- Trimolybdenum cluster compounds with two capping ethylidyne groups
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Three compounds containing equilateral-triangular trimolybdenum clusters capped on both sides by ethylidyne (CCH3) groups are described: [Mo3(CCH3)2(O2CCH3) 6(H2O)3]SbF6·3H2O (1), [Mo3(CCH3)2(O2CCH3) 6(H2O)3](CF3SO3) 2 (2), and [Mo3(CCH3)2(O2CCH3) 6(H2O)3](p-CH3C6H 4SO3)2·10H2O (3). All three are obtained by suitable workup of the reaction mixture after refluxing Mo(CO)6 with a 10:1 v/v mixture of acetic acid and acetic anhydride. For the last two permanganate oxidation is used. The crystal structures of the three compounds have been solved and refined. In 1, where there are five electrons for the Mo3 cluster, the Mo-Mo bond orders are 5/6 and the mean Mo-Mo distance is 2.814 (5) A?; this is about 0.06 A? longer than that in a closely related cluster with Mo-Mo bond orders of 1.0. In 2 and 3, which each contain a bicapped Mo3 cluster with only four electrons, and hence a bond order of 2/3, the mean Mo-Mo distances are 2.883 (1) A? and 2.892 (1) A?, i.e., about 0.13 A? longer than for the Mo-Mo bonds of order 1.0. The cation in 1 has one unpaired electron showing an essentially constant g factor slightly above 2.0 in the range 4-300 K according to bulk susceptibility measurements. It shows no EPR spectrum but has a sharp 360-MHz 1H NMR spectrum in which the resonance of the O2CCH3 protons is shifted to 14 ppm downfield while that of the CCH3 protons is broadened and shifted 85 ppm downfield. The cations in 2 and 3 appear to be paramagnetic, but the temperature dependence is unusual and still under study. The cation gives an 1H NMR spectrum with lines at 15.6 and 27.1 ppm with relative intensities of 3.3 to 1.0.
- Ardon, Michael,Bino, Avi,Cotton, F. Albert,Dori, Zvi,Kaftory,Kolthammer, Brian W. S.,Kapon, Moshe,Reisner
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- Dimolybdenum tetracarboxylates as auxiliary chromophores in chiroptical studies of vic-diols
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The aim of the present work was to check the suitability of dimolybdenum carboxylates, other than commonly used [Mo2(OAc)4], as auxiliary chromophores for determining the absolute configuration of optically active vic-diols by means of electronic circular dichroism (ECD). To this end, a set of dimolybdenum tetracarboxylates was synthesized, and subsequently, the two most promising compounds were selected, namely dimolybdenum tetrakis(μ-pivalate) and tetrakis(μ-isovalerate). The selection was based on their solubility in commonly used solvents, their stability in solution, their tolerance to air exposure, as well as their utility for dichroic studies. The stability of the obtained in situ chiral complexes was verified by measuring the dependence of ECD, UV-vis, and NMR spectra on time, temperature, and concentration. We have shown that the ECD spectra of diverse vic-diols with these complexes are suitable for configurational assignment based on the correlation between signs of Cotton effects (CEs) arising in the spectra and the stereostructure of the ligand. Furthermore, to aid in the interpretation of experimental results, a separate set of DFT calculations has been incorporated to provide additional insight into the structure of the chiral complexes involved. In contrast to the earlier assumptions, experiments showed that the chelating mode of ligation is preferred for the studied complexes.
- Jawiczuk, Magdalena,Gorecki, Marcin,Suszczynska, Agata,Karchier, Michal,Jazwinski, Jaroslaw,Frelek, Jadwiga
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- Hierarchically Ordered Two-Dimensional Coordination Polymers Assembled from Redox-Active Dimolybdenum Clusters
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Coordination polymers (CPs) supporting tunable through-framework conduction and responsive properties are of significant interest for enabling a new generation of active devices. However, such architectures are rare. We report a redox-active CP composed of two-dimensional (2D) lattices of coordinatively bonded Mo2(INA)4 clusters (INA = isonicotinate). The 2D lattices are commensurately stacked and their ordering topology can be synthetically tuned. The material has a hierarchical pore structure (pore sizes distributed between 7 and 33 ?) and exhibits unique CO2 adsorption (nominally Type VI) for an isotherm collected at 195 K. Furthermore, cyclic voltammetry and electrokinetic analyses identify a quasi-reversible feature at E1/2 = -1.275 V versus ferrocene/ferrocenium that can be ascribed to the [Mo2(INA)4]0/-1 redox couple, with an associated standard heterogeneous electron transfer rate constant ks = 1.49 s-1. The tunable structure, porosity, and redox activity of our material may render it a promising platform for CPs with responsive properties.
- Claire, F. James,Tenney, Stephanie M.,Li, Minyuan M.,Siegler, Maxime A.,Wagner, Justine S.,Hall, Anthony Shoji,Kempa, Thomas J.
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- Preparation of core-shell coordination molecular assemblies via the enrichment of structure-directing codes of bridging ligands and metathesis of metal units
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A series of molybdenum- and copper-based MOPs were synthesized through coordination-driven process of a bridging ligand (3,3′-PDBAD, L1) and dimetal paddlewheel clusters. Three conformers of the ligand exist with an ideal bridging angle between the two carboxylate groups of 0° (H2α-L1), 120°(H2β-L1), and of 90°(H2γ-L1), respectively. At ambient or lower temperature, H2L1 and Mo2(OAc)4 or Cu2(OAc)4 were crystallized into a molecular square with γ-L1 and Mo2/Cu2 units. With proper temperature elevation, not only the molecular square with γ-L1 but also a lantern-shaped cage with α-L1 formed simultaneously. Similar to how Watson-Crick pairs stabilize the helical structure of duplex DNA, the core-shell molecular assembly possesses favorable H-bonding interaction sites. This is dictated by the ligand conformation in the shell, coding for the formation and providing stabilization of the central lantern shaped core, which was not observed without this complementary interaction. On the basis of the crystallographic implications, a heterobimetallic cage was obtained through a postsynthetic metal ion metathesis, showing different reactivity of coordination bonds in the core and shell. As an innovative synthetic strategy, the site-selective metathesis broadens the structural diversity and properties of coordination assemblies.
- Park, Jinhee,Chen, Ying-Pin,Perry, Zachary,Li, Jian-Rong,Zhou, Hong-Cai
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- Microwave-assisted synthesis of dimolybdenum tetracarboxylates and a decanuclear osmium cluster
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An improved method for the synthesis of dimolybdenum tetracarboxylates has been developed. The standard procedure for the preparation of these compounds involves extended reflux (up to 20 h) of a mixture of Mo(CO)6 and the appropriate carboxylic acid, along with its anhydride, under an inert atmosphere. Using a microwave reactor and a closed vessel, Mo2(acetate)4, Mo2(propionate)4 and Mo2(benzoate)4 have been prepared in superior yields in less than 1 h. Furthermore, this new method does not require the use of the acid anhydride or the use of an inert gas. An improved method for the preparation of [N(PPh3)2]2[Os10C(CO)24] directly from Os3(CO)12 has also been developed. The published synthesis of this osmium cluster calls for the pyrolysis of Os3(CO)11(py) for 64 h. Microwave irradiation of a mixture of Os3(CO)12 and diglyme in a closed vessel yields the desired product in just over 1 h.
- Johnson, Kara D.,Powell, Gregory L.
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- Syntheses and structures of di(carboxylato)hexakis(acetonitrile)-dimolybdenum(II) bis(tetrafluoroborate) and trans-[di(μ-acetato)-di(acetonitrile)di(μ-bis(diphenylphosphino)amine) dimolybdenum (II)] bis(tetrafluoroborate)
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Di(carboxylato)hexakis(acetonitrile)dimolybdenum(II) bis(tetrafluoroborate) s, [Mo2(μ-O2CR)2(CH3CN) 6](BF4)2(R = CH3,CH2Cl, C(CH3)3, CF3) (3a-d), are easily accessible by reacting [Mo2(CH3CN)8](BF4)4 (2) with a stoichiometric amount or a slight excess of the appropriate carboxylic acid and anhydride in acetonitrile. A large excess of carboxylic acid leads to the formation of tetracarboxylates. As an example cis-[Mo2(μ-O2CCH2Cl)2(CH 3CN)6](BF4)2 (3b) has been structurally characterized. Crystallographic data are as follows: space group: I42d (No. 122), a = b = 10.733(2), c = 59.448(5) A?, V = 6848(2) A?3, Z = 8, d(Mo-Mo) = 2.140(1) A?. Trans-[Mo2(μ-O2CCH3)2(dppa) 2(CH3CN)2](BF4)2 (4) can be synthesized from cis-[Mo2(μ-O2CCH3)2(CH 3CN)6](BF4)2 (3a) and bis(diphenylphosphino)amine (dppa) at room temperature. This result contradicts earlier reports where bulky diphosphines such as dppm (sterically very similar to dppa) did not lead to bis-diphosphine products. Furthermore our results indicate that in all the syntheses reported to date for [Mo2(μ-O2CCH3)2(LL) 2](BF4)2 type-compounds [Mo2(μ-O2CCH3)2(CH 3CN)6](BF4)2 acts as the precursor compound. Crystallographic data for 4 are as follows: P21/c (No. 14), a = 19.683(3), b = 15.129(2), c = 21.084(1) A?, β = 101.30(1)°, V = 6848(2) A?3, Z = 4. There are two independent molecules of the cation in the unit cell, d(Mo-Mo) = 2.133(1) and 2.136(1) A?.
- Cotton, F. Albert,Kühn, Fritz E.
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- Lewis acid enhanced axial ligation of [Mo2]4+ complexes
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We report here the syntheses, X-ray crystal structures, electrochemistry, and density functional theory (DFT) single-point calculations of three new complexes: tetrakis(monothiosuccinimidato)dimolybdenum(II) [Mo 2(SNO5)4, 1a], tetrakis(6-thioxo-2-piperidinonato) dimolybdenum(II) [Mo2(SNO6)4, 1b], and chlorotetrakis(monothiosuccinimidato)pyridinelithiumdimolybdenum(II) [pyLiMo2(SNO5)4Cl, 2-py]. X-ray crystallography shows unusually short axial Mo2-Cl bond lengths in 2-py, 2.6533(6) A, and dimeric 2-dim, 2.644(1) A, which we propose result from an increased Lewis acidity of the Mo2 unit in the presence of the proximal Li + ion. When 2-py is dissolved in MeCN, the lithium reversibly dissociates, forming an equilibrium mixture of (MeCNLiMo2(SNO5) 4Cl) (2-MeCN) and [Li(MeCN)4]+[Mo 2(SNO5)4Cl]- (3). Cyclic voltammetry was used to determine the equilibrium lithium binding constant (room temperature, K eq = 95 ± 1). From analysis of the temperature dependence of the equilibrium constant, thermodynamic parameters for the formation of 2-MeCN from 3 (ΔH = -6.96 ± 0.93 kJ mol-1 and ΔS = 13.9 ± 3.5 J mol-1 K-1) were extracted. DFT calculations indicate that Li+ affects the Mo-Cl bond length through polarization of metal-metal bonding/antibonding molecular orbitals when lithium and chloride are added to the dimolybdenum core.
- Dolinar, Brian S.,Berry, John F.
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- Synthesis and crystal structure of [Re(CO)3(μ-CH3CO2)(THF)]4
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A tetrameric complex [Re(CO)3(μ-CH3CO2)(THF)]4 (1) is formed in high yield when the reaction product of Re(CO)5Cl with acetic acid in refluxing 1,2-dichlorobenzene is dissolved in THF. The use of Re2(CO)10 instead of rhenium pentacarbonyl chloride also affords 1. The characterization of 1·3THF·0.5C6H14 has been accomplished by X-ray crystallography. The structure of the tetrameric molecule 1 consists of four rhenium(I) atoms bridged by four acetate ligands. The coordination of each metal center is fulfilled by three CO groups and one THF molecule in a way that all carbonyls are trans to oxygen atoms. The geometry of each acetate bridge is anti-syn providing a Re to Re separation of 5.40 A. This bonding mode is seen here for the first time in rhenium carboxylates. Different coordination types for Re-RCO2 interaction are also discussed in the paper.
- Cotton, F. Albert,Dikarev, Evgeny V.,Petrukhina, Marina A.
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- Synthesis, X-ray Structure Analysis and Spectroscopic Characterization of trans-Aquabis(μ-benzoato-κ2 O:O′) bis[μ-N,N′-bis(4-methoxyphenyl) formamidinato-κ2 N:N′] dimolybdenum(II)
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Abstract: The title compound, trans-Mo2(DAniF)2(OOCC6H5)2(H2O) (I) has a quadruply bonded Mo2 4+ unit equatorially coordinated by two N,N′-bis(4-methoxyphenyl)formamidinate (referred as DAniF) ligands and two benzoate (OOCC6H5) groups in transverse, and axially coordinated by one aqua oxygen atom. The compound crystallizes in the space group C2/c with one molecule in the asymmetric unit and features a Mo–Mo bond length of 2.0983(4) ?, which is typical for dimolybdenum quadruple bonds. In the crystal, the offsetstacking between pairs of phenyl rings creating a one-dimensional linear chain perpendicular to the Mo–Mo directions, with a distance between phenyl rings of 3.44?? and the center-to-center distance of 3.83??. The coordinated water oxygen atoms act as donors and uncoordinated methoxyl group oxygen atoms act as acceptors in intermolecular O–H?O hydrogen bonds.stacking between phenyl rings assemble the molecules into a three-dimensional framework. Graphical Abstract: The offsetstacking between phenyl rings of quadruply bonded Mo2 4+ paddle-wheel molecules create a one-dimensional linear chain. [Figure not available: see fulltext.].
- Kong, Ya-Jie,Han, Li-Juan
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p. 208 - 214
(2017/09/06)
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- Dicarboxylate-bridged (Mo2)n (n = 2, 3, 4) paddle-wheel complexes: Potential intermediate building blocks for metal-organic frameworks
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The treatment of the dimeric paddle-wheel (PW) compound [Mo 2(NCCH3)10][BF4]41 with oxalic acid (0.5 equiv.), 1,1-cyclobutanedicarboxylic acid (1 equiv.), 5-hydroxyisophthalic acid (1 equiv.) (m-bdc-OH) or 2,3,5,6- tetrafluoroterephthalic acid (0.5 or 1 equiv.) leads to the formation of macromolecular dicarboxylate-linked (Mo2)n entities (n = 2, 3, 4). The structure of the compounds depends on the length and geometry of the organic linkers. In the case of oxalic acid, the dimeric compound [(CH 3CN)8Mo2(OOC-COO)Mo2(NCCH 3)8][BF4]62 is formed selectively, whereas the use of 2,3,5,6-tetrafluoroterephthalic acid affords the square-shaped complex [(CH3CN)6Mo2(OOC-C 6F4-COO)]4[BF4]83. Bent linkers with a bridging angle of 109° and 120°, respectively, lead to the formation of the molecular loop [(CH3CN)6Mo 2(OOC-C4H6-COO)]2[BF 4]44 and the bowl-shaped molecular triangle [(CH 3CN)6Mo2(m-bdc-OH)]3[BF 4]65. All complexes are characterised by X-ray single crystal diffraction, NMR (1H, 11B, 13C and 19F) and UV-Vis spectroscopy.
- Koeberl, Mathias,Cokoja, Mirza,Bechlars, Bettina,Herdtweck, Eberhardt,Kuehn, Fritz E.
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p. 11490 - 11496
(2012/01/04)
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- Organometallic chemistry in a conventional microwave oven: The facile synthesis of group 6 carbonyl complexes
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Syntheses proceeding by reflux may be improved, accelerated and simplified, by carrying out the reaction in a modified conventional microwave oven. To demonstrate the potential of this method, the synthesis of over 20 group 6 organometallic compounds is reported. Hexacarbonyls, most notably Mo(CO)6, react with a range of mono, and bi, and tridentate ligands in a modified conventional microwave oven. They generally proceed without an inert atmosphere, yields are high and reaction times are short. For example, cis -[Mo(CO)4(dppe)] is prepared in >95% yield in 20 min. Reaction of Mo(CO)6 with dicyclopentadiene affords a simple one-step synthesis of [CpMo(CO)3]2 in >90% yield, which reacts further with alkynes in toluene to produce dimetallatetrahedrane derivatives, [Cp2Mo2(CO)4 (μ-RC2R)]; presumably via the in situ formation of air-sensitive [CpMo(CO)2]2. Dimolybdenum tetra-acetate is also prepared in 48% yield in 45 min, however, this reaction requires an inert atmosphere. While W(CO)6 reacts rapidly with amines to give cis diamine adducts in high yields, direct reactions with phosphines are not so clean. Bis(phosphine) complexes are, however, cleanly formed when a small amount of piperidine is added to the reaction mixture, presumably via the bis(piperidine) complex cis-[W(CO)4(pip)2]. Reactions with Cr(CO)6 generally require an inert atmosphere and proceed less cleanly, although the important synthon [Cr(CO)5 Cl][NEt4] was prepared in 30 min (74% yield), while [(η6-C6H5OMe)Cr(CO)3] can be prepared in 45% after 4 h.
- Ardon, Michael,Hogarth, Graeme,Oscroft, Daniel T.W.
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p. 2429 - 2435
(2007/10/03)
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- Quadruply bonded dimolybdenum complexes containing pairs of bridging diphosphine and acetate ligands; synthesis and structural characterization of trans-Mo2Cl2(OAc)2(μ-dppa)2 and its transformation to Mo2Cl4(μ-dppa)2, where dppa is N,N-bis(diphenylphosphino)amine
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By reaction of Mo2(OAc)4 with (CH3)3SiCl and dppa (dppa = Ph2PN(H)PPh2) in THF, two complexes can be prepared. The red complex trans-Mo2Cl2(OAc)2(μ-dppa)2 (1) was obtained in 42% yield while the green complex Mo2Cl4(μ-dppa)2 (2) was prepared in 31% yield. Complex 2 can also be derived by reacting K4Mo2Cl8 or Mo2Cl4(PPh3)2(CH3OH)2 with dppa in methanol and acetone, respectively. Reaction of 1 with (CH3)3SiCl leads to the formation of 2. Their UV-Vis and (31)P{(1)H} NMR spectra have been recorded and the structures of both 1 and 2 have been determined. Crystal data for 1: space group Pbca, a = 16.699(1), b = 16.784(1), c = 19.728(2)?, V = 5529.3(7)?**3, Z = 4, with final residuals R = 0.0606 and Rw = 0.0620. The diphosphine ligands are bridged to the metal centers with an eclipsed configuration around the metal-metal bond. The chloride atoms are forced to coordinate to the Mo atoms in the axial positions. Crystal data for 2: space group Ibca, a = 16.165(2)?, b = 16.576(2)?,c = 37.024(3)?, V = 9921(2)?**3, Z = 8, with final residuals R = 0.0933 and Rw = 0.0990. The two dppa ligands are bridged to the metal centers. The interconversions between 1 and 2 are discussed.
- Wu, Ying-Yann,Chen, Jhy-Der,Liou, Lin-Shu,Wang, Ju-Chun
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p. 193 - 200
(2008/10/08)
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- A New Reaction Vessel for Accelerated Syntheses using Microwave Dielectric Super-heating Effects
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Using a thick-walled glass reaction vessel a number of transition-metal organometallic and co-ordination compounds have been synthesised using microwave dielectric super-heating effects.Super-heating by 40-60 deg C is maintained by controlling the pressure at 10 atm and results in a decrease in the reaction time required for conventional reflux reactions by a factor of ca. 102.Full details of the design of the apparatus, the modification of a conventional microwave oven and the electrical circuitry for the pressure control are provided.
- Baghurst, David R.,Mingos, D. Michael P.
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p. 1151 - 1156
(2007/10/02)
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- Models for organometallic polymers. Zigzag chains of Mo2(O2CCH3)4 units linked by DMPE and TMED ligands
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Infinite zigzag chains of Mo2(O2CCH3)4 units linked by the bidentate ligands 1,2-bis(dimethylphosphino)ethane (dmpe) and tetramethylethylenediamine (tmed) crystallize from solutions of Mo2(O2CCH3)4 (1) dissolved in the respective neat ligand. Single-crystal X-ray structures of the light yellow polymers ∞1[Mo2(O2CCH3) 4(dmpe)] (2) and ∞1[Mo2(O2CCH3) 4(tmed)] (3) showed that the compounds were isostructural. Compound 2 crystallizes in space group P1 (-135°C) with a = 8.473 (2) A?, b = 9.562 (3) A?, c = 7.654(3) A?, α = 110.59 (2)°, β = 100.06 (2)°, ? = 69.26 (2)°, Z = 1, V = 541.9(3) A?3, R = 0.058, and Rw = 0.058. Compound 3 crystallizes in space group P1 (20°C) with a = 8.388 (1) A?, b = 8.445 (2) A?, c = 8.840 (2) A?, α = 105.95 (2)°, β = 115.62(1)°, γ = 91.63(2)°, Z = 1, V = 535.1 (2) A?3, R = 0.025, and Rw = 0.033. The ligands dmpe and tmed are coordinated axially through weak Mo-L bonds to relatively unperturbed Mo2(O2CCH3)4 centers. The solid-state Raman spectrum of 3 reveals a small decrease in the Mo-Mo stretching frequency 1 (νMo-Mo = 391 cm-1) relative to 1 (νMo-Mo = 405 cm-1). TGA and powder X-ray diffraction studies involving 3 showed that solid-state thermolysis results in the expulsion of tmed at 92 °C and the formation of crystalline 1.
- Kerby, Michael C.,Eichhorn, Bryan W.,Creighton, J. Alan,Vollhardt, K. Peter C.
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p. 1319 - 1323
(2008/10/08)
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- Activated molybdenum-molybdenum quadruple bonds. Synthesis, structure, and properties of [Mo2(O2CMe)2(en)4][(O 2CMe)2]·en: A solid-state model for a solvent-shared ion pair
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Mo2(O2CMe)4 [Mo-4Mo] reacts with neat ethylenediamine (en) to form [Mo2(O2CMe)2(en)4][(O 2CMe)2]·en (1) in high yield. The Mo2(O2CMe)2(en)42+ ion in 1 contains a quadruply bonded Mo24+ center [Mo-Mo = 2.125 (1) A?] supported by two axial and two spanning en ligands in addition to two spanning acetates. The complex exists as an ion pair in which the displaced acetates are separated from the Mo2 coordination sphere by the two spanning en ligands. The acetate counterions are hydrogen bonded to the spanning en ligands [N-O = 2.86 (2) A? (av)]. Compound 1 converts back to Mo2(O2CMe)4 at 120°C in the solid state. NMR studies show that dissociated and coordinated acetate ligands are present in neat en whereas, in D2O, only dissociated en and acetate are observed. Crystal data for 1 (20°C): a = 25.548 (7) A?, b = 9.277 (3) A?, c = 14.292 (4) A?, β = 107.43 (2)°, Z = 4, Dcalc = 1.374 g/cm3, and space group C2/m.
- Eichhorn, Bryan W.,Kerby, Michael C.,Haushalter, Robert C.,Vollhardt, K. Peter C.
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p. 723 - 728
(2008/10/08)
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- M3X13 Type of Equilateral-Triangular Metal Atom Cluster Compound with Several Unprecedented Features: 3-CH3C)(μ2-Br)3(η2,μ2-CH3CO2)3(H2O)3>ClO4*4H2O
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From the reaction of Mo(CO)6 with a refluxing mixture of acetic acid and acetic anhydride in the presence of NaBr and under nitrogen, the title compound is obtained after a suitable workup in which the reaction mixture is diluted with water and the trinuc
- Birnbaum, Amira,Cotton, F. Albert,Dori, Zvi,Kapon, Moshe,Marler, David,Reisner, George M.
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p. 2405 - 2410
(2007/10/02)
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