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In the title complex, [Co(CH3CN)2(H2O)4]Br2, the CoII atom lies on an inversion centre and is octahedrally coordinated by two trans acetonitrile molecules and four water molecules. Hydrogen bonding between the water molecules and lattice bromide ions yields a three-dimensional structure.
Supporting information
CCDC reference: 140921
Crystals of [Co(CH3CN)2(H2O)4]Br2 were obtained after unintentional co-extraction of excess CoBr2, with CH2Cl2, from the reaction of excess CoBr2 with hexakis(2-pyridoxy)cyclotriphosphazene (prior to extraction with CH2Cl2, CH3CN solvent was evaporated from the reaction mixture).
The hydrogen atoms bound to O1 and O2 were located from a difference Fourier synthesis and refined unrestrained; methyl hydrogen atoms are in calculated positions. The residual electron-density maximum is 0.97 Å from Br1.
Data collection: SMART (Siemens, 1996); cell refinement: SMART; data reduction: SAINT (Siemens, 1994) and SADABS (Sheldrick, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997a); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997b); molecular graphics: WinGX (Farrugia, 1998), ORTEP-3 (Farrugia, 1997) and
PLATON (Spek, 1990).
Crystal data top
[Co(CH3CN)2(H2O)4]Br2 | Z = 2 |
Mr = 372.92 | F(000) = 362 |
Monoclinic, P21/c | Dx = 1.917 Mg m−3 |
a = 6.843 (4) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 12.553 (7) Å | µ = 7.50 mm−1 |
c = 8.076 (5) Å | T = 158 K |
β = 111.370 (8)° | Block, pale brown |
V = 646.0 (6) Å3 | 0.44 × 0.22 × 0.16 mm |
Data collection top
CCD area detector diffractometer | 925 reflections with I > 2σ(I) |
ϕ and ω scans | Rint = 0.056 |
Absorption correction: multi-scan [SAINT (Siemens, 1994) and SADABS (Sheldrick, 1996)] | θmax = 26.4°, θmin = 3.2° |
Tmin = 0.151, Tmax = 0.301 | h = −8→7 |
4724 measured reflections | k = −6→15 |
1313 independent reflections | l = −9→10 |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.038 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.087 | H atoms treated by a mixture of independent and constrained refinement |
S = 0.90 | w = 1/[σ2(Fo2) + (0.0515P)2] where P = (Fo2 + 2Fc2)/3 |
1313 reflections | (Δ/σ)max = 0.004 |
78 parameters | Δρmax = 1.05 e Å−3 |
0 restraints | Δρmin = −0.52 e Å−3 |
Crystal data top
[Co(CH3CN)2(H2O)4]Br2 | V = 646.0 (6) Å3 |
Mr = 372.92 | Z = 2 |
Monoclinic, P21/c | Mo Kα radiation |
a = 6.843 (4) Å | µ = 7.50 mm−1 |
b = 12.553 (7) Å | T = 158 K |
c = 8.076 (5) Å | 0.44 × 0.22 × 0.16 mm |
β = 111.370 (8)° | |
Data collection top
CCD area detector diffractometer | 1313 independent reflections |
Absorption correction: multi-scan [SAINT (Siemens, 1994) and SADABS (Sheldrick, 1996)] | 925 reflections with I > 2σ(I) |
Tmin = 0.151, Tmax = 0.301 | Rint = 0.056 |
4724 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.038 | 0 restraints |
wR(F2) = 0.087 | H atoms treated by a mixture of independent and constrained refinement |
S = 0.90 | Δρmax = 1.05 e Å−3 |
1313 reflections | Δρmin = −0.52 e Å−3 |
78 parameters | |
Special details top
Refinement. Notes for referees. H atoms bound to O(1) and O(2) were located from a difference Fourier synthesis; methyl H atoms are in calculated positions. The O(1)—H(12) bond distance has refined to be "short" (Level C warning); however we consider there is no justification for constraining it (or the other O—H bond lengths) given satisfactory stereochemistry and a value which is reasonable given the bond e.s.d.. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
Br1 | 0.80513 (9) | 0.36647 (4) | 0.09870 (7) | 0.02719 (19) | |
Co1 | 0.5000 | 0.0000 | 0.0000 | 0.0209 (3) | |
O1 | 0.6058 (9) | 0.1359 (4) | −0.0864 (7) | 0.0483 (14) | |
N1 | 0.3483 (7) | 0.0933 (3) | 0.1350 (6) | 0.0271 (10) | |
O2 | 0.7574 (7) | 0.0029 (5) | 0.2329 (6) | 0.0466 (13) | |
C1 | 0.2895 (9) | 0.1283 (4) | 0.2364 (7) | 0.0244 (11) | |
C2 | 0.2160 (9) | 0.1744 (5) | 0.3683 (7) | 0.0313 (13) | |
H2A | 0.2317 | 0.2520 | 0.3689 | 0.038* | |
H2B | 0.2989 | 0.1460 | 0.4860 | 0.038* | |
H2C | 0.0678 | 0.1563 | 0.3388 | 0.038* | |
H11 | 0.684 (10) | 0.193 (5) | −0.008 (9) | 0.05 (2)* | |
H12 | 0.644 (11) | 0.132 (5) | −0.148 (9) | 0.04 (2)* | |
H21 | 0.790 (11) | 0.038 (5) | 0.334 (9) | 0.048 (19)* | |
H22 | 0.803 (16) | −0.052 (8) | 0.260 (13) | 0.11 (4)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Br1 | 0.0284 (3) | 0.0315 (3) | 0.0243 (3) | −0.0049 (3) | 0.0127 (2) | −0.0008 (2) |
Co1 | 0.0218 (6) | 0.0248 (5) | 0.0189 (5) | 0.0007 (4) | 0.0109 (4) | −0.0009 (4) |
O1 | 0.077 (4) | 0.035 (3) | 0.058 (3) | −0.017 (2) | 0.056 (3) | −0.015 (2) |
N1 | 0.029 (3) | 0.028 (2) | 0.027 (3) | 0.0044 (19) | 0.014 (2) | 0.0027 (19) |
O2 | 0.040 (3) | 0.064 (3) | 0.029 (3) | 0.020 (3) | 0.004 (2) | −0.016 (2) |
C1 | 0.026 (3) | 0.028 (3) | 0.021 (3) | 0.000 (2) | 0.011 (2) | 0.001 (2) |
C2 | 0.032 (3) | 0.036 (3) | 0.032 (3) | 0.006 (3) | 0.020 (3) | −0.003 (2) |
Geometric parameters (Å, º) top
Co1—O2i | 2.056 (5) | N1—C1 | 1.125 (6) |
Co1—O2 | 2.056 (5) | O2—H21 | 0.88 (7) |
Co1—O1 | 2.071 (5) | O2—H22 | 0.76 (10) |
Co1—O1i | 2.071 (5) | C1—C2 | 1.454 (7) |
Co1—N1i | 2.112 (4) | C2—H2A | 0.9800 |
Co1—N1 | 2.112 (4) | C2—H2B | 0.9800 |
O1—H11 | 0.98 (7) | C2—H2C | 0.9800 |
O1—H12 | 0.64 (6) | | |
| | | |
O2i—Co1—O2 | 180.0 (2) | Co1—O1—H11 | 124 (4) |
O2i—Co1—O1 | 89.7 (2) | Co1—O1—H12 | 119 (6) |
O2—Co1—O1 | 90.3 (2) | H11—O1—H12 | 106 (7) |
O2i—Co1—O1i | 90.3 (2) | C1—N1—Co1 | 164.9 (4) |
O2—Co1—O1i | 89.7 (2) | Co1—O2—H21 | 134 (4) |
O1—Co1—O1i | 180.0 (3) | Co1—O2—H22 | 112 (8) |
O2i—Co1—N1i | 86.34 (18) | H21—O2—H22 | 104 (8) |
O2—Co1—N1i | 93.66 (18) | N1—C1—C2 | 179.2 (6) |
O1—Co1—N1i | 89.13 (19) | C1—C2—H2A | 109.5 |
O1i—Co1—N1i | 90.87 (19) | C1—C2—H2B | 109.5 |
O2i—Co1—N1 | 93.66 (18) | H2A—C2—H2B | 109.5 |
O2—Co1—N1 | 86.34 (18) | C1—C2—H2C | 109.5 |
O1—Co1—N1 | 90.87 (19) | H2A—C2—H2C | 109.5 |
O1i—Co1—N1 | 89.13 (19) | H2B—C2—H2C | 109.5 |
N1i—Co1—N1 | 180.0 (3) | | |
| | | |
O2i—Co1—N1—C1 | 139.2 (18) | O1i—Co1—N1—C1 | 49.0 (18) |
O2—Co1—N1—C1 | −40.8 (18) | N1i—Co1—N1—C1 | 0 (18) |
O1—Co1—N1—C1 | −131.0 (18) | Co1—N1—C1—C2 | 91.4 (18) |
Symmetry code: (i) −x+1, −y, −z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H11···Br1 | 0.98 (7) | 2.38 (6) | 3.315 (6) | 161 (5) |
O1—H12···Br1ii | 0.64 (7) | 2.65 (7) | 3.295 (6) | 175 (7) |
O2—H21···Br1iii | 0.88 (7) | 2.42 (7) | 3.289 (5) | 169 (7) |
O2—H22···Br1iv | 0.76 (10) | 2.70 (11) | 3.283 (6) | 135 (10) |
Symmetry codes: (ii) x, −y+1/2, z−1/2; (iii) x, −y+1/2, z+1/2; (iv) −x+2, y−1/2, −z+1/2. |
Experimental details
Crystal data |
Chemical formula | [Co(CH3CN)2(H2O)4]Br2 |
Mr | 372.92 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 158 |
a, b, c (Å) | 6.843 (4), 12.553 (7), 8.076 (5) |
β (°) | 111.370 (8) |
V (Å3) | 646.0 (6) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 7.50 |
Crystal size (mm) | 0.44 × 0.22 × 0.16 |
|
Data collection |
Diffractometer | CCD area detector diffractometer |
Absorption correction | Multi-scan [SAINT (Siemens, 1994) and SADABS (Sheldrick, 1996)] |
Tmin, Tmax | 0.151, 0.301 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 4724, 1313, 925 |
Rint | 0.056 |
(sin θ/λ)max (Å−1) | 0.626 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.038, 0.087, 0.90 |
No. of reflections | 1313 |
No. of parameters | 78 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 1.05, −0.52 |
Selected geometric parameters (Å, º) topCo1—O2 | 2.056 (5) | N1—C1 | 1.125 (6) |
Co1—O1 | 2.071 (5) | C1—C2 | 1.454 (7) |
Co1—N1 | 2.112 (4) | | |
| | | |
O2—Co1—O1 | 90.3 (2) | O1i—Co1—N1 | 89.13 (19) |
O2—Co1—N1 | 86.34 (18) | C1—N1—Co1 | 164.9 (4) |
O1—Co1—N1 | 90.87 (19) | N1—C1—C2 | 179.2 (6) |
Symmetry code: (i) −x+1, −y, −z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H11···Br1 | 0.98 (7) | 2.38 (6) | 3.315 (6) | 161 (5) |
O1—H12···Br1ii | 0.64 (7) | 2.65 (7) | 3.295 (6) | 175 (7) |
O2—H21···Br1iii | 0.88 (7) | 2.42 (7) | 3.289 (5) | 169 (7) |
O2—H22···Br1iv | 0.76 (10) | 2.70 (11) | 3.283 (6) | 135 (10) |
Symmetry codes: (ii) x, −y+1/2, z−1/2; (iii) x, −y+1/2, z+1/2; (iv) −x+2, y−1/2, −z+1/2. |
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Despite there being numerous acetonitrile- and aqua-metal complexes reported in the literature, trans-bis(acetonitrile-N)tetraaquacobalt(II) bromide, (I), is the first reported structure of a metal complex where the ligands are exclusively coordinated water and acetonitrile molecules. The cobalt(II) atom lies on a centre of symmetry and is coordinated to two trans acetonitrile molecules and to four water molecules (Fig. 1). The metal coordination is close to octahedral (Table 1), with the maximum deviation (X—Co—Y) from 90° being 3.7 (2)°. The mean Co—O length, 2.063 Å, is consistent with reported Co—OH2 distances of tetraaqua complexes (2.060–2.124 Å) (Abrahams et al., 1996; de Meester & Skapski, 1973; Salas et al., 1992). Variations in the two Co—O bond lengths [0.15 (7) Å], although here barely significant, have been previously observed in tetraaquacobalt(II) complexes; for example, trans-tetraaquabis(adenine)cobalt(II) has Co—O bond lengths of 2.073 (4) and 2.114 (5) Å, which the authors attributed to different constraints imposed by hydrogen-bonding linkages (de Meester & Skapski, 1973).
All the coordinated water hydrogen atoms form hydrogen-bonds to adjacent bromide ions, creating a three-dimensional network (Fig. 2 and Table 2). Each bromide ion forms four hydrogen bonds in a distorted tetrahedral arrangement to different [Co(CH3CN)2(H2O)4]2+ cations with H···Br distances consistent with the reported distances of 2.30–2.68 Å (Mikenda, 1986; Tegenfeldt et al., 1979; Sieron & Bukowska-Strzyzewska, 1997). Three of the O—H.·Br angles are close to the most probable angle of 160° for a two-centre hydrogen bond (Jeffrey et al., 1985) while the fourth makes a smaller angle at the hydrogen, 135 (10)°, but with the Br···O contact the smallest at 3.283 (6) Å. The Br.·O distances range from 3.283 (6) to 3.315 Å compared with previously observed values between 3.195 (6) and 3.421 (3) Å (Kepert et al., 1996; Sieron & Bukowska-Strzyzewska, 1997; Cunningham et al., 1991).
As expected, the acetonitrile molecule is linear [N1—C1—C2 = 179.0 (6)°], but with bent coordination to the the cobalt(II) [Co—N1—C1 165.0 (4)°]. Such coordination has been observed in polymeric Co(O2PF2)2(CH3CN)2, 164.4° (Begley et al., 1985). Metal-acetonitrile bent coordination is indeed quite common with angles from 145.2 to 176.9°, and an average of 167°, having been reported (Agterberg et al., 1998; Begley et al., 1985; Chisholm et al., 1996; Holligan et al., 1992; Libby et al., 1993). This average is somewhat lowered by the two extreme low values for nickel(II) (Holligan et al., 1992) (145.2°) and manganese(III) (Libby et al., 1993) (149.1°) complexes, which have been attributed to hydrogen bonding and steric effects, respectively.