The title compound, [Mn
2(
-O)(C
6H
3NO
3)
2(C
5H
5N)
4]·H
2O, was isolated from the reaction of 2,6-pyridinedicarboxylic acid with [Mn
12O
12(CH
3COO)
16(H
2O)
4] in pyridine. The dimanganese complex has twofold symmetry; the Mn
III atoms are bridged by one oxo and two amidate ligands and show compressed octahedral Jahn-Teller distortion. The molecular packing comprises a three-dimensional structure constructed by means of extensive intermolecular interactions, including three kinds of hydrogen bonds and
-
interactions.
Supporting information
CCDC reference: 245861
Mn12-ac was prepared by the literature method (Lis, 1980). To a solution of Mn12-ac (0.05 mmol) in pyridine (10 ml) was added pdcH2 (0.4 mmol). After stirring for 30 min, the mixture was filtered and the dark-brown filtrate was left to stand, allowing slow evaporation of the solvent at room temperature. Brown block-shaped crystals of (I) suitable for X-ray analysis were obtained after four weeks. IR (KBr pellet, cm−1): 3198 (b), 3087 (m), 2923 (m), 1654 (m), 1632 (m), 1592 (s), 1570 (m), 1435 (m), 1396 (m), 1371 (m), 1278 (w), 1193 (w), 1015 (w), 910 (w), 785 (w), 720 (m), 699 (w), 661 (w).
H atoms were located from difference density maps and their coordinates were refined, with Uiso(H) = 0.0146 Å2. The C—H and O—H bond lengths are 0.80 (3)–1.00 (3) Å and 0.87 (2) Å, respectively.
Data collection: CrystalClear (Rigaku, 2001); cell refinement: CrystalClear; data reduction: TEXSAN (Molecular Structure Corporation & Rigaku, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); software used to prepare material for publication: TEXSAN.
Crystal data top
[Mn2O(C6H3NO3)2(C5H5N)4]·H2O | F(000) = 1504.0 |
Mr = 734.48 | Dx = 1.580 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.7107 Å |
Hall symbol: -c 2yc | Cell parameters from 4653 reflections |
a = 13.606 (8) Å | θ = 3.1–27.5° |
b = 16.379 (9) Å | µ = 0.88 mm−1 |
c = 14.289 (9) Å | T = 150 K |
β = 104.118 (7)° | Block, brown |
V = 3088 (3) Å3 | 0.20 × 0.15 × 0.15 mm |
Z = 4 | |
Data collection top
Rigaku/MSC Mercury CCD diffractometer | 3144 reflections with I > 2σ(I) |
Detector resolution: 14.62 pixels mm-1 | Rint = 0.034 |
ω scans | θmax = 27.5°, θmin = 3.1° |
Absorption correction: multi-scan (Jacobson, 1998) | h = −13→17 |
Tmin = 0.764, Tmax = 0.876 | k = −18→21 |
11903 measured reflections | l = −18→18 |
3512 independent reflections | |
Refinement top
Refinement on F2 | Only H-atom coordinates refined |
R[F2 > 2σ(F2)] = 0.050 | w = 1/[σ2(Fo2) + (0.0468P)2 + 5.1887P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.109 | (Δ/σ)max < 0.001 |
S = 1.12 | Δρmax = 0.40 e Å−3 |
3144 reflections | Δρmin = −0.46 e Å−3 |
260 parameters | |
Crystal data top
[Mn2O(C6H3NO3)2(C5H5N)4]·H2O | V = 3088 (3) Å3 |
Mr = 734.48 | Z = 4 |
Monoclinic, C2/c | Mo Kα radiation |
a = 13.606 (8) Å | µ = 0.88 mm−1 |
b = 16.379 (9) Å | T = 150 K |
c = 14.289 (9) Å | 0.20 × 0.15 × 0.15 mm |
β = 104.118 (7)° | |
Data collection top
Rigaku/MSC Mercury CCD diffractometer | 3512 independent reflections |
Absorption correction: multi-scan (Jacobson, 1998) | 3144 reflections with I > 2σ(I) |
Tmin = 0.764, Tmax = 0.876 | Rint = 0.034 |
11903 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.050 | 260 parameters |
wR(F2) = 0.109 | Only H-atom coordinates refined |
S = 1.12 | Δρmax = 0.40 e Å−3 |
3144 reflections | Δρmin = −0.46 e Å−3 |
Special details top
Refinement. The linear absorption coefficient, µ, for Mo—Kα radiation is 8.8 cm−1. A symmetry-related absorption correction using the program REQAB (Jacobason 1995–1998) was applied which resulted in transmission factors ranging from 0.76 to 0.88. The data were corrected for Lorentz and polarization effects. The structure was solved by direct methods and expanded using Fourier techniques. The non-hydrogen atoms were refined anisotropically. Refinement using reflections with F2 > −10.0 σ(F2). The weighted R-factor (wR) and goodness of fit (S) are based on F2. R-factor (gt) are based on F. The threshold expression of F2 > 2.0 σ(F2) is used only for calculating R-factor (gt). |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
Mn1 | 0.58631 (3) | 0.16515 (2) | 0.19278 (2) | 0.0228 (1) | |
O1 | 0.5192 (1) | 0.0847 (1) | 0.3886 (1) | 0.0297 (4) | |
O2 | 0.6932 (1) | 0.1181 (1) | 0.1417 (1) | 0.0268 (4) | |
O3 | 0.8395 (2) | 0.0521 (1) | 0.1821 (1) | 0.0427 (5) | |
O4 | 0.5000 | 0.2156 (1) | 0.2500 | 0.0252 (5) | |
O5 | 1.0000 | 0.0515 (2) | 0.7500 | 0.0424 (7) | |
N1 | 0.6409 (2) | 0.0784 (1) | 0.3006 (1) | 0.0240 (4) | |
N2 | 0.5556 (2) | 0.2523 (1) | 0.0750 (1) | 0.0257 (4) | |
N3 | 0.7118 (2) | 0.2555 (1) | 0.2699 (1) | 0.0283 (4) | |
C1 | 0.6019 (2) | 0.0548 (1) | 0.3756 (2) | 0.0253 (5) | |
C2 | 0.6569 (2) | −0.0049 (2) | 0.4417 (2) | 0.0285 (5) | |
C3 | 0.7470 (2) | −0.0340 (2) | 0.4319 (2) | 0.0308 (5) | |
C4 | 0.7860 (2) | −0.0089 (2) | 0.3537 (2) | 0.0300 (5) | |
C5 | 0.7297 (2) | 0.0459 (1) | 0.2898 (2) | 0.0253 (5) | |
C6 | 0.7594 (2) | 0.0728 (2) | 0.1992 (2) | 0.0277 (5) | |
C7 | 0.5118 (2) | 0.3234 (2) | 0.0869 (2) | 0.0310 (6) | |
C8 | 0.4805 (2) | 0.3789 (2) | 0.0126 (2) | 0.0366 (6) | |
C9 | 0.4965 (2) | 0.3616 (2) | −0.0768 (2) | 0.0368 (6) | |
C10 | 0.5439 (2) | 0.2896 (2) | −0.0888 (2) | 0.0379 (6) | |
C11 | 0.5720 (2) | 0.2362 (2) | −0.0120 (2) | 0.0311 (5) | |
C12 | 0.7163 (2) | 0.2782 (2) | 0.3605 (2) | 0.0405 (7) | |
C13 | 0.7876 (3) | 0.3334 (2) | 0.4094 (2) | 0.0524 (9) | |
C14 | 0.8557 (2) | 0.3672 (2) | 0.3655 (2) | 0.0457 (7) | |
C15 | 0.8516 (2) | 0.3444 (2) | 0.2713 (2) | 0.0402 (6) | |
C16 | 0.7793 (2) | 0.2884 (2) | 0.2269 (2) | 0.0339 (6) | |
H1 | 0.626 (2) | −0.022 (1) | 0.492 (2) | 0.0146* | |
H2 | 0.783 (2) | −0.069 (1) | 0.472 (2) | 0.0146* | |
H3 | 0.845 (2) | −0.031 (1) | 0.343 (2) | 0.0146* | |
H4 | 0.502 (2) | 0.335 (1) | 0.147 (2) | 0.0146* | |
H5 | 0.452 (2) | 0.425 (2) | 0.027 (2) | 0.0146* | |
H6 | 0.478 (2) | 0.398 (1) | −0.128 (2) | 0.0146* | |
H7 | 0.553 (2) | 0.274 (1) | −0.149 (2) | 0.0146* | |
H8 | 0.604 (2) | 0.188 (2) | −0.018 (2) | 0.0146* | |
H9 | 0.667 (2) | 0.249 (1) | 0.390 (2) | 0.0146* | |
H10 | 0.786 (2) | 0.346 (1) | 0.463 (2) | 0.0146* | |
H11 | 0.906 (2) | 0.406 (1) | 0.396 (2) | 0.0146* | |
H12 | 0.894 (2) | 0.367 (1) | 0.239 (2) | 0.0146* | |
H13 | 0.774 (2) | 0.271 (1) | 0.165 (2) | 0.0146* | |
H14 | 1.050 (2) | 0.018 (1) | 0.772 (2) | 0.0146* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Mn1 | 0.0331 (2) | 0.0201 (2) | 0.0143 (2) | 0.0001 (1) | 0.0040 (1) | 0.0006 (1) |
O1 | 0.040 (1) | 0.0304 (9) | 0.0192 (8) | 0.0071 (8) | 0.0076 (7) | 0.0045 (7) |
O2 | 0.0362 (10) | 0.0251 (8) | 0.0186 (7) | 0.0017 (7) | 0.0056 (7) | 0.0009 (6) |
O3 | 0.035 (1) | 0.054 (1) | 0.041 (1) | 0.0081 (10) | 0.0143 (9) | 0.0151 (9) |
O4 | 0.036 (1) | 0.021 (1) | 0.019 (1) | 0.0000 | 0.0057 (9) | 0.0000 |
O5 | 0.041 (2) | 0.028 (1) | 0.062 (2) | 0.0000 | 0.021 (1) | 0.0000 |
N1 | 0.032 (1) | 0.0201 (9) | 0.0174 (9) | −0.0008 (8) | 0.0024 (8) | 0.0004 (7) |
N2 | 0.033 (1) | 0.0229 (10) | 0.0196 (9) | −0.0023 (8) | 0.0021 (8) | 0.0020 (7) |
N3 | 0.035 (1) | 0.0240 (10) | 0.0234 (10) | 0.0008 (9) | 0.0021 (9) | −0.0014 (8) |
C1 | 0.035 (1) | 0.022 (1) | 0.0161 (10) | −0.0007 (10) | 0.0023 (9) | −0.0011 (8) |
C2 | 0.043 (2) | 0.023 (1) | 0.018 (1) | 0.002 (1) | 0.003 (1) | 0.0020 (9) |
C3 | 0.040 (2) | 0.024 (1) | 0.023 (1) | 0.004 (1) | −0.001 (1) | 0.0055 (10) |
C4 | 0.032 (1) | 0.026 (1) | 0.030 (1) | 0.002 (1) | 0.003 (1) | 0.0023 (10) |
C5 | 0.030 (1) | 0.022 (1) | 0.022 (1) | −0.0047 (9) | 0.0021 (9) | −0.0024 (9) |
C6 | 0.034 (1) | 0.023 (1) | 0.025 (1) | −0.003 (1) | 0.006 (1) | −0.0012 (9) |
C7 | 0.041 (2) | 0.027 (1) | 0.025 (1) | −0.001 (1) | 0.008 (1) | 0.0035 (10) |
C8 | 0.043 (2) | 0.027 (1) | 0.040 (1) | 0.004 (1) | 0.010 (1) | 0.009 (1) |
C9 | 0.036 (2) | 0.040 (1) | 0.034 (1) | 0.000 (1) | 0.007 (1) | 0.018 (1) |
C10 | 0.044 (2) | 0.047 (2) | 0.024 (1) | 0.002 (1) | 0.010 (1) | 0.007 (1) |
C11 | 0.039 (1) | 0.033 (1) | 0.022 (1) | 0.003 (1) | 0.008 (1) | 0.0016 (10) |
C12 | 0.048 (2) | 0.044 (2) | 0.028 (1) | −0.006 (1) | 0.007 (1) | −0.010 (1) |
C13 | 0.062 (2) | 0.058 (2) | 0.033 (2) | −0.009 (2) | 0.004 (1) | −0.024 (1) |
C14 | 0.042 (2) | 0.035 (2) | 0.051 (2) | −0.004 (1) | −0.007 (1) | −0.012 (1) |
C15 | 0.034 (2) | 0.038 (2) | 0.045 (2) | −0.004 (1) | 0.002 (1) | 0.004 (1) |
C16 | 0.038 (2) | 0.035 (1) | 0.027 (1) | −0.002 (1) | 0.005 (1) | −0.001 (1) |
Geometric parameters (Å, º) top
Mn1—Mn1i | 3.172 (1) | C8—C9 | 1.377 (4) |
Mn1—O1i | 2.083 (2) | C9—C10 | 1.375 (4) |
Mn1—O2 | 1.939 (2) | C10—C11 | 1.382 (4) |
Mn1—O4 | 1.789 (1) | C12—C13 | 1.384 (4) |
Mn1—N1 | 2.094 (2) | C13—C14 | 1.358 (5) |
Mn1—N2 | 2.169 (2) | C14—C15 | 1.385 (5) |
Mn1—N3 | 2.325 (2) | C15—C16 | 1.380 (4) |
O1—C1 | 1.282 (3) | O5—H14 | 0.87 (2) |
O2—C6 | 1.295 (3) | O5—H14ii | 0.87 (2) |
O3—C6 | 1.222 (4) | C2—H1 | 0.96 (3) |
N1—C1 | 1.363 (3) | C3—H2 | 0.87 (2) |
N1—C5 | 1.363 (3) | C4—H3 | 0.93 (3) |
N2—C7 | 1.338 (3) | C7—H4 | 0.92 (3) |
N2—C11 | 1.341 (3) | C8—H5 | 0.90 (3) |
N3—C12 | 1.334 (4) | C9—H6 | 0.93 (2) |
N3—C16 | 1.336 (4) | C10—H7 | 0.93 (3) |
C1—C2 | 1.437 (3) | C11—H8 | 0.92 (3) |
C2—C3 | 1.354 (4) | C12—H9 | 1.00 (3) |
C3—C4 | 1.410 (4) | C13—H10 | 0.80 (3) |
C4—C5 | 1.373 (3) | C14—H11 | 0.96 (2) |
C5—C6 | 1.513 (4) | C15—H12 | 0.90 (3) |
C7—C8 | 1.384 (4) | C16—H13 | 0.92 (3) |
| | | |
O1···C14iii | 3.597 (3) | O5···C8vii | 3.526 (3) |
O2···C2iv | 3.340 (3) | C1···C13iii | 3.578 (4) |
O2···C3iv | 3.534 (3) | C2···C13iii | 3.494 (4) |
O3···O5v | 2.748 (3) | C2···C14iii | 3.596 (4) |
O3···C9vi | 3.298 (4) | C3···C15viii | 3.507 (4) |
O3···C10vi | 3.471 (4) | C4···C15viii | 3.292 (4) |
O3···C3iv | 3.500 (3) | C4···C16viii | 3.555 (4) |
O5···C7iii | 3.137 (3) | C5···C15viii | 3.522 (4) |
O5···C7vii | 3.137 (3) | C10···C14ix | 3.572 (4) |
O5···C8iii | 3.526 (3) | C11···C14ix | 3.476 (4) |
| | | |
O1i—Mn1—O2 | 90.95 (8) | O3—C6—C5 | 121.8 (2) |
O1i—Mn1—O4 | 96.18 (8) | N2—C7—C8 | 122.5 (3) |
O1i—Mn1—N1 | 93.10 (7) | C7—C8—C9 | 119.2 (3) |
O1i—Mn1—N2 | 90.41 (7) | C8—C9—C10 | 118.6 (3) |
O1i—Mn1—N3 | 173.97 (8) | C9—C10—C11 | 119.3 (3) |
O2—Mn1—O4 | 172.80 (6) | N2—C11—C10 | 122.4 (3) |
O2—Mn1—N1 | 80.98 (8) | N3—C12—C13 | 122.2 (3) |
O2—Mn1—N2 | 89.37 (8) | C12—C13—C14 | 120.4 (3) |
O2—Mn1—N3 | 84.24 (8) | C13—C14—C15 | 117.9 (3) |
O4—Mn1—N1 | 97.59 (7) | C14—C15—C16 | 118.8 (3) |
O4—Mn1—N2 | 91.55 (8) | N3—C16—C15 | 123.3 (3) |
O4—Mn1—N3 | 88.71 (8) | H14—O5—H14ii | 102 (2) |
N1—Mn1—N2 | 169.78 (9) | C1—C2—H1 | 116 (1) |
N1—Mn1—N3 | 89.75 (7) | C3—C2—H1 | 123 (1) |
N2—Mn1—N3 | 85.91 (7) | C2—C3—H2 | 122 (1) |
Mn1i—O1—C1 | 132.1 (2) | C4—C3—H2 | 116 (1) |
Mn1—O2—C6 | 117.3 (2) | C3—C4—H3 | 121 (1) |
Mn1—O4—Mn1i | 125.0 (1) | C5—C4—H3 | 120 (1) |
Mn1—N1—C1 | 129.4 (2) | N2—C7—H4 | 118 (1) |
Mn1—N1—C5 | 110.3 (2) | C8—C7—H4 | 119 (1) |
C1—N1—C5 | 120.2 (2) | C7—C8—H5 | 116 (1) |
Mn1—N2—C7 | 118.8 (2) | C9—C8—H5 | 124 (1) |
Mn1—N2—C11 | 123.1 (2) | C8—C9—H6 | 121 (1) |
C7—N2—C11 | 118.0 (2) | C10—C9—H6 | 119 (1) |
Mn1—N3—C12 | 119.4 (2) | C9—C10—H7 | 121 (1) |
Mn1—N3—C16 | 123.1 (2) | C11—C10—H7 | 119 (1) |
C12—N3—C16 | 117.4 (2) | N2—C11—H8 | 116 (1) |
O1—C1—N1 | 122.0 (2) | C10—C11—H8 | 121 (1) |
O1—C1—C2 | 119.9 (2) | N3—C12—H9 | 113 (1) |
N1—C1—C2 | 118.1 (2) | C13—C12—H9 | 124 (1) |
C1—C2—C3 | 120.7 (2) | C12—C13—H10 | 118 (1) |
C2—C3—C4 | 120.3 (2) | C14—C13—H10 | 121 (1) |
C3—C4—C5 | 117.5 (3) | C13—C14—H11 | 123 (1) |
N1—C5—C4 | 123.1 (2) | C15—C14—H11 | 118 (1) |
N1—C5—C6 | 114.3 (2) | C14—C15—H12 | 120 (1) |
C4—C5—C6 | 122.6 (2) | C16—C15—H12 | 120 (1) |
O2—C6—O3 | 123.3 (2) | N3—C16—H13 | 114 (1) |
O2—C6—C5 | 114.9 (2) | C15—C16—H13 | 122 (1) |
Symmetry codes: (i) −x+1, y, −z+1/2; (ii) −x+2, y, −z+3/2; (iii) −x+3/2, −y+1/2, −z+1; (iv) x, −y, z−1/2; (v) −x+2, −y, −z+1; (vi) −x+3/2, −y+1/2, −z; (vii) x+1/2, −y+1/2, z+1/2; (viii) −x+3/2, y−1/2, −z+1/2; (ix) x−1/2, −y+1/2, z−1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O5—H14···O3v | 0.87 (2) | 1.88 (2) | 2.748 (3) | 178 (1) |
C2—H1···O2x | 0.96 (3) | 2.63 (2) | 3.340 (3) | 131 (2) |
C7—H4···O5iii | 0.92 (3) | 2.38 (2) | 3.137 (3) | 140 (2) |
Symmetry codes: (iii) −x+3/2, −y+1/2, −z+1; (v) −x+2, −y, −z+1; (x) x, −y, z+1/2. |
Experimental details
Crystal data |
Chemical formula | [Mn2O(C6H3NO3)2(C5H5N)4]·H2O |
Mr | 734.48 |
Crystal system, space group | Monoclinic, C2/c |
Temperature (K) | 150 |
a, b, c (Å) | 13.606 (8), 16.379 (9), 14.289 (9) |
β (°) | 104.118 (7) |
V (Å3) | 3088 (3) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.88 |
Crystal size (mm) | 0.20 × 0.15 × 0.15 |
|
Data collection |
Diffractometer | Rigaku/MSC Mercury CCD diffractometer |
Absorption correction | Multi-scan (Jacobson, 1998) |
Tmin, Tmax | 0.764, 0.876 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 11903, 3512, 3144 |
Rint | 0.034 |
(sin θ/λ)max (Å−1) | 0.649 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.050, 0.109, 1.12 |
No. of reflections | 3144 |
No. of parameters | 260 |
No. of restraints | ? |
H-atom treatment | Only H-atom coordinates refined |
Δρmax, Δρmin (e Å−3) | 0.40, −0.46 |
Selected geometric parameters (Å, º) topMn1—Mn1i | 3.172 (1) | Mn1—N1 | 2.094 (2) |
Mn1—O1i | 2.083 (2) | Mn1—N2 | 2.169 (2) |
Mn1—O2 | 1.939 (2) | Mn1—N3 | 2.325 (2) |
Mn1—O4 | 1.789 (1) | | |
| | | |
O1i—Mn1—O2 | 90.95 (8) | O2—Mn1—N3 | 84.24 (8) |
O1i—Mn1—O4 | 96.18 (8) | O4—Mn1—N1 | 97.59 (7) |
O1i—Mn1—N1 | 93.10 (7) | O4—Mn1—N2 | 91.55 (8) |
O1i—Mn1—N2 | 90.41 (7) | O4—Mn1—N3 | 88.71 (8) |
O1i—Mn1—N3 | 173.97 (8) | N1—Mn1—N2 | 169.78 (9) |
O2—Mn1—O4 | 172.80 (6) | N1—Mn1—N3 | 89.75 (7) |
O2—Mn1—N1 | 80.98 (8) | N2—Mn1—N3 | 85.91 (7) |
O2—Mn1—N2 | 89.37 (8) | Mn1—O4—Mn1i | 125.0 (1) |
Symmetry code: (i) −x+1, y, −z+1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O5—H14···O3ii | 0.87 (2) | 1.88 (2) | 2.748 (3) | 178 (1) |
C2—H1···O2iii | 0.96 (3) | 2.63 (2) | 3.340 (3) | 131 (2) |
C7—H4···O5iv | 0.92 (3) | 2.38 (2) | 3.137 (3) | 140 (2) |
Symmetry codes: (ii) −x+2, −y, −z+1; (iii) x, −y, z+1/2; (iv) −x+3/2, −y+1/2, −z+1. |
The discovery of the role of manganese at the active sites in various enzymatic systems has given considerable impetus to research in the field of polynuclear complexes of manganese. The manganese catalase in Lactobacillus platarum has been shown to contain a dimanganese unit with [MnIII2(µ-oxo)(µ-carboxylato)2] cores (Fronko et al., 1988). Several Mn complexes containing the [Mn2(µ-O)]4+ core have been reported so far (Sheats et al., 1987; Wieghardt et al., 1988; Wu et al., 1990; Hotzelmann et al., 1992; Vincent et al., 1993; Gultneh et al., 1995; Canada-Vilalta et al., 2004). The two Mn ions in those complexes are all bridged by µ-oxo and di-µ-carboxylate ligands, and complete six-coordination around each Mn ion with ligands such as water, CH3CN and bipyridine. We report here the crystal structure of the title compound, [Mn2(µ-O)(hpc)2(py)4]·H2O, (I), containing a [MnIII2(µ-O)]4+ core bridged by a 6-hydroxypicolinate ion (hpc2−). This complex was obtained during the course of our attempt to synthesize new multinuclear manganese complexes using 2,6-pyridinedicarboxylic acid (pdcH2) and [Mn12O12(CH3COO)16(H2O)4] (abbreviated to Mn12-ac) in pyridine (Equation 1). In this reaction, the pdcH2 ligand could not replace the acetate ions of Mn12-ac but was oxidized to hpc2− (see Equation 2). A possible mechanism may be oxidation of pdcH2 followed by removal of carbon dioxide.
Complex (I) consists of two hpc2− ions, four pyridine rings and two MnIII ions bridged by a µ-oxo ion (Fig. 1 and Table 1). The Mn ion is coordinated by two hpc2− ions in bridging and chelating fashions, so that the molecule has a twofold axis perpendicular to the line connecting the two MnIII ions and passing through the µ-oxo ion. The amidate group (N1/C1/O1) of an hpc2− ion bridges two MnIII ions, while the carboxypyridine group (N1/C5/C6/O2) chelates to an MnIII ion to form a five-membered ring. Coordination of two pyridines completes a distorted octahedral six-coordination around the Mn ion.
The Mn ion exhibits a marked Jahn–Teller (J–T) distortion, as expected for a high-spin d4 MnIII ion (Cotton et al., 1999). The Mn1—O2 and Mn1—O4 bond distances [1.939 (2) and 1.789 (1) Å, respectively] are the shortest among the six Mn—N or Mn—O bonds, and the other four are all longer than 2.00 Å, indicating a compression type of J–T distortion. Among nine complexes with similar [Mn2(µ-O)]4+ core structure, three show compressed J–T distortion; two of them (Wieghardt et al., 1985; Sheats et al., 1987) have tridentate capping ligands, such as Me3TACN (Me3TACN=N,N',N''-trimethyl-1,4,7-triazacyclononane) or HB(pz)3 [HB(pz)3 = hydrotris(1-pyrazolyl)borate], and the other example (Vincent et al., 1993) has a strong coordination with an N3− ligand. In (I), the effect of the tridentate hpc2− ion together with the strong coordination of the µ-oxo ligand probably induces a compressed J–T distortion. The Mn1—N1 (hpc2−) distance [2.094 (2) Å] is shorter than the Mn1—N2/N3 (py) bonds [2.169 (2) and 2.325 (2) Å], which fact is also attributable to the effect of the tridentate nature of hpc2−. The Mn1···Mn1i [symmetry code: (i) 1 − x, y, 1/2 − z] distance is 3.172 (1) Å, which is longer than those reported so far [3.14–3.16 Å] for a similar core structure of [Mn2(µ-O)]4+. This difference is due to the larger Mn—O—Mni angle of 125.0 (1)°.
The molecular packing is shown in Fig. 2. Water atom O5 lies on a twofold axis. Each complex is connected to neighboring ones through π–π interactions and hydrogen bonds (Table 2) to assemble a three dimensional structure. The shortest C···C distance between pyridine and hpc2− of neighboring complexes is 3.292 (4) Å for C4···C15(3/2 − x, y − 1/2, 1/2 − z), indicating a strong π–π interaction. The dihedral angle between these two planes is 17.28 (10)°. The absence of any counter-ions in (I) enables such rich intermolecular interactions.