- ARENE EXCHANGE REACTIONS OF (ARENE)TRICARBONYLCHROMIUM COMPLEXES.
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The kinetics of the reaction of (arene)tricarbonylchromium complexes with arenes have been investigated. The uncatalyzed reaction is first order in complex and first order in arene, indicating a displacement process. The reaction is catalyzed by cyclohexanone in a process which is first order in cyclohexanone and independent of arene concentration. The unreactive (hexamethylbenzene)tricarbonylchromium catalyzes exchange between benzene and (p-xylene)tricarbonylchromium, verifying and clarifying the results of Strohmeier. A simplified mechanism is proposed which incorporates the first-order, the second-order, and the catalyzed processes without requiring the production of free tricarbonylchromium.
- Traylor,Stewart,Goldberg
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- Comparative multinuclear magnetic resonance spectroscopic study of transition metal (Cr, W and Mn) mesitylene tricarbonyls and transition metal (Ru and Co) carbonyl clusters
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Three mononuclear 1,3,5-trimethylbenzene (mesitylene) carbonyl transition metal complexes, mesitylene tricarbonyl chromium, (CH3)3C6H3Cr(CO)3 (1), mesitylene tricarbonyl tungsten, (CH3)3C6H3W(CO)3 (2), mesitylene tricarbonyl manganese tetra-fluoroborate,
- Kolehmainen, E.,Laihia, K.,Rybinskaya, M. I.,Kaganovich, V. S.,Kerzina, Z. A.
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- Photochemical synthesis of new (η6-arene)Cr-hydrido stannyl and (η6-arene)Cr-bis-stannyl complexes. Ligand effects on the Sn-H interaction in the hydrido stannyl compounds
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Hydrido stannyl compounds containing the η2-H-SnPh3 ligand and bis-stannyl compounds containing two SnPh3 ligands have been obtained from the photolysis of (η6-arene)Cr(CO)3 and HSnPh3. New complexes with different arenes (mesitylene, trifluorotoluene and 1,4-dimethoxybenzene) have been obtained and characterized by X-ray diffraction: (η6-C6H4(OCH3) 2)Cr(CO)2(HSnPh3) (3a), (η6-C6H4(OCH3) 2)Cr(CO)2(SnPh3)2 (3b). Structural data for 3a: monoclinic; space group P21/c (No. 14); a=17.445(3), b=9.820(3) and c=16.302(5) A; Z=4; V=2539.2(12) A3; 3b: monoclinic; space group P21/n (No. 14); a=13.904(3), b=20.567(5) and c=13.911(3) A; Z=4; V=3994(2) A3. 1H-NMR as well as X-ray provided evidence for the existence of three-center two-electron bonds in the hydrido stannyl complexes. The effects of different ligands on bonding and spectroscopic parameters were studied. Arene exchange reactions of the bis-stannyl complexes, as well as reactions of some of these compounds with P(C2H5)3 and CO, were also investigated.
- Khaleel, Abbas,Klabunde, Kenneth J.,Johnson, Alison
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- Photochemical synthesis of (η6-arene)chromium hydrido stannyl and (η6-arene)chromium bis(stannyl) complexes
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Photolysis of (η6-arene)Cr(CO)3 complexes and HSnPh3 in aromatic solvents at room temperature has led to two classes of complexes: hydrido stannyl compounds containing the η2-H-SnPh3 ligand and bis(stannyl) compounds containing two SnPh3 ligands. The ratio between the two complexes simultaneously produced depends on the choice of the arene. Complexes with different arenes (mesitylene, toluene, benzene, fluorobenzene, and difluorobenzene) have been obtained and characterized including X-ray structures for (η-6C6H3(CH3) 3)Cr(CO)2 (H)(SnPh3) (1a). (η6-C6H3)3)(η 6CH3)3)Cr(CO)2(SnPhs 3)2 (1b), (η-C6-H6H3F)Cr(CO)2(SnPh 3)2 (4b), and (η-C6C6H4 (CO)2(SnPh3)2 (5b). X-ray crystallography of the last three compounds has given the following results: 1b, monoclinic, space group P21/c (No. 14), a = 13.905(4) A?, b = 18.499(2) A?, c = 17.708(2) A?, Z = 4, V = 4285(1) A?3; 4b, orthorhombic, space group Pca21 (No. 29), a = 16.717(2) A?, b = 18.453(2) A?, c = 25.766(2) A?, Z = 8, V = 7948(2) A?3; 5b, monoclinic, space group P21/c (No. 14), a = 13.756(2) A?, b = 18.560(2) A?, c = 17.159(2) A?, Z = 4, V = 4372(2) A?3. The relatively high J(119Sn-Cr-H) and J(117Sn-Cr-H) values as well as the X-ray structural data provide evidence for the existence of three-center two-electron bonds in the hydrido stannyl complexes. The 1H NMR data of the complexes are compared with chromium-arene bond distances, and a sensible trend is observed and discussed.
- Khaleel, Abbas,Klabunde, Kenneth J.
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p. 3223 - 3227
(2008/10/09)
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- Laser pulse photolysis and transient infrared investigation into the effect of solvent or substituents (X) on the reactivity of photogenerated (η6-C6H6-yXy)Cr(CO)2 intermediates
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Time-resolved infrared spectroscopy identified the first observable species following nanosecond laser photolysis of (benzene)Cr(CO)3 in alkane solution as (benzene)Cr(CO)2(alkane). UV/ vis-monitored laser flash photolysis was used to observe the reaction of this species with CO. The reactivity toward CO of the primary photoproducts derived from related arene complexes (arene = C6H5Cl, C5H5Me, p-ClC6H4Me, C6H5Et, C6H5But, o- and p-C6H4Me2, C6H3Me3, C6Me6, C6Et6) were also determined by this technique. The rate of reaction with CO was found to depend on the alkane solvent and on the nature and degree of substitution of the arene ligand. The enthalpies of activation for all reactions were constant (24 ± 2 kJ mol-1), while the entropy of activation increased upon methyl substitution of the arene and upon a change in the solvent from cyclohexane to a linear alkane.
- Creaven, Bernadette S.,George, Michael W.,Ginzburg, Allan G.,Hughes, Catherine,Kelly, John M.,Long, Conor,McGrath, Irene M.,Pryce, Mary T.
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p. 3127 - 3131
(2008/10/08)
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- Transition Metal Stannyl Complexes, 7. - Preparation of Carbene Complexes (?-Arene)(CO)2CrCR2 by the Reaction of the Anionic Stannyl Complexes - with R2CX2 or Y
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Carbene complexes (?-arene)(CO)2Cr=CR2 are formed in substitution/elimination reactions from the anionic stannyl complexes K and organic dihalides R2CX2 containing activated C-X bonds or ionic halides Y.Bis(stannyl)complexes (?-arene)(CO)2Cr(SnPh3)2 (3) and hydrido(stannyl)complexes (?-arene)(CO)2Cr(H)SnPh3 are formed as byproducts due to the reaction of the eliminated Ph3SnCl with the anionic starting complexes or electron transfer reactions, respectively.The portion and ration of the byproducts is largely influenced by the steric properties of both the (?-arene)(CO)2Cr fragment and the organic halide.Pyridinylidene complexes 2 are only obtained from 2-chloro-N-methylpyridinium tetrafluoroborate with 1a-c, but not with 1d.With the sterically less demanding halides Cl (n=3,4)> or 3,3-dichloro-1,2-diphenylcyclopropene the carbene complexes (?-arene)(CO)2Cr=C(H)NR2 or are obtained with all employed ?-arene ligands. Key Words: Carbene Complexes / Stannyl complexes / Chromium complexes / Anionic complexes
- Schubert, Juergen,Mock, Stefan,Schubert, Ulrich
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p. 657 - 664
(2007/10/02)
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- Stability and the gas chromatography of alkyl-substituted η6-benzenetricarbonylchromium(0) complexes
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Thermoanalytical and gas chromatographic data are reported for benzenetricarbonylchromium(0) and nine of its methyl- and t-butyl-substituted derivatives.The distinct trends found for the volatilities, thermal stabilities, air stabilities and gas chromatog
- Patsalides, E.,Pratten, S. J.,Robards, K.
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p. 169 - 180
(2007/10/02)
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- Intramolecular vibrational relaxation in n-alkyl benzene chromium tricarbonyls: State selective production of chromium atoms
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We have measured one color multiphoton dissociation/ionization (MPD/MPI) spectra for a series of n-alkyl substituted arene chromium tricarbonyls (ACTs) .Our data indicate that intramolecular vibrational relaxation (IVR) rates for methyl, ethyl, and propyl ACTs increase relative to the benzene analog in the ratio of 3:6:34.In contrast, the net relaxation rates of the p-xylene (dimethyl) and mesitylene (trimethyl) analogs are two and three times faster than benzene, respectively.The behavior of these latter analogs probably also reflects differences in electronic structure relative to the benzene ACT.Taken with the results of experiments on other analogs and the independently obtained results on the uncomplexed arenes, we have found a strong correlation between the presence of low frequency vibrations and the rate of IVR.The rate of IVR determines the distribution of neutral chromium atoms formed by MPD of the n-alkyl ACTs.
- Hossenlopp, Jeanne M.,Samoriski, Brian,Rooney, Dan,Chaiken, J.
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p. 3331 - 3337
(2007/10/02)
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- Synthesis of (η6-arene)2Cr2(CO)3 Complexes Containing a Formal CrCr Triple Bond Starting from η6-areneCr(CO)2NCCH3
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The photochemical reaction of η6-ArCr(CO)3 (Ar = benzene, toluene, m-xylene, mesitylene, methyl benzoate, and fluorobenzene) with acetonitrile in hexane or p-tolunitrile in THF, resp., yields complexes η6ArCr(CO)2NCR (1-10).Solutions of the red acetonitrile complexes yield on warming or UV photolysis by dissoziation of the nitrile and one CO ligand in the presence of benzene the new black coordination compounds (η6-Ar)2Cr2(CO)3 (11-16).The spectra and an X-ray structure determination of the benzene derivative 11 verify a Cr2-unit with a formal triple bond bridged by three CO ligands.The asymmetric unit of 11 contains two halves of molecules with Cr-Cr distances of 222.6 and 221.6 pm.
- Kluefers, Peter,Knoll, Lothar,Reiners, Christiane,Reiss, Karl
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p. 1825 - 1835
(2007/10/02)
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- ELECTRON TRANSFER FROM AROMATIC HYDROCARBONS AND THEIR pi -COMPLEXES WITH METALS. COMPARISON OF THE STANDARD OXIDATION POTENTIALS AND VERTICAL IONIZATION POTENTIALS.
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The energetics of electron transfer from an extensive series of alkyl-substituted benzenes are measured both in solution and in the gas phase. The standard oxidation potentials E//A//r degree stem from the reversible cyclic voltammograms (CV) in trifluoroacetic acid using the recently developed microvoltammetric electrodes. These values show an excellent correlation with the vertical ionization potentials I//p of the same aromatic hydrocarbons in the gas phase. Thermochemical analysis indicates that the slope of less than unity for the correlation arises mainly from solvation differences, particularly in the highly substituted polyalkylbenzenes.
- Howell,Goncalves,Amatore,Klasinc,Wightman,Kochi
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p. 3968 - 3976
(2007/10/02)
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- Darstellung und Eigenschaften von 1,3,2-Diazaborolin-Komplexen
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1,3-Di-tert-butyl-2-methyl-Δ4-1,3,2-diazaboroline (1a) and 2-methyl-1,3-bis(trimethylsilyl)-Δ4-1,3,2-diazaboroline (1b) react with (CH3CN)3Cr(CO)3 to form the diazaboroline complexes (ring)-Cr(CO)3 (2a, b).The synthesis of 2a also succeeds with Cr(CO)6 and 1a by UV-irradiation or thermically.The diazaborolines 1a and 1b serve as 6?-electron donors.In contrast, 2,4,5-trimethyl-1,3-diphenyl-Δ4-1,3,2-diazaboroline (1c) is coordinated to the Cr(CO)3 group via one of the phenyl rings (2c).P(C6H5)3 substitutes the diazaboroline in 2a to form (CO)4Cr2, whereas NO+ displaces one CO-group to give di carbonyl5-(1,3-di-tert-butyl-2-methyl-1,3,2-diazaboroline)>nitrosylchromium-hexafluorophosphate (3).Mesitylene substitutes the diazaboroline ring, while hexamethylborazine starts no reaction.As a result of IR, 1H-, 11B-, 13C-NMR as well as mass spectroscopic investigations, proposals for the molecular structures are made.
- Schulze, Joachim,Schmid, Guenter
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p. 495 - 504
(2007/10/02)
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