Bis([mu]-6-hydroxy­picolinato)-[mu]-oxo-bis­[di­pyridine­manganese(III)] monohydrate

The title compound, [Mn₂([mu]-O)(C₆H₃NO₃)₂(C₅H₅N)₄]·H₂O, was isolated from the reaction of 2,6-pyridine­di­carboxylic acid with [Mn₁₂O₁₂(CH₃COO)₁₆(H₂O)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 [pi]-[pi] interactions.

S1. Comment

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 [Mn^III₂(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 [Mn^III₂(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 Mn^III 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 Mn^III ions and passing through the µ-oxo ion. The amidate group (N1/C1/O1) of an hpc²⁻ ion bridges two Mn^III ions, while the carboxypyridine group (N1/C5/C6/O2) chelates to an Mn^III 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 Mn^III 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.

S2. Experimental

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).

S3. Refinement

H atoms were located from difference density maps and their coordinates were refined, with U_iso(H) = 0.0146 Ų. The C—H and O—H bond lengths are 0.80 (3)–1.00 (3) Å and 0.87 (2) Å, respectively.

Computing details

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.

Figures

	Fig. 1. The molecular structure of (I), with the atom-numbering scheme, showing 50% probability displacement ellipsoids. The atom labelled with an asterisk(*) is at the symmetry position (1 − x, y, 1/2 − z).
	Fig. 2. The molecular packing, showing intermolecular π–π interactions (– – –) and hydrogen bonds (···..). [Symmetry codes: (i) x, −y, z + 1/2; (ii) x + 1/2, 1/2 − y, z + 1/2; (iii) 2 − x, −y, 1 − z.]

(I)

Crystal data

[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) Å^3	0.20 × 0.15 × 0.15 mm
Z = 4

Data collection

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

Refinement on F^2	Only H-atom coordinates refined
R[F^2 > 2σ(F^2)] = 0.050	w = 1/[σ^2(Fo^2) + (0.0468P)^2 + 5.1887P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 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

Special details

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 (Ų)

	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 (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
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)

Mn1—Mn1^i	3.172 (1)	C8—C9	1.377 (4)
Mn1—O1^i	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—H14^ii	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···C14^iii	3.597 (3)	O5···C8^vii	3.526 (3)
O2···C2^iv	3.340 (3)	C1···C13^iii	3.578 (4)
O2···C3^iv	3.534 (3)	C2···C13^iii	3.494 (4)
O3···O5^v	2.748 (3)	C2···C14^iii	3.596 (4)
O3···C9^vi	3.298 (4)	C3···C15^viii	3.507 (4)
O3···C10^vi	3.471 (4)	C4···C15^viii	3.292 (4)
O3···C3^iv	3.500 (3)	C4···C16^viii	3.555 (4)
O5···C7^iii	3.137 (3)	C5···C15^viii	3.522 (4)
O5···C7^vii	3.137 (3)	C10···C14^ix	3.572 (4)
O5···C8^iii	3.526 (3)	C11···C14^ix	3.476 (4)
O1^i—Mn1—O2	90.95 (8)	O3—C6—C5	121.8 (2)
O1^i—Mn1—O4	96.18 (8)	N2—C7—C8	122.5 (3)
O1^i—Mn1—N1	93.10 (7)	C7—C8—C9	119.2 (3)
O1^i—Mn1—N2	90.41 (7)	C8—C9—C10	118.6 (3)
O1^i—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—H14^ii	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)
Mn1^i—O1—C1	132.1 (2)	C4—C3—H2	116 (1)
Mn1—O2—C6	117.3 (2)	C3—C4—H3	121 (1)
Mn1—O4—Mn1^i	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)

D—H···A	D—H	H···A	D···A	D—H···A
O5—H14···O3^v	0.87 (2)	1.88 (2)	2.748 (3)	178 (1)
C2—H1···O2^x	0.96 (3)	2.63 (2)	3.340 (3)	131 (2)
C7—H4···O5^iii	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.