- Email: [email protected]
Synthesis and structural characterization of five-, six-, and seven-coordinate mononuclear manganese(II) complexes with N-tridentate ligands
Inorganica Chimica Acta 357 (2004) 3430–3436 www.elsevier.com/locate/ica
Synthesis and structural characterization of five-, six-, and seven-coordinate mononuclear manganese(II) complexes with N-tridentate ligands Carole Baffert a, Isabel Romero a,b,*, Jacques Pecaut c, Antoni Llobet b, Alain Deronzier a, Marie-No€elle Collomb a,* a
c
Laboratoire d’Electrochimie Organique et de Photochimie Redox, UMR CNRS 5630, Institut de Chimie Moleculaire de Grenoble, FR CNRS 2607, Universite Joseph Fourier, Grenoble 1, BP 53, 38041 Grenoble Cedex 9, France b Departament de Quimica, Universitat de Girona, Campus de Montilivi, E-17071 Girona, Spain DRFMC-Service de Chimie Inorganique et Biologique, Laboratoire coordination et Chiralite, CEA-Grenoble, 38054 Grenoble Cedex, France Received 19 April 2004; accepted 8 May 2004 Available online 17 June 2004
Abstract A series of four mononuclear manganese (II) complexes with the N-tridentate neutral ligands 2,20 :6,200 -terpyridine (terpy) and N,N-bis(2-pyridylmethyl)ethylamine (bpea) have been synthesized and crystallographically characterized. The complexes have fiveto seven-coordinate manganese(II) ions depending on the additional ligands used. The [Mn(bpea)(Br)2 ] complex (1) has a fivecoordinated manganese atom with a bipyramidal trigonal geometry, while [Mn(terpy)2 ](I)2 (2) is hexa-coordinated with a distorted octahedral geometry. Otherwise, the reactions of Mn(NO3 )2 4H2 O with terpy or bpea afforded novel seven-coordinate complexes [Mn(terpy)(NO3 )2 (H2 O)] (3) and [Mn(bpea)(NO3 )2 ] (4), respectively. 3 has a coordination polyhedron best described as a distorted pentagonal bipyramid geometry with one nitrate acting as a bidentate chelating ligand and the other nitrate as a monodentate one. 4 possesses a highly distorted polyhedron geometry with two bidentate chelating nitrate ligands. These complexes represent unusual examples of structurally characterized complexes with a coordination number seven for the Mn(II) ion and join a small family of nitrate complexes. Ó 2004 Elsevier B.V. All rights reserved. Keywords: Manganese (II) complexes; Five, six, seven-coordinate complexes; N-tridentate ligands; Nitrate complexes, Crystal structures
1. Introduction Manganese complexes have been found as active sites in a number of metalloenzymes [1,2] including the oxygen-evolving complex (OEC) of photosystem II (PSII), the catalase (Cat) and the superoxide dismutase (SOD) [1–7]. These enzymes are of great biological importance: the OEC oxidizes water to molecular oxygen, Cat catalyzes hydrogen peroxide disproportionation while the SOD are able to dismutate the superoxide radical. Recent *
Corresponding authors. Tel.: +33-4-76-51-44-18; fax: +33-4-76-5142-67 (M.-N. Collomb), Tel.: +34-972-418262; fax: +34-972-418150 (I. Romero). E-mail addresses: [email protected] (I. Romero), [email protected] (M.-N. Collomb). 0020-1693/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2004.05.023
crystal structure determinations of these enzymes have shown that the active site of PSII contains a tetranuclear manganese center [8,9], a dinuclear manganese one is present in the Mn Cat [10,11], whereas the active site of Mn SOD is a penta-coordinated mononuclear manganese complex with a trigonal bipyramidal geometry [12–14]. While the design of polynuclear manganese complexes of potentially biomimetic systems for the active center of PS II or Mn Cat has attracted many groups [1,3,15–18], the synthesis of relatively simple mononuclear derivatives, with the exception of complexes with macrocyclic ligands [1], has received much less attention [19–25]. In this context, as part as our synthetic exploration of mononuclear Mn(III) [26,27] and binuclear Mn2 (II,II) [28,29], (III,III) and (III,IV) complexes [30,31] with the N-tridentate ligands 2,20 :6,200 -terpyridine (terpy) and
C. Baffert et al. / Inorganica Chimica Acta 357 (2004) 3430–3436
N,N-bis(2-pyridylmethyl)ethylamine (bpea), we described here the synthesis and the structural characterization of a series of five-, six- and seven-coordinated mononuclear Mn(II) complexes with these ligands. Although various coordination geometries are accessible to high-spin d5 metal ions due to the absence of ligand field stabilization energy, the most common coordination number of structurally characterized Mn(II) complexes is six [32], coordination numbers of five [22,33–42], seven [42–59] or eight [58–64] remaining still rare. Ligand steric and electronic effects appear to play a major role in defining these geometries. This is evidenced in our series of mononuclear complexes described in this article. Indeed, the new penta-coordinated [Mn(bpea)(Br)2 ] (1) presenting a trigonal bipyramidal geometry was isolated with bpea and Br anions, while þ the hexa-coordinated [MnII;II 2 (l-O2 CCH3 )2 (bpea)2 ] and II;II [Mn2 (l-Cl)2 (bpea)2 (Cl)2 ] dimeric complexes have been previously obtained in the presence of CH3 CO 2 or Cl anions, respectively [28,29]. An hexa-coordinated bis terpy complex [Mn(terpy)2 ](I)2 (2) with distorted octahedral geometry has been also isolated, while the analogous [Mn(bpea)2 ](PF6 )2 has been previously characterized [28]. Otherwise, the mono or bidentate coordination mode of NO 3 anions leads to the formation of the new heptacoordinated complexes [Mn(terpy)(NO3 )2 (H2 O)] (3) and [Mn(bpea)(NO3 )2 ] (4) with a distorted pentagonal bipyramidal geometry and a distorted polyhedral geometry, respectively. These complexes join the small family of mononuclear Mn(II) complexes with nitrato ligand [55–63,65].
2. Experimental 2.1. Materials All manipulations were carried out under ambient conditions. Solvents used in this work were of analytical grade. All chemicals were purchased from Aldrich or Fluka and used without further purification. 2.2. Ligand and complexes The ligand 2,20 :6’,200 -terpyridine (terpy) was purchased from Aldrich or Fluka. The ligand N,Nbis(2-pyridylmethyl)ethylamine (bpea) was synthesized according to a method described previously [66]. 2.2.1. [MnII (bpea)(Br)2 ] (1) Method A. To an aqueous solution of MnBr2 (0.094 g, 0.44 mmol) (2 ml), an ethanol solution (2 ml) of bpea ligand (0.100 g, 0.44 mmol) was added under stirring. The resulting solution was stirred for 1 h, then filtered and left to evaporate at room temperature. After several
3431
days, the white powder formed was redissolved in acetonitrile and the resulting solution was left evaporated at room temperature. After one day, air-stable, colorless crystals of 1 suitable for X-ray diffraction analysis were obtained. Yield: 0.0836 g (43%). Elemental Anal. Calc. for [MnII (bpea)(Br)2 ] (C14 H17 Br2 MnN3 (442.07)): C, 38.2; H, 3.87; N, 9.48. Found: C, 38.21; H, 3.94; N, 9.23%. FAB-MS (positive mode), m=z: [Mn(bpea)Br]þ , 363. IR in cm1 (KBr): 2902 (m), 1604 (s), 1572 (m), 1483 (m), 1444 (m), 1289 (m), 1047 (s), 1018 (s), 801 (m), 761 (s), 641 (m), 413 (m). Method B. A solution of the bpea ligand (0.100 g, 0.44 mmol) and MnBr2 (0.094 g, 0.44 mmol) in acetonitrile (12 ml) was stirred for 15 min at room temperature. After 10 min, a white precipitate was formed, that was collected by filtration, washed thoroughly with diethyl ether and finally dried in vacuum. Colorless crystals of 1 were obtained in acetonitrile as described in Method A. Yield: 0.097 g (50%). 2.2.2. [MnII (terpy)2 ](I)2 (2) To a methanol solution (5 ml) of MnI2 (0.125 g, 0.4 mmol), a methanol solution (15 ml) of terpy ligand (0.230 g, 0.987 mmol) was added under stirring. After few minutes, a yellow precipitate was formed, that was collected by filtration. The yellow powder obtained was redissolved in methanol and the resulting solution was left evaporated at room temperature. After one day, air-stable, yellow crystals of 2 3H2 O suitable for X-ray diffraction analysis were obtained. Elemental Anal. Calc. for [MnII (terpy)2 ](I)2 4H2 O (C30 H30 I2 MnN6 O4 (847.36): C, 42.52; H, 3.57; N, 9.92. Found: C, 42.26; H, 2.96; N, 9.83%. IR in cm1 (KBr): 2923 (m), 1593 (s), 1574 (m), 1557 (m), 1475 (s), 1450 (s), 1434 (s), 1316 (m), 1247 (m), 1189 (m), 1158 (m), 1013 (s), 766 (s). 2.2.3. [MnII (terpy)(NO3 )2 (H2 O)] (3) To an aqueous solution (1 ml) of MnII (NO3 )2 4H2 O (0.1121 g, 0.446 mmol), an ethanol solution (4 ml) of terpy ligand (0.060 g, 0.257 mmol) was added. The yellow solution was stirred for 30 min, then filtered, and left to evaporate at room temperature. After several days, yellow crystals of 3 suitable for X-ray diffraction analysis were obtained. Yield: 82 mg (74 %). Elemental Anal. Calc. for [MnII (terpy)(NO3 )2 (H2 O)] (C15 H13 MnN5 O7 (430.24)): C, 41.88; H, 3.05; N, 16.28. Found: C, 41.88; H, 3.12; N, 16.10%. IR in cm1 (KBr): 3367 (m), 1667 (m), 1595 (m), 1574 (m), 1480 (m), 1452 (s), 1439 (s), 1384 (s), 1351 (s), 1314 (s), 1190 (m), 1171 (m), 1043 (m), 1016 (m), 1009 (m), 819 (m), 774 (s), 736 (m), 650 (m), 638 (m), 511 (m), 404 (w). 2.2.4. [MnII (bpea)(NO3 )2 ] (4) To an aqueous solution (2 ml) of MnII (NO3 )2 4H2 O (0.197 g, 0.785 mmol), an ethanol solution (2 ml) of bpea ligand (0.113 g, 0.5 mmol) was added under stirring. The
3432
C. Baffert et al. / Inorganica Chimica Acta 357 (2004) 3430–3436
resulting yellow solution was stirred for 30 min, then filtered and left to evaporate at room temperature. After few days, the white powder formed was redissolved in acetonitrile and addition of diethyl ether yielded a microcrystalline product. Colorless crystals of 4 suitable for X-ray diffraction analysis were obtained by slow diffusion of diethyl ether into an acetonitrile solution of this complex. Yield: 0.070 g (35%). Elemental Anal. Calc. for [MnII (bpea)(NO3 )2 ] (C14 H17 MnN5 O6 (406.27)): C, 41.39; H, 4.22; N, 17.24. Found: C, 41.23; H, 4.22; N, 17.00%. FAB-MS (positive mode), m=z: [Mn(bpea)(NO3 )]þ , 344. IR in cm1 (KBr): 2923 (m), 2853 (w), 1606 (m), 1470 (s), 1442 (m), 1384 (m), 1307 (m), 1277 (m), 1044 (w), 1022 (m), 818 (m), 769 (m). 2.3. Spectroscopies Fast atom bombardment mass spectra (FAB) were obtained on an AEI Kratos MS 50 spectrometer fitted with an Ion Tech Ltd. gun (Centre de Recherche sur les Macromolecules Vegetales, Grenoble, France). Infrared spectra were recorded on a Perkin–Elmer Spectrum GX FTIR spectrometer. 2.4. X-ray structure analysis The data sets for the single-crystal X-ray studies were collected with Mo Ka radiation on a Bruker SMART
diffractometer. All calculations were performed on a Silicon Graphics system using the S H E L X T L program [67]. The specific data for the crystals and the refinements are collected in Tables 1 and 5. The structures were solved by direct methods and refined by full-matrix least-squares fits of F 2 .
3. Results and discussion 3.1. Five-coordinate manganese (II) complex: [Mn(bpea)(Br)2 ] Complex 1 crystallizes in the triclinic space group P 1 with two molecules per unit cell. Fig. 1 shows the ORTEP diagram of the complex and Tables 1 and 2 summarize crystal data and selected bond distances and angles, respectively. The geometry around the Mn(II) ion center is a distorted trigonal bipyramid, where the tridentate ligand adopts the uncommon meridional mode of coordination around the Mn(II). This coordination mode has only been observed in [MnIII (bpea)(X)3 ) (X ¼ N3 ; 2þ F) and [MnIV (X ¼ Cl; F) [27,68]. The 2 O2 (bpea)2 (X)2 ] equatorial plane is occupied by the two unidentate ligands, Br(1) and Br(2), and the central aliphatic nitrogen atom, N(1), of the ligand bpea. The distal aromatic
Table 1 Crystal data and details of the refinement of the crystal structures of [Mn(bpea)(Br)2 ] (1) and [Mn(terpy)2 ](I)2 3H2 O (2.3H2 O) Compound Chemical formula Formula weight Temperature (K) k (A) Crystal system Crystal size (mm mm mm) Space group a (A) b (A) c (A) a (°) b (°) c (°) 3 ) V (A Z l (mm1 ) Number of reflections collected Number of independent reflections [Rint ] Goodness-of-fit on F 2 Final R indices [I > 2rðIÞ] R indices (all data)
1 C14 H17 Br2 MnN3 442.07 298(2) 0.71073 triclinic 0.15 0.2 0.4
2.3H2 O C30 H28 I2 MnN6 O3 829.32 223(2) 0.71073 monoclinic 0.4 0.4 0.4
P 1 8.0447(10) 8.5828(11) 13.709(2) 78.454(3) 73.560(2) 66.716(2) 829.71(19) 2 5.604 5374
P 2ð1Þ=n 8.7037(12) 41.118(6) 8.9139(13) 90 92.334(2) 90 3187.5(8) 4 2.392 9343
3803 [0.0317]
6422 [0.0297]
0.971 R1 ¼ 0:0523 wR2 ¼ 0:1324 R1 ¼ 0:0687 wR2 ¼ 0:1409
0.963 R1 ¼ 0:0503 wR2 ¼ 0:1188 R1 ¼ 0:0871 wR2 ¼ 0:1303
C14 C3
C13
C1
C4
C7
C2
C9 C8
N1
C10 N2
N3 Mn
C5
Standard deviations are given in parentheses.
C1 1
C6 Br 2
Br 1
C12
Fig. 1. An ORTEP view of the molecular structure of 1.
Table 2 and bond angles (°) for 1 Selected bond lengths (A) Mn–N(1) Mn–N(2) Mn–N(3) Br(2)–Mn–Br(1) N(3)–Mn–N(2) N(3)–Mn–N(1) N(2)–Mn–N(1) N(3)–Mn–Br(1)
2.325(2) 2.236(2) 2.230(3) 113.69(2) 145.80(9) 72.89(8) 72.91(9) 98.54(6)
Mn–Br(1) Mn–Br(2) N(2)–Mn–Br(1) N(1)–Mn–Br(1) N(3)–Mn–Br(2) N(2)–Mn–Br(2) N(1)–Mn–Br(2)
2.5016(5) 2.5085(5) 97.69(6) 119.65(5) 101.35(6) 99.33(6) 126.64(5)
C. Baffert et al. / Inorganica Chimica Acta 357 (2004) 3430–3436
nitrogen atoms, N(2) and N(3), are in the axial positions. Compared to the idealized trigonal bipyramid, the angles between the Mn atom and the ligands show significant distortions. The spatially constrained nature of the tridentate meridional bpea ligand produces geometrical distortions manifested in the N(2)–Mn–N(3) angle equal to 145.80(9)° compared to 180°, the theoretical value (Table 2). The different electronic nature of the aliphatic and aromatic N-coordinating atoms of bpea induces also geometrical distortions from the ideal trigonal bipyramid, which are mainly manifested by significantly different Mn–N bond lengths. The largest corresponds to the Mn–N aliphatic bond (Mn–N(1): while the two shortest correspond to the 2.325(2) A), and Mn–N(3): aromatic ones (Mn–N(2): 2.236(2) A 2.230(3) A). The same tendency has been observed in the other complexes with bpea ligand, acting in a facial or meridional coordination mode [27–29,66,68]. The equatorial plane shows also significant distortions. The angles Br(1)–Mn–Br(2) (113.69(2)°) and N(1)–Mn–Br(1) (119.65(5)°) are smaller than the theorical value of 120° in a trigonal bipyramid, while the angle N(1)–Mn–Br(2) (126.64(5)°) is slightly higher. The bond angles between the axial and equatorial positions are obviously also different to 90° and the largest ones are between the axial positions and the Br atoms (N(2)–Mn–Br(2): 99.33(6); N(2)–Mn–Br(1): 97.69(6); N(3)–Mn–Br(1): 98.54(6) and N(3)–Mn–Br(2):101.35(6)°). The Br(1)–Mn–Br(2) angle of 113.69(2)° and the Mn– are consistent Br distances of 2.5016(5) and 2.5085(5) A with the values observed in other penta-coordinated mononuclear dibromo manganese(II) complexes [33,34]. 3.2. Six-coordinate Mn(II) complex: [MnII (terpy)2 ](I)2 3H2 O (2.3H2 O) Complex 2 crystallizes in the monoclinic space group P 2ð1Þ=n with four molecules per unit cell. Fig. 2 shows the ORTEP diagram of this complex. The structure consists of discrete [Mn(terpy)2þ 2 cations together with two iodide anions and three water molecules uncomplexed. The Mn atom is coordinated by six nitrogen atoms from two meridional terpy ligands in a distorted octahedral fashion. The distortion is more important than in the previously crystallized [Mn(terpy)2 ](ClO4 )2 [69] and [Mn(terpy)2 ](I3 )2 [70] complexes. Table 1 contains crystallographic data and Table 3 contains selected bond distances and angles. The coordination geometry around the Mn(II) ion is highly distorted from octahedral due to the spatially constrained nature of the tridentate terpy ligand. Thus, the N(1)–Mn–N(3) and N(21)–Mn–N(23) angles (144.47(10)° and 144.67(10)°, respectively) are about 35° below 180°. Similar distortions have been observed in the bis-terpy [69,70] and mono-terpy [Mn(terpy)(dmb)2 ]
3433 C34 C33 C35 C32
C13 C14
C12 C9 C8
C31
N3
C10
C15
C11 N2
C6
N23
C30
C29
Mn N1
C7
N22
C1
C5
C26
C2
C4
C28 N21
C3
C25
C27
C21 C24 C22 C23
Fig. 2. An ORTEP view of the molecular structure of the cation of complex 2 3H2 O.
Table 3 and bond angles (°) for 2.3H2 O Selected bond lengths (A) Mn–N(22) Mn–N(2) Mn–N(23) N(22)–Mn–N(2) N(22)–Mn–N(23) N(2)–Mn–N(23) N(22)–Mn–N(1) N(2)–Mn–N(1) N(23)–Mn–N(1) N(22)–Mn–N(3) N(2)–Mn–N(3)
2.201(3) 2.203(3) 2.236(3) 172.32(11) 72.51(10) 144.69(10) 110.12(10) 72.40(11) 97.62(10) 105.39(11) 72.23(11)
Mn–N(1) Mn–N(3) Mn–N(21) N(23)–Mn–N(3) N(1)–Mn–N(3) N(22)–Mn–N(21) N(2)–Mn–N(21) N(23)–Mn–N(21) N(1)–Mn–N(21) N(3)–Mn–N(21)
2.246(3) 2.253(3) 2.260(3) 93.98(10) 144.47(10) 72.16(10) 100.60(10) 144.67(10) 94.27(10) 95.37(10)
[40] complexes. The N(2)–Mn–N(22) interligand angle of 172.32(11)° is below the theoretical value of 180°. In addition, as expected, cis N–Mn–N interligand angles comprised between 93.98° and 114.69° are above 90°. Because of the large size of the Mn(II) ion, these distortions are greater for the manganese terpy complexes than for any of the other terpy first-row transition metal complexes and the Mn–Nterpy bonds longer [40]. Moreover, the Mn–Nterpy distances in 2 are normal with shorter Mn–Ncentral distances, (average 2.202(1) A) average). compared to Mn–Ndistal ones (2.249(10) A, This distortion, always observed in terpy complexes of the first-row transition metal complexes, is attributed to a more efficient overlap of the metal t2g orbitals with the p orbitals of the central pyridyl group compared to the distal pyridyl groups [71]. As a consequence, a tetragonal distortion of the coordination sphere along the N(2)–Mn–N(22) axis is observed.
3434
C. Baffert et al. / Inorganica Chimica Acta 357 (2004) 3430–3436
3.3. Seven-coordinate manganese(II) complexes Complexes 3 and 4 join a small family of seven-coordinate manganese (II) complex with nitrate ligands [55–57]. 3.3.1. [MnII (terpy)(H2 O)(NO3 )2 ] (3) The complex 3 crystallizes in the triclinic space group P 1 with two molecules per unit cell. Fig. 3 shows the ORTEP diagram of the complex and Table 4 summarizes crystal data and Table 6 selected bond distances and angles, respectively. The X-ray crystallography of 3 reveals a seven-coordinate Mn atom best described as a distorted pentagonal bipyramidal geometry, with three nitrogen atoms of the terpy ligand and two oxygen atoms of the bidentate chelating nitrate ligand (O(11) and O(12)) forming the equatorial plane. The axial positions are occupied by two oxygen atoms, one from the monodentate nitrate anion (O(21)) and the other one from the water ligand (O(1)) (O(1)–Mn–O(21), 161.80(6)°). The plane containing Mn, N(1), N(22), N(3), O(11), and from the plane, O(12) gives a mean deviation of 0.015 A with O(1) being 2.160 A above the plane and O(21) below the plane. Three of the five equabeing 2.163 A torial angles deviated significantly from the ideal value of the pentagonal bipyramidal geometry (72°), due to the restricted bite of the chelating nitrate group with an angle of 53.38(5)°, while the terpy ligand imposed two equatorial angles close to 72° (71.01(5)° and 71.78(5)°). The angles between the axial bonds and the equatorial ones are comprised between 76.18° and 103.73°, compared to the ideal value of 90°. This compound joins a small family of seven-coordinate manganese(II) complexes where the coordination polyhedron is a distorted pentagonal bipyramid [43,49,56], being the first one in which the organic ligand is the tridentate terpy. The Mn–N bond distances are similar to (ranging from 2.2422(14) to 2.3339(15) A) O1 C7
C8
C4
C3
C9
C5
N22 C6 C10
C2
C11
C12
N1
C1
Mn O11
N11
Compound Chemical formula Formula weight Temperature (K) k (A) Crystal system Crystal size (mm mm mm) Space group a (A) b (A) c (A) a (°) b (°) c (°) 3 ) V (A Z l (mm1 ) Number of reflections collected Number of independent reflections [Rint ] Goodness-of-fit on F 2 Final R indices [I > 2rðIÞ] R indices (all data)
3 C15 H13 MnN5 O7 430.24 223(2) 0.71073 triclinic 0.2 0.4 0.4
4 C14 H17 MnN5 O6 406.27 298(2) 0.71073 triclinic 0.15 0.2 0.45
P 1 7.6949(8) 9.8336(10) 12.3658(12) 71.911(2) 81.124(2) 72.990(2) 848.47(15) 2 0.831 5468
P 1 8.1999(8) 8.6596(9) 13.6658(14) 93.547(2) 92.628(2) 115.270(2) 871.50(15) 2 0.800 5701
3861 [0.0143]
4019 [0.0204]
1.036 R1 ¼ 0:0306 wR2 ¼ 0:0786 R1 ¼ 0:0418 wR2 ¼ 0:0842
0.905 R1 ¼ 0:0371 wR2 ¼ 0:0840 R1 ¼ 0:0699 wR2 ¼ 0:1034
Standard deviations are given in parentheses.
Table 5 and bond angles (°) for 3 Selected bond lengths (A) Mn–O(1) Mn–O(21) Mn–O(11) Mn–O(12) O(1)–Mn–O(21) O(1)–Mn–N(22) O(21)–Mn–N(22) O(1)–Mn–O(12) O(21)–Mn–O(12) N(22)–Mn–O(12) O(1)–Mn–N(3) O(21)–Mn–N(3) N(22)–Mn–N(3) O(12)–Mn–N(3) O(1)–Mn–N(1) O(21)–Mn–N(1) N(22)–Mn–N(1) O(12)–Mn–N(1)
2.1942(16) Mn–N(1) 2.2101(13) Mn–N(22) 2.4638(16) Mn–N(3) 2.3082(14) 161.80(6) 92.54(6) 101.17(5) 86.79(6) 86.38(5) 152.89(5) 91.85(6) 103.73(5) 71.78(5) 81.15(5) 88.29(6) 84.96(5) 71.01(5) 135.97(5)
N(3)–Mn–N(1) O(1)–Mn–O(11) O(21)–Mn–O(11) N(22)–Mn–O(11) O(12)–Mn–O(11) O(2)–Mn–O(5) N(3)–Mn–O(11) N(1)–Mn–O(11) O(13)–N(11)–O(11) O(13)–N(11)–O(12) O(11)–N(11)–O(12) O(23)–N(21)–O(22) O(23)–N(21)–O(21) O(22)–N(21)–O(21)
2.3339(15) 2.2422(14) 2.3111(15) 142.76(5) 86.21(6) 76.18(5) 153.66(5) 55.38(5) 123.87(7) 134.54(5) 82.65(5) 121.55(16) 120.43(16) 118.02(15) 121.83(17) 119.41(17) 118.68(15)
N3
O12
C15
C13 C14
O21
O13
Table 4 Crystal data and details of the refinement of the crystal structures of [Mn(terpy)(H2 O)(NO3 )2 ] (3) and [Mn(bpea)2 (NO3 )2 ] (4)
O22 N21 O23
Fig. 3. An ORTEP view of the molecular structure of complex 3.
those found in 2. The Mn–O bonds distances of the ; Mn– bidentate nitrate ligand (Mn–O(12): 2.3082(14) A are longer than the Mn–O bond O(11): 2.4638(16) A) distance in the monodentate nitrate ligand (Mn–O(21): The same tendency has been observed in 2.2101(13) A). manganese complexes with mono [65] and bidentate nitrate ligands [55–63]. The Mn–Oaqua bond length is shorter than the last Mn–O bonds and (2.1942(16) A)
C. Baffert et al. / Inorganica Chimica Acta 357 (2004) 3430–3436 Table 6 and °) Hydrogen bonds for 3 (A
Table 7 and bond angles (in °) for 4 Selected bond lengths (in A)
D–H. . .A
d(D–H)
d(H. . .A) d(D. . .A) <(DHA)
O(1)–H(2O). . .O(13)#1 O(1)–H(1O). . .O(22)#2
0.60(2) 0.89(4)
2.19(2) 1.93(4)
2.782(2) 2.778(2)
170(3) 158(3)
comparable to those of the Mn(II) complexes with aqua ligands [57,65]. The crystal structure is stabilized by hydrogen bonds involving the hydrogen atoms of the aquo ligand, the uncoordinated oxygen atom of the bidentate nitrate ligand, O(13), and one of the uncoordinated oxygen atom of the monodentate nitrate ligand, O(22), respectively. The hydrogen-bonding parameters are listed in Table 6. 3.3.2. [MnII (bpea)(NO3 )2 ] (4) The complex [MnII (bpea)(NO3 )2 ] crystallizes in the triclinic space group P 1 with two molecules per unit cell. Fig. 4 shows the ORTEP diagram of the complex and Tables 4 and 7 show crystal data and selected bond distances and angles, respectively. The structure indicates that the complex has a heptacoordinate metal center with a highly distorted polyhedral geometry. The coordination sphere of manganese consists of three nitrogen atoms of the bpea ligand and four oxygen atoms of two bidentate chelating nitrate ligands. This is the first example of complex having a tridentate ligand with two bidentate nitrate ligands. A feature of the structure is the coordination mode of the bpea ligand, which is close to a facial coordination mode, with an N(2)–Mn–N(3) angle of 112.04(8)°. However, this angle is higher compared to those ob-
Mn–O(1) Mn–O(2) Mn–O(4) Mn–O(5) N(2)–Mn–N(3) N(2)–Mn–O(4) N(3)–Mn–O(4) N(2)–Mn–O(2) N(3)–Mn–O(2) O(4)–Mn–O(2) N(2)–Mn–O(1) N(3)–Mn–O(1) O(4)–Mn–O(1) O(2)–Mn–O(1) N(2)–Mn–O(5) N(3)–Mn–O(5) O(4)–Mn–O(5) O(2)–Mn–O(5)
2.354(2) Mn–N(1) 2.301(2) Mn–N(2) 2.2578(19) Mn–N(3) 2.3605(19) 112.04(8) 161.40(8) 84.80(8) 97.28(8) 86.04(8) 91.54(8) 87.69(7) 138.64(7) 84.10(7) 54.64(7) 106.61(7) 126.83(7) 55.18(7) 123.87(7)
O(1)–Mn–O(5) N(2)–Mn–N(1) N(3)–Mn–N(1) O(4)–Mn–N(1) O(2)–Mn–N(1) O(1)–Mn–N(1) O(5)–Mn–N(1) O(3)–N(4)–O(1) O(3)–N(4)–O(2) O(1)–N(4)–O(2) O(6)–N(5)–O(5) O(6)–N(5)–O(4) O(5)–N(5)–O(4)
2.3691(19) 2.215(2) 2.219(2) 76.07(7) 73.30(7) 73.24(7) 105.86(7) 151.22(8) 148.02(7) 84.85(7) 121.6(3) 122.3(3) 116.1(2) 121.8(3) 121.7(2) 116.5(2)
served in the complexes [Mn(bpea)2 ]2þ , [MnII;II 2 (lþ Cl)2 (bpea)2 (Cl)2 ] and [MnII;II (l-O CCH ) (bpea) 2 3 2 2] 2 having the typical facial coordination mode (106.32(85)° (average), 97.78(5)°, 98.01(15)°, respectively) [28,29] but significantly smaller for a meridional coordination mode as in 1 (175.80(9)°). Otherwise, the three Mn–N bond distances of the bpea ligand are similar to those found in 1. The Mn–O bond distances of the two nitrate ligands and are comprised between 2.2578(19) and 2.3605(19) A the O–Mn–O bond angles are similar (64(7)° and 55.18(7)°).
4. Supplementary material
C4 C3
C5
C2 C1 C6
3435
N2 C14 O5
O1
N1
Crystallographic data for the structures included in this paper have been deposited with the Cambridge Crystallographic Data Center as supplementary publication nos. CCDC 233950-233953. Copies of the data can be obtained free of charge on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (Fax: +441223-336-033; E-mail: [email protected], www: http://www.ccdc.cam.ac.uk.
Mn N5 O6 N4 O3
C13
C7
References C8
O2
O4 N3
C9
C12 C10 C11 Fig. 4. An ORTEP view of the molecular structure of complex 4.
[1] D.C. Weatherburn, S. Mandal, S. Mukhopadhyay, S. Bhaduri, L.F. Lindoy, in: J.A. Cleverty, T.J. Meyer (Eds.), Comprehensive Coordination Chemistry II, vol. 4, Elsevier Pergamon, 2004, p. 1 (Chapter 41). [2] A. Sigel, H. Sigel, Manganese and its role in Biological Processes, Marcel Dekker, New York, 2000, p. 37. [3] A.J. Wu, J.E. Penner-Hahn, V.L. Pecoraro, Chem. Rev. 104 (2004) 903. [4] V.L. Pecoraro, Manganese Redox Enzymes, VCH, New York, 1992.
3436
C. Baffert et al. / Inorganica Chimica Acta 357 (2004) 3430–3436
[5] V.K. Yachandra, K. Sauer, M.P. Klein, Chem. Rev. 96 (1996) 2927. [6] K. Wieghardt, Angew. Chem., Int. Ed. Engl. 28 (1989) 1153. [7] G.C. Dismukes, Chem. Rev. 96 (1996) 2909. [8] A. Zouni, H.T. Witt, J. Kern, P. Fromme, N. Krauss, W. Saenger, P. Orth, Nature 409 (2001) 739. [9] N. Kamiya, J.-R. Shen, Proc. Natl. Acad. Sci. USA 100 (2003) 98. [10] S.V. Antonyuk, V.R. Melik-Adamyan, A.N. Popov, V.S. Lamzin, P.D. Hempstead, P.M. Harrison, P.J. Artymyuk, V.V. Barynin, Cryst. Rep. 45 (2000) 105. [11] V.V. Barynin, M.M. Whittaker, S.V. Antonyuk, V.S. Lamzin, P.V. Harrison, P.J. Artymyuk, V.J. Whittaker, Structure 9 (2001) 725. [12] J.W. Whittaker, M.M. Whittaker, J. Am. Chem. Soc. 113 (1991) 5528. [13] M.S. Lah, M.M. Dixon, K.A. Pattridge, W.C. Stallings, J.A. Fee, M.L. Ludwig, Biochemistry 34 (1995) 1646. [14] R.A. Edwards, H.M. Baker, M.M. Whittaker, J.W. Whittaker, G.B. Jameson, E.N. Baker, J. Biol. Inorg. Chem. 3 (1998) 161. [15] W. R€ uttinger, G.C. Dismukes, Chem. Rev. 97 (1997) 1. [16] M. Yagi, M. Kaneko, Chem. Rev. 101 (2001) 21. [17] J. Limburg, J.S. Vrettos, L.M. Liable-Sands, A.L. Rheingold, R.H. Crabtree, G.W. Brudvig, Science 283 (1999) 524. [18] L. Dubois, D.-F. Xiang, X.-S. Tan, J. Pecaut, P. Jones, S. Baudron, L. Le Pape, J.-M. Latour, C. Baffert, S. ChardonNoblat, M.-N. Collomb, A. Deronzier, Inorg. Chem. 42 (2003) 750, and references therein. [19] D.P. Riley, P.J. Lennon, W.L. Neumann, R.H. Weiss, J. Am. Chem. Soc. 119 (1997) 6522. [20] R. Kachadourian, I. Batinic-Haberle, I. Fridovich, Inorg. Chem. 38 (1999) 391. [21] C. Policar, S. Durot, F. Lambert, M. Cesario, F. Ramiandrasoa, I. Morgenstern-Baradau, Eur. J. Inorg. Chem. (2001) 1807. [22] A. Deroche, I. Morgenstern-Baradau, M. Cesario, J. Guilhem, B. Keita, L. Nadjo, C. Houee-Levin, J. Am. Chem. Soc. 118 (1996) 4567. [23] M. Geraghty, M. McCann, M.T. Casey, M. Curran, M. Devereux, V. McKee, J. McCrea, Inorg. Chim. Acta. 277 (1998) 257. [24] S. McCann, M. McCann, M.T. Casey, M. Jackman, M. Devereux, V. McKee, Inorg. Chim. Acta. 279 (1998) 279. [25] M.U. Triller, D. Pursche, W.-Y. Hsieh, V.L. Pecoraro, A. Rompel, B. Krebs, Inorg. Chem. 42 (2003) 6274. [26] J. Limburg, J.S. Vrettos, J.C. De Paula, R.H. Crabtree, G.W. Brudvig, A. Hassan, A.-L. Barra, C. Duboc-Toia, M.-N. Collomb, Inorg. Chem. 40 (2001) 1698. [27] C. Mantel, A. Hassan, J. Pecaut, A. Deronzier, M.-N. Collomb, C. Duboc-Toia, J. Am. Chem. Soc. 125 (2003) 12337. [28] I. Romero, L. Dubois, M.-N. Collomb, A. Deronzier, J.-M. Latour, J. Pecaut, Inorg. Chem. 41 (2002) 1795. [29] I. Romero, M.-N. Collomb, A. Deronzier, A. Llobet, E. Perret, J. Pecaut, L. Le Pape, J.-M. Latour, Eur. J. Inorg. Chem. (2001) 69. [30] M.-N. Collomb, A. Deronzier, A. Richardot, J. Pecaut, New J. Chem. 23 (1999) 351. [31] C. Baffert, M.-N. Collomb, A. Deronzier, J. Limburg, G.W. Brudvig, R.H. Crabtree, J. Pecaut, Inorg. Chem. 41 (2002) 1404. [32] B. Chiswell, E.D. McKenzie, L.F. Lindoy, in: G. Wilkinson, R.D. Gillard, J.A. McCleverty (Eds.), Comprehensive Coordination Chemistry, vol. 4, Pergamon, Oxford, 1987, p. 1 (Chapter 41). [33] R.J. Butcher, E. Sinn, J. Chem. Soc., Dalton Trans. (1976) 1186. [34] J. Delaunay, R.P. Hugel, Inorg. Chem. 25 (1986) 3957. [35] P. Turner, J.M. Gunter, W.B. Skelton, A.H. White, Aust. J. Chem. 51 (1998) 835. [36] F.L. Phillips, F.M. Schreeve, A.C. Skapski, Acta. Crystallogr. B32 (1976) 687. [37] W. Shuangxi, Z. Ying, Z. Fangjie, W. Qiuying, W. Liufang, Polyhedron 11 (1992) 1909.
[38] A.R. Oki, P.R. Bommarreddy, H. Zhang, N. Hosmane, Inorg. Chim. Acta. 231 (1995) 109. [39] R. Boca, L. Dlhan, W. Linert, H. Ehrenberg, H. Fuess, W. Haase, Chem. Phys. Lett. 307 (1999) 359. [40] L.S. Erre, G. Micera, E. Garribba, A.C. Benyei, New J. Chem. 24 (2000) 725. [41] W.R. Scheidt, K. Hatano, G.A. Rupprecht, P.L. Piciulo, Inorg. Chem. 18 (1979) 292. [42] M.S. Lah, H. Chun, Inorg. Chem. 36 (1997) 1782. [43] C. Ma, C. Chen, Q. Liu, D. Liao, L. Li, Eur. J. Inorg. Chem. (2003) 1227. [44] X.S. Tan, D.F. Xiang, W.X. Tang, J. Sun, Polyhedron 16 (1997) 689. [45] Z. Sun, P.K. Gantzel, D.N. Hendrickson, Polyhedron 17 (1998) 1511. [46] S. Gou, X. You, K. Yu, J. Lu, Inorg. Chem. 32 (1993) 1883. [47] S. Brooker, V. McKee, Acta. Crystallogr. C49 (1993) 441. [48] A. Bencini, A. Bianchi, P. Dapporto, E. Garcia-Espana, V. Marcelino, M. Micheloni, P. Paoletti, P. Paoli, Inorg. Chem. 29 (1990) 1716. [49] C. Pelizzi, G. Pelizzi, P. Tarasconi, J. Chem. Soc. Dalton Trans. (1985) 215. [50] N.A. Bailey, D.E. Fenton, S.J. Kitchen, T.H. Lilley, M.G. Williams, P.A. Tasker, A.J. Leong, L.F. Lindoy, J. Chem. Soc., Dalton Trans. (1991) 2989. [51] S. Richards, B. Pedersen, J.V. Silverton, J.L. Hoard, Inorg. Chem. 3 (1964) 27. [52] O. Horner, J.–J. Girerd, C. Philouze, L. Tchertanov, Inorg. Chim. Acta. 290 (1999) 139. [53] M. McCann, R.M.T. Casey, M. Devereux, M. Curran, C. Cardin, A. Todd, Polyhedron 15 (1996) 2117. [54] Y. Topcu, O. Andac, V.T. Yilmaz, W.T.A. Harrison, J. Mol. Struct. 610 (2002) 99. [55] A.R. Oki, P. Gogineni, M. Yurchenko, V.G. Young Jr., Inorg. Chim. Acta. 257 (1997) 279. [56] R. Keuleers, G.S. Papaefstathiou, C.P. Raptopoulou, V. Tangoulis, H.O. Desseyn, S. Perlepes, Inorg. Chem. Commun. 2 (1999) 472. [57] D.M. Hong, H.H. Wei, L.L. Gan, G.H. Lee, Y. Wang, Polyhedron 15 (1996) 2335. [58] M. Mikurija, Y. Hatano, E. Asato, Chem. Lett. (1996) 849. [59] M. Mikurija, Y. Hatano, E. Asato, Bull. Chem. Soc. Jpn. 70 (1997) 2495. [60] M. Louloudi, V. Nastopoulos, S. Gourbatsis, S.P. Perlepes, N. Hadjiliadis, Inorg. Chem. Commun. 2 (1999) 479. [61] I. Drummond, J.S. Wood, J. Chem. Soc. A (1970) 226. [62] J.E. Andrew, A.B. Blake, L.R. Fraser, J. Chem. Soc., Dalton Trans. (1975) 800. [63] M. Milinski, B. Ribar, Z. Culum, S. Djuric, Acta. Crystallogr. B33 (1977) 1678. [64] Y. Gultneh, A. Farooq, K.D. Karlin, S. Liu, J. Zubieta, Inorg. Chem. Acta. 211 (1993) 171. [65] X.-M. Chen, Y.-J. Zhu, Y.-J. Xu, X.-Y. Huang, Polyhedron 13 (1994) 1393. [66] S. Pal, M.K. Chan, W.H. Armstrong, J. Am. Chem. Soc. 114 (1992) 6398. [67] G.M. Sheldrick, SHELXTL version 6.1. An Integrated System for Solving, Refining and Displaying Crystal Structures from Diffraction Data, Siemens Analytical X-ray Instruments, Madison, WI, 1990. [68] S. Pal, M.M. Olmstead, W.H. Armstrong, Inorg. Chem. 34 (1995) 4708. [69] H. Oshio, H. Spiering, V. Ksenofontov, F. Renz, P. G€ utlich, Inorg. Chem. 40 (2001) 1143. [70] R. Bhula, D.C. Weatherburn, Aust. J. Chem. 44 (1991) 303. [71] P.E. Figgins, D.H. Busch, J. Phys. Chem. 65 (1961) 2236.
Synthesis and structural characterization of five-, six-, and seven-coordinate mononuclear manganese(II) complexes with N-tridentate ligands Carole Baffert a, Isabel Romero a,b,*, Jacques Pecaut c, Antoni Llobet b, Alain Deronzier a, Marie-No€elle Collomb a,* a
c
Laboratoire d’Electrochimie Organique et de Photochimie Redox, UMR CNRS 5630, Institut de Chimie Moleculaire de Grenoble, FR CNRS 2607, Universite Joseph Fourier, Grenoble 1, BP 53, 38041 Grenoble Cedex 9, France b Departament de Quimica, Universitat de Girona, Campus de Montilivi, E-17071 Girona, Spain DRFMC-Service de Chimie Inorganique et Biologique, Laboratoire coordination et Chiralite, CEA-Grenoble, 38054 Grenoble Cedex, France Received 19 April 2004; accepted 8 May 2004 Available online 17 June 2004
Abstract A series of four mononuclear manganese (II) complexes with the N-tridentate neutral ligands 2,20 :6,200 -terpyridine (terpy) and N,N-bis(2-pyridylmethyl)ethylamine (bpea) have been synthesized and crystallographically characterized. The complexes have fiveto seven-coordinate manganese(II) ions depending on the additional ligands used. The [Mn(bpea)(Br)2 ] complex (1) has a fivecoordinated manganese atom with a bipyramidal trigonal geometry, while [Mn(terpy)2 ](I)2 (2) is hexa-coordinated with a distorted octahedral geometry. Otherwise, the reactions of Mn(NO3 )2 4H2 O with terpy or bpea afforded novel seven-coordinate complexes [Mn(terpy)(NO3 )2 (H2 O)] (3) and [Mn(bpea)(NO3 )2 ] (4), respectively. 3 has a coordination polyhedron best described as a distorted pentagonal bipyramid geometry with one nitrate acting as a bidentate chelating ligand and the other nitrate as a monodentate one. 4 possesses a highly distorted polyhedron geometry with two bidentate chelating nitrate ligands. These complexes represent unusual examples of structurally characterized complexes with a coordination number seven for the Mn(II) ion and join a small family of nitrate complexes. Ó 2004 Elsevier B.V. All rights reserved. Keywords: Manganese (II) complexes; Five, six, seven-coordinate complexes; N-tridentate ligands; Nitrate complexes, Crystal structures
1. Introduction Manganese complexes have been found as active sites in a number of metalloenzymes [1,2] including the oxygen-evolving complex (OEC) of photosystem II (PSII), the catalase (Cat) and the superoxide dismutase (SOD) [1–7]. These enzymes are of great biological importance: the OEC oxidizes water to molecular oxygen, Cat catalyzes hydrogen peroxide disproportionation while the SOD are able to dismutate the superoxide radical. Recent *
Corresponding authors. Tel.: +33-4-76-51-44-18; fax: +33-4-76-5142-67 (M.-N. Collomb), Tel.: +34-972-418262; fax: +34-972-418150 (I. Romero). E-mail addresses: [email protected] (I. Romero), [email protected] (M.-N. Collomb). 0020-1693/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2004.05.023
crystal structure determinations of these enzymes have shown that the active site of PSII contains a tetranuclear manganese center [8,9], a dinuclear manganese one is present in the Mn Cat [10,11], whereas the active site of Mn SOD is a penta-coordinated mononuclear manganese complex with a trigonal bipyramidal geometry [12–14]. While the design of polynuclear manganese complexes of potentially biomimetic systems for the active center of PS II or Mn Cat has attracted many groups [1,3,15–18], the synthesis of relatively simple mononuclear derivatives, with the exception of complexes with macrocyclic ligands [1], has received much less attention [19–25]. In this context, as part as our synthetic exploration of mononuclear Mn(III) [26,27] and binuclear Mn2 (II,II) [28,29], (III,III) and (III,IV) complexes [30,31] with the N-tridentate ligands 2,20 :6,200 -terpyridine (terpy) and
C. Baffert et al. / Inorganica Chimica Acta 357 (2004) 3430–3436
N,N-bis(2-pyridylmethyl)ethylamine (bpea), we described here the synthesis and the structural characterization of a series of five-, six- and seven-coordinated mononuclear Mn(II) complexes with these ligands. Although various coordination geometries are accessible to high-spin d5 metal ions due to the absence of ligand field stabilization energy, the most common coordination number of structurally characterized Mn(II) complexes is six [32], coordination numbers of five [22,33–42], seven [42–59] or eight [58–64] remaining still rare. Ligand steric and electronic effects appear to play a major role in defining these geometries. This is evidenced in our series of mononuclear complexes described in this article. Indeed, the new penta-coordinated [Mn(bpea)(Br)2 ] (1) presenting a trigonal bipyramidal geometry was isolated with bpea and Br anions, while þ the hexa-coordinated [MnII;II 2 (l-O2 CCH3 )2 (bpea)2 ] and II;II [Mn2 (l-Cl)2 (bpea)2 (Cl)2 ] dimeric complexes have been previously obtained in the presence of CH3 CO 2 or Cl anions, respectively [28,29]. An hexa-coordinated bis terpy complex [Mn(terpy)2 ](I)2 (2) with distorted octahedral geometry has been also isolated, while the analogous [Mn(bpea)2 ](PF6 )2 has been previously characterized [28]. Otherwise, the mono or bidentate coordination mode of NO 3 anions leads to the formation of the new heptacoordinated complexes [Mn(terpy)(NO3 )2 (H2 O)] (3) and [Mn(bpea)(NO3 )2 ] (4) with a distorted pentagonal bipyramidal geometry and a distorted polyhedral geometry, respectively. These complexes join the small family of mononuclear Mn(II) complexes with nitrato ligand [55–63,65].
2. Experimental 2.1. Materials All manipulations were carried out under ambient conditions. Solvents used in this work were of analytical grade. All chemicals were purchased from Aldrich or Fluka and used without further purification. 2.2. Ligand and complexes The ligand 2,20 :6’,200 -terpyridine (terpy) was purchased from Aldrich or Fluka. The ligand N,Nbis(2-pyridylmethyl)ethylamine (bpea) was synthesized according to a method described previously [66]. 2.2.1. [MnII (bpea)(Br)2 ] (1) Method A. To an aqueous solution of MnBr2 (0.094 g, 0.44 mmol) (2 ml), an ethanol solution (2 ml) of bpea ligand (0.100 g, 0.44 mmol) was added under stirring. The resulting solution was stirred for 1 h, then filtered and left to evaporate at room temperature. After several
3431
days, the white powder formed was redissolved in acetonitrile and the resulting solution was left evaporated at room temperature. After one day, air-stable, colorless crystals of 1 suitable for X-ray diffraction analysis were obtained. Yield: 0.0836 g (43%). Elemental Anal. Calc. for [MnII (bpea)(Br)2 ] (C14 H17 Br2 MnN3 (442.07)): C, 38.2; H, 3.87; N, 9.48. Found: C, 38.21; H, 3.94; N, 9.23%. FAB-MS (positive mode), m=z: [Mn(bpea)Br]þ , 363. IR in cm1 (KBr): 2902 (m), 1604 (s), 1572 (m), 1483 (m), 1444 (m), 1289 (m), 1047 (s), 1018 (s), 801 (m), 761 (s), 641 (m), 413 (m). Method B. A solution of the bpea ligand (0.100 g, 0.44 mmol) and MnBr2 (0.094 g, 0.44 mmol) in acetonitrile (12 ml) was stirred for 15 min at room temperature. After 10 min, a white precipitate was formed, that was collected by filtration, washed thoroughly with diethyl ether and finally dried in vacuum. Colorless crystals of 1 were obtained in acetonitrile as described in Method A. Yield: 0.097 g (50%). 2.2.2. [MnII (terpy)2 ](I)2 (2) To a methanol solution (5 ml) of MnI2 (0.125 g, 0.4 mmol), a methanol solution (15 ml) of terpy ligand (0.230 g, 0.987 mmol) was added under stirring. After few minutes, a yellow precipitate was formed, that was collected by filtration. The yellow powder obtained was redissolved in methanol and the resulting solution was left evaporated at room temperature. After one day, air-stable, yellow crystals of 2 3H2 O suitable for X-ray diffraction analysis were obtained. Elemental Anal. Calc. for [MnII (terpy)2 ](I)2 4H2 O (C30 H30 I2 MnN6 O4 (847.36): C, 42.52; H, 3.57; N, 9.92. Found: C, 42.26; H, 2.96; N, 9.83%. IR in cm1 (KBr): 2923 (m), 1593 (s), 1574 (m), 1557 (m), 1475 (s), 1450 (s), 1434 (s), 1316 (m), 1247 (m), 1189 (m), 1158 (m), 1013 (s), 766 (s). 2.2.3. [MnII (terpy)(NO3 )2 (H2 O)] (3) To an aqueous solution (1 ml) of MnII (NO3 )2 4H2 O (0.1121 g, 0.446 mmol), an ethanol solution (4 ml) of terpy ligand (0.060 g, 0.257 mmol) was added. The yellow solution was stirred for 30 min, then filtered, and left to evaporate at room temperature. After several days, yellow crystals of 3 suitable for X-ray diffraction analysis were obtained. Yield: 82 mg (74 %). Elemental Anal. Calc. for [MnII (terpy)(NO3 )2 (H2 O)] (C15 H13 MnN5 O7 (430.24)): C, 41.88; H, 3.05; N, 16.28. Found: C, 41.88; H, 3.12; N, 16.10%. IR in cm1 (KBr): 3367 (m), 1667 (m), 1595 (m), 1574 (m), 1480 (m), 1452 (s), 1439 (s), 1384 (s), 1351 (s), 1314 (s), 1190 (m), 1171 (m), 1043 (m), 1016 (m), 1009 (m), 819 (m), 774 (s), 736 (m), 650 (m), 638 (m), 511 (m), 404 (w). 2.2.4. [MnII (bpea)(NO3 )2 ] (4) To an aqueous solution (2 ml) of MnII (NO3 )2 4H2 O (0.197 g, 0.785 mmol), an ethanol solution (2 ml) of bpea ligand (0.113 g, 0.5 mmol) was added under stirring. The
3432
C. Baffert et al. / Inorganica Chimica Acta 357 (2004) 3430–3436
resulting yellow solution was stirred for 30 min, then filtered and left to evaporate at room temperature. After few days, the white powder formed was redissolved in acetonitrile and addition of diethyl ether yielded a microcrystalline product. Colorless crystals of 4 suitable for X-ray diffraction analysis were obtained by slow diffusion of diethyl ether into an acetonitrile solution of this complex. Yield: 0.070 g (35%). Elemental Anal. Calc. for [MnII (bpea)(NO3 )2 ] (C14 H17 MnN5 O6 (406.27)): C, 41.39; H, 4.22; N, 17.24. Found: C, 41.23; H, 4.22; N, 17.00%. FAB-MS (positive mode), m=z: [Mn(bpea)(NO3 )]þ , 344. IR in cm1 (KBr): 2923 (m), 2853 (w), 1606 (m), 1470 (s), 1442 (m), 1384 (m), 1307 (m), 1277 (m), 1044 (w), 1022 (m), 818 (m), 769 (m). 2.3. Spectroscopies Fast atom bombardment mass spectra (FAB) were obtained on an AEI Kratos MS 50 spectrometer fitted with an Ion Tech Ltd. gun (Centre de Recherche sur les Macromolecules Vegetales, Grenoble, France). Infrared spectra were recorded on a Perkin–Elmer Spectrum GX FTIR spectrometer. 2.4. X-ray structure analysis The data sets for the single-crystal X-ray studies were collected with Mo Ka radiation on a Bruker SMART
diffractometer. All calculations were performed on a Silicon Graphics system using the S H E L X T L program [67]. The specific data for the crystals and the refinements are collected in Tables 1 and 5. The structures were solved by direct methods and refined by full-matrix least-squares fits of F 2 .
3. Results and discussion 3.1. Five-coordinate manganese (II) complex: [Mn(bpea)(Br)2 ] Complex 1 crystallizes in the triclinic space group P 1 with two molecules per unit cell. Fig. 1 shows the ORTEP diagram of the complex and Tables 1 and 2 summarize crystal data and selected bond distances and angles, respectively. The geometry around the Mn(II) ion center is a distorted trigonal bipyramid, where the tridentate ligand adopts the uncommon meridional mode of coordination around the Mn(II). This coordination mode has only been observed in [MnIII (bpea)(X)3 ) (X ¼ N3 ; 2þ F) and [MnIV (X ¼ Cl; F) [27,68]. The 2 O2 (bpea)2 (X)2 ] equatorial plane is occupied by the two unidentate ligands, Br(1) and Br(2), and the central aliphatic nitrogen atom, N(1), of the ligand bpea. The distal aromatic
Table 1 Crystal data and details of the refinement of the crystal structures of [Mn(bpea)(Br)2 ] (1) and [Mn(terpy)2 ](I)2 3H2 O (2.3H2 O) Compound Chemical formula Formula weight Temperature (K) k (A) Crystal system Crystal size (mm mm mm) Space group a (A) b (A) c (A) a (°) b (°) c (°) 3 ) V (A Z l (mm1 ) Number of reflections collected Number of independent reflections [Rint ] Goodness-of-fit on F 2 Final R indices [I > 2rðIÞ] R indices (all data)
1 C14 H17 Br2 MnN3 442.07 298(2) 0.71073 triclinic 0.15 0.2 0.4
2.3H2 O C30 H28 I2 MnN6 O3 829.32 223(2) 0.71073 monoclinic 0.4 0.4 0.4
P 1 8.0447(10) 8.5828(11) 13.709(2) 78.454(3) 73.560(2) 66.716(2) 829.71(19) 2 5.604 5374
P 2ð1Þ=n 8.7037(12) 41.118(6) 8.9139(13) 90 92.334(2) 90 3187.5(8) 4 2.392 9343
3803 [0.0317]
6422 [0.0297]
0.971 R1 ¼ 0:0523 wR2 ¼ 0:1324 R1 ¼ 0:0687 wR2 ¼ 0:1409
0.963 R1 ¼ 0:0503 wR2 ¼ 0:1188 R1 ¼ 0:0871 wR2 ¼ 0:1303
C14 C3
C13
C1
C4
C7
C2
C9 C8
N1
C10 N2
N3 Mn
C5
Standard deviations are given in parentheses.
C1 1
C6 Br 2
Br 1
C12
Fig. 1. An ORTEP view of the molecular structure of 1.
Table 2 and bond angles (°) for 1 Selected bond lengths (A) Mn–N(1) Mn–N(2) Mn–N(3) Br(2)–Mn–Br(1) N(3)–Mn–N(2) N(3)–Mn–N(1) N(2)–Mn–N(1) N(3)–Mn–Br(1)
2.325(2) 2.236(2) 2.230(3) 113.69(2) 145.80(9) 72.89(8) 72.91(9) 98.54(6)
Mn–Br(1) Mn–Br(2) N(2)–Mn–Br(1) N(1)–Mn–Br(1) N(3)–Mn–Br(2) N(2)–Mn–Br(2) N(1)–Mn–Br(2)
2.5016(5) 2.5085(5) 97.69(6) 119.65(5) 101.35(6) 99.33(6) 126.64(5)
C. Baffert et al. / Inorganica Chimica Acta 357 (2004) 3430–3436
nitrogen atoms, N(2) and N(3), are in the axial positions. Compared to the idealized trigonal bipyramid, the angles between the Mn atom and the ligands show significant distortions. The spatially constrained nature of the tridentate meridional bpea ligand produces geometrical distortions manifested in the N(2)–Mn–N(3) angle equal to 145.80(9)° compared to 180°, the theoretical value (Table 2). The different electronic nature of the aliphatic and aromatic N-coordinating atoms of bpea induces also geometrical distortions from the ideal trigonal bipyramid, which are mainly manifested by significantly different Mn–N bond lengths. The largest corresponds to the Mn–N aliphatic bond (Mn–N(1): while the two shortest correspond to the 2.325(2) A), and Mn–N(3): aromatic ones (Mn–N(2): 2.236(2) A 2.230(3) A). The same tendency has been observed in the other complexes with bpea ligand, acting in a facial or meridional coordination mode [27–29,66,68]. The equatorial plane shows also significant distortions. The angles Br(1)–Mn–Br(2) (113.69(2)°) and N(1)–Mn–Br(1) (119.65(5)°) are smaller than the theorical value of 120° in a trigonal bipyramid, while the angle N(1)–Mn–Br(2) (126.64(5)°) is slightly higher. The bond angles between the axial and equatorial positions are obviously also different to 90° and the largest ones are between the axial positions and the Br atoms (N(2)–Mn–Br(2): 99.33(6); N(2)–Mn–Br(1): 97.69(6); N(3)–Mn–Br(1): 98.54(6) and N(3)–Mn–Br(2):101.35(6)°). The Br(1)–Mn–Br(2) angle of 113.69(2)° and the Mn– are consistent Br distances of 2.5016(5) and 2.5085(5) A with the values observed in other penta-coordinated mononuclear dibromo manganese(II) complexes [33,34]. 3.2. Six-coordinate Mn(II) complex: [MnII (terpy)2 ](I)2 3H2 O (2.3H2 O) Complex 2 crystallizes in the monoclinic space group P 2ð1Þ=n with four molecules per unit cell. Fig. 2 shows the ORTEP diagram of this complex. The structure consists of discrete [Mn(terpy)2þ 2 cations together with two iodide anions and three water molecules uncomplexed. The Mn atom is coordinated by six nitrogen atoms from two meridional terpy ligands in a distorted octahedral fashion. The distortion is more important than in the previously crystallized [Mn(terpy)2 ](ClO4 )2 [69] and [Mn(terpy)2 ](I3 )2 [70] complexes. Table 1 contains crystallographic data and Table 3 contains selected bond distances and angles. The coordination geometry around the Mn(II) ion is highly distorted from octahedral due to the spatially constrained nature of the tridentate terpy ligand. Thus, the N(1)–Mn–N(3) and N(21)–Mn–N(23) angles (144.47(10)° and 144.67(10)°, respectively) are about 35° below 180°. Similar distortions have been observed in the bis-terpy [69,70] and mono-terpy [Mn(terpy)(dmb)2 ]
3433 C34 C33 C35 C32
C13 C14
C12 C9 C8
C31
N3
C10
C15
C11 N2
C6
N23
C30
C29
Mn N1
C7
N22
C1
C5
C26
C2
C4
C28 N21
C3
C25
C27
C21 C24 C22 C23
Fig. 2. An ORTEP view of the molecular structure of the cation of complex 2 3H2 O.
Table 3 and bond angles (°) for 2.3H2 O Selected bond lengths (A) Mn–N(22) Mn–N(2) Mn–N(23) N(22)–Mn–N(2) N(22)–Mn–N(23) N(2)–Mn–N(23) N(22)–Mn–N(1) N(2)–Mn–N(1) N(23)–Mn–N(1) N(22)–Mn–N(3) N(2)–Mn–N(3)
2.201(3) 2.203(3) 2.236(3) 172.32(11) 72.51(10) 144.69(10) 110.12(10) 72.40(11) 97.62(10) 105.39(11) 72.23(11)
Mn–N(1) Mn–N(3) Mn–N(21) N(23)–Mn–N(3) N(1)–Mn–N(3) N(22)–Mn–N(21) N(2)–Mn–N(21) N(23)–Mn–N(21) N(1)–Mn–N(21) N(3)–Mn–N(21)
2.246(3) 2.253(3) 2.260(3) 93.98(10) 144.47(10) 72.16(10) 100.60(10) 144.67(10) 94.27(10) 95.37(10)
[40] complexes. The N(2)–Mn–N(22) interligand angle of 172.32(11)° is below the theoretical value of 180°. In addition, as expected, cis N–Mn–N interligand angles comprised between 93.98° and 114.69° are above 90°. Because of the large size of the Mn(II) ion, these distortions are greater for the manganese terpy complexes than for any of the other terpy first-row transition metal complexes and the Mn–Nterpy bonds longer [40]. Moreover, the Mn–Nterpy distances in 2 are normal with shorter Mn–Ncentral distances, (average 2.202(1) A) average). compared to Mn–Ndistal ones (2.249(10) A, This distortion, always observed in terpy complexes of the first-row transition metal complexes, is attributed to a more efficient overlap of the metal t2g orbitals with the p orbitals of the central pyridyl group compared to the distal pyridyl groups [71]. As a consequence, a tetragonal distortion of the coordination sphere along the N(2)–Mn–N(22) axis is observed.
3434
C. Baffert et al. / Inorganica Chimica Acta 357 (2004) 3430–3436
3.3. Seven-coordinate manganese(II) complexes Complexes 3 and 4 join a small family of seven-coordinate manganese (II) complex with nitrate ligands [55–57]. 3.3.1. [MnII (terpy)(H2 O)(NO3 )2 ] (3) The complex 3 crystallizes in the triclinic space group P 1 with two molecules per unit cell. Fig. 3 shows the ORTEP diagram of the complex and Table 4 summarizes crystal data and Table 6 selected bond distances and angles, respectively. The X-ray crystallography of 3 reveals a seven-coordinate Mn atom best described as a distorted pentagonal bipyramidal geometry, with three nitrogen atoms of the terpy ligand and two oxygen atoms of the bidentate chelating nitrate ligand (O(11) and O(12)) forming the equatorial plane. The axial positions are occupied by two oxygen atoms, one from the monodentate nitrate anion (O(21)) and the other one from the water ligand (O(1)) (O(1)–Mn–O(21), 161.80(6)°). The plane containing Mn, N(1), N(22), N(3), O(11), and from the plane, O(12) gives a mean deviation of 0.015 A with O(1) being 2.160 A above the plane and O(21) below the plane. Three of the five equabeing 2.163 A torial angles deviated significantly from the ideal value of the pentagonal bipyramidal geometry (72°), due to the restricted bite of the chelating nitrate group with an angle of 53.38(5)°, while the terpy ligand imposed two equatorial angles close to 72° (71.01(5)° and 71.78(5)°). The angles between the axial bonds and the equatorial ones are comprised between 76.18° and 103.73°, compared to the ideal value of 90°. This compound joins a small family of seven-coordinate manganese(II) complexes where the coordination polyhedron is a distorted pentagonal bipyramid [43,49,56], being the first one in which the organic ligand is the tridentate terpy. The Mn–N bond distances are similar to (ranging from 2.2422(14) to 2.3339(15) A) O1 C7
C8
C4
C3
C9
C5
N22 C6 C10
C2
C11
C12
N1
C1
Mn O11
N11
Compound Chemical formula Formula weight Temperature (K) k (A) Crystal system Crystal size (mm mm mm) Space group a (A) b (A) c (A) a (°) b (°) c (°) 3 ) V (A Z l (mm1 ) Number of reflections collected Number of independent reflections [Rint ] Goodness-of-fit on F 2 Final R indices [I > 2rðIÞ] R indices (all data)
3 C15 H13 MnN5 O7 430.24 223(2) 0.71073 triclinic 0.2 0.4 0.4
4 C14 H17 MnN5 O6 406.27 298(2) 0.71073 triclinic 0.15 0.2 0.45
P 1 7.6949(8) 9.8336(10) 12.3658(12) 71.911(2) 81.124(2) 72.990(2) 848.47(15) 2 0.831 5468
P 1 8.1999(8) 8.6596(9) 13.6658(14) 93.547(2) 92.628(2) 115.270(2) 871.50(15) 2 0.800 5701
3861 [0.0143]
4019 [0.0204]
1.036 R1 ¼ 0:0306 wR2 ¼ 0:0786 R1 ¼ 0:0418 wR2 ¼ 0:0842
0.905 R1 ¼ 0:0371 wR2 ¼ 0:0840 R1 ¼ 0:0699 wR2 ¼ 0:1034
Standard deviations are given in parentheses.
Table 5 and bond angles (°) for 3 Selected bond lengths (A) Mn–O(1) Mn–O(21) Mn–O(11) Mn–O(12) O(1)–Mn–O(21) O(1)–Mn–N(22) O(21)–Mn–N(22) O(1)–Mn–O(12) O(21)–Mn–O(12) N(22)–Mn–O(12) O(1)–Mn–N(3) O(21)–Mn–N(3) N(22)–Mn–N(3) O(12)–Mn–N(3) O(1)–Mn–N(1) O(21)–Mn–N(1) N(22)–Mn–N(1) O(12)–Mn–N(1)
2.1942(16) Mn–N(1) 2.2101(13) Mn–N(22) 2.4638(16) Mn–N(3) 2.3082(14) 161.80(6) 92.54(6) 101.17(5) 86.79(6) 86.38(5) 152.89(5) 91.85(6) 103.73(5) 71.78(5) 81.15(5) 88.29(6) 84.96(5) 71.01(5) 135.97(5)
N(3)–Mn–N(1) O(1)–Mn–O(11) O(21)–Mn–O(11) N(22)–Mn–O(11) O(12)–Mn–O(11) O(2)–Mn–O(5) N(3)–Mn–O(11) N(1)–Mn–O(11) O(13)–N(11)–O(11) O(13)–N(11)–O(12) O(11)–N(11)–O(12) O(23)–N(21)–O(22) O(23)–N(21)–O(21) O(22)–N(21)–O(21)
2.3339(15) 2.2422(14) 2.3111(15) 142.76(5) 86.21(6) 76.18(5) 153.66(5) 55.38(5) 123.87(7) 134.54(5) 82.65(5) 121.55(16) 120.43(16) 118.02(15) 121.83(17) 119.41(17) 118.68(15)
N3
O12
C15
C13 C14
O21
O13
Table 4 Crystal data and details of the refinement of the crystal structures of [Mn(terpy)(H2 O)(NO3 )2 ] (3) and [Mn(bpea)2 (NO3 )2 ] (4)
O22 N21 O23
Fig. 3. An ORTEP view of the molecular structure of complex 3.
those found in 2. The Mn–O bonds distances of the ; Mn– bidentate nitrate ligand (Mn–O(12): 2.3082(14) A are longer than the Mn–O bond O(11): 2.4638(16) A) distance in the monodentate nitrate ligand (Mn–O(21): The same tendency has been observed in 2.2101(13) A). manganese complexes with mono [65] and bidentate nitrate ligands [55–63]. The Mn–Oaqua bond length is shorter than the last Mn–O bonds and (2.1942(16) A)
C. Baffert et al. / Inorganica Chimica Acta 357 (2004) 3430–3436 Table 6 and °) Hydrogen bonds for 3 (A
Table 7 and bond angles (in °) for 4 Selected bond lengths (in A)
D–H. . .A
d(D–H)
d(H. . .A) d(D. . .A) <(DHA)
O(1)–H(2O). . .O(13)#1 O(1)–H(1O). . .O(22)#2
0.60(2) 0.89(4)
2.19(2) 1.93(4)
2.782(2) 2.778(2)
170(3) 158(3)
comparable to those of the Mn(II) complexes with aqua ligands [57,65]. The crystal structure is stabilized by hydrogen bonds involving the hydrogen atoms of the aquo ligand, the uncoordinated oxygen atom of the bidentate nitrate ligand, O(13), and one of the uncoordinated oxygen atom of the monodentate nitrate ligand, O(22), respectively. The hydrogen-bonding parameters are listed in Table 6. 3.3.2. [MnII (bpea)(NO3 )2 ] (4) The complex [MnII (bpea)(NO3 )2 ] crystallizes in the triclinic space group P 1 with two molecules per unit cell. Fig. 4 shows the ORTEP diagram of the complex and Tables 4 and 7 show crystal data and selected bond distances and angles, respectively. The structure indicates that the complex has a heptacoordinate metal center with a highly distorted polyhedral geometry. The coordination sphere of manganese consists of three nitrogen atoms of the bpea ligand and four oxygen atoms of two bidentate chelating nitrate ligands. This is the first example of complex having a tridentate ligand with two bidentate nitrate ligands. A feature of the structure is the coordination mode of the bpea ligand, which is close to a facial coordination mode, with an N(2)–Mn–N(3) angle of 112.04(8)°. However, this angle is higher compared to those ob-
Mn–O(1) Mn–O(2) Mn–O(4) Mn–O(5) N(2)–Mn–N(3) N(2)–Mn–O(4) N(3)–Mn–O(4) N(2)–Mn–O(2) N(3)–Mn–O(2) O(4)–Mn–O(2) N(2)–Mn–O(1) N(3)–Mn–O(1) O(4)–Mn–O(1) O(2)–Mn–O(1) N(2)–Mn–O(5) N(3)–Mn–O(5) O(4)–Mn–O(5) O(2)–Mn–O(5)
2.354(2) Mn–N(1) 2.301(2) Mn–N(2) 2.2578(19) Mn–N(3) 2.3605(19) 112.04(8) 161.40(8) 84.80(8) 97.28(8) 86.04(8) 91.54(8) 87.69(7) 138.64(7) 84.10(7) 54.64(7) 106.61(7) 126.83(7) 55.18(7) 123.87(7)
O(1)–Mn–O(5) N(2)–Mn–N(1) N(3)–Mn–N(1) O(4)–Mn–N(1) O(2)–Mn–N(1) O(1)–Mn–N(1) O(5)–Mn–N(1) O(3)–N(4)–O(1) O(3)–N(4)–O(2) O(1)–N(4)–O(2) O(6)–N(5)–O(5) O(6)–N(5)–O(4) O(5)–N(5)–O(4)
2.3691(19) 2.215(2) 2.219(2) 76.07(7) 73.30(7) 73.24(7) 105.86(7) 151.22(8) 148.02(7) 84.85(7) 121.6(3) 122.3(3) 116.1(2) 121.8(3) 121.7(2) 116.5(2)
served in the complexes [Mn(bpea)2 ]2þ , [MnII;II 2 (lþ Cl)2 (bpea)2 (Cl)2 ] and [MnII;II (l-O CCH ) (bpea) 2 3 2 2] 2 having the typical facial coordination mode (106.32(85)° (average), 97.78(5)°, 98.01(15)°, respectively) [28,29] but significantly smaller for a meridional coordination mode as in 1 (175.80(9)°). Otherwise, the three Mn–N bond distances of the bpea ligand are similar to those found in 1. The Mn–O bond distances of the two nitrate ligands and are comprised between 2.2578(19) and 2.3605(19) A the O–Mn–O bond angles are similar (64(7)° and 55.18(7)°).
4. Supplementary material
C4 C3
C5
C2 C1 C6
3435
N2 C14 O5
O1
N1
Crystallographic data for the structures included in this paper have been deposited with the Cambridge Crystallographic Data Center as supplementary publication nos. CCDC 233950-233953. Copies of the data can be obtained free of charge on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (Fax: +441223-336-033; E-mail: [email protected], www: http://www.ccdc.cam.ac.uk.
Mn N5 O6 N4 O3
C13
C7
References C8
O2
O4 N3
C9
C12 C10 C11 Fig. 4. An ORTEP view of the molecular structure of complex 4.
[1] D.C. Weatherburn, S. Mandal, S. Mukhopadhyay, S. Bhaduri, L.F. Lindoy, in: J.A. Cleverty, T.J. Meyer (Eds.), Comprehensive Coordination Chemistry II, vol. 4, Elsevier Pergamon, 2004, p. 1 (Chapter 41). [2] A. Sigel, H. Sigel, Manganese and its role in Biological Processes, Marcel Dekker, New York, 2000, p. 37. [3] A.J. Wu, J.E. Penner-Hahn, V.L. Pecoraro, Chem. Rev. 104 (2004) 903. [4] V.L. Pecoraro, Manganese Redox Enzymes, VCH, New York, 1992.
3436
C. Baffert et al. / Inorganica Chimica Acta 357 (2004) 3430–3436
[5] V.K. Yachandra, K. Sauer, M.P. Klein, Chem. Rev. 96 (1996) 2927. [6] K. Wieghardt, Angew. Chem., Int. Ed. Engl. 28 (1989) 1153. [7] G.C. Dismukes, Chem. Rev. 96 (1996) 2909. [8] A. Zouni, H.T. Witt, J. Kern, P. Fromme, N. Krauss, W. Saenger, P. Orth, Nature 409 (2001) 739. [9] N. Kamiya, J.-R. Shen, Proc. Natl. Acad. Sci. USA 100 (2003) 98. [10] S.V. Antonyuk, V.R. Melik-Adamyan, A.N. Popov, V.S. Lamzin, P.D. Hempstead, P.M. Harrison, P.J. Artymyuk, V.V. Barynin, Cryst. Rep. 45 (2000) 105. [11] V.V. Barynin, M.M. Whittaker, S.V. Antonyuk, V.S. Lamzin, P.V. Harrison, P.J. Artymyuk, V.J. Whittaker, Structure 9 (2001) 725. [12] J.W. Whittaker, M.M. Whittaker, J. Am. Chem. Soc. 113 (1991) 5528. [13] M.S. Lah, M.M. Dixon, K.A. Pattridge, W.C. Stallings, J.A. Fee, M.L. Ludwig, Biochemistry 34 (1995) 1646. [14] R.A. Edwards, H.M. Baker, M.M. Whittaker, J.W. Whittaker, G.B. Jameson, E.N. Baker, J. Biol. Inorg. Chem. 3 (1998) 161. [15] W. R€ uttinger, G.C. Dismukes, Chem. Rev. 97 (1997) 1. [16] M. Yagi, M. Kaneko, Chem. Rev. 101 (2001) 21. [17] J. Limburg, J.S. Vrettos, L.M. Liable-Sands, A.L. Rheingold, R.H. Crabtree, G.W. Brudvig, Science 283 (1999) 524. [18] L. Dubois, D.-F. Xiang, X.-S. Tan, J. Pecaut, P. Jones, S. Baudron, L. Le Pape, J.-M. Latour, C. Baffert, S. ChardonNoblat, M.-N. Collomb, A. Deronzier, Inorg. Chem. 42 (2003) 750, and references therein. [19] D.P. Riley, P.J. Lennon, W.L. Neumann, R.H. Weiss, J. Am. Chem. Soc. 119 (1997) 6522. [20] R. Kachadourian, I. Batinic-Haberle, I. Fridovich, Inorg. Chem. 38 (1999) 391. [21] C. Policar, S. Durot, F. Lambert, M. Cesario, F. Ramiandrasoa, I. Morgenstern-Baradau, Eur. J. Inorg. Chem. (2001) 1807. [22] A. Deroche, I. Morgenstern-Baradau, M. Cesario, J. Guilhem, B. Keita, L. Nadjo, C. Houee-Levin, J. Am. Chem. Soc. 118 (1996) 4567. [23] M. Geraghty, M. McCann, M.T. Casey, M. Curran, M. Devereux, V. McKee, J. McCrea, Inorg. Chim. Acta. 277 (1998) 257. [24] S. McCann, M. McCann, M.T. Casey, M. Jackman, M. Devereux, V. McKee, Inorg. Chim. Acta. 279 (1998) 279. [25] M.U. Triller, D. Pursche, W.-Y. Hsieh, V.L. Pecoraro, A. Rompel, B. Krebs, Inorg. Chem. 42 (2003) 6274. [26] J. Limburg, J.S. Vrettos, J.C. De Paula, R.H. Crabtree, G.W. Brudvig, A. Hassan, A.-L. Barra, C. Duboc-Toia, M.-N. Collomb, Inorg. Chem. 40 (2001) 1698. [27] C. Mantel, A. Hassan, J. Pecaut, A. Deronzier, M.-N. Collomb, C. Duboc-Toia, J. Am. Chem. Soc. 125 (2003) 12337. [28] I. Romero, L. Dubois, M.-N. Collomb, A. Deronzier, J.-M. Latour, J. Pecaut, Inorg. Chem. 41 (2002) 1795. [29] I. Romero, M.-N. Collomb, A. Deronzier, A. Llobet, E. Perret, J. Pecaut, L. Le Pape, J.-M. Latour, Eur. J. Inorg. Chem. (2001) 69. [30] M.-N. Collomb, A. Deronzier, A. Richardot, J. Pecaut, New J. Chem. 23 (1999) 351. [31] C. Baffert, M.-N. Collomb, A. Deronzier, J. Limburg, G.W. Brudvig, R.H. Crabtree, J. Pecaut, Inorg. Chem. 41 (2002) 1404. [32] B. Chiswell, E.D. McKenzie, L.F. Lindoy, in: G. Wilkinson, R.D. Gillard, J.A. McCleverty (Eds.), Comprehensive Coordination Chemistry, vol. 4, Pergamon, Oxford, 1987, p. 1 (Chapter 41). [33] R.J. Butcher, E. Sinn, J. Chem. Soc., Dalton Trans. (1976) 1186. [34] J. Delaunay, R.P. Hugel, Inorg. Chem. 25 (1986) 3957. [35] P. Turner, J.M. Gunter, W.B. Skelton, A.H. White, Aust. J. Chem. 51 (1998) 835. [36] F.L. Phillips, F.M. Schreeve, A.C. Skapski, Acta. Crystallogr. B32 (1976) 687. [37] W. Shuangxi, Z. Ying, Z. Fangjie, W. Qiuying, W. Liufang, Polyhedron 11 (1992) 1909.
[38] A.R. Oki, P.R. Bommarreddy, H. Zhang, N. Hosmane, Inorg. Chim. Acta. 231 (1995) 109. [39] R. Boca, L. Dlhan, W. Linert, H. Ehrenberg, H. Fuess, W. Haase, Chem. Phys. Lett. 307 (1999) 359. [40] L.S. Erre, G. Micera, E. Garribba, A.C. Benyei, New J. Chem. 24 (2000) 725. [41] W.R. Scheidt, K. Hatano, G.A. Rupprecht, P.L. Piciulo, Inorg. Chem. 18 (1979) 292. [42] M.S. Lah, H. Chun, Inorg. Chem. 36 (1997) 1782. [43] C. Ma, C. Chen, Q. Liu, D. Liao, L. Li, Eur. J. Inorg. Chem. (2003) 1227. [44] X.S. Tan, D.F. Xiang, W.X. Tang, J. Sun, Polyhedron 16 (1997) 689. [45] Z. Sun, P.K. Gantzel, D.N. Hendrickson, Polyhedron 17 (1998) 1511. [46] S. Gou, X. You, K. Yu, J. Lu, Inorg. Chem. 32 (1993) 1883. [47] S. Brooker, V. McKee, Acta. Crystallogr. C49 (1993) 441. [48] A. Bencini, A. Bianchi, P. Dapporto, E. Garcia-Espana, V. Marcelino, M. Micheloni, P. Paoletti, P. Paoli, Inorg. Chem. 29 (1990) 1716. [49] C. Pelizzi, G. Pelizzi, P. Tarasconi, J. Chem. Soc. Dalton Trans. (1985) 215. [50] N.A. Bailey, D.E. Fenton, S.J. Kitchen, T.H. Lilley, M.G. Williams, P.A. Tasker, A.J. Leong, L.F. Lindoy, J. Chem. Soc., Dalton Trans. (1991) 2989. [51] S. Richards, B. Pedersen, J.V. Silverton, J.L. Hoard, Inorg. Chem. 3 (1964) 27. [52] O. Horner, J.–J. Girerd, C. Philouze, L. Tchertanov, Inorg. Chim. Acta. 290 (1999) 139. [53] M. McCann, R.M.T. Casey, M. Devereux, M. Curran, C. Cardin, A. Todd, Polyhedron 15 (1996) 2117. [54] Y. Topcu, O. Andac, V.T. Yilmaz, W.T.A. Harrison, J. Mol. Struct. 610 (2002) 99. [55] A.R. Oki, P. Gogineni, M. Yurchenko, V.G. Young Jr., Inorg. Chim. Acta. 257 (1997) 279. [56] R. Keuleers, G.S. Papaefstathiou, C.P. Raptopoulou, V. Tangoulis, H.O. Desseyn, S. Perlepes, Inorg. Chem. Commun. 2 (1999) 472. [57] D.M. Hong, H.H. Wei, L.L. Gan, G.H. Lee, Y. Wang, Polyhedron 15 (1996) 2335. [58] M. Mikurija, Y. Hatano, E. Asato, Chem. Lett. (1996) 849. [59] M. Mikurija, Y. Hatano, E. Asato, Bull. Chem. Soc. Jpn. 70 (1997) 2495. [60] M. Louloudi, V. Nastopoulos, S. Gourbatsis, S.P. Perlepes, N. Hadjiliadis, Inorg. Chem. Commun. 2 (1999) 479. [61] I. Drummond, J.S. Wood, J. Chem. Soc. A (1970) 226. [62] J.E. Andrew, A.B. Blake, L.R. Fraser, J. Chem. Soc., Dalton Trans. (1975) 800. [63] M. Milinski, B. Ribar, Z. Culum, S. Djuric, Acta. Crystallogr. B33 (1977) 1678. [64] Y. Gultneh, A. Farooq, K.D. Karlin, S. Liu, J. Zubieta, Inorg. Chem. Acta. 211 (1993) 171. [65] X.-M. Chen, Y.-J. Zhu, Y.-J. Xu, X.-Y. Huang, Polyhedron 13 (1994) 1393. [66] S. Pal, M.K. Chan, W.H. Armstrong, J. Am. Chem. Soc. 114 (1992) 6398. [67] G.M. Sheldrick, SHELXTL version 6.1. An Integrated System for Solving, Refining and Displaying Crystal Structures from Diffraction Data, Siemens Analytical X-ray Instruments, Madison, WI, 1990. [68] S. Pal, M.M. Olmstead, W.H. Armstrong, Inorg. Chem. 34 (1995) 4708. [69] H. Oshio, H. Spiering, V. Ksenofontov, F. Renz, P. G€ utlich, Inorg. Chem. 40 (2001) 1143. [70] R. Bhula, D.C. Weatherburn, Aust. J. Chem. 44 (1991) 303. [71] P.E. Figgins, D.H. Busch, J. Phys. Chem. 65 (1961) 2236.