35816-56-9Relevant academic research and scientific papers
Hydride participation in electron transfer processes between metal carbonyl anions and cations
Harrigan, Marcus J.,Atwood, Jim D.
, p. 846 - 849 (2008/10/09)
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.
Photochemistry of the metal-metal-bonded complexes . Crystal structure of the photoproduct 2(CN)-iPr-PyCa)Ru(Me)(CO)2>
Nieuwenhuis, Heleen A.,Loon, Annelies van,Moraal, Marieke A.,Stufkens, Derk J.,Oskam, Ad,Goubitz, Kees
, p. 165 - 178 (2007/10/02)
Photochemical reactions are reported for the metal-metal-bonded complexes iPr-PyCa), N,N'-diisopropyl-1,4-diaza-1,3-butadiene (iPr-DAB) upon irradiation into their lowest-energy absorption band.The radicals radical and radical are formed by homolytic splitting of the Mn-Ru bond; the latter radicals have been characterized by ESR spectroscopy.In THF, the iPr-DAB)>radical radicals dimerize to give iPr-DAB)>2, and the corresponding radicals from the iPr-PyCa complex gave an unidentified product.Irradiation of a solution of the complexes in CH2Cl2 or CHCl3 afforded and but in apolar solvents such as hexane, completely different photoproducts, viz. 2(CN),η2(C'N')-iPr-DAB)Ru(Me)(CO)2> and 2(CN)-iPr-PyCa)Ru(Me)(CO)2> were obtained.The crystal structure of the last complex was determined.The photochemical quantum yield for the disappearance of the iPr-DAB complex was ca. 0.30, but only 0.05 for the iPr-PyCa complex.Low-temperature measurements and flash photolysis data showed that this difference in behaviour is due to the thermal instability of the dimer iPr-PyCa)>2, which leads to partial regeneration of the parent complex at room temperature.At temperatures below 163 K, the photodecomposition into radicals was followed by electron transfer, leading to formation of the ions - and + in 2-MeTHF and the contact ion-pair -...Ru(Me)(CO)2(α-diimine)+> in 2-chlorobutane.Similar photodisproportionation products were formed upon irradiation of the complexes at room temperature in the presence of N- and P-donor ligands.Keywords: Manganese; Ruthenium; Metal-metal bonding; Photochemistry; Diimines; ESR spectroscopy
Electron and bromine transfer reactions between metal carbonyl anions and metal carbonyl bromides. Crystal and molecular structure of dimeric indenyl molybdenum tricarbonyl
Striejewske, William S.,See, Ronald F.,Churchill, Melvyn Rowen,Atwood, Jim D.
, p. 4413 - 4419 (2008/10/08)
Reactions of metal carbonyl anions with metal carbonyl halides proceed by two separate paths. When the reactant anion is a strong nucleophile, the halogen is transferred, resulting in a new metal carbonyl halide and a new metal carbonyl anion as intermediates. The ultimate products, in this case, are the homobimetallic complexes. In cases where the reactant metal carbonyl anion is a poor nucleophile, a single electron transfer occurs, leading to the two homobimetallic complexes and to the heterobimetallic complex. Halide effects and possible indenyl effects are examined. The complex [Mo(indenyl)(CO)3]2 crystallizes in the noncentrosymmetric orthorhombic space group P212121 (No. 19) with a = 7.3572(7) ?, b = 14.4539(12) ?, c = 19.983(2) ?, V = 2125.0(4) ?3, and Z = 4. Diffraction data were collected on a Siemens R3m/V diffractometer for 2θ = 5-45° (Mo Kα), and the structure was solved and refined to R = 3.21% and Rw = 3.23% for all 2786 independent reflections (R = 2.26% and Rw = 2.81% for those 2314 reflections with |Fo|> 6σ(|Fo|). The complex is held together by a Mo-Mo single bond (Mo(1)-Mo(2) = 3.251(1) ?), and has Mo-CO distances ranging from 1.956(6) to 1.988(7) ?, averaging 1.970 ± 0.016 A. Molybdenum-carbon distances to the η5-indenyl rings range from 2.300(7) to 2.427(6) ? for Mo(1) and 2.306(7) to 2.430(6) ? for Mo(2).
Charge-transfer salts of carbonylmetalates as outer-sphere ion pairs in photochemical and thermal electron transfer
Wei, C.-H.,Bockman, T. M.,Kochi, J. K.
, p. 85 - 97 (2007/10/02)
Highly colored, crystalline salts result from the combination of the carbonylmetalates Co(CO)4-, Mn(CO)5- and HFe(CO)4- with perphenyl-phosphonium and sulfonium cations.The unique colors are associated with the interionic
Group- and electron-transfer reactions of tetracarbonylferrate(2-)
Zhen, Yueqian,Atwood, Jim D.
, p. 2778 - 2780 (2008/10/08)
Reactions of Fe(CO)42- with metal carbonyl complexes lead to distinct mechanisms. Reaction with metal carbonyl cations gives a two-electron process that we interpret as a CO2+ transfer. Reaction with Mn2(CO)10 occurs by a single-electron transfer producing Fe2(CO)82- and Mn(CO)5-. Reaction with Mn(CO)5Br also occurs by a single-electron transfer. Reaction with Re(CO)5Br could be either SET or direct nucleophilic displacement. Kinetic studies are reported for several reactions.
Metal to ligand charge-transfer photochemistry of metal-metal-bonded complexes. 10. Photochemical and electrochemical study of the electron-transfer reactions of Mn(CO)3(α-diimine)(L)? (L = N-, P-Donor) radicals formed by irradiation of (CO)5MnMn(CO)3(??-diimine) complexes in the presence of L
Van Der Graaf,Hofstra,Schilder,Rijkhoff,Stufkens,Van Der Linden
, p. 3668 - 3679 (2008/10/08)
This article describes the catalytic properties of Mn(CO)3(α-diimine)(L)? radicals, formed by irradiation with visible light of the complexes (CO)5MnMn(CO)3(α-diimine) (1) in the presence of L (L = N-, P-donor). The radicals initiate the catalytic disproportionation of complexes 1 in an electron transfer chain (ETC) reaction to give Mn(CO)5- and [Mn(CO)3(α-diimine)(L)]+. The efficiency of this reaction is low if L is a hard base; it increases for ligands having smaller cone angles and, for phosphines, higher basicities. The Mn(CO)3(α-diimine)(L)? radicals also reduce several of the cluster compounds M3(CO)12-x(PR3)x (M = Fe, Ru; x = 0-2) and catalyze the substitution of CO by PR3. In that case the efficiency of the reaction is mainly determined by the reduction potentials of the [Mn(CO)3(α-diimine)(PR3)]+ cation and the cluster. These potentials have been measured with cyclic voltammetry and differential pulse voltammetry.
Metal to ligand charge-transfer photochemistry of metal-metal-bonded complexes. 8. Photochemistry of (CO)5MnMn(CO)3(α-diimine) complexes. Coupling reactions of the radicals formed and X-ray structure of the photoproduct (CO)4Mn(σ-N,σ-N′,η 2-CN-iPr-pyca)Mn(CO)3
Van Der Graaf, Tim,Stufkens, Derk J.,Oskam, Ad,Goubitz, Kees
, p. 599 - 608 (2008/10/08)
This article describes the photochemistry between 133 and 298 K of five metal-metal-bonded carbonyls (CO)5MnMn(CO)3(α-diimine) (1a-e) (α-diimine = 4,4′-dimethyl-2,2′-bipyridine (bpy′ (1a)), pyridine-2-carbaldehyde N-isopropylimine (iPr-pyca (1b)), 1,4-diisopropyl-1,4-diaza-1,3-butadiene (iPr-DAB (1c)), 1,4-di-p-tolyl-1,4-diaza-1,3-butadiene (pTol-DAB (1d)), 1,4-di-p-anisyl-1,4-diaza-1,3-butadiene (pAn-DAB (1e))) by irradiation into their metal to α-diimine charge-transfer (MLCT) band. At room temperature these complexes undergo homolysis of the metal-metal bond and the radicals formed dimerize to give Mn2(CO)10 and Mn2(CO)6(α-diimine)2 (2a-e). Of these dimers, 2d,e were thermally unstable at room temperature. They decomposed into their radicals, which were characterized with ESR in the case of 2d. Complexes 1b-e showed a side reaction at room temperature, giving rise to the formation of (CO)4Mn(σ-N,σ-N′,η 2-CN-iPr-pyca)Mn(CO)3 (3b) and (CO)3Mn(σ-N,σ-N′,η2-CN,η 2-C′N′-R-DAB) (4c-e), respectively. The crystal structure of 3b was determined, and the data are as follows: monoclinic, P21/a, with a = 15.425 (1) A?, b = 9.867 (1) A?, c = 12.988 (1) A?, β = 111.310 (9)°, and Z = 4; R = 0.041. Both Mn atoms possess a distorted octahedral geometry, and the Mn-Mn distance is shorter than that in Mn2(CO)10. The formation of these complexes 3b, 4c-e was quenched by radical scavengers and favored in viscous solvents such as paraffin. At lower temperatures, the quantum yields for the photoproduction of 2-4 decreased, and in the case of 1c, a novel complex, 5c, was formed at T ? 180 K by reaction of the Mn(CO)3(iPr-DAB) radicals. 5c was identified as Mn2(CO)4(σ-N,σ-N′,η 2-CN-iPr-DAB)2. Raising the temperature above 180 K caused a thermal conversion of 5c into Mn2(CO) 5(σ-N,σ-N′-iPr-DAB)(σ-N,σ-N′, η2-CN-iPr-DAB) (6c). A further increase of temperature above 200 K caused the formation of 2c out of 6c. At temperatures below 183 K, homolysis products were no longer formed, but instead the CO-loss complexes (CO)4Mn(μ-CO)Mn(CO)2(α-diimine) (7) were produced. The thermal and photochemical reactions of the CO-bridged complex 7a were studied. For both primary photoprocesses, homolysis and release of CO, the quantum yields were high and wavelength independent throughout the MLCT band. They are therefore proposed to occur from the same 3σbσ* state of the complex after intersystem crossing/internal conversion from the MLCT state(s). The relative quantum yields of homolysis and CO-loss reactions resemble the ones that were derived for Mn2(CO)10, which points to a similar mechanism for the photochemistry of both types of complexes.
Reduction of CO2 and other substrates using photochemical reactions of the W2(CO)102- complex
Silavwe, Ned D.,Goldman, Alan S.,Ritter, Robin,Tyler, David R.
, p. 1231 - 1236 (2008/10/08)
The photochemistry of the W2(CO)102- complex was investigated with the goal of determining if irradiation of this dimer generates a powerful reducing agent, presumably a 19-electron species. In general, the photochemistry of the W2(CO)102- complex is comparable to that of other metal-metal-bonded carbonyl dimers. Irradiation into the low-energy tail of the d π → σ* electronic transition of the W2(CO)102- complex led to W-W bond homolysis. The resulting 17-electron W(CO)5- radicals could be trapped with suitable ligands such as 4-cyanopyridine to give 19-electron adducts . (See ref 3 for an important definition of the phrase 19-electron adduct .) Evidence is presented that the ligands PPh3 and PBu3 also react with photogenerated W(CO)5- to form adducts: W(CO)5- + PR3 → W(CO)5PR3-. These adducts are powerful reducing agents, and they were used to reduce CO2 to formate and CO. The only organometallic product formed in the reaction was W(CO)5PPh3, the oxidized form of the 19-electron complex. In a similar manner, Mn2(CO)10 was reduced to Mn(CO)5-, Cp2Co+ to Cp2Co, benzophenone to the radical anion, and methylviologen (MV2+) to MV+. Alternative reduction mechanisms involving the W(CO)5- radical, W(CO)52-, or HW2(CO)10- as reductants were shown not to be operating. Nineteen-electron complexes generated by irradiation of Cp2Mo2(CO)6 proved incapable of reducing CO2.
Metalloporphyrins with metal-metal bonds. Synthesis, characterization, and electrochemistry of (P)TlMn(CO)5, (P)TlCo(CO)4, and (P)TlM(CO)3Cp where M = Cr, Mo, and W. Crystal structure of [(2,3,7,8,12,13,17,18-octaethylporphinato)thallium(III)]pentacarbonylmanganese
Guilard,Zrineh,Ferhat,Tabard,Mitaine,Swistak,Richard,Lecomte,Kadish
, p. 697 - 705 (2008/10/08)
The synthesis, physicochemical properties, and electrochemistry of a new series of metal-metal σ-bonded thallium porphyrins are reported. The metalate ligands σ-bonded to the thallium octaethyl- or tetraphenylporphyrin complexes were Mn(CO)5, Co(CO)4, W(CO)3Cp, Mo(CO)3Cp, and Cr(CO)3Cp. Each neutral complex was characterized by 1H NMR, IR, and UV-visible spectroscopy, all of which suggested a single metal-metal covalent bond. The crystal structure of (OEP)TlMn(CO)5 was also solved (triclinic, P1, a = 12.467 (2) A?, b = 13.528 (2) A?, c = 15.088 (3) A?, α = 62.04 (2)°, β = 61.62 (2)°, γ = 69.53 (2)°, Z = 2, R(F) = 0.027, Rw(F) = 0.033, w = (σ2(I) + 0.04I)-1). The σ Tl-Mn bond length is 2.649 (1) A?. Electrochemistry and spectroelectrochemistry techniques were used to characterize each oxidized and reduced complex in methylene chloride containing 0.1 M tetrabutylammonium hexafluorophosphate as supporting electrolyte. Each complex underwent two oxidations, which were centered at the porphyrin π ring system. Unlike the case for metal-metal-σ-bonded indium porphyrins, no cleavage of the σ-bond occurs following the first oxidation; i.e., the generated radical cations are stable on the cyclic voltammetry time scale. The metal-metal-bonded compounds could also be reduced by two one-electron additions, but the generated anion radical stability was very low. The ultimate products of electroreduction were the free base porphyrin radical anion and a bis(thallium(I)) compound that was formed from a transient mono(thallium(I)) porphyrin complex.
Formation of metal-metal bonds by ion-pair annihilation. Dimanganese carbonyls from manganate(-I) anions and manganese(I) cations
Lee,Kuchynka,Kochi
, p. 1886 - 1897 (2008/10/08)
The coupling of the anionic Mn(CO)5- and the cationic Mn(CO)6+ occurs upon mixing to afford the dimeric Mn2(CO)10 in essentially quantitative yields. Dimanganese decacarbonyl is formed with equal facility from the coupling of Mn(CO)5- with Mn(CO)5(py)+ and Mn(CO)5(NCMe)+. By way of contrast, the annihilation of Mn(CO)4PPh3- with Mn(CO)6+ yields a pair of homo dimers Mn2(CO)10 and Mn2(CO)8(PPh3)2 together with the cross dimer Mn2(CO)9PPh3. Extensive scrambling of the carbonylmanganese moieties also obtains with Mn(CO)4P(OPh)3- and Mn(CO)5PPh3+, as indicated by the production of Mn2(CO)8[P(OPh)3]2, Mn2(CO)8[P(OPh)3](PPh3), and Mn2(CO)8(PPh3)2 in more or less statistical amounts. These diverse Mn-Mn couplings can be accounted for by a generalized formulation (Scheme VI), in which the carbonylmanganese anions Mn(CO)4P- and the cations Mn(CO)5L+ undergo an initial electron transfer to produce Mn(CO)4P? and Mn(CO)5L?, respectively. The behaviors of these 17- and 19-electron radicals coincide with those independently generated in a previous study of the anodic oxidation of Mn(CO)4P- and the cathodic reduction of Mn(CO)5L+, respectively. The facile associative ligand substitution of 17-electron carbonylmanganese radicals by added phosphines provides compelling evidence for the interception of Mn(CO)4P? and its interconversion with 19-electron species in the course of ion-pair annihilation. The reactivity trend for the various ion pairs qualitatively parallels the driving force for electron transfer based on the oxidation and reduction potentials of Mn(CO)4P- and Mn(CO)5L+, respectively, in accord with the radical-pair mechanism in Scheme VI.
