The ionic title complex, bis(μ-ethylene glycol)-κ
3O,
O′:
O′;κ
3O:
O,
O′-bis[(ethylene glycol-κ
2O,
O′)(ethylene glycol-κ
O)sodium] bis(ethylene glycolato-κ
2O,
O′)copper(II), [Na
2(C
2H
6O
2)
6][Cu(C
2H
4O
2)
2], was obtained from a basic solution of CuCl
2 in ethylene glycol and consists of discrete ions interconnected by O—H
O hydrogen bonds. This is the first example of a disodium–ethylene glycol complex cation cluster. The cation lies about an inversion center and the Cu
II atom of the anion lies on another independent inversion center.
Supporting information
CCDC reference: 774072
All reagents were used as received without further purification. For the
preparation of the title compound, (I), CuCl2(H2O)2 (1 g, 5.87 mmol) and
4 equivalents of powdered NaOH (0.94 g, 23.46 mmol) were dissolved in ethylene
glycol (25 ml). The solution was heated under reflux under dry dinitrogen and
stirred magnetically (40 min); during this time the solution turned dark blue.
The solution was then allowed to cool to room temperature. Crystals suitable
for X-ray analysis were obtained from the solution by cooling to 248 K for 3 d
in a sealed flask under nitrogen. The ethylene glycol was decanted off and the
crystals were washed with diethyl ether (2 x 50 ml) and hexane (2
x 50 ml). Unoptimized yield: 2.4 g, 68% (based on Cu). M.p. 113–115
(dec.) FT–IR (cm-1, ATR) v(CO) 1245 (w), 1218 (w);
v(MO) 541 (w), 529 (w).
The crystals are deliquescent and readily form droplets within an hour of
sitting in the atmosphere. The crystals are insoluble in common organic
solvents, but dissolve readily with decomposition in alcohols and water.
Attempts to isolate a nickel intermediate from an analogous reaction using
NiCl2(H2O)6 were unsuccessful.
The pendant oxygen from the non-chelating ethylene glycol bound to sodium was
disordered over two positions, O8 and O8B, whose occupancy factors were
refined and then fixed at 0.911 and 0.089, respectively. The C8—O8 and
C8—O8B were restrained to be equivalent. All methylene H-atom
positions were calculated using the appropriate riding model, with
Uiso(H) = 1.2Ueq (parent atom) and with C—H distances of
0.99 Å. The hydroxy H atoms were located in a difference Fourier map and
refined freely.
Data collection: CrystalClear (Rigaku, 2008); cell refinement: CrystalClear (Rigaku, 2008); data reduction: CrystalClear (Rigaku, 2008); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: CIFTAB (Sheldrick, 2008).
bis(µ-ethylene
glycol)-
κ3O,
O':
O';
κ3O:
O,
O'-
bis[(ethylene
glycol-
κ2O,
O')(ethylene glycol-
κO)sodium]
bis(ethylene glycolato-
κO,
O')copper(II)
top
Crystal data top
[Na2(C2H6O2)6][Cu(C2H4O2)2] | F(000) = 319 |
Mr = 602.03 | Dx = 1.425 Mg m−3 |
Triclinic, P1 | Melting point: 386 K |
a = 8.7666 (12) Å | Mo Kα radiation, λ = 0.71069 Å |
b = 9.5089 (13) Å | Cell parameters from 5829 reflections |
c = 9.7804 (13) Å | θ = 6.8–54.8° |
α = 99.152 (4)° | µ = 0.88 mm−1 |
β = 101.983 (4)° | T = 100 K |
γ = 113.910 (4)° | Prism, blue |
V = 701.61 (16) Å3 | 0.09 × 0.09 × 0.08 mm |
Z = 1 | |
Data collection top
Rigaku AFC-12 with Saturn 724+CCD diffractometer | 3177 independent reflections |
Radiation source: fine-focus sealed tube | 2863 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.029 |
Detector resolution: 28.5714 pixels mm-1 | θmax = 27.4°, θmin = 3.4° |
ω–scan | h = −11→10 |
Absorption correction: multi-scan (ABSCOR; Higashi, 1995) | k = −12→12 |
Tmin = 0.573, Tmax = 0.9 | l = −12→12 |
7103 measured reflections | |
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)] = 0.034 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.080 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.07 | w = 1/[σ2(Fo2) + (0.023P)2 + 0.6667P] where P = (Fo2 + 2Fc2)/3 |
3177 reflections | (Δ/σ)max < 0.001 |
190 parameters | Δρmax = 0.36 e Å−3 |
1 restraint | Δρmin = −0.40 e Å−3 |
Crystal data top
[Na2(C2H6O2)6][Cu(C2H4O2)2] | γ = 113.910 (4)° |
Mr = 602.03 | V = 701.61 (16) Å3 |
Triclinic, P1 | Z = 1 |
a = 8.7666 (12) Å | Mo Kα radiation |
b = 9.5089 (13) Å | µ = 0.88 mm−1 |
c = 9.7804 (13) Å | T = 100 K |
α = 99.152 (4)° | 0.09 × 0.09 × 0.08 mm |
β = 101.983 (4)° | |
Data collection top
Rigaku AFC-12 with Saturn 724+CCD diffractometer | 3177 independent reflections |
Absorption correction: multi-scan (ABSCOR; Higashi, 1995) | 2863 reflections with I > 2σ(I) |
Tmin = 0.573, Tmax = 0.9 | Rint = 0.029 |
7103 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.034 | 1 restraint |
wR(F2) = 0.080 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.07 | Δρmax = 0.36 e Å−3 |
3177 reflections | Δρmin = −0.40 e Å−3 |
190 parameters | |
Special details top
Experimental. Instruments: Melting points were determined on an Electrothermal Melting Point
apparatus in sealed capillaries under nitrogen (1 atm.) and are uncorrected.
The IR data was collected on a Nicolet Avater 330 F T—IR with Smart
Performer ATR attachment. |
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. Refinement of F2 against ALL reflections. The weighted R-factor
wR and goodness 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. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
Cu1 | 0.0000 | 0.0000 | 0.5000 | 0.01124 (10) | |
Na1 | 0.23160 (9) | 0.10932 (9) | 0.03314 (8) | 0.01381 (16) | |
O1 | −0.02964 (17) | −0.16279 (15) | 0.60199 (14) | 0.0148 (3) | |
O2 | −0.02654 (18) | −0.15463 (16) | 0.33218 (14) | 0.0156 (3) | |
O3 | 0.03541 (17) | −0.12615 (16) | 0.08085 (15) | 0.0143 (3) | |
H3 | 0.027 (4) | −0.127 (3) | 0.153 (3) | 0.038 (9)* | |
O4 | 0.18312 (18) | −0.12527 (16) | −0.14889 (15) | 0.0141 (3) | |
H4 | 0.135 (4) | −0.130 (3) | −0.223 (3) | 0.029 (7)* | |
O5 | 0.50462 (19) | 0.12573 (18) | 0.16616 (16) | 0.0198 (3) | |
H5 | 0.579 (4) | 0.115 (3) | 0.146 (3) | 0.033 (8)* | |
O6 | 0.29490 (19) | 0.23625 (18) | 0.28251 (15) | 0.0186 (3) | |
H6 | 0.219 (4) | 0.210 (3) | 0.313 (3) | 0.031 (8)* | |
O7 | 0.32505 (19) | 0.26319 (17) | −0.13052 (16) | 0.0184 (3) | |
H7 | 0.239 (4) | 0.233 (3) | −0.199 (3) | 0.039 (8)* | |
O8 | 0.6992 (3) | 0.4700 (2) | −0.0151 (3) | 0.0431 (6) | 0.911 (4) |
H8 | 0.678 (4) | 0.526 (4) | 0.019 (4) | 0.040 (10)* | 0.911 (4) |
O8B | 0.531 (3) | 0.450 (3) | −0.296 (2) | 0.044 (5)* | 0.089 (4) |
C1 | −0.0800 (3) | −0.3121 (2) | 0.5009 (2) | 0.0179 (4) | |
H1A | −0.2091 | −0.3711 | 0.4615 | 0.021* | |
H1B | −0.0381 | −0.3784 | 0.5507 | 0.021* | |
C2 | −0.0010 (3) | −0.2803 (2) | 0.3782 (2) | 0.0179 (4) | |
H2A | 0.1257 | −0.2494 | 0.4120 | 0.022* | |
H2B | −0.0578 | −0.3782 | 0.2961 | 0.022* | |
C3 | 0.1027 (2) | −0.2374 (2) | 0.0444 (2) | 0.0142 (4) | |
H3A | 0.0375 | −0.3378 | 0.0686 | 0.017* | |
H3B | 0.2277 | −0.1916 | 0.1007 | 0.017* | |
C4 | 0.0827 (2) | −0.2712 (2) | −0.1154 (2) | 0.0155 (4) | |
H4A | 0.1241 | −0.3509 | −0.1432 | 0.019* | |
H4B | −0.0423 | −0.3158 | −0.1714 | 0.019* | |
C5 | 0.5744 (3) | 0.2480 (3) | 0.2984 (2) | 0.0337 (6) | |
H5A | 0.6151 | 0.3539 | 0.2784 | 0.040* | |
H5B | 0.6756 | 0.2445 | 0.3623 | 0.040* | |
C6 | 0.4348 (3) | 0.2236 (4) | 0.3726 (2) | 0.0367 (6) | |
H6A | 0.3922 | 0.1168 | 0.3908 | 0.044* | |
H6B | 0.4836 | 0.3054 | 0.4672 | 0.044* | |
C7 | 0.4533 (3) | 0.2471 (3) | −0.1933 (2) | 0.0228 (4) | |
H7A | 0.3994 | 0.1976 | −0.2993 | 0.027* | |
H7B | 0.4938 | 0.1758 | −0.1510 | 0.027* | |
C8 | 0.6074 (3) | 0.4068 (3) | −0.1660 (3) | 0.0315 (5) | |
H8A | 0.6854 | 0.3940 | −0.2217 | 0.038* | 0.911 (4) |
H8B | 0.5654 | 0.4807 | −0.2011 | 0.038* | 0.911 (4) |
H8C | 0.6293 | 0.4825 | −0.0736 | 0.038* | 0.089 (4) |
H8D | 0.7153 | 0.3976 | −0.1688 | 0.038* | 0.089 (4) |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Cu1 | 0.01155 (16) | 0.01460 (17) | 0.00850 (16) | 0.00675 (13) | 0.00358 (12) | 0.00261 (12) |
Na1 | 0.0126 (4) | 0.0164 (4) | 0.0126 (4) | 0.0067 (3) | 0.0038 (3) | 0.0039 (3) |
O1 | 0.0192 (7) | 0.0140 (7) | 0.0112 (6) | 0.0077 (5) | 0.0057 (5) | 0.0018 (5) |
O2 | 0.0214 (7) | 0.0182 (7) | 0.0105 (6) | 0.0121 (6) | 0.0051 (5) | 0.0036 (5) |
O3 | 0.0170 (7) | 0.0194 (7) | 0.0132 (7) | 0.0119 (6) | 0.0083 (6) | 0.0067 (5) |
O4 | 0.0137 (7) | 0.0165 (7) | 0.0121 (7) | 0.0065 (5) | 0.0044 (5) | 0.0047 (5) |
O5 | 0.0137 (7) | 0.0251 (8) | 0.0200 (7) | 0.0104 (6) | 0.0048 (6) | 0.0010 (6) |
O6 | 0.0138 (7) | 0.0277 (8) | 0.0169 (7) | 0.0105 (6) | 0.0077 (6) | 0.0060 (6) |
O7 | 0.0134 (7) | 0.0262 (8) | 0.0178 (7) | 0.0095 (6) | 0.0066 (6) | 0.0080 (6) |
O8 | 0.0207 (9) | 0.0245 (11) | 0.0667 (15) | 0.0121 (8) | −0.0102 (9) | −0.0075 (10) |
C1 | 0.0239 (10) | 0.0149 (9) | 0.0145 (9) | 0.0088 (8) | 0.0067 (8) | 0.0020 (7) |
C2 | 0.0248 (10) | 0.0208 (10) | 0.0147 (9) | 0.0157 (8) | 0.0076 (8) | 0.0046 (8) |
C3 | 0.0156 (9) | 0.0154 (9) | 0.0169 (9) | 0.0105 (7) | 0.0066 (7) | 0.0066 (7) |
C4 | 0.0154 (9) | 0.0136 (9) | 0.0175 (9) | 0.0065 (7) | 0.0061 (7) | 0.0031 (7) |
C5 | 0.0162 (10) | 0.0536 (16) | 0.0211 (11) | 0.0161 (11) | −0.0011 (9) | −0.0082 (10) |
C6 | 0.0293 (12) | 0.076 (2) | 0.0140 (10) | 0.0352 (13) | 0.0051 (9) | 0.0074 (11) |
C7 | 0.0178 (10) | 0.0266 (11) | 0.0283 (11) | 0.0117 (9) | 0.0111 (9) | 0.0091 (9) |
C8 | 0.0196 (11) | 0.0294 (13) | 0.0537 (16) | 0.0122 (9) | 0.0166 (11) | 0.0219 (11) |
Geometric parameters (Å, º) top
Cu1—O2 | 1.9252 (13) | O8—H8 | 0.69 (3) |
Cu1—O2i | 1.9252 (13) | O8B—C8 | 1.507 (15) |
Cu1—O1 | 1.9317 (13) | C1—C2 | 1.518 (3) |
Cu1—O1i | 1.9317 (13) | C1—H1A | 0.9900 |
Na1—O6 | 2.3816 (16) | C1—H1B | 0.9900 |
Na1—O7 | 2.3858 (16) | C2—H2A | 0.9900 |
Na1—O3 | 2.3945 (16) | C2—H2B | 0.9900 |
Na1—O5 | 2.4052 (16) | C3—C4 | 1.503 (3) |
Na1—O4 | 2.4453 (15) | C3—H3A | 0.9900 |
Na1—O3ii | 2.4545 (15) | C3—H3B | 0.9900 |
O1—C1 | 1.433 (2) | C4—H4A | 0.9900 |
O2—C2 | 1.424 (2) | C4—H4B | 0.9900 |
O3—C3 | 1.438 (2) | C5—C6 | 1.507 (3) |
O3—Na1ii | 2.4545 (15) | C5—H5A | 0.9900 |
O3—H3 | 0.72 (3) | C5—H5B | 0.9900 |
O4—C4 | 1.442 (2) | C6—H6A | 0.9900 |
O4—H4 | 0.74 (3) | C6—H6B | 0.9900 |
O5—C5 | 1.419 (3) | C7—C8 | 1.504 (3) |
O5—H5 | 0.75 (3) | C7—H7A | 0.9900 |
O6—C6 | 1.414 (3) | C7—H7B | 0.9900 |
O6—H6 | 0.75 (3) | C8—H8A | 0.9900 |
O7—C7 | 1.436 (2) | C8—H8B | 0.9900 |
O7—H7 | 0.81 (3) | C8—H8C | 0.9900 |
O8—C8 | 1.421 (3) | C8—H8D | 0.9900 |
| | | |
O2—Cu1—O2i | 180.0 | O2—C2—H2A | 109.9 |
O2—Cu1—O1 | 87.11 (5) | C1—C2—H2A | 109.9 |
O2i—Cu1—O1 | 92.89 (5) | O2—C2—H2B | 109.9 |
O1—Cu1—O1i | 180.0 | C1—C2—H2B | 109.9 |
O6—Na1—O7 | 120.74 (6) | H2A—C2—H2B | 108.3 |
O6—Na1—O3 | 85.75 (6) | O3—C3—C4 | 108.68 (15) |
O7—Na1—O3 | 151.04 (6) | O3—C3—H3A | 110.0 |
O6—Na1—O5 | 71.56 (5) | C4—C3—H3A | 110.0 |
O7—Na1—O5 | 100.58 (6) | O3—C3—H3B | 110.0 |
O3—Na1—O5 | 98.93 (6) | C4—C3—H3B | 110.0 |
O6—Na1—O4 | 147.89 (6) | H3A—C3—H3B | 108.3 |
O7—Na1—O4 | 87.66 (5) | O4—C4—C3 | 109.59 (15) |
O3—Na1—O4 | 71.16 (5) | O4—C4—H4A | 109.8 |
O5—Na1—O4 | 89.86 (5) | C3—C4—H4A | 109.8 |
O6—Na1—O3ii | 102.35 (5) | O4—C4—H4B | 109.8 |
O7—Na1—O3ii | 78.69 (5) | C3—C4—H4B | 109.8 |
O3—Na1—O3ii | 84.59 (5) | H4A—C4—H4B | 108.2 |
O5—Na1—O3ii | 172.59 (6) | O5—C5—C6 | 109.26 (19) |
O4—Na1—O3ii | 97.47 (5) | O5—C5—H5A | 109.8 |
C1—O1—Cu1 | 109.42 (11) | C6—C5—H5A | 109.8 |
C2—O2—Cu1 | 108.70 (10) | O5—C5—H5B | 109.8 |
C3—O3—Na1 | 102.62 (10) | C6—C5—H5B | 109.8 |
C3—O3—Na1ii | 133.07 (11) | H5A—C5—H5B | 108.3 |
Na1—O3—Na1ii | 95.41 (5) | O6—C6—C5 | 108.96 (19) |
C3—O3—H3 | 106 (2) | O6—C6—H6A | 109.9 |
Na1—O3—H3 | 122 (2) | C5—C6—H6A | 109.9 |
Na1ii—O3—H3 | 100 (2) | O6—C6—H6B | 109.9 |
C4—O4—Na1 | 111.25 (10) | C5—C6—H6B | 109.9 |
C4—O4—H4 | 107 (2) | H6A—C6—H6B | 108.3 |
Na1—O4—H4 | 112 (2) | O7—C7—C8 | 111.16 (18) |
C5—O5—Na1 | 108.46 (12) | O7—C7—H7A | 109.4 |
C5—O5—H5 | 109 (2) | C8—C7—H7A | 109.4 |
Na1—O5—H5 | 135 (2) | O7—C7—H7B | 109.4 |
C6—O6—Na1 | 112.10 (12) | C8—C7—H7B | 109.4 |
C6—O6—H6 | 109 (2) | H7A—C7—H7B | 108.0 |
Na1—O6—H6 | 116 (2) | O8—C8—C7 | 109.9 (2) |
C7—O7—Na1 | 118.73 (12) | C7—C8—O8B | 96.4 (9) |
C7—O7—H7 | 105 (2) | O8—C8—H8A | 110.5 |
Na1—O7—H7 | 106 (2) | C7—C8—H8A | 109.2 |
C8—O8—H8 | 113 (3) | O8—C8—H8B | 110.0 |
O1—C1—C2 | 109.13 (16) | C7—C8—H8B | 109.2 |
O1—C1—H1A | 109.9 | H8A—C8—H8B | 107.9 |
C2—C1—H1A | 109.9 | C7—C8—H8C | 112.5 |
O1—C1—H1B | 109.9 | O8B—C8—H8C | 111.9 |
C2—C1—H1B | 109.9 | C7—C8—H8D | 112.4 |
H1A—C1—H1B | 108.3 | O8B—C8—H8D | 113.1 |
O2—C2—C1 | 108.82 (15) | H8C—C8—H8D | 110.0 |
Symmetry codes: (i) −x, −y, −z+1; (ii) −x, −y, −z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O6—H6···O1i | 0.75 (3) | 1.93 (3) | 2.683 (2) | 175 (3) |
O4—H4···O1iii | 0.74 (3) | 1.89 (3) | 2.6153 (19) | 168 (3) |
O5—H5···O4iv | 0.75 (3) | 2.05 (3) | 2.779 (2) | 164 (3) |
O7—H7···O2ii | 0.81 (3) | 1.81 (3) | 2.612 (2) | 171 (3) |
O3—H3···O2 | 0.72 (3) | 1.94 (3) | 2.6566 (19) | 172 (3) |
O8—H8···O7v | 0.69 (3) | 2.14 (3) | 2.815 (3) | 167 (4) |
Symmetry codes: (i) −x, −y, −z+1; (ii) −x, −y, −z; (iii) x, y, z−1; (iv) −x+1, −y, −z; (v) −x+1, −y+1, −z. |
Experimental details
Crystal data |
Chemical formula | [Na2(C2H6O2)6][Cu(C2H4O2)2] |
Mr | 602.03 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 100 |
a, b, c (Å) | 8.7666 (12), 9.5089 (13), 9.7804 (13) |
α, β, γ (°) | 99.152 (4), 101.983 (4), 113.910 (4) |
V (Å3) | 701.61 (16) |
Z | 1 |
Radiation type | Mo Kα |
µ (mm−1) | 0.88 |
Crystal size (mm) | 0.09 × 0.09 × 0.08 |
|
Data collection |
Diffractometer | Rigaku AFC-12 with Saturn 724+CCD diffractometer |
Absorption correction | Multi-scan (ABSCOR; Higashi, 1995) |
Tmin, Tmax | 0.573, 0.9 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 7103, 3177, 2863 |
Rint | 0.029 |
(sin θ/λ)max (Å−1) | 0.648 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.034, 0.080, 1.07 |
No. of reflections | 3177 |
No. of parameters | 190 |
No. of restraints | 1 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.36, −0.40 |
Selected bond lengths (Å) topNa1—O6 | 2.3816 (16) | Na1—O5 | 2.4052 (16) |
Na1—O7 | 2.3858 (16) | Na1—O4 | 2.4453 (15) |
Na1—O3 | 2.3945 (16) | Na1—O3i | 2.4545 (15) |
Symmetry code: (i) −x, −y, −z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O6—H6···O1ii | 0.75 (3) | 1.93 (3) | 2.683 (2) | 175 (3) |
O4—H4···O1iii | 0.74 (3) | 1.89 (3) | 2.6153 (19) | 168 (3) |
O5—H5···O4iv | 0.75 (3) | 2.05 (3) | 2.779 (2) | 164 (3) |
O7—H7···O2i | 0.81 (3) | 1.81 (3) | 2.612 (2) | 171 (3) |
O3—H3···O2 | 0.72 (3) | 1.94 (3) | 2.6566 (19) | 172 (3) |
O8—H8···O7v | 0.69 (3) | 2.14 (3) | 2.815 (3) | 167 (4) |
Symmetry codes: (i) −x, −y, −z; (ii) −x, −y, −z+1; (iii) x, y, z−1; (iv) −x+1, −y, −z; (v) −x+1, −y+1, −z. |
Comparison of known copper ethylene glycolate and ethylene glycol complexes. topComplex | CSD refcode | Average Cu-O (Å) | Bite angle of (C2H4O2) |
Na2Cu(C2H6O2)6(C2H4O2)2 | This Work | 1.929 (3) | 87.11 (5) |
BaCu(C2H6O2)3(C2H4O2)2 | PAHFEJa | 1.921 (4) | 88.6 (3) |
BaCu(C2H6O2)6(C2H4O2)2 | PAHFAFa | 1.923 (5) | 86.65 (15) |
Li2Cu2(C2H4O2)2 | VOWKATb | 1.931 (13) | 87.22 (6) |
CuCl2(C2H6O2)2 | CETDCU10c | 1.978 (19) | 79.1 (1) |
CuCl2(C2H6O2)2 H2O | GLYCUHc | 1.986 (18) | 79.9 (1) |
Cu(C2H6O2)3(SO4) | ETDOCUd | 2.10 (10) | 79.2 (10) |
a, Pico et al. (1997); b, Habermann et al. (1992);
c, Antti (1976);
d, Antti et al. (1972). |
There has been considerable interest in the coordination chemistry of metal ions in polyol media as this has relevance to our understanding of the reaction kinetics and solvent and ion exchange during reduction reactions. Several papers have investigated the mechanism of the polyol process by the study of kinetic data obtained by UV–visible and IR spectroscopy (Bonet et al., 2000; Fievet et al., 1988; Pasquarello et al., 2001; Salmon et al., 1992). From these data, metal glycolates have been postulated as possible intermediates. However, these studies do not provide definitive structural details for these species. We report here the structure of a CuII glycolate, [Na2(C2H6O2)6][Cu(C2H4O2)2], (I), which was obtained from a basic solution of CuCl2 in ethylene glycol. A typical poylol reduction protocol was employed in which a basic ethylene glycol solution is used to reduce a metal such as CuII or NiII to the elemental form. The structure of the resulting complex consists of a di-chelate bis-ethylene glycolate dianion of CuII stabilized by ethylene glycol solvated Na ions. A survey of the literature reveals that only four examples of complexes containing the bis-ethylene glycolate CuII2- dianion have been crystallographically characterized (Habermann et al., 1992; Love et al., 1992; Pico et al., 1997). These complexes contain Li+, Ba2+ or Sr2+ as counterions. To the best of our knowledge, this is the first report of a crystal structure of an ethylene glycolate copper(II) dianion stabilized by ethylene glycol coordinated sodium counterions.
The molecular structure of complex (I) is illustrated in Fig. 1. Selected bond lengths are listed in Table 1. The anionic moiety consists of a bis-ethylene glycolate CuII2- dianion with the Cu atom on an inversion center, while the cation comprises two inversion-related Na ions complexed by chelating, bridging and monodentate ethylene glycol units.
The anion has square-planar coordination with fully deprotonated ethylene glycolate units which chelate the Cu2+ ion. The Cu1—O1 [1.9317 (13) Å] and Cu1—O2 [1.9252 (13) Å] distances fall between the previously reported Cu—O distances for Cu[C2H4O2]2- (Habermann et al., 1992; Love et al., 1992; Pico et al., 1997). A comparison of the Cu—O distances and angles from the previously reported structures of both ethylene glycolate and ethylene glycol copper complexes is given in Table 3. The Cu—O distances are consistently longer in the ethylene glycol complexes versus the glycolate complexes. More significantly, the bite angle of the glycolate ligand is much larger than the protonated form by an average of 8°.
In the [Na(C2H6O2)3]22+ cation the unique Na ion is bound by two chelating ethylene glycols, one bridging oxygen from an ethylene glycol that is chelating to the other inversion-related Na atom, and one monodentate ethylene glycol. The unique Na ion has a distorted octahedral coordination environment with Na—O distances in the range 2.3816 (16)–2.4545 (15) Å with the shortest distances coming from the non-bridging chelating O atoms Na1—O6, and the longest distances arising from the bridging interaction of a chelating ethylene glycol Na1—O3 (-x,-y,-z). A search of the Cambridge Structural Database (CSD, Version 5.30 plus three updates; Allen, 2002) reveals only one previously reported structure with ethylene glycol bound to Na ions (CSD ref. code: OBOBAI) (Schubert et al., 2000). In this structure the Na ions are directly attached to the anionic portion of the structure through bridging ethylene glycol units and are therefore not part of an independent sodium–ethylene glycol cationic cluster as reported here.
The cations are linked by O—H···O hydrogen bonds through interactions involving O5—H5···O4iv and O8—H8···O7v (see Table 3) to form sheets parallel to the (001) plane. The deprotonated O atoms, O1 and O2, of the anion are each hydrogen bonded to two different ethylene glycol O atoms of the cation as shown in Fig. 1 with details in Table 2. The association of the two cations and anions via classical O—H···O hydrogen bonding (Table 2) results in a three-dimensional network with alternating layers of cations and anions down the c axis (Fig. 2).
The IR spectrum of (I) revealed weak C—O stretches at 1245 and 1218 cm-1 and weak M—O stretches at 541 and 606 cm-1. These values are consistent with data obtained for the Cu—Sr structure, [Sr(C2H6O2)5][Cu(C2H4O2)2] (Pico et al., 1997).
The synthesis of this complex provides insight into complexes formed during the polyol process before metal reduction takes place. This study provides structural evidence of previously proposed metal glycolate formation during the polyol process.