Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S010827010302064X/de1219sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S010827010302064X/de1219Isup2.hkl |
CCDC reference: 226116
A batch of O-dpaH (0.1 g, 0.535 mmol) was dissolved in acetonitrile (20 ml), and copper(I) trifluoroacetate (CuCF3COO; 0.1 g, 0.568 mmol) was added. The resulting solution was stirred for 10 h in air at room temperature. The mixture was filtered and the filtrate was crystallized by diffusion of ether at room temperature. After several days, green single crystals of (I) were obtained. IR (cm−1): 3441.92, 3092.32, 1695.85, 1508.49, 1477.03, 1384.88, 1189.8, 1139.58, 753.28.
In the refinement, H atoms were allowed for as riding atoms, with C—H distances of 0.93 and 0.96 Å.
Data collection: CAD-4 EXPRESS (Enraf-Nonius, 1994); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek 2003); software used to prepare material for publication: WinGX (Farrugia, 1999).
[Cu2(C2F3O2)2(C10H8N3O)2]·C2H3N | F(000) = 1624 |
Mr = 807.62 | Dx = 1.619 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -C 2yc | Cell parameters from 2991 reflections |
a = 21.203 (4) Å | θ = 2.0–25.0° |
b = 7.468 (2) Å | µ = 1.37 mm−1 |
c = 22.123 (5) Å | T = 293 K |
β = 108.947 (15)° | Prism, green |
V = 3313.2 (13) Å3 | 0.38 × 0.25 × 0.22 mm |
Z = 4 |
Enraf-Nonius TurboCAD-4 diffractometer | 2106 reflections with I > 2σ(I) |
Radiation source: Enraf Nonius FR590 | Rint = 0.031 |
Graphite monochromator | θmax = 25.0°, θmin = 2.0° |
non–profiled ω/2θ scans | h = −25→0 |
Absorption correction: ψ scan (North et al., 1968) | k = −8→0 |
Tmin = 0.675, Tmax = 0.738 | l = −24→26 |
2991 measured reflections | 3 standard reflections every 60 min |
2905 independent reflections | intensity decay: 4% |
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)] = 0.033 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.095 | H-atom parameters constrained |
S = 1.02 | w = 1/[σ2(Fo2) + (0.0434P)2 + 4.4467P] where P = (Fo2 + 2Fc2)/3 |
2905 reflections | (Δ/σ)max < 0.001 |
226 parameters | Δρmax = 0.38 e Å−3 |
0 restraints | Δρmin = −0.31 e Å−3 |
[Cu2(C2F3O2)2(C10H8N3O)2]·C2H3N | V = 3313.2 (13) Å3 |
Mr = 807.62 | Z = 4 |
Monoclinic, C2/c | Mo Kα radiation |
a = 21.203 (4) Å | µ = 1.37 mm−1 |
b = 7.468 (2) Å | T = 293 K |
c = 22.123 (5) Å | 0.38 × 0.25 × 0.22 mm |
β = 108.947 (15)° |
Enraf-Nonius TurboCAD-4 diffractometer | 2106 reflections with I > 2σ(I) |
Absorption correction: ψ scan (North et al., 1968) | Rint = 0.031 |
Tmin = 0.675, Tmax = 0.738 | 3 standard reflections every 60 min |
2991 measured reflections | intensity decay: 4% |
2905 independent reflections |
R[F2 > 2σ(F2)] = 0.033 | 0 restraints |
wR(F2) = 0.095 | H-atom parameters constrained |
S = 1.02 | Δρmax = 0.38 e Å−3 |
2905 reflections | Δρmin = −0.31 e Å−3 |
226 parameters |
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 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. |
x | y | z | Uiso*/Ueq | ||
Cu1 | 0.077921 (19) | 0.82944 (5) | 0.242472 (18) | 0.03412 (14) | |
F1 | 0.05215 (19) | 0.8688 (7) | 0.03118 (14) | 0.1504 (18) | |
F2 | 0.15263 (18) | 0.8393 (6) | 0.04244 (14) | 0.1319 (15) | |
F3 | 0.0981 (2) | 0.6210 (5) | 0.05413 (15) | 0.1387 (16) | |
O1 | 0.13687 (12) | 0.6448 (3) | 0.28787 (11) | 0.0464 (6) | |
O2 | 0.08703 (13) | 0.7495 (3) | 0.16202 (11) | 0.0503 (6) | |
O3 | 0.16304 (15) | 0.9529 (4) | 0.15950 (15) | 0.0755 (9) | |
N1 | 0.14496 (13) | 0.6511 (4) | 0.35119 (13) | 0.0395 (6) | |
N2 | 0.06414 (12) | 0.8649 (3) | 0.32414 (11) | 0.0340 (6) | |
N3 | −0.02915 (12) | 1.0443 (3) | 0.30153 (12) | 0.0340 (6) | |
C1 | 0.18989 (18) | 0.5407 (5) | 0.39069 (18) | 0.0512 (9) | |
H1 | 0.2142 | 0.4619 | 0.3743 | 0.061* | |
C2 | 0.19980 (19) | 0.5444 (6) | 0.45463 (19) | 0.0591 (10) | |
H2 | 0.2311 | 0.4691 | 0.4822 | 0.071* | |
C3 | 0.1629 (2) | 0.6614 (5) | 0.47816 (18) | 0.0548 (10) | |
H3 | 0.1691 | 0.6643 | 0.5217 | 0.066* | |
C4 | 0.11725 (18) | 0.7727 (5) | 0.43759 (16) | 0.0453 (8) | |
H4 | 0.0923 | 0.8502 | 0.4538 | 0.054* | |
C5 | 0.10760 (15) | 0.7712 (4) | 0.37165 (15) | 0.0359 (7) | |
C6 | 0.03541 (15) | 1.0238 (4) | 0.33689 (14) | 0.0339 (7) | |
C7 | 0.06964 (17) | 1.1575 (4) | 0.37807 (16) | 0.0431 (8) | |
H7 | 0.1138 | 1.1408 | 0.4032 | 0.052* | |
C8 | 0.03727 (19) | 1.3151 (5) | 0.38110 (19) | 0.0507 (9) | |
H8 | 0.0590 | 1.4049 | 0.4093 | 0.061* | |
C9 | −0.02822 (19) | 1.3394 (5) | 0.34179 (19) | 0.0529 (9) | |
H9 | −0.0503 | 1.4471 | 0.3418 | 0.063* | |
C10 | −0.05926 (18) | 1.2014 (4) | 0.30325 (18) | 0.0463 (9) | |
H10 | −0.1031 | 1.2168 | 0.2770 | 0.056* | |
C11 | 0.12250 (18) | 0.8387 (5) | 0.13665 (16) | 0.0443 (8) | |
C12 | 0.1063 (2) | 0.7924 (7) | 0.0655 (2) | 0.0651 (12) | |
N21 | 0.2152 (3) | 1.0812 (8) | 0.3520 (4) | 0.151 (3) | |
C21 | 0.2817 (2) | 0.8861 (7) | 0.3010 (2) | 0.0771 (14) | |
H21A | 0.2522 | 0.8386 | 0.2617 | 0.116* | |
H21B | 0.3018 | 0.7894 | 0.3293 | 0.116* | |
H21C | 0.3158 | 0.9560 | 0.2924 | 0.116* | |
C22 | 0.2448 (2) | 0.9968 (7) | 0.3302 (3) | 0.0775 (14) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cu1 | 0.0416 (2) | 0.0280 (2) | 0.0355 (2) | 0.00198 (18) | 0.01635 (16) | 0.00041 (17) |
F1 | 0.127 (3) | 0.249 (5) | 0.0600 (18) | 0.080 (3) | 0.0104 (18) | 0.019 (2) |
F2 | 0.137 (3) | 0.207 (4) | 0.080 (2) | −0.034 (3) | 0.075 (2) | −0.003 (2) |
F3 | 0.253 (5) | 0.104 (3) | 0.081 (2) | −0.035 (3) | 0.083 (3) | −0.042 (2) |
O1 | 0.0577 (14) | 0.0426 (14) | 0.0423 (13) | 0.0188 (12) | 0.0209 (11) | 0.0026 (11) |
O2 | 0.0802 (18) | 0.0338 (12) | 0.0479 (14) | −0.0057 (13) | 0.0358 (13) | −0.0016 (11) |
O3 | 0.080 (2) | 0.068 (2) | 0.088 (2) | −0.0229 (18) | 0.0405 (17) | −0.0217 (18) |
N1 | 0.0421 (15) | 0.0333 (15) | 0.0432 (16) | 0.0060 (12) | 0.0142 (12) | 0.0055 (12) |
N2 | 0.0389 (14) | 0.0308 (15) | 0.0327 (14) | 0.0052 (11) | 0.0123 (12) | −0.0006 (11) |
N3 | 0.0372 (14) | 0.0276 (14) | 0.0386 (14) | 0.0026 (11) | 0.0141 (12) | −0.0028 (11) |
C1 | 0.047 (2) | 0.042 (2) | 0.061 (2) | 0.0118 (17) | 0.0136 (18) | 0.0081 (18) |
C2 | 0.052 (2) | 0.054 (2) | 0.059 (2) | 0.007 (2) | 0.0024 (19) | 0.017 (2) |
C3 | 0.063 (2) | 0.054 (2) | 0.0392 (19) | −0.009 (2) | 0.0050 (17) | 0.0071 (18) |
C4 | 0.055 (2) | 0.041 (2) | 0.0392 (19) | −0.0032 (17) | 0.0148 (17) | −0.0021 (16) |
C5 | 0.0388 (17) | 0.0289 (17) | 0.0414 (18) | −0.0018 (14) | 0.0150 (15) | −0.0018 (14) |
C6 | 0.0432 (18) | 0.0302 (16) | 0.0318 (15) | −0.0011 (14) | 0.0171 (14) | −0.0014 (13) |
C7 | 0.0452 (19) | 0.040 (2) | 0.0436 (19) | −0.0040 (16) | 0.0133 (15) | −0.0070 (16) |
C8 | 0.062 (2) | 0.0342 (19) | 0.059 (2) | −0.0067 (18) | 0.0225 (19) | −0.0137 (17) |
C9 | 0.062 (2) | 0.0287 (18) | 0.075 (3) | 0.0041 (17) | 0.032 (2) | −0.0093 (18) |
C10 | 0.045 (2) | 0.037 (2) | 0.057 (2) | 0.0064 (16) | 0.0175 (17) | −0.0009 (17) |
C11 | 0.056 (2) | 0.0371 (19) | 0.0447 (19) | 0.0072 (18) | 0.0231 (17) | 0.0015 (17) |
C12 | 0.080 (3) | 0.072 (3) | 0.053 (2) | 0.008 (2) | 0.035 (2) | 0.010 (2) |
N21 | 0.124 (4) | 0.101 (4) | 0.275 (8) | −0.014 (4) | 0.130 (5) | −0.056 (5) |
C21 | 0.059 (3) | 0.075 (3) | 0.103 (4) | 0.006 (2) | 0.034 (3) | −0.004 (3) |
C22 | 0.056 (3) | 0.059 (3) | 0.128 (4) | −0.006 (2) | 0.043 (3) | −0.005 (3) |
Cu1—O1 | 1.912 (2) | C2—C3 | 1.383 (6) |
Cu1—N2 | 1.940 (2) | C2—H2 | 0.93 |
Cu1—O2 | 1.945 (2) | C3—C4 | 1.367 (5) |
Cu1—N3i | 1.984 (3) | C3—H3 | 0.93 |
Cu1—N2i | 2.904 (3) | C4—C5 | 1.406 (4) |
Cu1—O3 | 3.103 (3) | C4—H4 | 0.93 |
F1—C12 | 1.287 (5) | C6—C7 | 1.387 (4) |
F2—C12 | 1.292 (5) | C7—C8 | 1.375 (5) |
F3—C12 | 1.305 (6) | C7—H7 | 0.93 |
O1—N1 | 1.356 (3) | C8—C9 | 1.390 (5) |
O2—C11 | 1.265 (4) | C8—H8 | 0.93 |
O3—C11 | 1.200 (4) | C9—C10 | 1.363 (5) |
N1—C1 | 1.345 (4) | C9—H9 | 0.93 |
N1—C5 | 1.367 (4) | C10—H10 | 0.93 |
N2—C5 | 1.347 (4) | C11—C12 | 1.539 (5) |
N2—C6 | 1.404 (4) | N21—C22 | 1.105 (6) |
N3—C10 | 1.343 (4) | C21—C22 | 1.428 (6) |
N3—C6 | 1.347 (4) | C21—H21A | 0.96 |
N3—Cu1i | 1.984 (3) | C21—H21B | 0.96 |
C1—C2 | 1.361 (5) | C21—H21C | 0.96 |
C1—H1 | 0.93 | ||
O1—Cu1—N2 | 83.09 (10) | N3—C6—C7 | 121.1 (3) |
O1—Cu1—O2 | 90.97 (10) | N3—C6—N2 | 113.9 (3) |
N2—Cu1—O2 | 169.65 (11) | C7—C6—N2 | 124.9 (3) |
O1—Cu1—N3i | 171.23 (11) | C8—C7—C6 | 119.0 (3) |
N2—Cu1—N3i | 97.73 (10) | C8—C7—H7 | 120.5 |
O2—Cu1—N3i | 89.44 (11) | C6—C7—H7 | 120.5 |
N1—O1—Cu1 | 111.06 (17) | C7—C8—C9 | 119.6 (3) |
C11—O2—Cu1 | 119.6 (2) | C7—C8—H8 | 120.2 |
C1—N1—O1 | 118.4 (3) | C9—C8—H8 | 120.2 |
C1—N1—C5 | 123.4 (3) | C10—C9—C8 | 118.3 (3) |
O1—N1—C5 | 118.2 (2) | C10—C9—H9 | 120.9 |
C5—N2—C6 | 120.9 (3) | C8—C9—H9 | 120.9 |
C5—N2—Cu1 | 112.6 (2) | N3—C10—C9 | 122.8 (3) |
C6—N2—Cu1 | 120.59 (19) | N3—C10—H10 | 118.6 |
C10—N3—C6 | 119.1 (3) | C9—C10—H10 | 118.6 |
C10—N3—Cu1i | 122.9 (2) | O3—C11—O2 | 129.5 (3) |
C6—N3—Cu1i | 117.6 (2) | O3—C11—C12 | 118.8 (4) |
N1—C1—C2 | 120.0 (3) | O2—C11—C12 | 111.6 (3) |
N1—C1—H1 | 120.0 | F1—C12—F2 | 107.1 (4) |
C2—C1—H1 | 120.0 | F1—C12—F3 | 106.5 (5) |
C1—C2—C3 | 119.3 (3) | F2—C12—F3 | 105.2 (4) |
C1—C2—H2 | 120.4 | F1—C12—C11 | 111.3 (4) |
C3—C2—H2 | 120.4 | F2—C12—C11 | 113.4 (4) |
C4—C3—C2 | 120.2 (4) | F3—C12—C11 | 112.9 (3) |
C4—C3—H3 | 119.9 | C22—C21—H21A | 109.5 |
C2—C3—H3 | 119.9 | C22—C21—H21B | 109.5 |
C3—C4—C5 | 120.7 (3) | H21A—C21—H21B | 109.5 |
C3—C4—H4 | 119.7 | C22—C21—H21C | 109.5 |
C5—C4—H4 | 119.7 | H21A—C21—H21C | 109.5 |
N2—C5—N1 | 113.9 (3) | H21B—C21—H21C | 109.5 |
N2—C5—C4 | 129.6 (3) | N21—C22—C21 | 178.6 (7) |
N1—C5—C4 | 116.3 (3) | ||
N2—Cu1—O1—N1 | −8.1 (2) | C3—C4—C5—N2 | 177.5 (3) |
O2—Cu1—O1—N1 | −179.6 (2) | C3—C4—C5—N1 | 1.4 (5) |
O1—Cu1—O2—C11 | −104.9 (3) | C10—N3—C6—C7 | 4.4 (4) |
N2—Cu1—O2—C11 | −159.7 (5) | Cu1i—N3—C6—C7 | −168.3 (2) |
N3i—Cu1—O2—C11 | 66.3 (3) | C10—N3—C6—N2 | −171.1 (3) |
Cu1—O1—N1—C1 | −173.8 (2) | Cu1i—N3—C6—N2 | 16.2 (3) |
Cu1—O1—N1—C5 | 5.3 (3) | C5—N2—C6—N3 | −141.4 (3) |
O1—Cu1—N2—C5 | 9.9 (2) | Cu1—N2—C6—N3 | 67.7 (3) |
O2—Cu1—N2—C5 | 65.3 (7) | C5—N2—C6—C7 | 43.3 (4) |
N3i—Cu1—N2—C5 | −161.3 (2) | Cu1—N2—C6—C7 | −107.6 (3) |
O1—Cu1—N2—C6 | 163.1 (2) | N3—C6—C7—C8 | −1.9 (5) |
O2—Cu1—N2—C6 | −141.6 (5) | N2—C6—C7—C8 | 173.0 (3) |
N3i—Cu1—N2—C6 | −8.1 (2) | C6—C7—C8—C9 | −1.8 (5) |
O1—N1—C1—C2 | 179.4 (3) | C7—C8—C9—C10 | 2.9 (6) |
C5—N1—C1—C2 | 0.3 (5) | C6—N3—C10—C9 | −3.3 (5) |
N1—C1—C2—C3 | 0.5 (6) | Cu1i—N3—C10—C9 | 169.0 (3) |
C1—C2—C3—C4 | −0.4 (6) | C8—C9—C10—N3 | −0.4 (6) |
C2—C3—C4—C5 | −0.6 (6) | Cu1—O2—C11—O3 | 15.3 (5) |
C6—N2—C5—N1 | −162.6 (3) | Cu1—O2—C11—C12 | −161.9 (2) |
Cu1—N2—C5—N1 | −9.6 (3) | O3—C11—C12—F1 | −99.8 (5) |
C6—N2—C5—C4 | 21.1 (5) | O2—C11—C12—F1 | 77.7 (5) |
Cu1—N2—C5—C4 | 174.2 (3) | O3—C11—C12—F2 | 21.1 (6) |
C1—N1—C5—N2 | −178.0 (3) | O2—C11—C12—F2 | −161.4 (4) |
O1—N1—C5—N2 | 2.9 (4) | O3—C11—C12—F3 | 140.6 (4) |
C1—N1—C5—C4 | −1.3 (5) | O2—C11—C12—F3 | −41.9 (5) |
O1—N1—C5—C4 | 179.6 (3) |
Symmetry code: (i) −x, y, −z+1/2. |
Experimental details
Crystal data | |
Chemical formula | [Cu2(C2F3O2)2(C10H8N3O)2]·C2H3N |
Mr | 807.62 |
Crystal system, space group | Monoclinic, C2/c |
Temperature (K) | 293 |
a, b, c (Å) | 21.203 (4), 7.468 (2), 22.123 (5) |
β (°) | 108.947 (15) |
V (Å3) | 3313.2 (13) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 1.37 |
Crystal size (mm) | 0.38 × 0.25 × 0.22 |
Data collection | |
Diffractometer | Enraf-Nonius TurboCAD-4 diffractometer |
Absorption correction | ψ scan (North et al., 1968) |
Tmin, Tmax | 0.675, 0.738 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2991, 2905, 2106 |
Rint | 0.031 |
(sin θ/λ)max (Å−1) | 0.594 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.033, 0.095, 1.02 |
No. of reflections | 2905 |
No. of parameters | 226 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.38, −0.31 |
Computer programs: CAD-4 EXPRESS (Enraf-Nonius, 1994), CAD-4 EXPRESS, XCAD4 (Harms & Wocadlo, 1995), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), PLATON (Spek 2003), WinGX (Farrugia, 1999).
Cu1—O1 | 1.912 (2) | O1—N1 | 1.356 (3) |
Cu1—N2 | 1.940 (2) | N1—C1 | 1.345 (4) |
Cu1—O2 | 1.945 (2) | N1—C5 | 1.367 (4) |
Cu1—N3i | 1.984 (3) | N2—C5 | 1.347 (4) |
Cu1—N2i | 2.904 (3) | N2—C6 | 1.404 (4) |
Cu1—O3 | 3.103 (3) | ||
O1—Cu1—N2 | 83.09 (10) | O1—N1—C5 | 118.2 (2) |
O1—Cu1—O2 | 90.97 (10) | C5—N2—C6 | 120.9 (3) |
N2—Cu1—N3i | 97.73 (10) | C5—N2—Cu1 | 112.6 (2) |
O2—Cu1—N3i | 89.44 (11) | C6—N2—Cu1 | 120.59 (19) |
Symmetry code: (i) −x, y, −z+1/2. |
Subscribe to Acta Crystallographica Section C: Structural Chemistry
The full text of this article is available to subscribers to the journal.
- Information on subscribing
- Sample issue
- Purchase subscription
- Reduced-price subscriptions
- If you have already subscribed, you may need to register
In attempts to develop polynuclear compounds of transition metals using multidentate N-donor groups as ligands (Shieh et al., 1997; Wang et al., 1998; Chang et al., 1999; Peng et al., 2000), we have noticed the behavior of the polypyridylamine N-oxides, because N-oxides offer functional group manipulation and structural modification possibilities that are not usually accessible by other methods (Cope & Ciganek, 1963). In our research system, 2-(2-pyridylamino)pyridine 1-oxide [O-dpaH; dpa is the di(2-pyridyl)amide anion and H represents the dissociable amine H atom] is the simplest multipyridylamine oxide. The O-dpaH frame is stable in air but, to the best of our knowledge, no transition metal complexes of O-dpaH have been reported. We report here the synthesis and structure of the title dinuclear CuII complex, (I).
As shown in Fig. 1, the complex has crystallographically imposed twofold symmetry and the O-dpaH ligand is both bidentate and bridging, linking two Cu atoms with a separation of 3.4270 (11) Å. The O-dpaH ligand takes the syn form, with each Cu atom coordinated to four atoms, viz. an amide N atom, an N-oxide O atom of one O-dpa− anion, with a bite angle O1—Cu1—N2 of 83.09 (10)°, a pyridine N atom of another O-dpa− anion, and an O atom of a trifluoroacetate group. The Cu1 atom is 0.1648 (10) Å from the best plane of the CuN2O2 moiety. Although this compound can be considered as basically four-coordinate, atoms N2a and O3 (see Fig. 1) occupy possible fifth and sixth coordination sites, with Cu1···N2a = 2.904 (3) Å (N2 is at the equivalent position −x, y, 1/2 − z) and Cu1···O3 = 3.103 (3) Å. This type of coordination is perhaps best described as intermediate between square-planar four-coordination and distorted octahedral geometry. The eight-membered Cu1—N3A—C6A—N2A—Cu1A—N3—C6—N2 chelate ring (Fig. 1) adopts a boat conformation. The individual pyridyl rings are essentially planar [the maximum deviation from the plane is 0.008 (2) Å for atom C5]. In the O-dpa− ligand the pyridyl ring planes form a dihedral angle of 55.11 (12)°. There is no H atom on amide atom N2; the original amide H atom is eliminated rather than being transferred to the N atom of a pyridine ring. The N2—C6 bond length [1.404 (4) Å] is almost equal to that in the free ligand [1.395 (2) Å], while the N2—C(5) bond length is apparently shortened from 1.367 (2) Å in the free ligand to 1.347 (4) Å in the complex (Thellend et al., 1997; Bergstad & Backvall, 1998; Jiao & Yu, 2001). The suggested mechanism is illustrated in the reastion scheme above (Wu et al., 1990). The dehydrogenation in (I) only occurs as a consequence of the oxidation of CuI to CuII in the presence of air and traces of water.