- Volatile Rhenium(I) Compounds with Re-N Bonds and Their Conversion into Oriented Rhenium Nitride Films by Magnetic Field-Assisted Vapor Phase Deposition
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New heteroleptic rhenium(I) compounds, [fac-Re(I)(CO)3(L)] (e.g., L= tfb-dmpda, (N,N-(4,4,4-T.
- Frank, Michael,Jürgensen, Lasse,Leduc, Jennifer,Stadler, Daniel,Graf, David,Gessner, Isabel,Zajusch, Fabian,Fischer, Thomas,Rose, Marc-André,Mueller, David N.,Mathur, Sanjay
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- Synthesis of N-heterocyclic carbene rhenium(i) carbonyl complexes
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Reaction of aminophosphinimine [RHN(CH2)2NPPh 3] (R = H, Et) with Re2(CO)10 provided the NH-functionalized carbene rhenium complex [Re2(CNHCH 2CH2NR)(CO)9] (3a, R = H, 3b, R = Et). Treatment of 3 with Br2 provided the mono nuclear [Re(CNHCH 2CH2NR)(CO)4Br] (1, R = H, 2, R = Et). However, NH-functionalized carbene complexes 1-3 did not undergo N-alkylation with alkyl halides to yield the N-substituted NHC complexes. The direct ligand substitution of [Re(CO)5Br] with a carbene donor was employed to prepare [Re(IMes2)(CO)4Br] (6a, IMes2 = 1,3-di-mesitylimidazol-2-ylidene; 6b, IMes2 = 1,3-dimesityl-4,5- dihydroimidazol-2-ylidene). Analyses of spectroscopic and crystal data of 6a and 6b show similar corresponding data among these complexes, suggesting the saturated and unsaturated NHCs have similar bonding with ReI metal centers. Reduction of 6a and 6b with LiEt3BH yielded the corresponding hydrido complexes 7a-b [ReH(CO)4(IMes2)], but not 1 and 2. Ligand substitution of 1, 6a and 6b toward 2,2′- bipyridine (bipy) was investigated. Crystal structures of 1, 3a-b, 6a-b and 7b were determined for characterization and comparison. The Royal Society of Chemistry 2012.
- Chen, Chang-Hung,Liu, Yi-Hung,Peng, Shie-Ming,Chen, Jwu-Ting,Liu, Shiuh-Tzung
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- Preparation and properties of heterometallic cube derivatives Mo3M′S4 from [Mo3S4(H2O)9]4+ with M′ = 3 Pt, Rh and Re, and [W3S4(H2O)9]
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Three heterometallic Mo3M′S4 derivatives (M′ = Pt, Rh, Re) of the incomplete single-metal depleted cube [Mo3S4(H2O)9]4+ have been prepared by reactions with [PtCl4]su
- Sokolov,Villagra,El-Hendawy,Kwak,Elsegood,Clegg,Geoffrey Sykes
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- Reaction of 2,3-bis(methylthio)pyrrolo[1,2-a]benzimidazol-1-one with BrRe(CO)3(THF)2: X-ray diffraction structure, redox chemistry, and luminescence behavior of fac-BrRe(CO)3{N,S-2,3- bis(methylthio)pyrrolo[1,2-a]benzimidazol-1-one}
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The reaction of the heterocyclic ligand 2,3-bis(methylthio)pyrrolo[1,2-a] benzimidazol-1-one with the rhenium(I) compound BrRe(CO)3(THF) 2 has been explored and found to give the new complex fac-BrRe(CO)3(N,S-heterocycle) (1) upon stirring at room temperature. The same product has also been isolated in lower yield by heating BrRe(CO) 5 and the starting heterocycle. Compound 1 has been isolated and characterized in solution by IR and NMR spectroscopies, and the N,S-chelation mode exhibited by the ancillary heterocyclic ligand has been confirmed by X-ray diffraction analysis. The redox properties of 1 have been investigated by cyclic voltammetry, where an irreversible reduction is observed at Epc=-0.63V. The nature of the LUMO in 1 has been evaluated through the means of extended Hückel MO calculations, and the electrochemical and MO data are discussed relative to the parent heterocyclic ligand that possesses a low-lying, ligand-based π* LUMO. The photophysical behavior of the starting heterocycle and compound 1 has been analyzed in CH2Cl2 and MeCN solvents; emission quantum yields at room temperature are on the order of 10-5 in CH2Cl2 and one order of magnitude higher in MeCN. The lowest excited state arises from an intraligand (IL) transition resulting from a π → π* excitation that is confined to the heterocycle.
- Wu, Guanmin,Glass, David R.,May, Daniel,Watson, William H.,Wiedenfeld, David,Richmond, Michael G.
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- Generation and reactivity of a triosmium carbon radical. Hydrogen abstraction, arene addition, and the formation of [H3Os3(CO)9(μ3-CCO)]2, a dialkylidyne, diketone complex
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Photolyzing a mixture of Re2(CO)10 and H3Os3(CO)9(μ3-CBr) under CO (～2 atm) is a convenient method of generating the radical H3Os3(CO)9(μ3-C ?). This species abstracts hydrogen from cyclohexane and toluene and adds to benzene. In deuteriated hydrocarbons H3Os3(CO)9(μ3-CD) is produced, but in cyclohexane-d12 a diketone complex, [H3Os3(CO)9(μ3-CCO)]2, also is formed.
- Strickland, Debra S.,Wilson, Scott R.,Shapley, John R.
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- A mechanistic investigation of the photoinduced reduction of carbon dioxide mediated by tricarbonylbromo(2,2′-bipyridine)rhenium(I)
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A mechanistic study of the photoinduced reduction of carbon dioxide to carbon monoxide in the triethanolamine/dimethylformamide/ReBr(CO)3(bpy) (bpy is 2,2′-bipyridine) system is described. Continuous photolysis at 436 nm results in the highly specific formation of CO with a quantum yield, φCO, that reaches 0.15. The value of φCO decreases with increasing triethanolamine concentration in the range 0.75-3.8 M; addition of 10% water to the solvent medium also lowers φCO. Luminescence measurements reveal that triethanolamine reductively quenches the Re-to-bpy charge-transfer excited state of ReBr(CO)3(bpy) with a rate constant of 6 × 107 M-1 s-1, whereas CO2 undergoes no discernible interaction with the photoexcited complex. Formation and decay of the initial reduction product [ReBr(CO)3(bpy)]- have been observed in flash photolysis experiments. The amount of [ReBr(CO)3(bpy)] produced correlates with the value of CO2 thereby implicating this 19e complex in the mechanism of CO2 reduction. Evidence that [ReBr-(CO)3(bpy)]- reacts directly with CO2 has been obtained, although the identity of the resulting product is unknown at present.
- Kutal, Charles,Weber, Michael A.,Ferraudi, Guillermo,Geiger, David
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- New fac -tricarbonyl rhenium(I) semicarbazone complexes: Synthesis, characterization, and biological evaluation
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Expanding our previous work on salicylaldehyde semicarbazone metal complexes as prospective anti-trypanosomal agents, five new fac-Re I(CO)3-containing complexes with ligands of this semicarbazone series were synthesized and characte
- Machado, Ignacio,Fernandez, Soledad,Becco, Lorena,Garat, Beatriz,Gancheff, Jorge S.,Rey, Ana,Gambino, Dinorah
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- A Water-Soluble Rhenium(I) Catalyst for the Regio- And Stereoselective C(sp2)-H Alkenylation of N-Pyridyl-/ N-Pyrimidylindole and the N-H Alkenylation of N-Pyrimidylaniline Derivatives with Ynamides
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A water-soluble and low-valent rhenium(I) catalyst for the C2 alkenylation of N-pyridyl/N-pyrimidylindole derivatives with ynamides under mild conditions using water as the solvent has been described. The reaction of N-pyridyl/N-pyrimidyl indole with the ynamide afforded the C2-Z-selective alkenylation derivative as the sole product, and the reactions of N-pyrimidylanilines delivered the corresponding N-alkenylated product rather than the expected C-H alkenylation products in high yields under the same conditions.
- Sarathkumar, Sundaramoorthi,Kavala, Veerababurao,Yao, Ching- Fa
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- Exploring the synthesis and characterization of fac-Re(CO)3L complexes using diethylenetriamine derivative functionalized at the central nitrogen
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The aim of this research is to develop new rhenium complexes with favorable bio-distribution properties which can be used as radiometal complexes or for conjugation with biomolecules for the development of targeted radiolabelled biopharmaceuticals. Two metals of interest utilized in radiopharmaceuticals are technetium and rhenium, both of which share similar chemical and structural properties. The coordination chemistry of these metals is highly dependent upon ligands that are structurally and chemically robust among other factors. The synthesis of new symmetrical tridentate ligands and ligand conjugation methods will expand the likelihood of developing suitable fac-[Re(CO)3L]n compounds with promising biomedical properties and were consequently the subject of this investigation. In order to accomplish this, the design, synthesis, characterization and X-ray structure of new water-soluble rhenium complexes for assessing metal binding to biomolecules were investigated. Three diethylenetriamine (dien) derivatives, 2-(bis(2-aminoethyl)amino)-N-(2-oxo-4-(trifluoromethyl)-2H-chromen-7-yl)acetamide (atfcdien, 3), 2-(bis(2-aminoethyl)amino)-N-(3,5-bis(trifluoromethyl)benzyl)acetamide (tfmedien, 6), and N-benzyl-2-(bis(2-aminomethyl)amino)acetamide (badien, 9) and their rhenium complexes were synthesized. 1H NMR spectroscopy, mass spectrometry and X-ray crystallography techniques were employed to characterize the ligands and their rhenium complexes [Re(CO)3atfcdien]Br (10), [Re(CO)3tfmedien]Br (11) and [Re(CO)3badien]Br (12). 1H NMR studies were conducted to examine chelated Re complexes revealed a consistent downfield shift of the CH signal of the dien moiety for all three new ligands.
- Ndinguri, Margaret W.,Black, Carrie A.,Gosser, Anna L.,Reitz, Sara,Sutphin, Cody,Fronczek, Frank R.,Cormier, Lindsay E.
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- Novel Trithioanhydride Complexes of Transition Metals; X-Ray Crystallographic Characterization of -S(Fp)>SO3CF3,
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Nucleophilic addition of the thione sulphur atom in the complexes n> n = Fp or Re(CO)5; Fp = Fe(CO)2(η-C5H5)> at the thiocarbonyl carbon atom in the complexes + gives five-membered metallacycles (η-C5H
- Albano, Vincenzo G.,Braga, Dario,Busetto, Luigi,Monari, Magda,Zanotti, Valerio
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- Multi-step and multi-component organometallic synthesis in one pot using orthogonal mechanochemical reactions
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We demonstrate that the mechanochemical strategies for oxidative addition and ligand substitution on organometallic centers can be mutually orthogonal, permitting the rational design of multi-component mechanochemical reaction procedures for assembling complex or solution-sensitive organometallic species from three, four or even five components in one pot. The herein established synthetic procedures represent a new level of complexity in mechanochemical reactions by milling and are the first to combine redox and ligand substitution reactions into mechanochemical strategies for either one-pot sequential ( telescoping ) or one-pot multi-component syntheses. This ability to combine mechanochemical transformations has enabled the solvent-free, room-temperature syntheses of relatively complex organometallics directly for simple zerovalent metal carbonyls as the simplest precursors. In particular, we demonstrate the efficiency of mechanochemical oxidative addition by targeting selected pentacarbonyl halides (fluoride, chloride, bromide, iodide) of rhenium(i) and manganese(i), and illustrate the potential of multi-step organometallic mechanochemistry in the syntheses of selected fac-tricarbonyl complexes of these metals.
- Hernandez, Jose G.,Butler, Ian S.,Friscic, Tomislav
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p. 3576 - 3582
(2014/08/18)
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- Metal-metal bond cleavage of carbene complexes by halogens: The crystal and molecular structures of ax-[Mn2(CO)9{C(OEt)2-thienyl}], [Mn(CO)4(I){C(OEt)2-thienyl}] and eq-[Mn2(CO) 9{C(NH2)2-thienyl}]
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The metal-metal bond in [M2(CO)9{C(OEt)R}] (M = Mn (1), Re (2), R = 2-thienyl (a), 2-bithienyl (b)) is readily cleaved with halogens to afford cis-[M(CO)4(X){C(OEt)R}] (M = Mn (3), X = I; M = Re (4), X = Br). In the binuclear manganese complex, the carbene ligand is found in an axial position due to steric reasons, whereas the electronically favoured equatorial position is found for the carbene ligands in the corresponding rhenium complexes and in [Mn2(CO)9{C(NH 2)thienyl}] (5a), containing a sterically less demanding NH 2-substituent.
- Lotz, Simon,Landman, Marilé,Bezuidenhout, Daniela I.,Olivier, Andrew J.,Liles, David C.,Van Rooyen, Petrus H.
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p. 5929 - 5937
(2007/10/03)
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- Nucleophilic vinylic substitution with transition metal carbonyl anions - A rare case of a halophilic reaction mechanism. Formation of halo(acyl)rhenate complexes and X-ray structure of cis-[CF2=CF(CO)Re(CO)4Br]Na
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Reactions of polyfluorinated alkenyl halides Z-(CF3) 3CCF=6;CFHal (Hal=Cl,I-Cl, Hal=Br, I-Br) and CF2=CFBr (II-Br) with [CpFe(CO)2]K (FpK) and [Re(CO)5]Na proceed through the initial attack of metal carbonyl anion on halogen. Reaction with FpK gives minor amounts of σ-alkenyl complexes Z-RfCF=CFFe(CO)2Cp (I-Fe, II-Fe) (3-30%), but primarily leads to dimer [CpFe(CO)2] 2. Reaction with [Re(CO)5]Na produces anionic halo(acyl)rhenates cis-[Z-RfCF=CF(CO)Re(CO)4Hal]Na (V-Cl, V-Br, VI) (70-90%) which were isolated, and halo(acyl)rhenate VI (Rf=F) was characterized by X-ray structure analysis. Halo(acyl)rhenates result from the attack of the intermediate carbanion [RfCF=CF]- on the carbonyl ligand of Re(CO) 5Hal. The involvement of [RfCF=CF]- is demonstrated by their trapping with t-BuOH or CH-acid, which gives the protodehalogenated alkenes I-H and II-H, and suppresses the nucleophilic substitution reaction leading to I-Fe, II-Fe or V-Cl. Arguments against a radical/SET mechanism for the substitution reaction are also advanced.
- Sazonov,Artamkina,Khrustalev,Antipin,Beletskaya
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- Rate constants for reactions of Cl abstraction from CCl4 by CCl3CH2 .CHR radicals and Br abstraction from CCl3CH2CHBrR (R = Bun, AcO, OCNC4H8, CN) by .
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The rate constants for reactions of Cl abstraction from CCl4 by CCl3CH2 .CHR radicals and Br abstraction from CCl3CH2CHBrR (R = Bun, AcO, OCNC4H8, CN) by s
- Gasanov
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- Formation of cis-[R(f)(CO)Re(CO)4Hal]Na complexes as an evidence of halogen-metal exchange between [Re(CO)5]Na and polyfluorinated aryl and vinyl halides
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Halo(acyl)rhenate complexes cis-[R(f)(CO)Re(CO)4Hal]Na (Hal = Cl, Br; R(f) = C6F5, trans-(CF3)3CCF=CF) are the primary products of the reactions of [Re(CO)5]Na with the corresponding aryl o
- Artamkina, Galina A.,Sazonov, Petr K.,Ivushkin, Vasily A.,Beletskaya, Irina P.
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p. 970 - 972
(2007/10/03)
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- Electron-Transfer Reactions of Re(CO)5: Atom-Transfer-Concerted Mechanism vs Bimetallic Intermediate Formation
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Flash photochemically generated Re(CO)5 reacts with halide complexes, Cu(Me4[14]-1,3,8,10-tetraeneN4)X+, Cu(Me2pyo[14]trieneN4)X+, and Ni(Me2pyo[14]trieneN4
- Sarakha,Ferraudi
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p. 313 - 317
(2008/10/09)
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- Reactivity studies on bimetallic μ-malonyl complexes: cleavage and alkylation chemistry of the malonyl ligand
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The bimetallic μ-malonyl complexes: 5-C5Me5)(NO)(PPh3)Re1:C3>Re(CO)4(Br)>-Li+ (1), 5-C5Me5)(NO)(PPh3)Re1:C3>Re(CO)4(PMe3)> * Li+OSO2CF3- (2), and (η5-C5Me5)(NO)(PPh3)Re1,O3:C3>Re(CO)4 (3) undergo carbon-carbon bond cleavage reactions of the malonyl ligand upon exposure to HCl.Deprotonation of (η5-C5Me5)Re(NO)(PPh3)(μ-η1,η2-COCH2CO)Re(CO)4 (3), in THF solution and addition of CH3I leads to the C-alkylation product, (η5-C5Me5)Re(NO)(PPh3)1,O3:C3>Re(CO)4(11), isolated as a single diastereomer (85percent yield).Deprotonation of 11 and alkylation with CD3I leads to (η5-C5Me5)Re(NO)(PPh3)1,O3:C3>Re(CO)4 (12-d3) with > 97percent diastereoselectivity.Alkylation of the enolate anion derived from deprotonation of 11 with ethyl iodide led to isolation of (η5-C5Me5)(NO)(PPh3)Re-C1,O3:C3>Re(CO)4 (21) in 84percent yield.Quenching of the enolate anion of 3 with excess ethyl iodide led to formation of a 11:89 mixture of (η5-C5Me5)(NO)(PPh3)Re1:C3,O3>Re(CO)4 (15) and (η5-C5Me5)(NO)PPh3)Re1,O3:C3>Re(CO)4 (16) in 87percent combined yield.When the enolate anion of 3 was treated with allyl bromide, both C ad O alkylation products (η5-C5Me5)(NO)(PPh3)Re-C1:C3,O1>Re(CO)4 (17) and (η5-C5Me5)(NO)(PPh3)Re-C1,O3:C3>Re(CO)4 (18) were formed in a 32:68 ratio (84percent combined yield).Alkylation with benzyl bromide gave (η5-C5Me5)(NO)(PPh3)Re1,O3:C3>Re(CO)4 (19) in 76percent yield.
- O'Connor, Joseph M.,Uhrhammer, Roger,Chadha, Raj K.,Tsuie, Barbara,Rheingold, Arnold L.
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p. 143 - 156
(2007/10/02)
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- Comparison of the thermal and photochemical reactions of (η1-cyclopentadienyl)Re(CO)5 and (η1-9-fluorenyl)Re(CO)5: Nonthermal chemical reactions from the lowest excited state
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Near-UV (366 nm) irradiation of the new complexes (η1-R)Re(CO)5 (R = C5H5, 9-fluorenyl) in alkane solution at 295 K yields predominantly radical products, whereas thermolysis yields only the fully ring-slipped (η5-R)Re(CO)3 species. Irradiation at 366 nm of (η-C5H5)Re(CO)5 in deoxygenated alkane solutions at 295 K yields some CO loss to give (η5-C5H5)Re(CO)3, Φ= 0.007 ± 0.002, and mainly Re-R bond cleavage giving Re(CO)5 and R radicals with Φ = 0.06 ± 0.02. The ultimate radical products are Re2(CO)10 and C10H10 in the absence of radical traps. Only Re-R cleavage is observed for (η1-9-fluorenyl)Re(CO)5 upon irradiation at 366 nm with Φ = 0.04 ± 0.004 in deoxygenated alkane to give Re2(CO)10 and 9,9′-bifluorene. Thermolysis of (η1-R)Re(CO)5 (R = C5H5, 9-fluorenyl) leads to quantitative conversion to the fully ring-slipped products, (η5-C5H5)Re(CO)3 or (η5-fluorenyl)Re(CO)3, respectively. Thermal ring slippage of (η1-9-fluorenyl)Re(CO)5 to (η5-fluorenyl)Re(CO)3 is reversible and occurs with a rate of ～1 × 10-3 s-1 at 400 K. The rate of ring slippage is suppressed by a factor of > 100 under 1 atm of CO. In the presence of 0.05 M PPh3, (η1-9-fluorenyl)Re(CO)4PPh3 is the exclusive thermolysis product and forms with ΔH ? of 28.3 ± 1 kcal mol-1 and ΔS? of 7 ± 3 cal mol-1 K-1. (η5-Fluorenyl)Re(CO)3 reacts at 295 K with CO to quantitatively regenerate (η1-9-fluorenyl)Re(CO)5 with a rate of 9.7 × 10-5 s-1 under 1 atm of CO. The rate of thermal ring slippage of (η1-C5H5)Re(CO)5 to (η5-C5H5)Re(CO)3 is 4.2 × 10-4 s-1 at 325 K (ΔH? = 25.2 ± 1.6 kcal mol-1 and ΔS? = 7 ± 3 cal mol-1 K-1) and is not affected by 1 atm of CO. The rate of thermal ring slippage is decreased by ～60% at 295 K by 1200 psig CO. (η5-C5H5)Re(CO)3 does not react with up to 1200 psig of CO at 295 K. Optical and photochemical measurements on CH3Re(CO)5 show lowest excited state behavior consistent with results for the η1-C5H5 and η1-9-fluorenyl species. The thermal behavior of CH3Re(CO)5 (qualitatively slower reactions) is in accord with the conclusion that CO loss from η1-C5H5 and η1-9-fluorenyl species is assisted by the unsaturated hydrocarbon ligand. Irradiation at 254 or 366 nm of (η1-C5H5)Re(CO)5 in alkane glasses at 95 K leads to CO loss as the only detectable photoprocess: the ring-slipped (η3-C5H5)Re(CO)4 and (η5-C5H5)Re(CO)3 are formed. Irradiation at 254 nm of (η1-9-fluorenyl)Re(CO)5 under the same conditions leads to the formation of (η3-fluorenyl)Re(CO)4 and a new, isomeric (fluorenyl)Re(CO)5 product, but 366-nm irradiation yields predominantly (>90%) isomerization, not CO loss. The identities of the η3 intermediates from (η1-C5H5)Re(CO)5 and (η1-9-fluorenyl)Re(CO)5 have been established spectroscopically and by chemical trapping experiments.
- Young, Kent M.,Miller, Timothy M.,Wrighton, Mark S.
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p. 1529 - 1537
(2007/10/02)
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- Photochemical reactions between dinuclear metal carbonyl complexes and alkyl halides. Formal oxidative addition across a metal-metal single bond proceeding by a free radical chain mechanism
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Photochemical reactions between (L = CO, PBu3, PEt3, P(OMe)3, P(OPh)3, PPh3) and alkyl halides (RX) yield both alkyl and halo complexes, and , in equimolar quantities.Kinetic and quantum yield studies suggest that these reactions proceed by a radical chain pathway involving CO dissociation from the dinuclear complex and metal-metal bond homolysis of the coordinatively unsaturated dinuclear intermediate.
- Biddulph, Michael A.,Davis, Reg,Wilson, Fiona I. C.
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p. 277 - 293
(2007/10/02)
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- Syntheses, reactions, and structures of dioxycarbene complexes of rhenium
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The cyclic dioxycarbene complex Re(CO)4Br(COCH2CH2O) (I) reacts with PPh3 to give initially fac-Re(CO)3(PPh3)Br-(COCH2CH2O) (II) and upon further reaction Re(CO)2(PPh3)2Br(COCH2CH 2O) (III). The reaction of I with the diphosphines Ph2P(CH2)nPPh2 (n = 1,2) gives the diphosphine-bridged complexes [Re(CO)3Br(COCH2CH2O)]2(Ph 2P(CH2)nPPh2) (IV, n = 1; V, n = 2). The structures of I and V were established by X-ray diffraction studies. The crystals of I are orthorhombic, space group Pbca, with a = 11.764 (2) ?, b = 17.579 (4) ?, c = 10.658 (2) ?, and Z = 8, while those of V are triclinic, space group P1, with a= 11.160(2) ?, b= 11.369 (3) ?, c = 10.090(3) ?, a = 111.58 (3)°, β = 95.40 (2)°, γ = 92.78 (2)°, Z = 1, and two acetones ((CH3)2CO) of crystallization. The dimethyldithiocarbamate ion, -S2CN(CH3)2, reacts with I to remove in effect ethylene oxide from the carbene ligand, giving Re(CO)5Br and HOCH2CH2SC(=S)N(CH3)2.
- Miessler, Gary L.,Kim, Sangsoo,Jacobson, Robert A.,Angelici, Robert J.
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p. 1690 - 1695
(2008/10/08)
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- Steric and electronic effects on atom transfer reactions of Re(CO)4L· radicals with organic halides and HSn(n-C4H9)3
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Re(CO)4L·(L = CO, P(OR)3, PR3, AsEt3) radicals, generated by laser flash photolysis of L(CO)4Re-Re(CO)4L, react with halogen atom donors (CH2Br2, CHCl3, CCl4) or hydrogen atom donors (HSn(n-Bu)3) in solution to produce cis-Re(CO)4LX (X = H, Cl, Br). Bimolecular rate constants for halogen and hydrogen atom transfers to Re(CO)4L·were measured by following the decay of the transient Re(CO)4L·absorbance in the 550-nm region. The rate constants for both the halogen and hydrogen atom transfer processes are influenced by steric and electronic properties of the substituent L. Both bromine and chlorine atom transfer processes depend to a similar extent on the electronic properties of L. The bromine atom transfer reactions show a slightly greater steric dependence than the chlorine atom transfer reactions. The steric dependence of the hydrogen atom transfer reaction is similar to that of the halogen atom transfers, but the dependence on the electronic properties of L is smaller. Increasing electron density at the metal center enhances the rate of atom transfer; polar effects are more evident in the halogen atom transfer. Rate constants for both atom transfer reactions fit a two-parameter free energy relationship, wherein electronic and steric effects of L are represented.
- Hanckel, John M.,Lee, Kang-Wook,Rushman, Paul,Brown, Theodore L.
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p. 1852 - 1856
(2008/10/08)
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- Organometallic Lewis Acids, XVI. Reactions of Pentacarbonyl(tetrafluoroborato)rhenium(I) with Simple and Complex Anions
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A series of monomeric complexes (OC)5ReX 1b-h (X=SCN, SeCN, ONO2, NO2, O2CH, p-SC6H4NO2, CN) and of ligand bridged complexes (OC)5ReXRe(CO)5 4-6 (X=oxalate, quadratate, tetrathioquadratate), (+)BF4(-) 11, 12 (X=CN, OC(H)O) has been obtained from (OC)5ReFBF3.Reaction of (OC)5ReCH3 with Ph3C(+)PF6(-) or HPF6*Et2O yields the fluoro bridged complex (+)PF6(-) (3) which reacts with acetonitrile to produce (OC)5ReF (1a) and (+)PF6(-).The Lewis acid"Re(CO)5(+)" can be added to the N- or S-atom of cyano- and isothiocyanato complexes to give NCAuCNRe(CO)5 (7), (+)BF4(-) (8), (NC)2Pt2 (9), 4>(2+)(BF4(-))2 (10), and (SCN)3Cr3 (13), respectively.From the reaction of (OC)5ReFBF3 with aqueous alkali a tetrametric μ3-carbon dioxide bridged complex 2 (15) has been obtained.The dihydrogen sulfide complex (+)BF4(-) (2) is formed from (OC)5ReFBF3 and H2S.
- Raab, Klaus,Beck, Wolfgang
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p. 3830 - 3848
(2007/10/02)
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- Mechanism of Halogenation of Dimanganese, Manganese-Rhenium, and Dirhenium Decacarbonyls
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The reactions between halogens (X2 = Cl2, Br2, I2, and ICl) and M2(CO)10 (M2 = Mn2, MnRe, and Re2) in CH3CN solvent yield equal amounts of M(CO)5X and +.For X2 = I2 the rate law was shown to obey second-order kinetics, k.For M2 = Re2 the activation parameters were ΔH = 5.8+/- 0.2 kcal/mol and ΔS = -34.9 +/-0.9 cal/(mol K), for M2 = MnRe ΔH = 6.3 +/- 1.5 kcal/mol and ΔS = -41 +/- 6 cal/(mol K), and for M2 = Mn2 ΔH = 8.5 +/- 1.4 kcal/mol and ΔS = -39 +/- 5 cal/(mol K).The relative rates of halogenation follow the order Re2(CO)10 > MnRe(CO)10 > Mn2(CO)10, which opposes the order expected based upon homolysis of the metal-metal bond.The rate of iodination varies by more than a millionfold depending on the solvent.In nonpolar solvents such as decalin or toluene the oxidation proceeds slowly to yield M(CO)5I, whereas in CH3CN or CH3NO2 the reaction proceeds rapidly to produce both M(CO)5I and +.The evidence suggests that halogen attacks the metal-metal bond via one end of the dihalogen molecule and that heterolytic cleavage of the halogen-halogen bond takes place to yield free halide ion and a halogenium-bridged metal dimer.In many respects this resembles the mechanism for the bromination of alkenes.
- Schmidt, Steven P.,Trogler, William C.,Basolo, Fred
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p. 1308 - 1313
(2007/10/02)
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- Sonochemistry of Mn2(CO)10 and Re2(CO)10
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Irradiation of liquids with high-intensity ultrasound creates, via cavitation, localized hot spots with transient pressures of > 300 atm and temperatures ca. 3000 K.We report the first studies of the chemical effects of the ultrasound on Mn2(CO)10, MnRe(C
- Suslick, Kenneth S.,Schubert, Paul F.
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p. 6042 - 6044
(2007/10/02)
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- Preparation of Some Metallodithiocarboxylato- and Metallodithiocarbene-metal Complexes
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The reaction between the carbon disulphide adduct of dicarbonyl(cyclopentadienyl)iron, (1+) (cp=η5-C5H5), and (M=Mn or Re) produces in good yield the heterodinuclear complexes in which the CS2 group acts as a bridge in the unit FeC(=S)SM.Depending on the reaction conditions, both the chelato-complex and the unidentate derivative are obtained.Alkylation of the thione sulphur atom in the unit FeC(=S)SRe produces the dithiocarbene (1+) in good yield.The reaction of this metallodithiocarbenemetal complex with methylamine yields and .The compounds and were formed from the reaction of (1+) with LiBr.
- Busetto, Luigi,Palazzi, Antonio,Monari, Magda
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p. 1631 - 1634
(2007/10/02)
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- Characterization of MnTc(CO)10 and TcRe(CO)10
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The heteronuclear decacarbonyls of MnTc and TcRe have been synthesized and characterized according to the infrared and mass spectra. Optimum conditions have been established for their preparation and purification, which may be applicable to the production of mixed-metal carbonyls in general.
- Michels, Gary D.,Svec, Harry J.
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p. 3445 - 3447
(2008/10/08)
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