- Reactivity of Cr(III) μ-oxo compounds: Catalyst regeneration and atom transfer processes
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Oxidation of CpCr[(XylNCMe)2CH] (Xyl = 2,6-Me2C 6H3) with pyridine N-oxide or air generated the μ-oxo dimer, {CpCr[(XylNCMe)2CH]}2(μ-O). The μ-oxo dimer was converted to paramagnetic Cr(III
- MacLeod, K. Cory,Patrick, Brian O.,Smith, Kevin M.
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p. 688 - 700
(2012/03/07)
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- Reinvestigation of arylmanganese chemistry - Synthesis and molecular structures of [(thf)4Mg(μ-Cl)2Mn(Br)Mes], [Mes(thf)Mn(μ-Mes)]2, and (MnPh2)∞ (Ph = C6H5; Mes = mesityl, 2,4,6-Me3C6H2)
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The reaction of 2,4,6-trimethylphenylmagnesium bromide (MesMgBr) with manganese(II) chloride in an equimolar ratio yields [(thf)4Mg(μ-Cl)2Mn(Br)Mes] (1) with two bridging chloro ligands and a Mn-C bond length of 2.136(5) A??. A molar ratio of 2:1 leads to a metathesis reaction and the formation of [Mes(thf)Mn(μ-Mes)]2 (2) with two bridging mesityl groups. Whereas THF-free [MnMes2]3 crystallizes as a trimer from toluene solution, the reduced bulkiness of the phenyl groups in (MnPh2)∞ (3) leads to the formation of a chain-like structure with Mn-C bond lengths of 2.245(3) A??.
- Fischer, Reinald,G?rls, Helmar,Friedrich, Manfred,Westerhausen, Matthias
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p. 1107 - 1111
(2009/07/26)
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- Ferromagnetic coupling in hexanuclear gadolinium clusters
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The magnetic susceptibilities of hexanuclear gadolinium clusters in the compounds Gd(Gd6Zl12) (Z = Co, Fe, or Mn) and CsGd(Gd 6Col12)2 are reported and subjected to theoretical analysis with the help of density functional theory (DFT) computations. The single-crystal structure of Gd(Gd6Col12) is reported here as well. We find that the compound with a closed shell of cluster bonding electrons, Gd(Gd6Col12), exhibits the effects of antiferromagnetic coupling over the entire range of temperatures measured (4-300 K). Clusters with unpaired, delocalized cluster bonding electrons (CBEs) exhibit enhanced susceptibilities consistent with strong ferromagnetic coupling, except at lower temperatures (less than 30 K) where intercluster antiferromagnetic coupling suppresses the susceptibilities. The presence of two unpaired CBEs, as in [Gd6Mnl12] 3-, yields stronger coupling than when just one unpaired CBE is present, as in [Gd6Fel12]3- or [Gd 6Col12]2-. DFT calculations on model molecular systems, [Gd6Col12](OPH3)6 and [Gd6Col12]2(OPH3)10, indicate that the delocalized cluster bonding electrons are highly effective at mediating intracluster ferromagnetic exchange coupling between the Gd atom 4f7 moments and that intercluster coupling is expected to be antiferromagnetic. The DFT calculations were used to calculate the relative energies of various 4f7 spin patterns and form the basis for construction of a simple spin Hamiltonian describing the coupling within the [Gd6Col12] cluster.
- Sweet, Lucas E.,Roy, Lindsay E.,Meng, Fanqin,Hughbanks, Timothy
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p. 10193 - 10201
(2007/10/03)
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- Thermodynamic data of the dimerisation of gaseous CrI2(g), MnI2(g), FeI2(g), and CoI2(g), experimental and quantum chemical investigations
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By means of quantum chemical methods molar heats and entropies as a function of temperature for the monomeric and dimeric diiodides of 3d-metals have been calculated. From mass-spectrometric measurements of the dimerisation equilibria of gaseous CrI2, MnI2, FeI2, and CoI2 using the Knudsen-effusion method the heats of dimerisation and the heats of formation of the monomeric and dimeric iodides could be derived using the results of the quantum chemical calculations. WILEY-VCH Verlag GmbH, 2001.
- Schiefenhoevel,Binnewies,Janetzko,Jug
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p. 1513 - 1517
(2008/10/08)
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- Synthesis and Reactivity Towards Dioxygen of Some Manganese(II) Complexes of Tertiary Amines. Crystal Structures of >, 2> and
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Some manganese(II)-tertiary amine complexes of stoichiometry MnX2(NR3) have been prepared for the first time.Magnetic susceptibility and X-ray crystallographic studies on (R=Et or n-Pr) indicate that the complexes have a dimeric structure, in contrast to the analogous tertiary phosphine complexes which are polymeric.The crystal structure of which contains a mononuclear manganese site has also been determined.This complex is postulated to arise from reaction of a solution of with trace quantities of moisture.The reaction of the complexes with dioxygen has also been examined: shows no interaction, absorbs 2 mol of dioxygen per mol of complex, whereas absorbs anly 1.In contrast to the analogous tertiary phosphine complexes, the complexes do not exhibit reversible binding of dioxygen.
- Lane, Helen P.,Godfrey, Stephen M.,Pritchard, Robin G.,McAuliffe, Charles A.
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p. 701 - 706
(2007/10/02)
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- Thermal analysis of some complexes with malonamide
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In alkaline medium, malonamide forms anionic planar complexes [ML2](2-) . xH2O where M is Ni or Cu. Thermograms and vibrational spectra clearly indicate that three different nickel anion complexes could be isolated, with x being respectively 2, 1 and 0. O
- De Beukeleer, S. H. J.,Desseyn, H. O.,Perlepes, S. P.,Mullens, J.
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p. 149 - 162
(2008/10/09)
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- The Reaction of Bromo- and Iodo-phosphoranes with Unactivated Coarse Grain Manganese Metal Powder to Yield and n> (X = Br or I) by Insertion of Mn into the P-X Bond. The Crystal Structure of
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The novel reaction of crude manganese metal powder with dibromo- and diiodo-phosphoranes, R3PX2, has been studied.Reaction of the phosphoranes R3PI2 (R = phenyl or substituted aryl) with manganese allows insertion of the metal into P-X bonds and gives the
- Godfrey, Stephen M.,McAuliffe, Charles A.,Pritchard, Robin G.
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p. 371 - 376
(2007/10/02)
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- Iodomanganates(II): Synthesis and Crystal Structures of (Ph4P)MnI3L, MnI2L3, I3 and (I3)2 (L = Tetrahydrofuran)
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The compounds (Ph4P)MnI3L (1), MnI2L3 (2), I3 (3), and (I3)2 (4) (L = C4H8O, thf) were prepared in thf solution and their structures determined from single crystal X-ray diffraction data. 1 crystallizes in the monoclinic space group C2/c with a = 1743.6(1), b = 1985.8(1), c =1806.7(1) pm, β = 98.74(1) deg, Z = 8.The structure of 1 exhibits tetrahedral anions.The Mn-I distance was found to be 268.0 pm (mean). 2: monoclinic, C2/c with a = 1252.3(2), b = 1255.0(3), c = 1271.8(3) pm, β = 113.88(2) deg, Z = 4.The characteristic feature of the structure of 2 is the existence of neutral MnI2L3 molecules with a distorted trigonal bipyramidal geometry and the iodine atoms in equatorial positions (Mn-I: 271.1 pm).The compound crystallizes from a solution of MnI2 in tetrahydrofuran. 3: monoclinic, C2/c with a = 1695.3(1), b = 1123.1(1), c = 1646.2(1) pm, β = 96.91(1) deg, Z = 4.The preparation of 3 from 2 and iodine yields octahedral MnIL5(+) cations (Mn-I: 278.8 pm) and triiodide anions. 4: monoclinic, P21/n with a = 1005.5(1), b = 1056.8(1), c = 1835.6(2) pm, β = 91.16(1) deg, Z = 2. 4 is prepared from 3 and iodine in thf solution, and shows octahedral MnL6(2+) cations and triiodide anions. - Keywords: Iodo-Complexes of Manganese(II), Synthesis, Crystal Structure
- Stolz, Peter,Pohl, Siegfried
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p. 175 - 181
(2007/10/02)
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- Rare-earth-metal iodide clusters centered by transition metals: Synthesis, structure, and bonding of R7I12M Compounds (R = Sc, Y, Pr, Gd; M = Mn, Fe, Co, Ni)
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The compounds R7I12M (M = Co, Ni for R = Sc; M = Fe, Co for R = Y; M = Mn, Fe, Co for R = Gd; M = Mn, Fe, Co, Ni for R = Pr) have been synthesized by reactions of RI3, MI2, and R metals at 750-950°C in sealed Nb or Ta containers. These compounds all adopt the Sc(Sc6Cl12B) structure (space group R3, Z = 3) with a transition metal at the cluster center (in place of boron). The seventh isolated R3+ ion can be substituted by Ca2+ in several of the Pr and Gd cases. The structural details of Sc7I12Co, Y7I12Fe, and (Ca0.65Pr0.35)(Pr6I12Co) were determined by single-crystal X-ray diffraction methods (a = 14.800, 15.351, 15.777 A?; c = 10.202, 10.661, 10.925 A?; R = 3.3, 3.8, 3.4%; Rw = 6.7, 3.3, 3.5%, respectively). The last of these presented twinning difficulties endemic to this structure type, but these were overcome satisfactorily by an approximate separation procedure. R-M distances in the clusters are short; Pr-Co = 2.770, Y-Fe = 2.621, and Sc-Co = 2.431 A?. While MO theory provides some useful guides to these compounds' stability, the true breadth of the chemistry possible remains to be explored.
- Hughbanks, Timothy,Corbett, John D.
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p. 2022 - 2026
(2008/10/08)
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- ENCAPSULATION OF THE TRANSITION METALS CHROMIUM THROUGH COBALT IN ZIRCONIUM CLUSTER IODIDES.
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The zirconium iodide phases discussed all possess clusters with a formal electron count of 18 or more. We detail our efforts concerning the synthesis, structural characterization, magnetic properties, and electronic structure of zirconium iodide cluster compounds featuring the enclosure of the transition metals Cr, Mn, Fe, and Co. It is found that the iron-zirconium bonding in the cluster is notably greater than that in Zr//3Fe. The phase CsZr//6I//1//4Mn is properly diamagnetic, while the magnetic susceptibility data for the 19-electron Zr//6I//1//2Mn are well described by a high-temperature mu //e//f//f of 1. 84 mu //B and an intracluster spin-orbit coupling that partially quenches the moment at lower temperatures.
- Hughbanks,Rosenthal,Corbett
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p. 1511 - 1516
(2007/10/02)
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- STUDIES ON TRANSITION-METAL PICOLINE COMPLEXES - I. PREPARATION AND THERMOANALYTICAL INVESTIGATIONS.
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A large number of transition-metal picoline halides were prepared, and their thermal decompositions were investigated by TG, DTG, DTA and thermomicroscopy. The compounds were classified on the basis of their thermal properties and two possible mechanisms of thermal decomposition were established.
- Liptay,Borbely-Kuszmann,Nagy
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- Monocyclopentadienyl compounds of manganese(II). Synthesis, structure, magnetism, and NMR spectra
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A series of 13 manganese(II) half-sandwich compounds [(RnCp)MnXL]2, type L, and (Rcp)MnXL2, type K, have been prepared on different routes. These routes include the new starting materials Mn(DME)2I2 and [Mn3I6(AsEt3)4n. In general, K is favored only when small powerful donor ligands are used. In solution K and L are in equilibrium when R = Me, X = I, and L = PMe3. Byproducts of low solubility may force the equilibrium entirely to K, e.g., for R = H, X = I, and L = PMe3. A systematic paramagnetic NMR study shows that the compounds may be characterized easily. In particular, the distinction between K and L, the delocalization of unpaired electrons, and hyperconjugative effects in the phosphine-transition-metal bonding are shown. According to the NMR data and to solid-state magnetic measurements all compounds have five unpaired electrons per manganese at room temperature. For [Mecp)MnX(PEt3)]2 (X - Cl (2), X = Br (3), = I (4)) the magnetism has been followed down to 1.25 K, and antiferromagnetic interaction with J = -4.8, -5.0, and -4.7 cm-1 has been found. The J values are shown to be typical for superexchange in high-spin maganese(II) dimers. As determined by X-ray crystallography 2, 3, and 4 are halogen-bridged centrosymmetric dimers with pseudotetrahedral metal centers. Crystals of 2 and 3 are orthorhombic, space group Pbca, with a = 13.691 (3)/13.869 (1) ?, b = 15.314 (2)/15.248 (1) ?, c = 14.402 (3)/14.640 (1) ?, V = 3019.6/3074.8 ?3, and dcalcd = 1.265/1.435 g cm-3 for Z = 4. Refinement converged at R = 0.055/0.046 for 156/136 refined parameters and 1611/1572 observables. 4 is monoclinic, space group P21/c, with a = 15.099 (4) ?, b = 15.365 (3) ?, c = 14.576 (4) ?, β = 108.11 (2)°, V = 3214.1 ?3, and dcald = 1.567 g cm-3 for Z = 4. Refinement converged at R = 0.071 for 227 refined parameters and 2697 observed reflections. There is a clear halogen dependence for the geometry of the central Mn2X2 unit. All distances and the angle X-Mn-X increase on going from Cl to I while Mn-X-Mn* decreases. The latter effect is attributed to increasing halogen repulsion.
- K?hler, Frank H.,Hebendanz, Nikolaus,Müller, Gerhard,Thewalt, Ulf,Kanellakopulos, Basil,Klenze, Reinhard
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p. 115 - 125
(2008/10/08)
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