0.87, 0.65 |
Supplementary Material
Crystal structure: contains datablock(s) I. DOI: 10.1107/S2056989015020290/wm5229sup1.cif
Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989015020290/wm5229Isup2.hkl
CCDC reference: 1433399
Additional supporting information: crystallographic information; 3D view; checkCIF report
Acknowledgments
FK thanks the Deutsche Forschungsgemeinschaft for his Heisenberg professorship.
supplementary crystallographic information
Crystal data
| [Co(NH3)6][Co(CO)4]2 | Dx = 1.801 Mg m−3 |
| Mr = 503.07 | Mo Kα radiation, λ = 0.71073 Å |
| Trigonal, R3 | Cell parameters from 15618 reflections |
| a = 9.3679 (4) Å | θ = 3.3–33.4° |
| c = 18.3089 (18) Å | µ = 2.70 mm−1 |
| V = 1391.48 (18) Å3 | T = 100 K |
| Z = 3 | Block, orange |
| F(000) = 759 | 0.16 × 0.12 × 0.08 mm |
Data collection
| Stoe IPDS-2T diffractometer | 994 independent reflections |
| Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focus | 910 reflections with I > 2σ(I) |
| Plane graphite monochromator | Rint = 0.087 |
| Detector resolution: 6.67 pixels mm-1 | θmax = 31.0°, θmin = 3.3° |
| rotation method scans | h = −13→13 |
| Absorption correction: integration (X-RED32 and X-SHAPE; Stoe & Cie, 2009) | k = −13→13 |
| Tmin = 0.649, Tmax = 0.907 | l = −26→26 |
| 7025 measured reflections |
Refinement
| Refinement on F2 | Hydrogen site location: difference Fourier map |
| Least-squares matrix: full | All H-atom parameters refined |
| R[F2 > 2σ(F2)] = 0.034 | w = 1/[σ2(Fo2) + (0.0529P)2 + 1.0515P] where P = (Fo2 + 2Fc2)/3 |
| wR(F2) = 0.090 | (Δ/σ)max < 0.001 |
| S = 1.08 | Δρmax = 0.87 e Å−3 |
| 994 reflections | Δρmin = −0.64 e Å−3 |
| 52 parameters | Extinction correction: SHELXL2014 (Sheldrick, 2015), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
| 0 restraints | Extinction coefficient: 0.0040 (8) |
Special details
| 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)
| x | y | z | Uiso*/Ueq | ||
| Co1 | 0.0000 | 0.0000 | 0.0000 | 0.01863 (18) | |
| Co2 | −0.6667 | −0.3333 | 0.04221 (2) | 0.01972 (17) | |
| O1 | −0.61903 (19) | −0.02591 (18) | 0.10467 (9) | 0.0315 (3) | |
| O2 | −0.6667 | −0.3333 | −0.11725 (14) | 0.0298 (5) | |
| N1 | −0.0266 (2) | −0.2037 (2) | 0.06820 (9) | 0.0245 (3) | |
| C1 | −0.6354 (2) | −0.1451 (2) | 0.07846 (10) | 0.0231 (3) | |
| C2 | −0.6667 | −0.3333 | −0.05497 (19) | 0.0237 (5) | |
| H1A | −0.121 (5) | −0.295 (5) | 0.0656 (19) | 0.054 (10)* | |
| H1B | 0.034 (4) | −0.247 (4) | 0.0558 (17) | 0.038 (7)* | |
| H1C | −0.001 (4) | −0.176 (4) | 0.1135 (19) | 0.043 (8)* |
Atomic displacement parameters (Å2)
| U11 | U22 | U33 | U12 | U13 | U23 | |
| Co1 | 0.0160 (2) | 0.0160 (2) | 0.0240 (3) | 0.00799 (10) | 0.000 | 0.000 |
| Co2 | 0.01726 (19) | 0.01726 (19) | 0.0247 (3) | 0.00863 (9) | 0.000 | 0.000 |
| O1 | 0.0323 (7) | 0.0236 (7) | 0.0410 (8) | 0.0158 (6) | −0.0025 (6) | −0.0036 (5) |
| O2 | 0.0316 (8) | 0.0316 (8) | 0.0262 (12) | 0.0158 (4) | 0.000 | 0.000 |
| N1 | 0.0209 (7) | 0.0212 (7) | 0.0307 (7) | 0.0101 (6) | −0.0002 (5) | 0.0015 (5) |
| C1 | 0.0192 (7) | 0.0203 (7) | 0.0292 (8) | 0.0095 (6) | −0.0007 (6) | 0.0009 (6) |
| C2 | 0.0198 (8) | 0.0198 (8) | 0.0317 (15) | 0.0099 (4) | 0.000 | 0.000 |
Geometric parameters (Å, º)
| Co1—N1i | 2.1876 (16) | Co2—C1 | 1.7664 (18) |
| Co1—N1ii | 2.1876 (16) | Co2—C1vi | 1.7664 (18) |
| Co1—N1iii | 2.1876 (16) | Co2—C1vii | 1.7664 (18) |
| Co1—N1iv | 2.1876 (16) | Co2—C2 | 1.779 (3) |
| Co1—N1 | 2.1877 (16) | O1—C1 | 1.153 (2) |
| Co1—N1v | 2.1877 (16) | O2—C2 | 1.140 (4) |
| N1i—Co1—N1ii | 180.00 (9) | N1iii—Co1—N1v | 90.65 (6) |
| N1i—Co1—N1iii | 90.65 (6) | N1iv—Co1—N1v | 89.35 (6) |
| N1ii—Co1—N1iii | 89.35 (6) | N1—Co1—N1v | 180.0 |
| N1i—Co1—N1iv | 89.35 (6) | C1—Co2—C1vi | 106.76 (7) |
| N1ii—Co1—N1iv | 90.65 (6) | C1—Co2—C1vii | 106.75 (7) |
| N1iii—Co1—N1iv | 180.00 (11) | C1vi—Co2—C1vii | 106.75 (7) |
| N1i—Co1—N1 | 89.35 (6) | C1—Co2—C2 | 112.07 (6) |
| N1ii—Co1—N1 | 90.65 (6) | C1vi—Co2—C2 | 112.07 (6) |
| N1iii—Co1—N1 | 89.35 (6) | C1vii—Co2—C2 | 112.07 (6) |
| N1iv—Co1—N1 | 90.65 (6) | O1—C1—Co2 | 177.07 (17) |
| N1i—Co1—N1v | 90.65 (6) | O2—C2—Co2 | 180.0 |
| N1ii—Co1—N1v | 89.35 (6) |
Symmetry codes: (i) x−y, x, −z; (ii) −x+y, −x, z; (iii) y, −x+y, −z; (iv) −y, x−y, z; (v) −x, −y, −z; (vi) −y−1, x−y, z; (vii) −x+y−1, −x−1, z.
Hydrogen-bond geometry (Å, º)
| D—H···A | D—H | H···A | D···A | D—H···A |
| N1—H1A···O1vii | 0.87 (4) | 2.49 (4) | 3.159 (2) | 135 (3) |
| N1—H1C···O1viii | 0.87 (3) | 2.59 (3) | 3.290 (2) | 138 (3) |
| N1—H1C···O2ix | 0.87 (3) | 2.49 (3) | 3.249 (3) | 146 (3) |
Symmetry codes: (vii) −x+y−1, −x−1, z; (viii) x−y+2/3, x+1/3, −z+1/3; (ix) x+2/3, y+1/3, z+1/3.
References
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Crystal structure: contains datablock(s) I. DOI: 10.1107/S2056989015020290/wm5229sup1.cif
Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989015020290/wm5229Isup2.hkl
CCDC reference: 1433399
Additional supporting information: crystallographic information; 3D view; checkCIF report