- KOMPLEXKATALYSE. XVI. UEBER DIE REAKTION VON TRICHLORO-MONONITROSYL-MOLYBDAEN(II)- UND DICHLORO-DINITROSYL-MOLYBDAEN(0)-VERBINDUNGEN MIT EtAlCl2. NACHWEIS EINES Mo0Cl(NO)-KOMPLEXFRAGMENTS IN DEN KATALYSATORLOESUNGEN FUER DIE OLEFINMETATHESE
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The formation of an unstable Mo0Cl(NO)-containing complex in the reaction of trichloronitrosylmolybdenum(II) or dichlorodinitrosylmolybdenum(0) complexes MoCl3(NO)(OPPh3)2 or MoCl2(NO)2(PPh3)2 with EtAlCl2 has been proved by trapping experiment
- Seyferth, Karl,Taube, Rudolf
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- UEBERGANGSMETALLKOMPLEXE MIT SCHWEFELLIGANDEN. XXIX. REDOXGEKOPPELTE SCHWEFELLIGAND-TRANSFERREAKTIONEN ZWISCHEN EISEN- UND MOLYBDAEN-ZENTREN: SYNTHESE, STRUKTUR UND REAKTIVITAET VON 2> * 2H2O UND 2>(2-) (dttd(2-) = 2,3,8,9-DIBENZO-1,4,7,10-TETRATHIADE...
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The reaction of (dttd(2-) = 2,3,8,9-Dibenzo-1,4,7,10-tetrathiadecan(-2)) with (nor = norbornadiene) leads to the Mo(I) complex 2> by way of a redox coupled ligand transfer.The reaction proceeds by transferring the dttd(2-) ligand from to yielding 2>(2-) which is subsequently oxidized by Fe(II) to give 2>.Reduction of the latter by LiBEt3H/CO regenerates 2>(2-).In 2> both Mo centers are connected in three different ways viz., by a Mo-Mo bond, thiolato S atoms of dttd(2-) and the clamp of the SC2H4S bridge.The latter preserves the binuclearity when the closed 2> is reduced to the open 2>(2-).The reaction of Li22> with NOPF6 yields 2>.The structures of 2>, (NMe4)22> and (for the sake of comparison) of (NMe4) have been determined from X-ray diffraction studies.
- Sellmann, Dieter,Binker, Gerhard,Schwarz, Joerg,Knoch, Falk,Boese, Roland,et al.
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- Syntheses, Structures, and Molecular Orbital Analysis of Hydridotris(pyrazolyl)borate (Tp) Molybdenum Carbonyls: Paramagnetic TpMo(CO)3 and Triply Bonded Tp2Mo2(CO)4 (Mo Mo)
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Tris(pyrazolyl)borate ion, HB(C3N2H3)3- (Tp), reacts with Mo(CO)6 to give the anion, TpMo(CO)3-, which in turn is easily oxidized to the paramagnetic radical, TpMo(CO)3 (1), by a variety of mild oxidizing agents, e.g., Cp2Fe+.EHMO and 1H NMR studies of 1 show the odd electron occupies a doubly degenerate orbital and that the odd electron is delocalized onto the pyrazolyl rings of the Tp ligand by ?-bonding.The bonding of Tp and Cp ligands is compared in light of the EHMO results.Decarbonylation of 1 gives the triply bonded complex, Tp2Mo2(CO)4 (Mo Mo) (2).Compound 2 is largely unreactive toward nucleophiles, and the MoMo triple bond is cleaved in reaction with Br2, S8, etc.Several attempts to prepare mixed ligand dimers of the type TpCpMo2(CO)n are described.Compound 1 crystallizes in the trigonal system: space group , Z = 2, a = b = 11.359 (4) Angstroem, c = 8.161 (2) Angstroem, V = 911.9 (3) Angstroem3.The refinement converged with R1, R2 = 0.0383, 0.0435 based on 440 reflections with I > 2.33?(I).The molecule has strict C3 symmetry with Mo-N = 2.207 (7) Angstroem, Mo-C = 2.013 (11) Angstroem, C-O = 1.126 (11) Angstroem, C-Mo-N = 94.8 (3) deg, C-Mo-C = 87.8 (4) deg, and N-Mo-N = 82.5 (3) deg.The structure of 2 was determined on a solvate, 2*CHCl3, which crystallized in the orthorombic system, space group Pbca, Z = 8, a,b,c = 12.995 (2), 16.974 (4), 29.396 (6) Angstroem, V = 6485 (2) Angstroem3.The refinement, based on 2957 reflections with I > 3?(I), converged with R1,R2 = 0.055, 0.063.The molecule has approximate C2 symmetry.The N-donor atoms are in two general locations, one trans to the MoMo bond (Mo-N = 2.21 Angstroem) and one cis to the MoMo bond and trans to the carbonyls (Mo-N = 2.23 Angstroem).The carbonyls are also divided into two sets, one semibridging (Mo-C = 1.93 Angstroem, Mo-Mo-C = 70.5 deg) and one terminal (Mo-C = 1.96 Angstroem, Mo-Mo-C = 83.4 deg).The MoMo bond length is 2.507 (1) Angstroem.
- Curtis, M. David,Shiu, Kom-Bei,Butler, W. M.,Huffman, John C.
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- Activation parameters in flash photolysis studies of Mo(CO)6
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Reported is a combined time-resolved optical (TRO) and infrared (TRIR) spectroscopic investigation of the flash photolysis of Mo(CO)6 in cyclohexane solution. TRIR studies using 308 nm excitation led to transient bleaching of the strong νCO band at 1987 cm-1 of Mo(CO)6 and appearance of new bands at 1931 and 1964 cm-1 attributed to Mo(CO)5(Sol). Using a high pressure/variable temperature flow cell, the kinetics of back reaction with CO (kCO) to regenerate the hexacarbonyl was studied over the PCO range 1-20 atm and at five temperatures. These data gave kCO=4.6±0. 2×106 M-1 s-1 (298 K) and the activation parameters ΔHCO?=32.6±3 kJ/mol and ΔSCO?=-7.3±11 J mol-1 K-1 from which an interchange mechanism was proposed. The analogous species seen in the TRO experiment displayed a transient absorbance at 420 nm and analogous kinetics properties although at lower PCO self-trapping with Mo(CO)6 (to give Mo2(CO)11) is a competitive process. The Mo(CO)5(Sol) transient could also be trapped by nPrBr (kRBr=5.3??0.7×10 7 M-1 s-1).
- Kayran, Ceyhan,Richards, Margaret,Ford, Peter C.
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- Synthese und Reaktivitaet kohlenwasserstoffueberbrueckter Komplexe von Mangan, Rhenium, Molybdaen und Wolfram
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The hydrocarbon-bridged complexes M(CH2)nM (M=MN(CO)5: n=5 (2b), 10 (2c); M=Re(CO)5: n=5 (3b), 10 (3c); M=(η5-C5H5)Mo(CO)3: n=5 (4b), 10 (4c); M=(η5-C5H5)W(CO)3: n=10 (5c)) are obtained by reaction of the bistriflates Y(CH2)nY (Y=F3CSO3, n=5 (1b), 10 (1c)) with the carbonyl metalates - (M=Mn (2), Re (3)) and 5-C5H5)M(CO)3>- (M=Mo (4), W (5)) in diethyl ether and THF, respectively.Depending on the solvent, the reaction of 1b with 2 also affords the cyclic carbene complex 2d.The action of SO2 and CO, respectively, on the complexes 2a-c and 4b,c results in the formation of the sulfinato-S complexes 5-C5H5)(OC)3MoSO2(CH2)nO2SMo(CO)3(η5-C5H5)> (n=5 (4b'), 10 (4c')) and the diacyl-bridged compounds (n=3 (2a'), 10 (2c')).According to an X-ray structural analysis, the monoacyl complex (2e) crystallizes in the orthorhombic space group Cmca with Z=4, the acyl function being disordered. 1H NMR spectroscopic investigations indicate a hindered rotation about the Cα-Cβ-? bond in 2b, c and 3b, c.
- Lindner, Ekkehard,Pabel, Michael,Fawzi, Riad,Mayer, Hermann A.,Wurst, Klaus
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- Molybdenum-Carbon Bond Dissoiation Energies in Mo(CO)6
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The pressure dependence of the recombination rate constants for Mo(CO)n (n = 3, 4, and 5) with CO has been studied by time-resolved infrared laser absorption spectroscopy.These data, in conjuntion with an RRKM model for unimoleular decay of the activated
- Ganske, Jane A.,Rosenfeld, Robert N.
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- Synthesis and structure of the first η6-pyrazine complex 6-Me4pyrazine)2> and related studies
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The synthesis of vanadium and molybdenum complexes derived from nitrogen-containing heterocyclic aromatic ligands are described.The first η-pyrazine sandwich complex, 6-Me4pyrazine)2>, has been prepared by metal vapour synthesis and crystallographically characterized.The synthesis of 6-2,6-lutidine)2> has been substantially improved, and provides a convenient starting material for the preparation of the new half-sandwich compounds 6-2,6-lutidine)(PMe3)3> and 6-2,6-lutidine)(η3-allyl)Cl>2.
- McGhee, William D.,Sella, Andrea,O'Hare, Dermot,Cloke, F. Geoffrey N.,Mehnert, Christian,Green, Malcolm L. H.
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- Further kinetics studies of intermediates formed by flash photolysis of Mo(CO)6
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Kinetics studies of the behavior of Mo(CO)5(CH) in the presence of radical initiators were conducted in cyclohexane (CH) solution by laser flash photolysis with time-resolved infrared detection. Activation parameters were determined for reactio
- Diz, Enrique Lozano,Ford, Peter C.
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- Imido-titanium/molybdenum heterobimetallic systems. Switching from η6-arene to fischer-type aminocarbene complexes by tuning reactivity conditions
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Two types of bimetallic titanium/molybdenum systems are described: the first possesses unprecedented η6-arene-imido groups, while the second has Fischer-type aminocarbene ligands bridging the two metals. The (η6-arene)-Mo imido-Ti complex Ti[=N(η6-Ar)Mo(CO) 3]Cl2(NHMe2)2 (2; Ar = 2, 6-'Pr 2-C6H3) has been prepared through the reaction of (η6-ArNH2)Mo(CO)3 (3) and TiCl 2(NMe2)2. The alternative route from 2 and Ti(NMe2)4/Me3SiCl also afforded 1, but it was contaminated with a small amount of Ti(=NAr)Cl2(NHMe 2)2 (1). The reaction between the dimeric complexes {Ti(μ-NAr)(NMe2)2}2 and Mo(CO)6 gave complex mixtures of products, among which the Fischer-type aminocarbene complex [(CO)5Mo{=C(NMeCH2NMe2)O}Ti(=N 2,6-Pri2-C6H3)(NMe 2)(NHMe2)] (4) could be characterized. The formation of 4 resulted from the nucleophilic attack of the amido -NMe2 to the carbonyl that afforded the titanoxy aminocarbene linker between the Mo and the Ti centers, followed by a subsequent C-H activation of a methyl group of the aminocarbene and C,N coupling with an amido ligand on titanium. Treatment of Ti(NMe2)4 with 1 equiv of Mo(CO)6 produced the titanoxy aminocarbene [(CO)5Mo{=C(NMe2)O}Ti(NMe 2)3] (5), while in the presence of 1 equiv of ArNH 2 the imido complex [(CO)5Mo{=C(NMe2)O} Ti(=N-2, 6Pr'2-C6H3)(NMe2)(NHMe 2)2] (6) is formed. The molecular structures of 1-6 have been determined by X-ray diffraction.
- Lorber, Christian,Vendier, Laure
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- Borylene transfer under thermal conditions for the synthesis of rhodium and iridium borylene complexes
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(Chemical Equation Presented) Borylene transfer reactions to [(η5-C5R5)M(CO)2] (M = Rh, R = H; M = Ir, R = Me) using [(OC)5Mo=BN(SiMe3)2] as a borylene source proceed at room temperature and generate terminal rhodium and iridium borylene complexes (see scheme). Iridium complex 1 was characterized by X-ray crystallography.
- Braunschweig, Holger,Forster, Melanie,Kupfer, Thomas,Seeler, Fabian
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- PHOTOCHEMISTRY OF Mo(CO)6 IN THE GAS PHASE
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We report a study of the photochemistry of Mo(CO)6 in the gas phase.Time-resolved infrared laser absorption spectroscopy is used to monitor the vibrational spectroscopy and lifetimes of the coordinatively unsaturated species formed upon photolyses at 351, 248, and 193 nm.The infrared spectra observed indicate that Mo(CO)5 has C4ν symmetry, Mo(CO)4 has C2ν symmetry, and Mo(CO)3 has C3ν symmetry.All three unsaturated species undergo rapid association reactions with Mo(CO)6 and with CO.Mo(CO)5 recombines with CO with a high-pressure limiting rate constant of 2.0(+/-0.2) x 1E6 Torr-1s-1.The corresponding rate constants for Mo(CO)4 and Mo(CO)3 are 7.5 (+/-1.5) x 1E6 and 1.8 (+/-1.0) x 1E7 torr-1s-1, respectively.
- Ganske, Jane A.,Rosenfeld, Robert N.
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- Synthesis of 1-aza-2-borabutatriene rhodium complexes by thermal borylene transfer from [(OC)5Mo=BN(SiMe3)2]
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Borylene on me: An unprecedented borylene transfer to metal-carbon double bonds afforded the title compounds. Preliminary studies revealed a thermally induced change of coordination mode from B-C to C-C and subsequent highly stereoselective C-H activation by the B=C bond. [(η5-C 5H5)Rh(PCy3){(B,C-η2)-(SiMe 3)2N=B=C=CH2)}] and its rearrangement product were both characterized by X-ray crystallography (see picture).
- Braunschweig, Holger,Ye, Qing,Damme, Alexander,Kupfer, Thomas,Radacki, Krzysztof,Wolf, Justin
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p. 9462 - 9466
(2011/10/30)
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- Borylene-based functionalization of iron-alkynyl-σ-complexes and stepwise reversible metal-boryl-to-borirene transformation: Synthesis, characterization, and density functional theory studies
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Thermally induced chemoselective borylene transfer from [(OC)5Mo = BN(SiMe3)2] (2a) to the carbon-carbon triple bond of an iron dicarbonyl alkynyl complex [(η5-C5Me 5)Fe(CO)2C≡CPh] (3) led to the isolation of an iron aminoborirene complex [(η5-C5Me5)(OC) 2Fe{μ-BN(SiMe3)2C = C}Ph] (4) in satisfactory yield. Room temperature photolysis of 4 resulted in an unprecedented rearrangement and a concurrent decarbonylation, affording the novel C2 side-on coordinated iron boryl complex [(η5- C5Me5)(OC)FeBN(SiMe3)2(η 2-CC)Ph] (5). Carbonylation of 5 under CO atmosphere at ambient temperature yielded [(η5-C5Me5)(OC) 2FeBN(SiMe3)2CCPh] (6), which is an isomer of 4. Decarbonylation of 6 at 80 °C led to 5, which could be upon introduction of CO gas further converted into 4 under same conditions. Reaction of 5 with PMe3 at 80 °C yielded the phosphane complex [(η5- C5Me5)(OC)(PMe3)Fe{μ-BN(SiMe 3)2C = C}Ph] (7). All above-mentioned iron complexes 4-7 were isolated as air and moisture sensitive crystalline solids in good yields and have been fully characterized in solution and by X-ray crystallography. Quantum chemical calculations using density functional theory (DFT) have been carried out to understand the mechanisms of the experimentally observed reactions and to analyze the bonding situation in the molecules 4-7.
- Braunschweig, Holger,Ye, Qing,Radacki, Krzysztof,Brenner, Peter,Frenking, Gernot,De, Susmita
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- Binuclear carbyne and ketenyl derivatives of the alkyl-bridged complexes [Mo2(η5-C5H5) 2(μ-CH2R)(μ-PCy2)(CO)2] (R = H, Ph)
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The 30-electron benzylidyne complex [Mo2Cp2(μ-CPh) (μ-PCy2)(μ-CO)] (Cp = η5-C5H 5) could be conveniently prepared upon photolysis of the benzyl-bridged complex [Mo2Cp2(μ-CH2Ph) (μ-PCy2)(CO)2]. It reacted with CO to give the ketenyl complex [Mo2Cp2{μ-C(Ph)CO}(μ-PCy2)(CO) 2] (2.6101(2) A), which in turn could be selectively decarbonylated at 353 K to give the 32-electron benzylidyne derivative [Mo 2Cp2(μ-CPh)(μ-PCy2)(CO)2] (Mo-Mo = 2.666(1) A). Related methylidyne complexes could be obtained from the methyl-bridged complex [Mo2Cp2(μ-CH 3)(μ-PCy2)(CO)2] via its trinuclear derivative [Mo3Cp2(μ3-CH)(μ-PCy 2)(CO)7]. Thus, the carbonylation of the latter cluster gave the ketenyl complex [Mo2Cp2{μ-C(H)CO}(μ- PCy2)(CO)2], whereas its reaction with P(OMe)3 gave the substituted cluster [Mo3Cp2(μ3-CH) (μ-PCy2)(CO)6{P(OMe)3}], which in turn could be thermally degraded to give selectively the 30-electron methylidyne derivative [Mo2Cp2(μ-CH)(μ-PCy2)(μ-CO) ] (Mo-Mo = 2.467(1) A). DFT calculations on the phenylketenyl complex revealed that the metal-ligand interaction is intermediate between the extreme descriptions represented by the acylium (3-electron donor) and ketenyl (1-electron donor) canonical forms of this ligand.
- Alvarez, M. Angeles,Garcia, M. Esther,Garcia-Vivo, Daniel,Martinez, M. Eugenia,Ruiz, Miguel A.
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p. 2189 - 2199
(2011/05/11)
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- A study of molybdenum catalysts in the polymerization of 2,5-didodecyl-1,4-dipropynylbenzene
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The reaction of 2,5-didodecyl-1,4-dipropynylbenzene with different molybdenum sources (Mo(CO)6, norbornadiene-Mo(CO)4, cyclooctadiene-Mo(CO)4, cycloheptatriene-Mo(CO)3, (PhCCPh)3Mo(CO), (acac)2MoO2/AlEt3) was investigated in the presence of 4-chlorophenol or 2-fluorophenol. Upon heating to 105-130°C, the formation of didodecyl-PPE resulted. The degree of polymerization of the PPE is dependent on the used phenol and to the utilized molybdenum precursor. The most active catalyst forms from (acac) 2MoO2, AlEt3 and 2-fluorophenol. This catalyst combination gives high molecular weight PPEs after 6 h at 105°C.
- Bly, Ruta K.,Dyke, Kristen M.,Bunz, Uwe H.F.
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p. 825 - 829
(2007/10/03)
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- Synthesis, electrochemistry, and crystal and molecular structures of some molybdenum(0) arene derivatives with fluorinated and phenyl-substituted arene ligands
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Compounds of general formula Mo(η6-arene) (CO)3, arene=diphenyl, 1; 1,3,5-triphenylbenzene, 2; C6H5F, 3; C6H5 CF3, 4, have been prepared in good yields by reacting fac-Mo(CO)3(DMF)3, DMF=N,N-dimethylformamide, with BF3 · OEt2 and the appropriate arene. The crystal and molecular structures of 1, 3, and 4, are reported. The dinuclear derivative Mo2(η6:η6 -C6H5-C6H5)(CO)6, 5, was obtained by thermal reaction of Mo(η6-toluene) (CO)3 with Mo(η6-diphenyl)(CO)3. An electrochemical study has been performed on the new complexes, showing that the dimolybdenum complex undergoes a single two-electron reduction at about the same potential as the corresponding dichromium complex, the molybdenum dianion being less stable than the chromium analogue.
- Antonini, Sara,Calderazzo, Fausto,Englert, Ulli,Grigiotti, Emanuela,Pampaloni, Guido,Zanello, Piero
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p. 2158 - 2168
(2007/10/03)
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- A new approach to studying the mechanism of catalytic reactions: An investigation into the photocatalytic hydrogenation of norbornadiene and dimethylfumarate using polyethylene matrices at low temperature and high pressure
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This paper presents a new method for investigating the mechanisms of homogeneously catalyzed reactions involving gases, particularly H2. We show how the combination of polyethylene (PE) matrices and high pressure - low temperature (HPLT) experiments can be used to provide new mechanistic information on hydrogenation processes. In particular, we show how we are able to generate reaction intermediates at low temperature, and then to extract the contents of the PE film at room temperature to characterize the organic products using GC-MS. We have used our new technique to probe both the hydrogenation of dimethyl fumarate (DF), using Fe(CO)4(η2-DF) as the catalytic species, and the hydrogenation of norbornadiene (NBD), using (NBD)M(CO)4 (M = Cr or Mo) as the catalytic species. Irradiation of Fe(CO)4(η2-DF) in a PE matrix at 150 K resulted in the formation of an intermediate complex tentatively assigned Fe(CO)3(η4-DF). Warming this complex to 260 K under H2 leads to the formation of Fe(CO)3(η2-DF)(η2-H2). Further warming of the reaction system results in the hydrogenation of the coordinated DF, to generate dimethyl succinate (DS). Characterization of the intermediate species was obtained using FTIR spectroscopy. Formation of DS was confirmed using both FTIR spectroscopy and GC-MS analysis. UV photolysis of (NBD)M(CO)4 in PE under H2 in the presence of excess NBD results in the formation of the hydrogenated products norbornene (NBN) and nortricyclene (NTC), with trace amounts of norbornane (NBA) being observed. These products were in similar ratios to those observed in fluid solution. However, for (NBD)Mo(CO)4, the relative amounts of the organic products change considerably when the reaction is repeated in PE under H2 in the absence of free NBD, with NBA being the major product. The use of our HPLT cell allows us to vent and exchange high pressures of gases with ease, and as such we have performed gas exchange reactions with H2 and D2. Analysis of the reaction products from these exchange reactions with GC-MS provides evidence for the mechanism of formation of NBA, in both the presence and absence of excess NBD, a reaction which has been largely ignored in previous studies.
- Childs,Cooper,Nolan,Carrott,George,Poliakoff
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p. 6857 - 6866
(2007/10/03)
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- Thermal Catalytic HYdrosilylation of Conjugated Dienes with Triethylsilane in the presence of Tricarbonyl(o-xylene)metal Complexes
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The thermal catalytic hydrosilylation of 1,3-butadiene (1), trans-2-methyl-1,3-pentadiene (2), 2,3-dimethyl-1,3-butadiene (3) and isoprene (4), with triethylsilane were studied in the presence of M(CO)3(o-xylene) (M=Cr, Mo, W) complexes in polar and nonpolar solvents such as tetrahydrofuran, hexane and toluene. Mo(CO)3(o-xylene) was found to be the only active catalyst for the hydrosilylation of 3 with triethylsilane, which gave1-triethylsilyl-2,3-dimethyl-2-butene (3a), as hydrosilylated product i n tetrahydrofuran. The product was identified by means of (1)H and (13)CNMR and GLC. The same catalyst, Mo(CO)3(o-xylene), decomposed to Mo(CO) 6 without giving hydrosilylated products of 1, 2 and 4 in tetrahydrofuran. M(CO)3(o-xylene) (M=Cr, Mo, W) complexes were found to be stable for about 6 h in hexane and toluene, and showed no catalytic activity for the hydrosilylation of 1, 2, 3 and 4.
- Kayran, Ceyhan,Rouzi, Pazilaiti
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- Cooperative effects in π-ligand bridged dinuclear complexes XXII. New dinuclear bis(cyclopentadienediyl)ketone complexes containing molybdenum, tungsten, cobalt and iron
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Hydrolysis of the siloxyfulvene compounds {M}[η5-C5H4C(OTMS)(C5Me 4)] ({M}=Mo(CO)3Me: 1a; {M}=W(CO)3Me: 1b) affords {M}[η5-C5H4C(O)(C5
- Koernich, Jan,Haubold, Stephan,He, Jin,Reimelt, Oliver,Heck, Juergen
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p. 329 - 337
(2007/10/03)
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- Photochemistry of (η6-arene)Mo(CO)3 and the role of alkane solvents in modifying the reactions of coordinatively unsaturated metal carbonyl fragments
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The reactions of (η6-arene)Mo(CO)2(Sol) and M(CO)5(Sol) with CO have been studied in a range of alkane solvents (Sol), and the kinetic and activation parameters have been determined (M = Cr, Mo, or W). For M = Cr the ΔH? is constant (22 ± 2 kJ mol-1), while the ΔS? term becomes less negative as the alkane chain length increases. For the larger metals the variation in kinetic and activation parameters is less significant. Solvent displacement by CO involves an interchange mechanism for the Cr system, while for Mo or W complexes the mechanism is more associative in character. The photochemistry of (η6-arene)Mo(CO)3 (arene = benzene, mesitylene, p-xylene, or hexamethylbenzene) compounds was investigated by laser flash photolysis, supported by matrix isolation and time-resolved infrared spectroscopy (TRIR). In contrast to the behavior to the analogous (η6-arene)Cr-(CO)3, it is found that the efficiency for photochemical expulsion of CO from (η6-mesitylene)-Mo(CO)3 is markedly wavelength dependent (ΦCO = 0.587, 0.120, and 0.053 at 266, 313, and 334 nm, respectively).
- Breheny, Ciara J.,Kelly, John M.,Long, Conor,O'Keeffe, Siobhan,Pryce, Mary T.,Russell, Graham,Walsh, Margaret M.
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p. 3690 - 3695
(2008/10/08)
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- Four-coordinate group-14 elements in the formal oxidation state of zero - Syntheses, structures, and dynamics of [{(CO)5Cr}2Sn(L2)] and related species
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The sodium salts Na2[{(CO)5M}2EX2] (M = Cr, Mo, W; E = Ge, Sn, Pb; X = Cl, I, OOCCH3) react with 2,2′-bipyridine (bipy) to form neutral compounds [{(CO)5M}2E(bipy)] (E = Sn: 1a-1c; E = Ge: 3a; E = Pb: 4). 1,10-Phenanthroline (phen) analogues of compounds 1a-1c and 3a [{(CO)5M}2E(phen)] (E = Sn: 1d-1f, E = Ge: 3b) are as well accessible. The 2,2′-bipyridine ligand in 1 may be formally replaced by two pyridine (py) ligands resulting in [{(CO)5M}2Sn(py)2] (1g: M = Cr, 1h: M = W). The bis-bidentate ligand 2,2′-bipyrimidine (bpmd) is found to coordinate just one [{(CO)5M}2Sn] entity in [{(CO)5M}2Sn(bpmd)] (2b: M = Cr, 2c: M = W). The biimidazolato (biim) ligand binds two [{(CO)5Cr}2Sn] moieties in [{(CO)5Cr}2Sn(biim)Sn{Cr(CO)5} 2]2-, 2a. It is shown by 1H-NMR that the pyrimidine entities in these compounds (2b, 2c) are able to rotate by a full 180° turnaround with respect to one another. This process must involve complete de-coordination of at least one of the two nitrogen donors in again at least one of the chelate cycles, the activation energy for this process being around 60 kJ/ mol. By 119Sn-NMR spectroscopy of almost all of the tin compounds described it is shown that equilibria between [{(CO)5M}2Sn(L2)] and [{(CO)5M}2Sn(L)] + L exist in all cases. From the temperature dependence of the δ values it is concluded that the activation barriers for this association/ dissociation process is below 10 kJ/mol. The structures of all new compounds are documented by X-ray analyses and all compounds are characterized by the usual analytical and spectroscopical techniques.
- Kircher, Peter,Huttner, Gottfried,Heinze, Katja,Schiemenz, Berthold,Zsolnai, Laszlo,Buechner, Michael,Driess, Alexander
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p. 703 - 720
(2007/10/03)
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- Chromium, molybdenum and tungsten carbonyl derivatives of distibinomethane ligands
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Substituted Group 6 carbonyl complexes of the distibinomethane ligands Ph2SbCH2SbPh2 (dpsm) and Me2SbCH2SbMe2 (dmsm) of types [M(CO)5(η1-dpsm)] (M = Cr, Mo or W), [(OC)5M(μ-dpsm)M(CO)5] (M ≠ Mo), [(OC)5M(μ-dmsm)M(CO)5], [(OC)4M(μ-dpsm)2M(CO)4], [(OC)4M(μ-dmsm)2M(CO)4] and fac-[M(CO)3(η1-dpsm)3] have been isolated and characterised by chemical analysis, IR, NMR (1H, 13C-{1H}, 95Mo) spectroscopy and FAB mass spectrometry. The crystal structures of [W(CO)5(dpsm)], [{W(CO)5}2(dpsm)], [{W(CO)4(dpsm)}2] and [{W(CO)4(dmsm)}2] have been determined. Complexes of η1-dmsm have been observed but are too unstable to isolate in a pure state. Both the ligands function as monodentate or bridging bidentates in the complexes characterised, but no examples with chelated distibinomethanes have been prepared. Comparisons are drawn with complexes of related diphosphine ligands.
- Hill, Angela M.,Holmes, Nicholas J.,Genge, Anthony R. J.,Levason, William,Webster, Michael,Rutschow, Synke
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p. 825 - 832
(2007/10/03)
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- Mixed Fe/Mo mixed-chalcogenide 'hour-glass' clusters, [FE4Mo(CO)14(μ3-E)2(μ 3-E′)2] and [Fe3Mo(CO)11(μ3-E)(μ 3-E′)-(μ-E′-E′)] (E, E′ = S, Se or Te)
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The room-temperature reactions of [Fe2(CO)6(μ-EE′)] (EE′ = SeTe, STe, SSe, S2 or Se2) with [Mo(CO)5(thf)] (thf = tetrahydrofuran) yielded two types of mixed-metal, mixed-chalcogenide 'hour-glass' clusters: [Fe4Mo-(CO)14(μ3-E)2(μ 3-E′)2] (E, E′ = Se, Te 1; S, Te 2; S, Se 4; S, S 7; Se, Se 9) and [Fe3Mo(CO)11(μ3-E)(μ 3-E′)(μ-E′-E′)] ( E, E′ = S, Te, E′-E′ = Te-Te 3; E, E′ = S, Se, E′-E′ = Se-Se 5; E, E′ = S, S, E′-E′ = S-Se 6; E, E′ = S, S, E′-E′ = S-S 8; E, E′ = Se, Se, E′-E′ = Se-Se 10). The crystal structures of 2, 5, 6 and 8 were elucidated by X-ray methods. The structure of 2 consists of two distorted square-pyramidal cores in each of which the alternate corners of the base are occupied by Fe and chalcogen atoms and a Mo atom occupies the common apical site. In 5, 6 and 8 a Mo atom occupies the common apical site of a square-pyramidal core and a tetrahedral core. The base of the square-pyramidal unit consists of alternate Fe and chalcogen atoms and the tetrahedral base consists of a Fe atom and two chalcogen atoms.
- Mathur, Pradeep,Sekar, Perumal,Rheingold, Arnold L.,Liable-Sands, Louise M.
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p. 2949 - 2954
(2007/10/03)
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- Synthesis and reactions of [Mo(2,6-lutidine)(η-allyl)] derivatives
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The syntheses of the η-lutidine(η-allyl)molybdenum compounds [Mo(2,6-lutidine)(η-C3H5)Cl]2 1, [Mo(η-2,6-lutidine)(η-C3H5)(η2-O2CR)] (2: R = CH3, 3: R = C(CH3/sub
- Mehnert, Christian P.,Chernega, Alexander N.,Green, Malcolm L.H.
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p. 247 - 253
(2007/10/03)
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- Reaction of chromium and molybdenum arenetricarbonyl complexes with molecular oxygen
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Chromium and molybdenum arenetricarbonyl complexes AreneM(CO)3 react with oxygen by a bimolecular mechanism to form the AreneM(CO)3·O2 complex, which converts further into a radical-ion salt, [AreneM(CO)3]+O2.. Probable pathways of conversion of this salt into the reaction products, including the mechanism of intramolecular oxidation of the arene and carbonyl ligands are discussed. Quantitative data on the reactivity of AreneM(CO)3 toward oxygen are reported.
- Fomin,Lunin
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p. 811 - 816
(2007/10/03)
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- Synthesis and Characterization of 1,3,5-Hexahydrotriazine Complexes of Mo(0) and Mo(VI)
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Organo-substituted 1,3,5-hexahydrotriazine complexes of the type (RNCH2)3Mo(CO)3 (R = CH3, i-C3H7 and CH2C6H5) are obtained by ligand displacement from η6-C7H8Mo(CO)3 in high yields.These products have been characterized by 1H, 13C, 95Mo NMR, IR as well as mass spectroscopy and contain an electron-rich Mo(CO)3 center bonded to the 1,3,5-hexahydrotriazine 6e donor via three Mo-N bonds.Oxidation of the Mo(0) complex 1,3,5-(CH3NCH2)3Mo(CO)3 with H2O2 under carefully controlled conditions allows isolation of 1,3,5-(CH3NCH2)3MoO3 containing a Mo(VI) center.Chemical and spectroscopic properties of these complexes are compared with those of related Mo complexes with neutral macrocyclic ligands containing N(3) donor sets. - Heywords: 1,3,5-Hexahydrotriazines, Carbonyl Complexes, Oxo Complexes, Redox Chemistry, Multinuclear NMR Spectra
- Schumann, Hans
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p. 1038 - 1044
(2007/10/02)
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- Reactions of Complex Ligands, LXI. - Oxacycloalkenylidene Complexes of Chromium, Molybdenum, and Tungsten: Synthesis, Their Annulation with Alkynes and Diels-Alder Reaction with Dienes
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Lithiiated propargylic ether 1 reacts with M(CO)6 (M = Cr, Mo, W) to give the 2-oxacyclic carbene complexes 2-4 containing an α,β-double bond and a cyclic acetal structure which serves as a protected benzoyl group.Reaction of the chromium complex 2 with tolan leads to an acyl hydroquinone derivative 5.The tungsten complex 3 undergoes a cycloaddition with cyclopentadiene to give two diastereomeric oxatricyclic carbene complexes 6 and 7 with an endo/exo selectivity of 3:1.The stereochemistry of the Diels-Alder reaction is controlled by the configuration of the acetal carbon center.Key Words: Carbene ligands/ Chromium complexes/ Molybdenum complexes/ Tungsten complexes/ Annulation reaction/ Diels-Alder reaction/ Oxacyclopentenylidene ligands
- Christoffers, Jens,Doetz, Karl Heinz
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p. 157 - 162
(2007/10/02)
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- Preparation of α-Diazines and α-2-Pyridylazines containing (1R)-(+)-Camphor or (1R)-(-)-Fenchone Residues and their Complexes with Group 6 Metal Carbonyls
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New 2,3,6,7-tetraaza-1,3,5,7-octatetraene (α-diazine) derivatives camph=N-N=CH-CH=N-N=camph I, where camph is a (1R)-(+)-camphor residue, C10H16, and fench=N-N=CH-CH=N-N=fench II, where fench is a 1R-(-)-fenchone residue, C10H16, have been obtained together with the 2'-pyridyl derivatives camph=N-N=CHC5H4N III and fench=N-N=CHC5H4N IV.The configurations around the four C=N bonds of I or II are E,E,E,E whilst those around the two azine C=N bonds in III and IV are E,E.Complexes of the types (M = Cr, Mo or W; L = I-IV), (L = I, L' = NCMe, PPh3 or AsPh3; L = II-IV, L' = PPh3), (L = III or IV) and 3-CH2CH=CH2)L> (L = I, III or IV) containing these azines as ligands have also been obtained.Complexes of II are the most unstable and these together with tetracarbonyl complexes of IV appear to show restricted rotation around the N-N bond(s) caused by the steric requirements of the methyl groups on the fenchone residue(s).All the complexes have been characterised by multinuclear NMR (1H, 13C and 31P), IR and UV/VIS spectroscopies and mass spectrometry.The crystal structures of camph=N-N=CH-CH=N-N=camph I and fench=N-N=CHC5H4N IV have been determined.
- Shaw, Bernard L.,Thornton-Pett, Mark,Vessey, Jonathan D.
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p. 3597 - 3606
(2007/10/02)
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- Water-soluble organometallic compounds. 3. Kinetic investigations of dissociative phosphine substitution processes involving water-soluble group 6 metal derivatives in miscible aqueous/organic media
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Mechanistic aspects of ligand substitution reactions of group 6 metal carbonyl derivatives containing the trisulfonated phosphine P(m-C6H4SO3Na)3 (hereafter referred to as TPPTS) in pure water and water/THF media have been investigated by examination of the reactions of these derivatives with carbon monoxide as an incoming ligand. The reactions, which were carried out under 500 psi of CO in the temperature range 110-160°C, were monitored in situ by infrared spectroscopy employing a cylindrical internal reflectance reactor. Kinetic measurements show the reactions are first-order in metal complex concentration and independent of CO pressure at high CO pressures, and the rates are retarded by added TPPTS. The activation parameters for TPPTS dissociation from M(CO)5TPPTS derivatives (M = Mo, W), e.g., in 1:1 THF/H2O, ΔH? = 28.8 ± 1.4 kcal/mol and ΔS? = -4.2 ± 3.5 eu and ΔH? = 31.8 ± 1.5 kcal/mol and ΔS? = -0.73 ± 3.6 eu, respectively were shown to be quite similar to those determined for the analogous processes involving the nonsulfonated PPh3 ligand in the same solvent systems. In addition only small solvent effects were noted in going from aqueous to organic solvents for these dissociative processes. For the cis-Mo(CO)4[TPPTS]2 derivative, in which the sodium ions are encapsulated by a cryptand, kryptofix-221, a steric acceleration of TPPTS dissociation is noted relative to its PPh3 analog. The steric requirements of the TPPTS ligand were defined by X-ray structural data obtained on [Na-kryptofix-221]3[W(CO)5P(C6H 4SO3)3] and Fe(CO)4TPPTS. By way of contrast for the cis-Mo(CO)4[TPPTS]2 derivative in which the Na+ ions are free to interact with the sulfonate groups, a stabilizing effect is noted which is attributed to intramolecular interligand interactions via the Na+ cations. In the case of cis-W(CO)4[TPPTS]2 and cis-W(CO)4[PPh3]2 an intramolecular rearrangement to the corresponding trans product was observed.
- Darensbourg, Donald J.,Bischoff, Christopher J.
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- Rare gas-metal carbonyl complexes: Bonding of rare gas atoms to the group VI pentacarbonyls
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Transient infrared spectroscopy has been used to study reactions of M(CO)5 generated by 355-nm photolysis of M(CO)6 where M = Cr, Mo, and W. At 298 K, M(CO)5 reacts with CO with bimolecular rate constants of (1.4 ± 0.2) × 10-10, (1.5 ± 0.1) × 10-10, and (1.4 ± 0.1) × 10-10 cm3 molecule-1 s-1 for Cr, Mo, and W, respectively. M(CO)5 also reacts with Xe with bimolecular rate constants of (0.9 ± 0.4) × 10-10, (0.9 ± 0.4) × 10-10, and (2.6 ± 0.2) × 10-10 cm3 molecule-1 s-1 for Cr, Mo, and W, respectively. Infrared absorptions attributed to M(CO)5Xe and W(CO)5Kr were observed. The rate of dissociative loss of the Xe atom from the M(CO)5Xe complexes was determined by the observation of the rate of regeneration of M(CO)6 in a reaction mixture consisting of M(CO)5, CO, and Xe. The bond dissociation energy for the loss of the Xe atom from M(CO)5Xe for all three metals is the same within experimental error and has an average value of 8.5 kcal/mol. A bond dissociation energy was estimated for the loss of Kr from W(CO)5Kr, and an upper limit can be estimated for the bond dissociation energy for loss of Ar from W(CO)5Ar.
- Wells,Weitz, Eric
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p. 2783 - 2787
(2007/10/02)
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- Stereochemical nonrigidity in heterobimetallic complexes containing the bent metallocene-thiolate fragment
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The physical properties and reactions of Cp2Ti(S-p-C6H4X)2 (1) and Cp2Ti(μ-S-p-C6H4X)2Mo(CO) 4 (2) (X = Cl, H, CH3, OCH3) complexes as well as the mechanism of the Cp site equilibration process in bimetallic complexes were investigated. Cyclic voltammographs recorded in CH2Cl2 showed two reversible waves for Ti(IV) ? Ti(III) and Mo(0) ? Mo(I) processes in 2 and one reversible wave for Ti(IV) ? Ti(III) in 1. Positions of these waves varied uniformly with the Hammett σ parameter of the X substituent. Variable-temperature 1H NMR studies provided values for ΔG? of the Cp equilibration process which are ca. 30 kJ/mol smaller than ΔG? for Cp2Ti(S-p-C6H4X)2 displacement from 2 by CO. This indicates that the fluxional process in 2 does not occur through a ligand dissociation process and argues for a mechanism of pyramidal inversion on sulfur. The X-ray structure for Cp2Ti(μ-S-p-C6H4Cl)2Mo(CO) 4 (2a) is reported. Complex 2a crystallizes in the monoclinic space group P21/n, with a = 12.396 (7) A?, b = 16.78 (2) A?, c = 12.838 (9) A?, β = 94.29 (5)°, Z = 4, and V = 2662 (3) A?3. The Ti atom is in pseudotetrahedral coordination environment whereas the Mo is octahedrally coordinated. The S1-Ti-S2 and S1-Mo-S2 angles are obtuse (100.8 (1) and 97.6 (1)°, respectively) and Ti-S-Mo angles are acute (80.8 (1)°) in the planar Ti-S2-Mo ring, supportive of metal-metal interactions implied by spectroscopic and electrochemical data. The phenyl groups are in an anti arrangement with respect to the Ti-S2-Mo plane.
- Darensbourg, Marcetta Y.,Pala, Magdalena,Houliston, Stephen A.,Kidwell, K. Paul,Spencer, David,Chojnacki, Stephen S.,Reibenspies, Joseph H.
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p. 1487 - 1493
(2008/10/08)
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- Tris(η4-1-oxa-1,3-diene)molybdenum and -tungsten: Preparation and properties of new homoleptic enone complexes
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Homoleptic tris(η4-1-oxa-1,3-diene)complexes of tungsten and molybdenum have been prepared in moderate to high yields starting from the α,β-unsaturated ketones 1-3 and tricarbonyltris(propionitrile)tungsten(0) or from 1 and η6-benzen
- Schmidt, Thomas,Neis, Stephan
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- Carbon monoxide induced allyl coupling from Mo2(μ2-η3-allyl)2(η 3-allyl)2 yielding the labile complex Mo(CO)4(η4-1,5-hexadiene)
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Carbon monoxide induces the reductive elimination of two pairs of allylic ligands from Mo2(μ2-η3-allyl)2(η 3-allyl)2 with the accompanying cleavage of the Mo-Mo quadruple bond. Mo(η4-1,5-hexadiene)(CO)4 is obtained from the reaction of 8 equiv of CO with Mo2(μ2-η3-allyl)2(η 3-allyl)2. Structural data for and the reactivity of Mo(η4-1,5-hexadiene)(CO)4 suggest that 1,5-hexadiene is bound very weakly to molybdenum.
- Blau, Reed J.,Siriwardane, Upali
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p. 1627 - 1630
(2008/10/08)
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- Siliciumhaltige Carben-Komplexe XIII. Darstellung und Eigenschaften der 16-Elektronen Carben-Komplexe (CO)4MC(NR2)SiR'3 (M = Cr, Mo, W)
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Dialkylaminocarbene complexes (CO)5MC(NR2)SiR'3 (1-3) (M = Cr, Mo, W; SiR'3 = SiPh3, SiPh2Me, SiPhMe2; NR2 = NMe2, NMeEt, NC4H8, NC5H10) are obtained by reaction of (CO)5MC(OEt)SiR'3 with HNR2.If the sterically more demanding amines HNEt2, HNBunMe or HN(CH2Ph)Me are used, monoalkylamino-substituted carbene complexes (CO)5MC(NHR)SIR'3 are formed instead, owing to cleavage of one of the organic substituents at nitrogen.However, diethyl-amino-substituted carbene complexes can be synthetized by reaction of the anionic complexes Li with Et3O+ and show no unusual chemical behaviour.The anionic complexes are prepared by deprotonation of (CO)5MC(NHEt)SiR'3.On heating the pentacarbonyl complexes 1-3 to 100-150 deg C, in the case of some of the chromium and molybdenum complexes already during their synthesis, a cis-CO ligand is lost to give the stable 16-electron carbene complexes (CO)4MC(NR2)SiR'3 (8-10).An X-ray structure analysis of (CO)4WC(NC5H10)SiPh3 (8d) reveals that the empty coordination site that results is screened by a phenyl substituent and that relaxation of the steric strain induced by the bulky carbene ligand, seems to be the driving force for the formation of the 16-electron species.In solution the 16-electron complexes 8-10 are fluxional.In a CO atmosphere the complexes 8-10 are retransformed quantitatively into the pentacarbonyl complexes 1-3.Reaction of (CO)4WC(NMe2)SiPh3 (8a) with methyl isonitrile or phosphines exclusively yields cis-substituted (CO)4LWC(NMe2)SiPh3 (L = MeNC, PR3).
- Hepp, Wolfgang,Schubert, Ulrich
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p. 221 - 245
(2007/10/02)
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- Synthese und Reaktionen von (CO)5Mo
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The pentacarbonyl(α-ethoxybenzyl)molybdates NEt4> react with HBF4 .Et2O by abstraction of the ethoxy group to give the benzylidene complexes (CO)5Mo (R = Me (2a), OMe (2b)).The compounds 2 are thermally very labile and react rapidly even at -100 deg C with a number of nucleophiles.The addition of PPh3 to the benzylidene carbon atom of 2a gives the ylide complex (CO)5Mo and that of PPh2Cl gives the phosphine complex (CO)5MoPPh2 under rearrangement.The reaction of 2b with PPhCl2 stereoselecti vely gives RS/SR-(CO)5Mo> and with - (X = S, Se) gives the heterobenzaldehyde complexes (CO)5Mo (X = S (6b), Se (7b)).The thioacrylamide complex (CO)5Mo is obtained from the reaction of 6b with MeCCNEt2.The -cycloaddition of 7b with cyclopentadiene gives a (CO)5Mo-coordinated selenanorbornene derivative.Cyclopropanation is observed in the reaction of 2b with cyclopentadiene.The resulting bicyclohexene which is coordinated to (CO)5Mo via the C=C bond can be cleaved off the metal by air.
- Fischer, Helmut,Reindl, David
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p. 351 - 361
(2007/10/02)
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- The photochemistry of M(CO)4(η4-norbornadiene) complexes of group 6 transition metals (M= Cr, Mo, W) in low-temperature matrices
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Photolysis of M(CO)4(η4-norbornadiene) group 6 metal complexes (1) in low-temperature matrices involves both loss of CO and cleavage of metal-olefin bonds to an extent depending on the metal and on the excitation wavelength.In inert matrices me
- Grevels, Friedrich-Wilhelm,Jacke, Juergen,Koltzbuecher, Werner E.,Schaffner, Kurt,Hooker, Richard H.,Rest, Antony J.
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p. 201 - 224
(2007/10/02)
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- Synthesis and chemistry of chelating phosphinite complexes of group 6 metal carbonyls with crown ether and aza-crown ether characteristics. The effect of preferential lithium cation binding by the product molecule on the reactivity of coordinated carbon monoxide
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Twenty-seven α,ω-bis(diphenylphosphinite) ligands, prepared from the reaction of 2 equiv of Ph2PCl with the appropriate α,ω-diol in the presence of Et3N, react with M(CO)4(norbornadiene) (M = Cr, Mo, W) under high dilution conditions to give metalla-crown and metalla-aza-crown ether tetracarbonyl complexes. Within the series of complexes cis-Mo(CO)4{Ph2POCH2(CH2OCH 2)nCH2OPPh2} the 16C5 (n = 3) system will complex Li+ but not Na+ and the 19C6 (n = 4) system will complex Li+ and Na+ but not K+, while the IOCS (n = 1) and 13C4 (n = 2) systems do not readily complex Li+. Addition of MeLi and PhLi to these group 6 metal carbonyl-crown ether systems results in the formation of the isolable acylate/benzoylate complexes "fac-M(CO)3(RCOLi)P2]" for 11C3, 12C3, 13C4, and 14C4 ring systems while other ring sizes and complexes such as cis-Mo(CO)4{Ph2PO(CH2)nOPPh 2} (n = 3, 5) and cis-Mo(CO)4-(PPh2OMe)2 do not react with RLi reagents. Equilibrium studies of the reaction "M(CO)4P2 + RLi ? M(CO)3(RCOLi)P2" indicate that the features favoring Li+ binding and product stabilization are (i) a ligand should be one donor atom short of providing Li+ with a "full" coordination sphere, (ii) 12-14 atom metalla-crown ether rings, (iii) the ligand must accommodate the stereochemical requirements of the bridging M(RC=O)→Li+ unit, and (iv) the crown ether donor atoms should be as basic as possible {tertiary N > O, and Ph2P-O >>> Ph2P-NMe}. Kinetic studies of the rate of the reaction of "[M(CO)3(PhCOLi)P2]" systems with H2O in THF, to give "M(CO)4P2", LiOH, and benzene, provide information (kd data) regarding the relative rate of Li+ decomplexation. 12C3 benzoylate complexes and Mo(CO)5(PhCOLi) react with H2O in THF to give the starting carbonyl complex, LiOH, and benzene by a process that is first order in both [benzoylate complex] and [H2O], while the reaction of 13C4 and 14C4 benzoylates with H2O in THF gives rise to a rate law that is first order in [benzoylate] and second order in [H2O]. Equilibrium constant data and the ka data indicate that 13C4 and 14C4 benzoylates are the most stable. The complexes fac-M(CO)3(RCOLi){Ph2POCH2(CH 2OCH2)2CH2OPPh2} (i) react with Me3O+BF4 or MeSO3F to give the carbene complexes fac-M(CO)3{C(OMe)R}{Ph2POCH2(CH 2OCH2)2CH2OPPh2}, (ii) react with Me3SiCl followed by H2O/MeOH hydrolysis to give the hydroxycarbene fac-M(CO)3{C(OH)R}{Ph2POCH2-(CH 2OCH2)2CH2OPPh2}, and (iii) react with HX to give [M(CO)3X{Ph2POCH2(CH2OCH 2)2CH2OPPh2}]-Li + (X = Cl, Br). This latter compound reacts with silver salts in the presence of added ligand to give fac-M(CO)3L{Ph2POCH2(CH2OCH 2)2CH2OPPh2} (e.g. L = P(OMe)3, tBuNC).
- Powell, John,Gregg, Michael R.,Kuksis, Anda,May, Christopher J.,Smith, Stuart J.
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p. 2918 - 2932
(2008/10/08)
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- Complexes with unbridged dative bonds between osmium and a group 6 element. Structures of (Me3P)(OC)4OsM(CO)5 (M = Cr, W)
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Complexes of the type (R3P)(OC)4OsM(CO)5 (R = Me, OMe, Ph, etc.; M = Cr, Mo, W) have been prepared from the reaction of Os(CO)4(PR3) and M(CO)5(THF) in hexane. The structures of (Me3P)(OC)4OsCr(CO)5 (1) and (Me3P)(OC)4OsW(CO)5 (2) have been determined by X-ray crystallography: Compound 1 crystallizes in the space group P21/n, with a = 9.231 (1) ?, b = 18.153 (1) A, c = 10.865 (1) ?, β = 91.08 (1)°, and Z = 4; R = 0.023, Rw = 0.028 for 1748 observed reflections. Compound 2 crystallizes in the space group P21/n, with a = 8.832 (1) ?, b = 16.241 (2) ?, β = 12.988 (2) ?, β = 101.99 (1)°, and Z = 4; R = 0.019, Rw = 0.023 for 2189 observed reflections. In both 1 and 2 the Os(CO)4(PMe3) molecule acts as a ligand to the M(CO)5 fragment via an unbridged donor-acceptor metal-metal bond (Os-Cr = 2.9787 (14) ?; Os-W = 3.0756 (5) ?); the phosphine ligand is trans to the metal-metal bond. The major spectroscopic features of the (R3P)(OC)4OsM(CO)5 complexes indicate these compounds adopt the same structure in solution. There are, however, weak signals in the 13C (and 1H and 31P) NMR spectra that are consistent with small amounts of the isomer with the phosphorus ligand cis to the metal-metal bond. For 2, the isomers were shown to be in rapid equilibrium by the spin saturation transfer technique. The well-known mechanism that involves pairwise carbonyl exchange between metal atoms accounts for the observations regarding the isomerization. The homoleptic derivative (OC)5OsCr(CO)5 has also been prepared. Although unstable in solution at room temperature, the 13C NMR spectrum in CD2Cl2 at -40°C indicates it also has a structure with an unbridged, Os-Cr dative bond.
- Davis, Harry B.,Einstein, Frederick W. B.,Glavina, Paul G.,Jones, Terry,Pomeroy, Roland K.,Rushman, Paul
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p. 1030 - 1039
(2008/10/08)
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- Siliciumhaltige Carben-Komplexe XII. Synthese kleiner organischer Ringsysteme aus alkoxy- oder alkylthio-substituirten Silylcarben-Komplexen (CO)5MC(XEt)SiR3 (M=Cr, Mo, W; X=O, S) und davon abgeleiteten Ketenen R3Si(EtX)C=C=O
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Ketenes R3Si(EtO)C=C=O (1), prepared in situ from the carbene complexes (CO)5MC(OEt)SiR3 (M=Cr, Mo, W) by reaction with CO, react with ethyl vinyl ether or cyclopentadiene by -cycloaddition.Two stereoisomeric cyclobutanone derivatives, in which the positions of the R3Si and the EtO group are interchanged, are obtained in each case.The reactions proceed with high stereoselectivity.Ethyl vinyl ether also reacts directly with the carbene complexes to yield a single stereoisomer of 1,2-diethoxy-1-silyl-cyclopropane (6).Reaction of the ethyl-thio-substituted ketene Ph3Si(EtS)C=C=O (2) with 2,3-dihydrofuran gives the corresponding cyclobutanone only as a by-product. 3-Oxa-8-silyl-1-thia-bicyclooctan-7-one (8) is formed as the main product by loss of an ethylene unit.Ketene 1 reacts with N-methyl- or N-phenylbenzimine, but not with cyclic imines, to give β-lactames.Each of these reactions also yields two stereoisomers.
- Kron, Johanna,Schubert, Ulrich
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p. 203 - 220
(2007/10/02)
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- Heat of reaction of (norbornadiene)molybdenum tetracarbonyl with monodentate and bidentate ligands. Solution thermochemical study of ligand substitution in the complexes cis-L2Mo(CO)4
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The enthalpy of reaction of (NBD)Mo(CO)4 (NBD = norbornadiene) with a number of monodentate and bidentate ligands forming cis-L2Mo(CO)4 has been measured at 30°C in THF solution. The heats of reaction span a range of 33 kcal/mol. The order of stability for monodentate ligands is PCl3 6H5)3 6H5)3 3 6H5)3 6H5)2(CH3) 6H5)(CH3)2 3)3 3 6H11)NC 3 3. The series of chelating bidentate phosphines R2P-(CH2)nPR2 (n = 1-4, R = C6H5; n = 1, 2, R = CH3) and several related ligands were investigated. The chelating ring systems in the metallacycles show strain energies of about 8 kcal/mol for four-membered rings. The mixed ligand (C6H5)2PCH2CH2-As(C 6H5)2 shows a heat of binding midway between the heats of binding of (C6H5)2PCH2CH2P(C 6H5)2 and (C6H5)2AsCH2C-H2As(C 6H5)2, implying group additivity in this system. The complex (phen)Mo(CO)4 is some 5 kcal/mol more stable than (bpy)Mo(CO)4, presumably due to conformational effects in the free ligand. The ligand 1,5-cyclooctadiene forms a complex 2 kcal/mol less stable than that of norbornadiene. The influences of steric and electronic factors in determining the Mo-L bond strength are discussed.
- Mukerjee, Shakti L.,Nolan, Steven P.,Hoff, Carl D.,Lopez De La Vega, Ramon
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- OXIDATION OF η6-ARENE COMPLEXES OF GROUP VI METALS. III. DI-IODINE-CATALYSED CARBONYLATION OF MOLYBDENUM(0)-η6-ARENE COMPLEXES TO Mo(CO)6 AND EXPERIMENTAL EVIDENCE OF AN INNER-SPHERE ELECTRON-TRANSFER REACTION BETWEEN CENTRES OF MOLYBDENUM(II) AND MOLYBDENUM(0)
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Carbonylation of Mo(CO)3(η6-arene) has been found to be catalysed by I2, or by 6-arene)> or by Mo2I4(CO)8.Earlier papers in this series have shown the latter molybdenum(II) complexes to be the products of Mo(CO)3(η6-arene) oxidation by I2 in the absence or in the presence of carbon monoxide, respectively.The rate of carbonylation to Mo(CO)6 decreases with the methyl substitution on the carbocyclic ligand.A fast process between Mo(CO)3(η6-arene) and 6-arene')>X (X = BF4, ) leading to Mo(CO)3(η6-arene') and 6-arene)>X has been observed in dichloromethane solution.This is believed to be in fact an inner-sphere iodide transfer process, i.e. an Mo(0)-Mo(II) two-electron transfer simulating an arene exchange.The 6-arene)>(+) cation is believed to play an important role in both the apparent arene exchange and the carbonylation process via an iodide-bridged mixed-valence common intermediate.
- Barbati, Aldo,Calderazzo, Fausto,Poli, Rinaldo
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p. 589 - 594
(2007/10/02)
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- Thermal Decarbonylation of Molybdenium(II) Carbonyl-Iodide Complexes. Molecular and Electronic Structures of the Mixed-Valence Trinuclear Clusters Mo3HI7L3 (L=Tetrahydrofuran, Acetonitrile, Benzonitrile) and Molecular Structures of MoI3(EtCN)3 and Mo2I4(PhCN)4
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Trinuclear cluster compounds of the type Mo3HI7L3 (L=THF,CH3CN,C6H5CN) can be obtained by decarbonylation of carbonyl-iodide complexes of molybdenum(II) in the presence of hard-donor ligands.In tetrahydrofuran (THF) an oligonuclear compound of stoichiometry x (1) is formed as the main product.The trinuclear cluster Mo3HI7(THF)3*THF (2) is obtained from the same reaction in low yields.When MeCN and EtCN are used as solvents, solutions containing the quadruply bonded dimers Mo2I4(RCN)4 are obtained, together with other minor insoluble products.Interaction of compound 1 with RCN also gives Mo2I4(RCN)4, which is unstable toward loss of the nitrile and cannot be isolated for R=Me and Et.A ligand-exchange reaction with PhCN affords Mo2I4(PhCN)4 (6), which is stable in the solid state.Other compounds that are produced in smaller yields in these reactions have been isolated and characterized, namely Mo3HI7(MeCN)3*MeCN (3), MoI3(EtCN)3 (4), and Mo3HI7(PhCN)3*C6H5CH3 (5).Compound 1 also reacts with PMe3 to afford Mo2I4(PMe3)4 and with I- to produce the - anion.A different form of the trinuclear cluster with coordinated THF has also been obtained, Mo3HI7(THF)3 (7).Crystal data are the following.Compound 2: orthorhombic; space group Pcam; a=21.216(3), b=8.459(1), c=18.477(2) Angstroem; V=3316(1) Angstroem3; Z=4; dcalcd=2.933 g*cm-3; R=0.0461, Rw=0.0743 for 148 parameters and 1716 observed data 02 > 3?(F02)>.Compound 3: orthorhombic; space group Pcmb; a=7.703(1), b=17.903(2), c=20.179(2) Angstoem; V=2783 (1) Angstroem3; Z=4; dcalcd=3.199 g*cm-3; R=0.0355, Rw=0.0478 for 103 parameters and 1661 observations with F02 > 3?(F02).Compound 4: monoclinic; space group P21/n; a=11.065(5), b=13.174(3), c=12.974(5) Angstroem; β=103.70 (3)deg; V=1836 (2) Angstroem3; Z=4; dcalcd=2.321 g*cm-3; R=0.0570, Rw=0.0680 for 145 parameters and 1379 observations with F02 > 3?(F02).Coumpound 5: monoclinic; space group P21/m; a=8.606(3), b=18.471(10), c=12.628(6) Angstroem; β=96.38(4)deg; V=1995(3) Angstroem3; Z=2; dcalcd=2.626 g*cm-3; R=0.0495, Rw=0.0728 for 144 parameters and 1594 observations with F02 > 3?(F02).Coumpound 6: orthorhombic; space group Fddd; a=22.941(2), b=39.516(12),c=17.336(8) Angstroem; V=15715(15) Angsroem3; Z=16; dcalcd=1.879 g*cm-3; R=0.0664, Rw=0.0827 for 92 parameters and 851 observations with F02 > 3?(F02).Coumpond 7: trigonal; space group R3m; a=17.112(4), c=8.599(2) Angstroem; V=2180.5(14) Angstroem3; Z=3; dcalcd=4.158 g*cm-3; R=0.0428, Rw=0.0583 for 43 parameters and 321 observations with F02 > 3?(F02).The structure of the Mo3HI7L3 (L=THF,MeCN, PhCN) clusters consists of an equilateral-triangular arrangement of the metals with strong metal-metal bonding interactions.The faces of the triangle are capped by an iodide and a hydride ligand,and a bridging iodide ion spans each edge.The sructure is completed by three terminal iodide ions and three terminal ligands L.The Mo3I7 core of the molecules can ...
- Cotton, F. Albert,Poli, Rinaldo
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p. 830 - 841
(2007/10/02)
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- Reductive Disproportionation of Carbon Dioxide by Dianionic Carbonylmetalates of the Transition Metals
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Carbon dioxide reacts readily with M2 (M=Li, Na, K, M'=W; M=K, M'=Cr, Mo, W) to give the corresponding group 6 hexacarbonyls and alkali metal carbonates.The reaction of Li2 with excess 13CO2 at -78 deg C gives , con
- Lee, Gary R.,Maher, John M.,Cooper, N. John
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p. 2956 - 2962
(2007/10/02)
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- Siliciumhaltige Carben-Komplexe IX. Thermische Fragmentierung von Alkoxy(triphenylsilyl)carben-Komplexen, (CO)5MC(OR)SiPh3 (M=Cr, Mo, W)
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On thermolysis of (CO)3M=C(OEt)SiPh3 (M=W, Mo, Cr) in the solid state or in solution three different decomposition pathways are observed, which are unusual for Fischer-type carbene complexes; fragmentation of the complex to give triphenylsilane, ethylene
- Schubert, Ulrich,Hoernig, Hannelore
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p. 307 - 316
(2007/10/02)
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- Borole derivatives X. Syntheses of (η5-borole)metal complexes via borole ammonia adducts. Complexes of the chromium group metals and the crystal and molecular structures of tetracarbonyl 5-(1-phenylborole)>chromium and its molybden
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The 1H-Borole ammonia adducts C4H4Br*NH3 (R=Me,Ph) (Ia,b) have been made by ammonia degradation of the (η5-borole)carbonyliodocobalt complexes (C4H4BR)Co(CO)2I (VIa,b).They are the simplest 1H-borole derivatives obtained to date, and have been
- Herberich, G.E.,Hessner, B.,Negele, M.,Howard, J.A.K.
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- Preparation and properties of metal carbonyl teflates, including the structure and reactivity of Mn(CO)5(OTeF5)
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A number of metal carbonyl complexes of the teflate anion (OTeF5-) have been prepared and isolated or generated in solution, including Mn(CO)5(OTeF5), Re(CO)5(OTeF5), CpFe(CO)2(OTeF5), [N(n-Bu)4+][Mo(CO)5(OTeF5) -], and [N(n-Bu)4+][W-(CO)5(OTeF5) -]. Infrared and 19F NMR spectroscopic data provide information about the stability of the molecules, the nature of the metal-oxygen bonds, and the donor strength of teflate as compared with the halides, triflate (CF3SO3-), and perchlorate. The compound Mn(CO)5(OTeF5) was studied in detail. It crystallized from dichloromethane in the orthorhombic system, space group Pna21. Unit cell parameters are a = 12.462 (3) ?, b = 7.612 (2) ?, c = 12.539 (2) ?, and Z = 4. The Mn-O bond distance of 2.04 (1) ? is indicative of a reasonably strong Mn-O single bond. However, other structural and spectroscopic data indicate that this bond possesses a large degree of ionic character. The reactions of Mn(CO)5(OTeF5) and the corresponding triflate and perchlorate complexes with tetrahydrofuran (THF) were studied. In all three cases the first-formed products were Mn(CO)3-(THF)2(X) (X = OTeF5-, CF3SO3-, ClO4-), formed by rate-determining CO dissociation from the parent complexes. Rate constants for CO dissociation are measurably different for the three complexes, but only vary by a factor of 10. Although teflate is a measurably stronger ligand than triflate or perchlorate, the stability and reactivity of Mn(CO)5(OTeF5) are not qualitatively different from those of Mn(CO)5(CF3SO3) and Mn(CO)5(ClO4). Thus, in the role as a terminal, monodentate ligand in coordinatively saturated complexes, teflate is not unique relative to other weakly basic oxyanions.
- Abney, Kent D.,Long, Kim M.,Anderson, Oren P.,Strauss, Steven H.
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p. 2638 - 2643
(2008/10/08)
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- COORDINATION CHEMISTRY OF SILOLES: VINYL-, ALLYL- AND ALKYNYL-SILOLES; SYNTHESIS AND STRUCTURE OF η4,η2-1-ALLYL- AND 1-VINYL-2,5-DIPHENYLSILACYCLOPENTADIENE COMPLEXES
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The reactions of 1-allyl-1-methyl- (8), 1-vinyl-1-methyl- (10), 1,1-diallyl- (14), 1,1-divinyl- (16), 1-ethenyl-1-methyl- (2a) and 1-propynyl-1-methyl-2,5-diphenylsilacyclopentadiene (2b) (or siloles) with transition metals are described.Competition between complexation of the diene and that of the triple bond of the propynylsilole is observed with Co2(CO)8, but with Fe2(CO)9, the η4-complexes are obtained in all cases.Co2(CO)8 reacts with the vinyl- and allyl-siloles to give η4-complexes, but Mo(CO)4(COD) (COD = 1,5-cyclooctadiene) or W(CO)3(CH3CN)3 gives η4,η2-complexes.The crystal structures of (η4-(η2-endo-1-allyl)-exo-1-methyl)- (9a) and (η4-(η2-endo-1-vinyl)-exo-1-methyl-2,5-diphenylsilacylopentadiene)tricarbonyl molybdenum (12a) have been determined.They show that the dihedral angle between the diene and the C(1)-Si-C(2) plane is 28 deg in the case of the allyl derivative 9a but only 8.9 deg in the vinyl complex 12a.
- Carre, F.,Corriu, R. J. P.,Guerin, C.,Henner, B. J. L.,Kolani, B.,Wong Chi Man, W. W. C.
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- Redox Reactions with Metal Carbonyls of Group V
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The carbonylmetalates of cobalt(-I), manganese(-I), chromium(-I), molybdenum(-I), tungsten(-I), and the anionic carbonyl cyclopentadienyl derivatives of the zerovalent Group VI metals (-, M = Cr, Mo, W) are readily oxidized by hexacarbonylvanadium(0) to give the neutral metal carbonyls.In the case of the V(CO)6/- system, by 13CO-labeling of the oxidizing agent V(CO)6, it is shown that the redox reaction occurs via an outer-sphere mechanism.On the other hand, hexacarbonylvanadium(0) behaves as a reducing agent towards NiCp2 and MnCp2, the reduced products being Ni(CO)4 and MnCp(CO)3, respectively.The hexacarbonylmetalates of niobium(-I) and tantalum(-I) are oxidized by a number of oxidizing agents, exclusively by a two-electron transfer process to niobium(I) and tantalum(I).When the acetylacetonato complexes of nickel(II) and iron(III) are used as oxidizing agents, the M(acac)(CO)4THF complexes (M = Nb, Ta) were obtained, the oxidation by nickel(II) being the preferred one from a preparative point of view.The crystal and molecular structure of the tantalum complex, Ta(acac)(CO)4THF, has been solved by X-ray diffraction methods.Crystals are orthorhombic, space group P212121, a = 15.347(3), b = 12.227(3), c = 8.642(3) Angstroem, V = 1621.6 Angstroem3, Dc = 1.900 g*cm-3, Z = 4.The tantalum atom is heptacoordinated, being surrounded by the bidentate acetylacetonato ligand, by four carbon monoxide groups, and by the oxygen atom of the THF ligand.The THF ligand of the complexes is easily substituted, together with one of the carbonyl groups, by isocyanides, and a bidentate tertiary phosphane, while with the monodentate triphenylphosphane a substitutional equilibrium is established.
- Calderazzo, Fausto,Pampaloni, Guido,Zanazzi, Pier Francesco
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p. 2796 - 2814
(2007/10/02)
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