- Ionic and covalent mixed-metal complexes by reaction of transition metal M-H acids (M = Mo, Mn, Fe, Co) with [Ir(PMe3)4CH 3] or [Rh(PMe3)3CH3] and structurally related Rh-M and Ir-M heterobimetallics (M = Mn, Fe, Ru)
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Treatment of [Ir(PMe3)4CH3] with equimolar quantities of the carbonyl hydrides [M(CO)nH] (M=Mn, Co; n=5, 4) or [CpM(CO)nH] (M=Mo, Fe; n=3, 2) resulted in clean protonation of the d8 substrate producing cis-[Ir(PMe 3)4(H)(CH3)][X], where X-=[Mn(CO) 5]- (1), [Co(CO)4]- (2), [CpMo(CO)3]- (3), and [CpFe(CO)2]- (4), respectively. Combination of [Rh(PMe3)3CH 3] with [Mn(CO)5H] furnished [(Me3P) 3Rh(μ-CO)2Mn(CO)3PMe3] (5), which was also isolated from the salt elimination reaction between [Rh(PMe 3)4]Cl and Na[Mn(CO)5]. [(Me3P) 2Rh(μ-CO)2Fe(PMe3)Cp] (6), [(Me 3P)3Ir(μ-CO)2Fe(PMe3)Cp] (7), and [(Me3P)3Ir(μ-CO)2Ru(PMe3)Cp] (8) were obtained similarly by reacting [Rh(PMe3)4]Cl or [Ir(PMe3)4]Cl with the potassium salts K[CpM(CO) 2] (M=Fe, Ru). The crystal structure analysis of 3 demonstrates that in the solid state the hexacoordinate [Ir(PMe3)4(H) (CH3)]+ cation and its [CpMo(CO)3]- counterion exist as well-separated ion pairs. The structures of 5-8 comprise (Me3P)nRh (n=3, 2) or (Me3P)3Ir groups attached to Mn(CO)3PMe3 or M(PMe3)Cp fragments (M=Fe, Ru) by doubly carbonyl-bridged metal-metal bonds of normal length: Rh-Mn, 2.6695(14); Rh-Fe, 2.5748(6); Ir-Fe, 2.6470(7); Ir-Ru, 2.7348(14) A?.
- Dahlenburg, Lutz,Hache, Roland
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- Resurgence of Organomanganese(I) Chemistry. Bidentate Manganese(I) Phosphine-Phenol(ate) Complexes
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As part of the United Nations 2019 celebration of the periodic table of elements, we are privileged to present our studies with the element manganese in this Forum Article series. Catalysis with organomanganese(I) complexes has recently emerged as an important area with the discovery that pincer manganese(I) complexes that can activate substrates through metal-ligand cooperative mechanisms are active (de)hydrogenation catalysts. However, this rapidly growing field faces several challenges, and we identify these in this Forum Article. Some of our efforts in addressing these challenges include using alternative precursors to Mn(CO)5Br to prepare manganese(I) dicarbonyl complexes, the latter of which is usually a component of active catalysts. Specifically, the synthesis of a new bidentate phosphine-phenol ligand along with its corresponding coordination chemistry of five new manganese(I) complexes is described. The complexes having two phenol-phenolate moieties interact with the secondary coordination sphere to enable facile loss of the bromido ligand and even one of the CO ligands to afford manganese(I) dicarbonyl centers.
- Kadassery, Karthika J.,MacMillan, Samantha N.,Lacy, David C.
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- Rh4(CO)12-catalyzed hydroformylation of cyclopentene promoted with HMn(CO)5. Another example of Rh4(CO) 12/HMn(CO)5 bimetallic catalytic binuclear elimination
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A detailed in situ high-pressure FTIR spectroscopic study was performed to investigate the bimetallic origins of catalytic synergism in homogeneous catalysis. The reaction chosen was the homogeneous catalyzed hydroformylation of cyclopentene to cyclopentanecarbox-aldehyde, starting with unmodified rhodium and manganese carbonyls as catalyst precursors in n-hexane as solvent. The spectra were analyzed by an advanced signal processing and statistical technique. Only four organometallic spectra could be found. These were RCORh-(CO)4, Rh4(CO)12, HMn(CO)5, and Mn2(CO)10. A very significant increase in aldehyde formation was observed in the experiments when both rhodium carbonyl and manganese carbonyl complexes were used simultaneously. The kinetics of product formation shows a distinct linear-bilinear form in observable organometallics; k1[RCORh(CO)4][H2][CO]-1 + k2[RCORh(CO)4] [HMn(CO)5] [CO]-1.6. The determined activation parameters for the bilinear term were ΔH ? = 47 ± 8 kJ/mol and ΔS? = -88 ± 28 J/(mol K). The results, particularly the bilinear term and the negative entropy of activation, suggest that the origin of synergism is the presence of bimetallic catalytic binuclear elimination: namely, the hydride attack on the acyl species. The present results are consistent with observations and conclusions reached for a previously studied Rh4(CO) 12/HMn(CO)5/3,3-dimethylbut-1-ene hydroformylation system.
- Li, Chuanzhao,Widjaja, Effendi,Garland, Marc
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- Mechanism of the Hydrometalation ( Insertion ) and Stoichiometric Hydrogenation Reactions of Conjugated Dienes Effected by Manganese Pentacarbonyl Hydride: Processes Involving the Radical Pair Mechanism
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Manganese pentacarbonyl hydride (I) reacts with 1,3-butadiene, isoprene, and 2,3-dimethyl-1,3-butadiene to form predominantly the hydrometalated products of 1,4-addition of H-Mn(CO)5 to the dienes, i.e. R, R'=H, Me Monoolefins, the products of stoichiometric 1,2- and 1,4-addition of two hydrogen atoms to the dienes, are also formed as minor products, i.e. Hydrogenation is the predominant process with 1,3-cyclohexadiene.The hydrometalation reactions are first order in both I and diene, and the reaction rates are unaffected by added carbon monoxide (1 atm), while careful NMR monitoring of the early stages of the reactions under appropriate conditions reveals striking CIDNP polarizations for the 1H resonances of both the products of hydrometalation and of hydrogenation.The experimental evidence thus suggests that the reactions do not proceed via prior coordination of the olefin to the metal followed by conventional migratory insertion and reductive elimination processes but rather via hydrogen atom abstraction from I by the diene to give the corresponding radical pair.The latter can couple to give the hydrometalated compounds or diffuse apart to react with a second molecule of I to give Mn2(CO)10 and the monoolefins.For both types of products, the signs and, where measureable, the relative intensities of the CIDNP polarizations are completely consistent with the radical pair mechanism.
- Wassink, Berend,Thomas, Marian J.,Wright, Steven C.,Gillis, Daniel J.,Baird, Michael C.
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- Protonolysis reactions in the series RMn(CO)5 and RC(O)Mn(CO)5
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Proton cleavage (protonolysis) of the R-Mn bond in RMn(CO)5 complexes occurs readily and cleanly with CF3SO3H to give the corresponding RH compounds.The relative order of reactivity in the series of RMn(CO)5 compounds we have prepared is R = H, CH3, Ph, p
- Motz, Philip L.,Sheeran, Daniel J.,Orchin, Milton
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- Mild reduction with silanes and reductive amination of levulinic acid using a simple manganese catalyst
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A manganese-based catalytic system using the commercially available complex [Mn(CO)5Br] was studied for the selective reduction of levulinic acid (LA) to 2-methyl-tetrahydrofuran (MTHF). We further studied the production of pyrrolidines via its reductive amination using silanes (phenylsilane and tetramethyldisiloxane). The results showed high efficiency and selectivity for this reaction leading to high yields using mild reaction conditions.
- Garcia, Juventino J.,Roa, Diego A.
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- Diverse Fates of β-Silyl Radical under Manganese Catalysis: Hydrosilylation and Dehydrogenative Silylation of Alkenes
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Manganese-catalyzed hydrosilylation of alkenes has been underdeveloped for a long time. Herein, we describe a general, chemo- and regio- selective hydrosilylation of alkenes by using the Mn(CO)5Br catalyst with ample substrate scopes. Meanwhile, dehydrogenative silylation of aryl olefins can be selectively achieved upon the catalysis of dinuclear Mn2(CO)10. Mechanistic experiments revealed diverse fates of the common intermediate β-silyl radical, namely, hydrogen atom transfer (HAT) for the hydrosilylation and organometallic β-H elimination for the dehydrogenative silylation of olefins.
- Yang, Xiaoxu,Wang, Congyang
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supporting information
p. 1047 - 1051
(2018/09/27)
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- Heterobimetallic complexes of rhodium dibenzotetramethylaza[14]annulene [(tmtaa)RH-M]: Formation, structures, and bond dissociation energetics
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A rhodium(II) dibenzotetramethylaza[14]annulene dimer ([(tmtaa)Rh]2) undergoes metathesis reactions with [CpCr(CO)3]2, [CpMo(CO)3]2, [CpFe(CO)2]2, [Co(CO)4]2, and [Mn(CO)5]2 to form (tmtaa)Rh-M complexes (M = CrCp(CO)3, MoCp(CO)3, FeCp(CO)2, Co(CO)4, or Mn(CO)5). Molecular structures were determined for (tmtaa)Rh-FeCp(CO)2, (tmtaa)Rh-Co(μ-CO)(CO)3, and (tmtaa)Rh-Mn(CO)5 by X-ray diffraction. Equilibrium constants measured for the metathesis reactions permit the estimation of several (tmtaa)Rh-M bond dissociation enthalpies (Rh-Cr = 19 kcal mol-1, Rh-Mo = 25 kcal mol-1, and Rh-Fe = 27 kcal mol-1). Reactivities of the bimetallic complexes with synthesis gas to form (tmtaa)Rh-C(O)H and M-H are surveyed.
- Imler, Gregory H.,Peters, Garvin M.,Zdilla, Michael J.,Wayland, Bradford B.
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p. 273 - 279
(2015/03/13)
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- Formation of sub-valent carbenoid ligands by metal-mediated dehydrogenation chemistry: Coordination and activation of H2Ga{(NDippCMe) 2CH}
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Reactions of the β-diketiminato ('Nacnac') stabilized gallium dihydride H2Ga{(NDippCMe)2CH} with a range of mono- and dinuclear metal carbonyl reagents are characterized by loss of dihydrogen and formation of donor/acceptor complexes featuring the Ga(i) carbenoid ligand:Ga{(NDippCMe)2CH}. Thus, far from simply mimicking the chemistry of the corresponding alane H2Al{(NDippCMe)2CH}, which yields κ1 and κ2 Al-H σ-complexes with similar reagents, the weaker nature of Ga-H bonds leads to extensive bond activation chemistry and enables an unprecedented dehydrogenative route to Ga(i) ligand systems. By consideration of the chemistry of dinuclear systems, two alternative pathways are revealed for this chemistry, with either H2 or M-H bonds acting as the ultimate hydrogen sink. The Royal Society of Chemistry 2013.
- Turner, Joshua,Abdalla, Joseph A. B.,Bates, Joshua I.,Tirfoin, Remi,Kelly, Michael J.,Phillips, Nicholas,Aldridge, Simon
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p. 4245 - 4250
(2013/10/22)
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- Stoichiometric H2 production from H2O upon Mn 2(CO)10 photolysis
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Photolysis of Mn2(CO)10 in an alkane/water biphasic system has resulted in the generation of 1.80 ± 0.16 mol of hydrogen per mol of Mn2(CO)10. Various studies including deuteration have indeed shown water to be the H2 source while kinetic studies have indicated a strong correlation between the concentration of the key intermediate MnH(CO)5 with the production rate of H2. Some of the oxygen atoms of water have been incorporated into a white solid assigned to MnCO3. A mechanism accounting for MnH(CO)5 formation from Mn2(CO)10 photolysis and subsequently H2 production from MnH(CO)5 has been proposed.
- Kee, Jun Wei,Chong, Che Chang,Toh, Chun Keong,Chong, Yuan Yi,Fan, Wai Yip
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- Hydride participation in electron transfer processes between metal carbonyl anions and cations
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Kinetic studies of selected metal carbonyl anions establish their reactivity as nucleophiles or for electron transfer. The iron species, [HFe(CO)3L]- (L = CO, PPh3), behave as metal-centered nucleophiles when reacted with [M(CO)6]+ (M = Mn, Re). Determination of the deuterium kinetic isotope ratio from kinetic studies of [HFe(CO)4]- and [DFe(CO)4]-, kH/kD = 2.8, indicates primary isotope effects for reaction with Mn(CO)6+. Initial products from transfer of a CO and back transfer of two electrons are observed in some cases. For Re-(CO)6+ exclusive formation of HRe(CO)5 as a rhenium product strongly indicates a hydrogen transfer mechanism.
- Harrigan, Marcus J.,Atwood, Jim D.
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p. 846 - 849
(2008/10/09)
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- Synthesis, characterization and chemistry of some long chain alkoxycarbonyl manganese pentacarbonyl complexes [Mn(CO)5{C(O)OR}] (where R=n-C7H15 to n-C10H21, n-C12H25, n-C14
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The long chain alkoxycarbonyl complexes, [Mn(CO)5{C(O)OR}], where R=CH2R′, and R=n-C7H15 to n-C10H21, n-C12H25 and n-C16H33, have been synthesize
- Yin, Xiaolong,Andersen, Jo-Ann M.,Cotton, Alan,Moss, John R.
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p. 267 - 276
(2007/10/03)
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- An octahedral stannylmanganese stannylene complex1,2
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Treatment of decacarbonyldimanganese with the alkylarylstannylene RR′Sn (2), R=2,4,6-tBu3C6H2, R′=CH2C(CH3)2-3,5-tBu2C6H3, furnishes the tetracarbonyl-stannylmanganese stannylene complex 3, in which the tin atom of the stannyl group is part of a stannaindan ring system. Reaction of 2 with [(OC)2Fe(NO)2] yields the tetrahedral iron stannylene complex [OC(NO)2Fe=SnRR′] (4). The structures of 3 and 4 were determined by X-ray crystallography.
- Weidenbruch, Manfred,Stilter, Artur,Saak, Wolfgang,Peters, Karl,Von Schnering, Hans Georg
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p. 125 - 129
(2007/10/03)
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- Reactivity and structure of (η6-C6(CH3)6)Mn(CO) 2H: Stable alkylrhenium analogues
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The reactivity of Mr′H (2; Mr′ = (η6-C6(CH3)6)Mn(CO)2) with protic acids, Lewis bases, and transition-metal organometallics is reported. Reaction of 2 with triflic acid or HBF4·Et2O generates H2 and [Mr′(S)]+ (S = CH2Cl2, OEt2, CF3SO3-). Treatment of 2 with CpW(CO)3X (X = Cl, I), CpFe(CO)2X (X = Cl, I), and Mn(CO)6Br results in metathesis to give Mr′X and CpW(CO)3H, CpFe(CO)2H, and Mn(CO)5H, respectively. Reaction of 2 with [CpFe(CO)2]2 produces CpFe(CO)2H and the new complex Mr′Fe(CO)2Cp. The reaction of [Rr′CO]PF6 (Rr??? = (η6-C6(CH3)6)Re(CO)2) with (CH3)3NO and (n-Bu)4NCl results in the formation of Rr′Cl (5a). Reaction of 5a with t-BuLi produces Rr′(C(CH3)3), while reaction with K(C2H5)3BH yields Rr′C2H5. The structures of 2 and 5a, determined by single-crystal X-ray diffraction studies, are reported here. Compound 2 crystallizes in the space group Pna21 with unit cell dimensions α = 11.918(1) A?, b = 10.826(2) A?, c = 10.465(1) A?, Z = 4, V = 1350.2 A?3, R1 = 0.042, and R2 = 0.043. Compound 5a crystallizes in the space group Pbca with unit cell dimensions a = 13.689(0) A?, b = 13.573(0) A?, c = 15.298(0) A?, Z = 8, V = 2842.4 A?3, R1 = 0.085, and R2 = 0.18.
- Schlom, Peter J.,Morken, Ann M.,Eyman, Darrell P.,Baenziger, Norman C.,Schauer, Steven J.
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p. 3461 - 3467
(2008/10/08)
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- Low-temperature neutron diffraction study of HMn2Re(CO)14 and studies of a metal metal exchange equilibrium that converts HMn2Re(CO)14 into HMnRe2(CO)14
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The crystal and molecular structure of (CO)5Re(μ-H)Mn(CO)4Mn(CO)5, prepared from reaction of Mn2-(CO)9(η1-tolualdehyde) with HRe(CO)5, has been determined from neutron diffraction measurements at 15 K: unit-cell constants, a = 9.145 (1) A?, b = 15.557 (3) A?, c = 14.040 (3) A?, β = 106.60 (2)°, monoclinic, space group P21/n, Z = 4, V = 1914.2 (6) A?3, R(F2) = 0.110 for 4859 reflections with F02 ≥ 3σ(F02) and (sin θ/λ)max = 1.054 A?-1. The Re-H distance (1.827 (4) A?) is longer than the Mn-H distance (1.719 (5) A?). Spectroscopic and crystallographic data indicate that a small amount (~9%) of (CO)5Re(μ-H)Mn(CO)4Re(CO)5 has cocrystallized with the major component. Further evidence for the identity of (CO)5Re(μ-H)Mn(CO)4Re(CO)5 comes from an independent synthesis by a known route. A mechanism is proposed that accounts for the formation of (CO)5Re(μ-H)Mn(CO)4Re(CO)5 from the reaction of (CO)5Re(μ-H)Mn(CO)4Mn(CO)5 with HRe(CO)5. The equilibrium constant for the metal-metal exchange equilibrium, (CO)5Re(μ-H)Mn(CO)4Mn(CO)5 + HRe(CO)5 = (CO)5Re(μ-H)Mn(CO)4Re(CO)5 + HMn(CO)5, has been determined; Keq = 1.00 ± 0.05 at 22 °C in C6D6.
- Bullock, R. Morris,Brammer, Lee,Schultz, Arthur J.,Albinati, Alberto,Koetzle, Thomas F.
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p. 5125 - 5130
(2007/10/02)
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- Flash photolysis studies of the reactions of dinuclear manganese carbonyl compounds with tributyltin hydride and triethylsilane
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The reactions of Mn2(CO)8L2 (L = CO, PMe3, P(n-Bu)3, P(i-Bu)3, P(i-Pr)3, P(C6H11)3) with HSnBu3 and of Mn2(CO)10 with HSiEt3 were studied via flash photolysis, employing a conventional xenon flash lamp apparatus. The flash photolysis results are consistent with the conclusions based on continuous photolysis studies. The predominant reaction involves oxidative addition of the hydride to manganese at the site of CO loss. The rate of oxidative addition decreases as the steric requirements of L increase. Following oxidative addition, reductive elimination occurs. For HSnBu3, HMn(CO)4L and Bu3SnMn(CO)3L are formed. In the reaction of HSiEt3 with Mn2(CO)10, reformation of HSiEt3 dominates over formation of HMn(CO)5. The lifetime of the intermediate product resulting from the initial addition varies greatly with L. For small L. such as CO or PMe3, the intermediate persists for several seconds. With increasing size of L the addition process is slowed and the rate of elimination increases. A complete model for the reaction systems takes account of the semibridging form of the CO-loss product as the prevalent species in a noncoordinating solvent. Detailed modeling of the reaction system indicates that the on-off equilibrium involving coordination of the semibridging CO to the vacant manganese site is kinetically important. Formation of the semibridging form from the open form appears to have a significant energy barrier.
- Sullivan, Richard J.,Brown, Theodore L.
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p. 9162 - 9169
(2007/10/02)
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- Photochemical reaction of dinuclear manganese carbonyl compounds with tributyltin hydride and with silanes
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The photochemical reactions of Mn2(CO)8L2 (L = CO, PMe3, P(n-Bu)3, P(i-Pr)3) with HSnBu3 or HSiEt3 in hexane solutions have been studied, using 366- or 313-nm irradiation, and under CO or Ar atmospheres. Under CO, 1.1-3.7 atm, the products of the reaction of Mn2(CO)10 with HSnBu3 are HMn(CO)5 and Bu3SnMn(CO)5. Under Ar or low CO pressures, a third product, assigned as HMn(CO)4(SnBu3)2, is formed at the expense of Bu3SnMn(CO)5. For a given photon flux, the reaction rate is inversely related to [CO]. The behavior of the system is consistent with a reaction pathway that involves oxidative addition of the hydride to the coordinatively unsaturated metal center formed upon CO loss. Analogous results are observed for the phosphine-substituted manganese carbonyl dinners. Reaction with HSiEt3 proceeds much more slowly under equivalent conditions of irradiation. In the reaction with Mn2(CO)5, only HMn(CO)5 is seen as a significant product, with trace amounts of Et3SiMn(CO)5 also observed. These results are also consistent with oxidative addition to the Co-loss product as the only pathway for the photochemical reaction. None of the manganese dimers undergo photochemical reaction with either fluorene or triphenylmethane, in spite of the comparatively low C-H bond energy in each case.
- Sullivan, Richard J.,Brown, Theodore L.
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p. 9155 - 9161
(2007/10/02)
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- Pentacarbonylmanganese enolate and dienolate complexes. Preparative and mechanistic considerations
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Reactions of pentacarbonyl manganate anion with 4-halocrotonate esters or 2-halocarboxylate esters result in a complex set of inorganic and organic products, usually including the expected dienolate (or enolate) complexes.The reaction variables include the counterion, solvent, and halo group.The mechanism of the reaction has been investigated by conducting a thorough characterization of the reaction products under various conditions and also by carrying out model reactions.One can rationalize most of the non-organometallic products using either a radical or carbanion mechanism, but the latter seems to fit the available data better.Experimental procedures for optimizing the yield of the organometallic dienolate or enolate complexes have been worked out.
- Masters, Andrew P.,Sorensen, Ted S.
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p. 492 - 501
(2007/10/02)
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- Phosphido-bridged heterodinuclear complexes of CrPd, MoPd, WPd, and MnPd. X-ray crystal structures of and
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A series of phosphido-bridged heterodinuclear complexes has been prepared by the low temperature reaction of the labile chain complexes trans-2(PhCN)2> (m = Cr, Mo, W(CO)2Cp; Mn(CO)4) with 3 molar equivalents of PCy2H or PPh2H.The crystal struc
- Braunstein, Pierre,Jesus, Ernesto de,Tiripicchio, Antonio,Camellini, Marisa Tiripicchio
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- Homologation of methanol catalyzed by manganese carbonyl in alkali-metal formate-methanol solutions
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In this work, Mn2(CO)10 was found to be an active catalyst for the homologation of methanol in alkali-metal formate-methanol solutions at 200°C and elevated CO and H2 pressures. Mn2(CO)10 is converted to Mn(CO)5- by its reaction with H2 and/or HCO2-, and methanol is activated by the formation of methyl formate. The latter reaction is catalyzed by HCO2-. It is proposed that HCO2- catalyzes the formation of methyl formate by the reverse of the known pathway for base-catalyzed hydrolysis of carboxylate esters. The methyl-transfer reaction between Mn(CO)5- and HCO2CH3 to give CH3Mn(CO)5 is rate-limiting in the homologation process and follows second-order kinetics, with a rate constant of 2.4 × 10-3 M-1 s-1 at 200°C. Subsequent reactions of CH3Mn(CO)5 lead to the formation of ethanol, acetaldehyde, acetals, methane, and traces of ethyl formate and methyl acetate. Methane is produced with a yield of 5-50%, decreasing with increasing partial pressure of CO. The homologation reaction generates CO2 as the coproduct according to the reaction CH3OH + 2CO + H2 → CH3CH2OH + CO2.
- Chen,Rathke
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p. 1833 - 1838
(2008/10/08)
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- THE SYNTHESIS AND REACTIVITY OF μ(1,4)-BUTANEDIYLBIS(MANGENESE PENTACARBONYL)
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The synthesis of μ(1,4)-butanediylbis(manganese pentacarbonyl) and its reactions with a number of nucleophilic and electrophilic reagents are described.
- Mapolie, Selwyn F.,Moss, John R.,Scott, Louise G.
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- Mechanisms of the carbon-hydrogen bond-forming binuclear reductive elimination reactions of benzyl- and hydridomanganese carbonyls
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The reactions between RMn(CO)4L [R = p-MeOC6H4CH2; L = CO (1a), L = (p-MeOC6H4)3P (1c)] and HMn(CO)4L [L = CO (2a), L = (p-CH3OC6H4)s
- Nappa, Mario J.,Santi, Roberto,Halpern, Jack
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- Intermolecular formation of C-H bonds: Application to the synthesis of heterobimetallic complexes
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The reactions of various alkylmetal carbonyl complexes (e.g., MeMn(CO)5, EtRe(CO)5, MeFe(CO)2Cp, Me2Os(CO)4) with various transition-metal hydrides (e.g., HRe(CO)5, H2Os(CO)4, HMn(CO)5, HW(CO)3Cp) have been examined in solvents of different coordinating abilities. In coordinating solvents the metal-containing products are solvated dinuclear complexes; in noncoordinating solvents the metal-containing products are polynuclear hydrides, formed by the coordination of a second equivalent of the hydride reactant. The vacant coordination site is created on the metal that originally bears the alkyl ligand: in CH3CN, MeMn(CO)5 and HRe(CO)5 give (CH3CN)Mn(CO)4Re(CO)5, whereas EtRe(CO)5 and HMn(CO)5 give (CH3CN)Re(CO)4Mn(CO)5. The organic products eliminated are generally aldehydes (although alkane elimination is also seen, particularly when the initial alkyl carbonyl complex is a dialkyl). The reaction is fastest in coordinating solvents and for the alkyl carbonyl complexes that most readily form acyls: MeMn(CO)5 and those complexes of other metals (e.g., EtRe(CO)5) that contain alkyl groups that migrate more readily than methyl. When heated in acetonitrile solution, EtRe(CO)5, i-BuRe(CO)5, and some other alkyl carbonyl complexes equilibrate with solvated acyl complexes such as cis-RC(O)(CH3CN)Re(CO)4; these solvated acyl complexes react rapidly at low temperatures with hydrides to eliminate aldehydes. In favorable cases, the reactions of alkyl carbonyls with transition-metal hydrides are synthetically attractive routes to heterobimetallic complexes.
- Warner, Keith E.,Norton, Jack R.
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p. 2150 - 2160
(2008/10/08)
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- Organometallic Lewis Acids, XIV. Ethylene Bridged Manganese and Rhenium Carbonyls; Low Temperature X-Ray Structure of (OC)5ReCH2CH2Re(CO)5
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The tetrafluoroborato complexes (OC)5MFBF3 (M = Mn, Re) which are obtained by methyl abstraction from (OC)5MCH3 using Ph3CBF4 react with ethylene or propene at room temperature and 1 bar to give (+)BF4(-).By nucleophilic addition of the carbonylmetalates (-) (M = Mn, Re) to the coordinated alkene in these cationic complexes (+) the alkene bridged complexes (OC)5MCH2CH(R)M(CO)5 (M = Mn, Re; R = H, Me) are formed.Also the mixed-metal complex (OC)5MnCH2CH2Re(CO)5 has been isolated.According to an X-ray structure at low temperature(OC)5ReCH2CH2Re(CO)5 can be considered as a dimetal substituted ethane with a carbon-carbon distance of 152 pm. - Keywords: Tetrafluoroborato Complexes, Organometallic Lewis Acids
- Raab, Klaus,Nagel, Ulrich,Beck, Wolfgang
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p. 1466 - 1476
(2007/10/02)
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- Bimetallic anionic formyl complexes: Synthesis and properties
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Three bimetallic anionic formyl complexes, Li+[Mn2(CO)9(CHO)]- (2), Li+[ReMn(CO)9(CHO)]- (3), and Li+[cis-Re2(CO)9(CHO)]- (4), are prepared by the reaction of Li(C2H5)3BH with the corresponding neutral metal carbonyl dimers MM′(CO)10. Whereas 2 has a half-life of ca. 8 min at room temperature, 4 is stable for days and is easily isolated as a THF solvate. When 2-4 are treated with electrophiles such as benzaldehyde, Fe(CO)5, and n-octyl iodide, hydride transfer occurs to give benzyl alcohol (after protonation), Li+[Fe(CO)4(CHO)]-, and octane, respectively. Heterobimetallic formyl 3 is a weaker hydride donor than 2 and 4. Reaction of 4 with CH3I gives CH4 (ca. 50%). However, complex reactions occur when 2 and 4 are treated with CH3SO3F and strong acids, contrary to our original report of CH4 and H2 evolution. Formyl 2 is stabilized by added (C2H5)3B and decomposes disproportionatively to Mn2(CO)10 (0.5 equiv), Li+[Mn(CO)5]- (1.0 equiv), and H2 (0.5 equiv). An initial Mn-Mn bond cleavage step is proposed. The only characterizable product from the thermolysis of 4 is Re2(CO)10, but photolysis gives Li+[Re2(CO)9(H)]-. When K+[Re2(CO)9(CHO)]- is treated with 1 equiv of K(sec-C4H9)3BH, reduction to formaldehyde (21%) and K2[Re2(CO)9] (92%) occurs.
- Tam, Wilson,Marsi, Marianne,Gladysz
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p. 1413 - 1421
(2008/10/08)
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- Reaction of HCl with photoproduced base-substituted manganese carbonyl radicals
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Near-UV irradiation of Mn2(CO)8L2 (L = PBu3, P(OEt)3) in the presence of HCl and a variety of solvents yields both HMn(CO)4L and Mn(CO)4(L)Cl. Evidence suggests the mechanism involves oxidative addition of HCl to 15- and 17-electron metal carbonyl radicals.
- Byers, Blaine H.,Curran, Timothy P.,Thompson, Michael J.,Sauer, Linda J.
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p. 459 - 460
(2008/10/08)
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- Photochemistry of matrix-isolated HMn(CO)5: Evidence for two isomers of HMn(CO)4
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UV photolysis of HMn(CO)5, isolated in Ar or CH4 matrices at 20 K, produces HMn(CO)4 and CO. A combination of 13CO enrichment and IR spectroscopy is used to show that HMn(CO)4 has a Cs structure (3). There is a substantial shift (2500 cm-1) in the UV/visible absorption maximum between CH4 and Ar matrices, probably due to a significant HMn(CO)4...CH4 interaction. Narrow-band photolysis (367 nm in CH4 matrices, 403 nm in Ar) results in the formation of small amounts of a second isomer of HMn(CO)4, most probably with C4v structure (2). Prolonged irradiation of HMn(CO)5 in an Ar matrix, with a pulsed ArF excimer laser (193 nm), yields a significant amount of Mn(CO)5, but the quantum yield for H loss is much lower than that for CO loss from HMn(CO)5.
- Church, Stephen P.,Poliakoff, Martyn,Timney, John A.,Turner, James J.
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p. 3259 - 3266
(2008/10/08)
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- SOME OBSERVATIONS ON PENTACARBONYLMANGANESE-SUBSTITUTED TIN HYDRIDES
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The substituted tin hydrides, (CO)5MnSnH3, (CO)5MnSnMeH2, and (CO)5MnSnMe2H, have been synthesised and characterised with reasonable certainty by IR, MS and 1H NMR spectroscopy, despite some difficulties with decomposition. (CO)5MnSnH3 is the least stable
- Foster, Stephen P.,Mackay, Kenneth M.
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- THE REACTION OF FORMYL FLUORIDE WITH TRANSITION METAL COMPLEXES
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Formyl fluoride reacts with metal carbonyl anions in a manner similar to acetic formic anhydride.Although formyl complexes may have been formed as unstable intermediates, no neutral formyl complexes could be isolated but rather the expected decomposition products, the metal carbonyl hydrides or dimers, were produced.The attempted oxidative addition of formyl fluoride to various coordinately unsaturated metal complexes also did not result in the formation of formyl derivatives.HF adducts were obtained from the reaction of Ir(CO)Cl(PR3)2 or M(PPh3)4 (M=Pt or Pd) with formyl fluoride whereas Ru(NO)Cl(PPh3)2 and Rh(PPh3)3Cl give the CO complexes Ru(NO)(CO)Cl(PPh3)2 and Rh(CO)Cl(PPh3)2, respectively.
- Doyle, Gerald
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p. 355 - 362
(2007/10/02)
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- THE HYDROGENATION OF 9,10-DIMETHYLANTHRACENE BY HYDRIDOPENTACARBONYLMANGANESE(I). EVIDENCE FOR A FREE-RADICAL MECHANISM
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The reaction of 9,10-dimethylanthracene with HMn(CO)5 yields a nearly equimolar mixture of cis- and trans-9,10-dihydro-9,10-dimethylanthracene.The results of kinetic and isotopic tracer studies provide support for a free-radical mechanism in which the rate-determining step is the transfer of a hydrogen atom from HMn(CO)5 to 9,10-dimethylanthracene.
- Sweany, Ray,Butler, Steven C.,Halpern, Jack
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p. 487 - 492
(2007/10/02)
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