Comments Inorg. Chem. 2002, 249 (original) (raw)
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Dalton Transactions, 2010
A novel amine-thiolate ligand, H 3 3‚6HCl (N,N′,N′′-tris-[2-thio-3-aminomethyl-5-tert-butylbenzyl]-1,1,1-tris-(aminomethyl)ethane), has been synthesized and used in the preparation of dinuclear complexes of Fe, Co, and Ni. The nonadentate N 6 S 3 ligand H 3 3 is formally derived from the symmetric tridentate N 2 S ligand H 1 1 (2,6bis(aminomethyl)-4-tert-butylthiophenol). It provides two dissimilar octahedral N 3 S 3 and N′ 3 S 3 coordination sites to give complexes with a central N 3 M(µ 2 -SR) 3 MN′ 3 core structure (N and N′ denote primary and secondary amine nitrogen atoms, respectively). The complexes of H 3 3 exist as dinuclear [M II 2 (3)] + , [M III M II (3)] 2+ , or [M III 2 -(3)] 3+ species which are all accessible by chemical or electrochemical reduction/oxidation. The following complexes were isolated as microcrystalline solids: [Co III 2 (3)][ClO 4 ] 3 (4b), [Ni III Ni II (3)][BPh 4 ] 2 (5b), and [Fe III Fe II (3)][BPh 4 ] 2 (6b). The chemical and physicochemical properties of the respective species are very similar to those of Fe, Co, and Ni complexes of H 1
Inorganic Chemistry, 2005
The syntheses, structures, and magnetic properties are reported of [Mn 12 O 12 (O 2 CPe t) 16 (MeOH) 4 ] (4), [Mn 6 O 2-(O 2 CH 2)(O 2 CPe t) 11 (HO 2 CPe t) 2 (O 2 CMe)] (5), [Mn 9 O 6 (OH)(CO 3)(O 2 CPe t) 12 (H 2 O) 2 ] (6), and [Mn 4 O 2 (O 2 CPe t) 6 (bpy) 2 ] (7, bpy) 2,2′-bipyridine), where Pe t) tert-pentyl (Pe t CO 2 H) 2,2-dimethylbutyric acid). These complexes were all prepared from reactions of [Mn 12 O 12 (O 2 CPe t) 16 (H 2 O) 4 ] (3) in CH 2 Cl 2. Complex 4‚2MeCN crystallizes in the triclinic space group P1 h and contains a central [Mn IV 4 O 4 ] cubane core that is surrounded by a nonplanar ring of eight alternating Mn III and eight µ 3-O 2ions. This is only the third Mn 12 complex in which the four bound water molecules have been replaced by other ligands, in this case MeOH. Complex 5‚ 1 / 2 CH 2 Cl 2 crystallizes in the monoclinic space group P2 1 /c and contains two [Mn 3 (µ 3-O)] 7+ units linked at two of their apexes by two Pe t CO 2ligands and one µ 4-CH 2 O 2 2bridge. The complex is a new structural type in Mn chemistry, and also contains only the third example of a gem-diolate unit bridging four metal ions. Complex 6‚H 2 O‚Pe t CO 2 H crystallizes in the orthorhombic space group Cmc2 1 and possesses a [Mn III 9 (µ 3-O) 6 (µ-OH)(µ 3-CO 3)] 12+ core. The molecule contains a µ 3-CO 3 2ion, the first example in a discrete Mn complex. Complex 7‚2H 2 O crystallizes in the monoclinic space group P2 1 /c and contains a known [Mn III 2 Mn II 2 (µ 3-O) 2 ] 6+ core that can be considered as two edge-sharing, triangular [Mn 3 O] units. Additionally, the synthesis and magnetic properties of a new enneanuclear cluster of formula [Mn 9 O 7 (O 2 CCH 2-Bu t) 13 (THF) 2 ] (8, THF) tetrahydrofuran) are reported. The molecule was obtained by the reaction of [Mn 12 O 12 (O 2-CCH 2 Bu t) 16 (H 2 O) 4 ] (2) with THF. Complexes 2 and 4 display quasireversible redox couples when examined by cyclic voltammetry in CH 2 Cl 2 ; oxidations are observed at −0.07 V (2) and −0.21 V (4) vs ferrocene. The magnetic properties of complexes 4−8 have been studied by direct current (DC) and alternating current (AC) magnetic susceptibility techniques. The ground-state spin of 4 was established by magnetization measurements in the 1.80− 4.00 K and 0.5−7 T ranges. Fitting of the reduced magnetization data by full matrix diagonalization, incorporating a full powder average and including only axial anisotropy, gave S) 10, g) 2.0(1), and D) −0.39(10) cm-1. The complex exhibits two frequency-dependent out-of-phase AC susceptibility signals (M ′′) indicative of slow magnetization relaxation. An Arrhenius plot obtained from M ′′ vs T data gave an effective energy barrier to relaxation (U eff) of 62 and 35 K for the slower and faster relaxing species, respectively. These studies suggest that complex 4 is a single-molecule magnet (SMM). DC susceptibility studies on complexes 5−8 display overall antiferromagnetic behavior and indicate ground-state spin values of S e 2. AC susceptibility studies at <10 K confirm these small values and indicate the population of low-lying excited states even at these low temperatures. This supports the small groundstate spin values to be due to spin frustration effects.
Inorganic Chemistry Communications, 2003
Several reaction schemes involving di-2-pyridyl ketone oxime, (py) 2 CNOH, Mn sources, RCO À 2 ligands and X À in MeCN or MeCN/EtOH lead to the new family of mixed-valence complexes [Mn II 2 Mn III 2 (O 2 CR) 2 X 2 {(py) 2 CNO} 2 {(py) 2 CO 2 } 2 ] (R ¼ Me, Ph; X ¼ Cl, Br; (py) 2 CO 2À 2 ¼ the gem-diolate(-2) form of di-2-pyridyl ketone). The products have been characterized by single crystal Xray crystallography and exhibit the same structural motif. Magnetic studies indicate weak antiferromagnetic exchange interactions in the complexes.
European Journal of Inorganic Chemistry, 2004
The use of phenyl 2-pyridyl ketone [(ph)(2-py)CO] and its oxime [(ph)(2-py)CNOH] in manganese benzoate chemistry has been investigated. The reaction of an excess of (ph)(2-py)CNOH with Mn(O 2 CPh) 2 •2H 2 O affords the mononuclear complex [Mn II (O 2 CPh) 2 {(ph)(2-py)CNOH} 2 ]•1.2H 2 O (1•1.2H 2 O) in high yield. The Mn II ion is coordinated by two monodentate benzoates and two N,NЈ-bidentate chelating (ph)(2-py)CNOH molecules in a cis-cis-trans fashion. The comproportionation reaction between Mn(O 2 CPh) 2 •2H 2 O and NnBu 4 MnO 4 (3:1) in the presence of (ph)(2-py)CNOH in MeCN/EtOH/CH 2 Cl 2 leads to the isolation of the mixed-valent cluster [Mn 8 O 2 (OH) 2 (O 2 CPh) 10 {(ph)(2-py)CNO} 4 ]• 4CH 2 Cl 2 (2•4CH 2 Cl 2) in about 55% yield. A second synthetic procedure that leads to pure 2 involves the reaction between the known starting material (NnBu 4)[Mn 4 III O 2 (O 2 CPh) 9-(H 2 O)] and four equivalents of the oxime ligand in CH 2 Cl 2. The centrosymmetric octanuclear molecule contains four Mn II and four Mn III ions held together by two µ 4-O 2− ligands and two µ 3-OH − ions to give the unprecedented [Mn 8 (µ 4-Ο) 2 (µ 3-ΟΗ) 2 ] 14+ core, with peripheral ligation provided by ten PhCO 2 − (two η 1 , four syn,syn η 1 :η 1 :µ 2 and four η 1 :η 2 :µ 3) and
Inorganic Chemistry, 2008
The employment of the anion of 2,6-diacetylpyridine dioxime (dapdoH 2) as a pentadentate chelate in transition metal cluster chemistry is reported. The syntheses, crystal structures, and magnetochemical characterization are described for [Mn 6 O 2 (OMe) 2 (dapdo) 2 (dapdoH) 4 ](ClO 4) 2 (1), [Mn 6 O 2 (OMe) 2 (dapdo) 2 (dapdoH) 4 ][Ca(NO 3) 4 ] (2), and [Mn 8 O 4 (OH) 4 (OMe) 2 (N 3) 2 (dapdo) 2 (dapdoH) 2 (H 2 O) 2 ] (3). The reaction of [Mn 3 O(O 2 CMe) 6 (py) 3 ](ClO 4) with 3 equiv of dapdoH 2 (with or without 2 equiv of NEt 3) in MeOH gave 1. The same cation, but with a [Ca(NO 3) 4 ] 2anion, was found in complex 2, which was obtained from the reaction in MeOH between Mn(NO 3) 2 , Ca(NO 3) 2 , and dapdoH 2 in the presence of NEt 3. In contrast, addition of NaN 3 to several reactions comprising MnCl 2 , dapdoH 2 , and NEt 3 in MeOH gave the octanuclear complex 3. Complexes 1−3 all possess rare topologies and are mixed-valence: 2Mn II , 4Mn III for 1 and 2, and 2Mn II , 6Mn III for 3. The core of the cation of 1 and 2 consists of two edge-sharing Mn 4 tetrahedra at the center of each of which is a µ 4-O 2ion. Peripheral ligation is provided by two µ-OMe-, four µ-dapdoH-, and two µ 3-dapdo 2groups. The core of 3 consists of two [Mn II Mn III 3 (µ 3-O) 2 ] 7+ "butterfly" units linked together by one of the µ 3-O 2ions, which thus becomes µ 4. Peripheral ligation is provided by four µ-OMe-, two µ-OH-, two µ-dapdoH-, and two µ 4-dapdo 2groups. Variable-temperature, solid-state dc and ac magnetization studies were carried out on complexes 1−3 in the 5.0−300 K range; the data for 1 and 2 are identical. Fitting of the obtained magnetization versus field (H) and temperature (T) data by matrix diagonalization and including only axial anisotropy (zero-field splitting, D) established that 1 possesses an S) 5 ground state with D) −0.24 cm-1. For 3, low-lying excited states precluded obtaining a good fit from the magnetization data, and the ground state was instead determined from the ac data, which indicated an S) 1 ground state for 3. The combined work demonstrates the ligating flexibility of pyridyl-dioxime chelates and their usefulness in the synthesis of new polynuclear Mn x clusters without requiring the co-presence of carboxylate ligands.