33635-55-1Relevant articles and documents
Alkyne ligand enhancement of the substitution lability of mononuclear osmium, ruthenium, and iron carbonyls
Pearson, Jean,Cooke, Jason,Takats, Josef,Jordan
, p. 1434 - 1440 (2007/10/03)
The kinetic influence of an alkyne ligand, hexafluorobut-2-yne (HFB), as been investigated by studying the reactions of phosphines (PR3) with the complexes M(CO)4(η2-HFB) (M = Fe, Ru, Os). The rate of production of M(CO)3(PR3)(η2-HFB) is independent of the nature and concentration of the phosphine in all cases, indicating that the rate-controlling step is CO dissociation. The kinetic parameters, k1 (s-1, 25 °C). ΔH* (kJ mol- 1), and ΔS* (cal mol-1 K-1) are: 9.5, 88.2 ± 2.3, 70 ± 10 (Fe), 1.25 x 10-2, 103.6 ± 2.4, 66 ± 8.6 (Ru); 3.5 x 10-3, 99.5 ± 0.8, 21 + 2.7 (Os). When the rate constants at 25 °C for M(CO)4(η2-HFB) are compared to those of the parent M(CO)5, the ratios are ~3 x 1013, 1.8 x 102 and 1 x 107 for M = Fe, Ru, an Os, respectively. Clearly the alkyne increases the substitution lability, and the effect is spectacular with Fe, very large with Os, and substantial but relatively more modest with Ru. The increased lability results mainly from a reduced ΔH* of ~80, 10, and 33 kJ mol-1 for Fe, Ru, and Os, respectively, and this is attributed largely to stabilization of the transition state by 4-electron donation from the alkyne ligand. Also reported are kinetics of formation of some trans M(CO)2(PR3)2(η2-HFB) complexes and an extension of earlier work on the Os(CO)5/PPh3 system.
Metal-Containing Heterocycles: Preparations, Properties, Reactions, LXIV. - Preparation and Investigations about the Reactivity of η2-Olefin Complexes and Four- to Six-Membered Metallacycloalkanes of Ruthenium and Osmium
Lindner, Ekkehard,Jansen, Rolf-Michael,Hiller, Wolfgang,Fawzi, Riad
, p. 1403 - 1410 (2007/10/02)
The olefin complexes (η2-CH2=CHR)M(CO)4 (3a,b, 5a,b) a), Os (b)> and four- to six-membered metallacycloalkanes (7a,b, 9b) , (11a,b, 15a,b) , (13a,b) are obtained by nucleophilic elimination-cycloaddition on the alkanediyl bis(trifluoromethanesulfonates) YCH2CHRY , (YCH2)2CR2 , Y-n-Y , cyclo-C6H10(YCH2)2 (12) (Y = CF3SO2O) with the divalent anions (2-) (1a,b).The corresponding osmium compounds are much more stable then their lower ruthenium homologues.On the basis of the 1H-NMR spectrum 7b has a planar conformation.According to an X-ray structural analysis 15b crystallizes in the triclinic space group P with Z = 2 and has a chair conformation.Heating of 7b results in the formation of cyclopropane (16).Under argon the ruthena- and osmacycloalkanes 11a,b and 15a,b decompose with formation of the olefins 17-23.In the presence of CO from 7b, 11a,b and 15b the three- to six-membered cycloalkanones 24-27 are isolated at elevated temperatures. - Keywords: Ruthenacyloalkanes / Osmacycloalkanes
Wavelegth-Dependent Primary Photoprocesses of Os3(CO)12 in Fluid Solution and in Rigid Alkane Glasses at Low Temperature: Spectroscopic Detection, Characterization, and Reactivity of Coordinatively Unsaturated Os3(CO)11
Bentsen, James G.,Wrighton, Mark S.
, p. 4518 - 4530 (2007/10/02)
Wavelegth-dependent photochemistry is reported for Os3(CO)12 in hydrocarbon solutions at 298 and 195 K and in rigid hydrocarbon glasses at 90 K.Near-UV and vis irradiation of 0.2 mM Os3(CO)12 at 298 k in alkane solutions containing 5 mM L yields mainly Os3(CO)11L (L = PPh3, P(OMe)3) as the initial photoproduct with a wavelegth-dependent quantum yield Φ436nm 366nm =0.017 +/- 0.001, and Φ313nm = 0.050 +/- 0.003 for L = PPh3, independent of the presence of added o.1 M tetrahydrofuran.Photosubstitution of PPh3 for CO is not affected by added 1 M CCl4, and the 366 nm quantum yield does not change on increasing the PPh3 concentration to 0.1 M, consistent with photodissociative loss of CO from an upper level excited state.Electronic spectral features for Os3(CO)12 become well-resolved in an alkane glass of 90 K; low-energy excitation into the first (382 nm: 10a1' -> 16e'; 1A1' -> 1E') or second (320 nm: 15e' -> 6a2'; 1A1' -> 1E') absorbtions for Os(CO)12 yields no net photochemistry in the 90 K alkane glass.However, excitation into the third electronic absorbtion (278 sh nm: 14e' -> 6a2'; 1A1' -> 1E') of 0.1 mM Os3(CO)12 yields loss of one CO as the only FTIR detected photoreaction to yield a single product, formulated as axially vacant Os3(CO)11 on the basis of FTIR and UV-vis spectral characterization and reaction chemistry.While the photogenerated Os(CO)11 reacts with 13CO at low temperature to give an axial-13CO-Os3(CO)11(13CO), UV irradiation of axial-13CO-Os3(CO)11(13CO) in a 90 K methylcyclohexane glass yields dissociative CO loss in a ratio of 12CO/13CO of greater than 28.These results suggest photodissociative loss of equatorial CO from Os3(CO)12, followed by rearrangement of equatorially vacant Os3(CO)11 to the axially vacant form.Photogenerated Os3(CO)11 reacts with two electron donor ligands to yield Os3(CO)11L complexes (L = N2,C2H4, PPh3, 1-pentene, 2-MeTHF) and with H2 to yield H2Os3(CO)11.The H2Os3(CO)11 complex has been detected by FTIR as an intermediate in the direct photoconversion (Φ366nm = 0.02) of Os3(CO)12 to H2Os3(CO)10 in H2-saturated alkane solutions at 298 K.Near-UV irradiation of H2Os3(CO)11 cleanly yields H2Os3(CO)10 and free CO at 298 or 90 K.Selective excitation into the second absorbtion of Os3(CO)12 at 90 K yields inefficient associative photosubstitution of strong ?-acceptors (C2H4, C5H10, 13CO) but not N2 or 2-MeTHF for CO.In fluid solutions, competitive photofragmentation is correlated with long wavelegth irradiation and with strong ?-acceptor ligands (CO, C2H4, not PPh3).
