- Highly reduced organometallics 52. Synthesis and chemistry of tricarbonylnitrosylmanganate(2-), [Mn(CO)3(NO)]2-
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Treatment of Mn(CO)3(NO)(PPh3) in THF at 20°C with excess sodium amalgam, followed by treatment with cryptand 2.2.2, or with two equiv. of potassium tri-sec-butylborohydride afforded high isolated yields (≥ 80%) of air sensitive yellow solids identified as [Na(crypt.2.2.2)]2[Mn(CO)3(NO)] and K2[Mn(CO)3(NO)], respectively. These products contain the only known mixed carbonylnitrosylmetallate dianion, isoelectronic with [Fe(CO)4]2- and [Mn(CO)4]3-. Reactions of [Mn(CO)3(NO)]2- with Ph3SnCl, Mn(CO)4(NO) and Fe(CO)5, followed by metathesis, provided the new derivatives [Et4N][Mn(CO)3(NO)(SnPh3)], [PPN]2[Mn2(CO)6(NO)2], and [PPN]2[MnFe(CO)7(NO)]. On the basis of IR spectral data the latter two have been formulated to contain non-bridged structures analogous to that previously established for the isoelectronic salt [PPN]2[Fe2(CO)8]. (C) 2000 Elsevier Science S.A.
- Chen, Yu-Sen,Ellis, John E.
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p. 675 - 682
(2008/10/08)
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- Interfacial electron transfer to the zeolite-encapsulated methylviologen acceptor from various carbonylmanganate donors. Shape selectivity of cations in mediating electron conduction through the zeolite framework
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The series of (one-electron) reductions of methylviologen (MV2+) intercalated into zeolite-Y by various carbonylmanganate donors [C+Mn(CO)4L-, L = CO, P(OPh)3] are very selective and highly dependent on the size/shape of the counterion C+, although the same electron transfers carried out (homogeneously) in solution always occur spontaneously, irregardless of C+. For example, the complete reduction of MV2+ extensively doped into zeolite-Y proceeds rapidly and quantitatively when the Na+ salts of the carbonylmanganates are employed as the reductants, but only to a very limited extent (1%) when the large PPN+ [bis(triphenylphosphine)iminium] salts of the carbonylmanganates are employed. The medium-size tetraethylammonium (TEA+) salt of Mn(CO)4P(OPh)3- slowly effects an intermediate conversion (80%). Based on the fact that the large phosphite-substituted Mn(CO)4P(OPh)3- donor cannot enter the supercage of zeolite-Y, we propose interfacial electron transfer from the carbonylmanganate to the MV2+ acceptor to occur only at the zeolite periphery. Importantly, the strong dependence of the further progress of the redox reaction with decreasing size of the cation C+ (i.e., shape selectivity) predicts that electron conduction throughout the zeolite framework requires the simultaneous transport of these cations in order to effect the complete reduction of all the encapsulated MV2+, as presented in Chart 5.
- Yoon,Park,Kochi
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p. 12710 - 12718
(2007/10/03)
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- Electron transfer between mononuclear metal carbonyl anions (M(CO)5-, M = Mn, Re; CpFe(CO)2-; CpM(CO)3-, M = Cr, Mo) and trinuclear clusters (M3(CO)12, M = Fe, Ru, Os) and between trinuclear dianions (M3(CO)112-, M = Fe, Ru, Os) and metal carbonyl dimers (Mn ...
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Full title: Electron transfer between mononuclear metal carbonyl anions (M(CO)5-, M = Mn, Re; CpFe(CO)2-; CpM(CO)3-, M = Cr, Mo) and trinuclear clusters (M3(CO)12, M = Fe, Ru, Os) and between trinuclear dianions (M3(CO)112-, M = Fe, Ru, Os) and metal carbonyl dimers (Mn2(CO)10 and Cp2M2(CO)6, M = Cr, Mo, W). Reaction of mononuclear metal carbonyl anions with trinuclear clusters of group 8 (M3(CO)12, M = Fe, Ru, Os) at ambient conditions leads to four separate outcomes: (1) formation of the metal carbonyl dimer and the trinuclear dianion which occurs whenever the two-electron reduction potential for the dimer is more negative than for the trinuclear cluster, (2) formation of MFe2(CO)7- by elimination of Fe(CO)5 which occurs for M = Re(CO)5, Mn(CO)5, and CpMo(CO)3, (3) formation of the adduct, MRu3(CO)11-, which occurs for Re(CO)5, and (4) no reaction when the two-electron reduction potential for the trinuclear complex is more negative than for the dimer. For complexes where the two-electron potential for the cluster is more negative than for the dimer, reaction of M3′(CO)112- with M2 to give M3′(CO)12 and 2M- is observed. The observed reactions allow an estimate of the two-electron reduction potentials for the trinuclear clusters. The kinetics of all of these reactions indicate a first-order dependence on the oxidant and on the reductant and are most consistent with outer-sphere electron transfer.
- Shauna Corraine,Atwood, Jim D.
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p. 2647 - 2651
(2008/10/08)
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- Reaction of metal carbonyl anions with metal carbonyl dimers: Thermodynamic and kinetic factors that control the reactions
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The reactions of mononuclear metal carbonyl anions, M- (M- = Co(CO)4-, CpFe(CO)2-, Re(CO)5-, Mn(CO)4L-, L = PPh3, PBu3, P(OPh)3, CpM(CO)3- (M = Cr, Mo, W)) with metal carbonyl dimers, M′2 (M′2 = Co2(CO)8, Cp2Fe2(CO)4, Re2(CO)10, Mn2(CO)10, Cp2M2(CO)6 (M = Cr, Mo, W), and Cp2Ru2(CO)4)), are described: 2M- + M′2 → M2 + 2M′- To determine the thermodynamic parameters, we have derived values for the two-electron-reduction potentials (M2 + 2e- → 2M-) and shown that these values correctly predict the direction of reaction. The order of these reduction potentials is (all are negative) Co2(CO)8 > Cp2Cr2(CO)6 > Cp2Mo2(CO)6 > Mn2(CO)10 > Re2(CO)10 > Cp2Fe2(CO)4. In each case a clean reaction is observed with only M2 and 2M′- produced. The kinetics show that the rate has a first-order dependence on [M-]; rate = k[M-][M′2]. All dimers that contain a cyclopentadienyl ligand react more rapidly than expected from the potential. Product distributions for reactions of heterobimetallic complexes are also consistent with a different mechanism for dimers with a cyclopentadienyl ligand.
- Corraine, M. Shauna,Atwood, Jim D.
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p. 2315 - 2318
(2008/10/08)
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- Solution Homolytic Bond Dissociation Energies of Organotransition-Metal Hydrides
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The homolytic bond dissociation energies (BDEs) of the mononuclear metal carbonyl hydride complexes (η5-C5H5)M(CO)3H (M = Cr, Mo, W), (η5-C5Me5)Mo(CO)3H, (η5-C5H5)W(CO)2(PMe3)H, (η5-C5H5)M(CO)2H (M = Fe, Ru), H2Fe(CO)4, Mn(CO)4PPh3H, Mn(CO)5H, Re(CO)5H, and Co(CO)3LH (L = CO, PPh3, P(OPh)3) have been estimated in acetonitrile solution by the use of a thermochemical cycle that reguires knowledge of the metal hydride pKa and the oxidation potential of its conjugate base (anion).The BDE values obtained by this method fall in the range 50-67 kcal/mol.In mostcases, these results agree well with literature data.Our data provide strong support for the common assumption that the M-H bond energies are greater for third-row and for second-row metals than for first-row metals, the difference being 5-11 kcal/mol.Effects of neither phosphine or phosphite substitution nor permethylation of the cyclopentadienyl ring on the M-H bond energies could be detected within the error limits of the method.The results are discussed in relation to previous M-H BDE estimates and metal hydride reactivity patterns.
- Tilset, Mats,Parker, Vernon D.
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p. 6711 - 6717
(2007/10/02)
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- Steric and Electronic Factors That Control Two-Electron Processes between Metal Carbonyl Cations and Anions
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Reactions of metal carbonyl cations (Mn(CO)6(+), Re(CO)6(+), Mn(CO)5PPh3(+), Mn(CO)4(PPh3)2(+), Mn(CO)5PEt3(+), Mn(CO)5PPh2Me(+), Re(CO)5PPh3(+), and CpFe(CO)3(+)) with metal carbonyl anions (Co(CO)3PPh3(-), Co(CO)4(-), Mn(CO)5(-), Mn(CO)4PPh3(-), Mn(CO)4PEt3(-), Mn(CO)4PPh2Me(-), Mn(CO)3(PPh3)2(-), CpFe(CO)2(-), Re(CO)5(-), and Re(CO)4PPh3(-)) are reported.Peak potentials are reported for all ions, and nucleophilicites (as measured by reaction with MeI) are reported for the anions.Reaction of any metal carbonyl cation with any metal carbonyl anion leads ultimately to binuclear products, which are the thermodynamic products.The binuclear products are formed by single-electron transfer.In over half of the reactions between metal carbonyl cations and anions, a two-electron change results in a new metal carbonyl cation and anion.The two-electron change may be considered mechanistically as a CO(2+) transfer with the more nucleophilic of the two anions retaining the CO(2+).The kinetic and thermodynamic driving forces and the suggested mechanism are examined.
- Zhen, Yueqian,Feighery, William G.,Lai, Chung-Kung,Atwood, Jim D.
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p. 7832 - 7837
(2007/10/02)
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- Nucleophilic nitrosylations of metal carbonyls using bis(triphenylphosphine)nitrogen(1+) nitrite
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Bis(triphenylphosphine)nitrogen(1+) nitrite (PPN(NO2)) has been found to be very effective for converting metal carbonyls into nitrosyl carbonyl complexes. The reactions are conducted in dipolar aprotic solvents such as tetrahydrofuran (THF) or acetonitrile and characteristically give high yields with no side products. The reaction has been successfully applied to Fe(CO)5, [Mn(CO)6]+, [Mn(CO)5(CH3CN)]+, [Fe(CO)2(PPh3)2(NO)]+, Mn(CO)4(NO), Mn2(CO)10, Co2(CO)8, Fe3(CO)12, Ru3(CO)12, Os3(CO)12, and Ru6C(CO)17 to generate CO2, a two-electron donor ligand (L), and the product, resulting in replacement of CO and L with NO and a negative charge. A kinetic analysis of the reaction of Fe(CO)5 and PPN(NO2) in acetonitrile verifies that the reaction is first order in iron and nitrite with k = 0.111 ± 0.007 M-1 s-1 at 26 ± 1°C. The addition of a 10-fold excess of PPh3 had no effect on the rate of the reaction. The new nitrosylcarbonylmetalate, [Mn(CO)2(NO)2]-, was characterized by a single-crystal X-ray crystallographic study (P21/a space group, Z = 4, a = 21.890 (5) A?, b = 9.194 (3) A?, c = 17.495 (3) A?, β = 96.25 (2)°), which shows that it has a tetrahedral geometry with disordered NO and CO ligands. Characterization of the new clusters [Ru3(CO)10(NO)]- and [Os3(CO)10(NO)]- establishes that the NO is bridging one edge of the metal triangle, while spectroscopic evidence suggests that [Ru6C(CO)15(NO)]- contains a terminal nitrosyl ligand. Nitrogen-15 magnetic resonance spectra of the bridging nitrosyls exhibit a 400 ppm downfield shift relative to the resonance of mononuclear nitrosyl carbonyl compounds. In some cases PPN(NO2) simply substitutes a NO2- for a carbonyl. This occurs with Co(CO)3(NO) to give the new nitro nitrosyl product [Co(NO2)(C-O)2(NO)]-.
- Stevens, Robert E.,Gladfelter, Wayne L.
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p. 2034 - 2042
(2008/10/08)
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