58201-22-2Relevant academic research and scientific papers
Chelation kinetics of bidentate phosphine ligands on pentacoordinate ruthenium carbonyl complexes
Bunten, Kevin A.,Farrar, David H.,Po?, Anthony J.,Lough, Alan J.
, p. 3674 - 3682 (2008/10/08)
Chelation kinetics of the complexes Ru(CO)4(η1-(P-P)) have been studied in heptane, where P-P = Ph2P(CH2)nPPh2 (n = 1, 2, 3, or 4, i.e., dppm, dppe, dppp, or dppb), Ph2P(NMe)PPh2 (dppma), Ph2P(o-C6H4)PPh2 (dpp-benzene), or R2P(CH2)2PR2 (R = Me or Cy, i.e., dmpe or dcpe). The complexes were prepared in situ by reaction of the bidentate ligands with Ru(CO)4(C2H4), which itself was prepared in situ by photolysis of Ru3(CO)12 under C2H4. The initially formed Ru(CO)4(η1-(P-P)) complexes react cleanly to form axial-equatorial Ru(CO)3(η2-(P-P)), as shown by the crystallographic structures of the products when P-P = dppe, dmpe, and dpp-benzene and the close similarity of their FTIR spectra to those of the other products. The chelated products undergo further reaction in solution or the solid state, and the product when P-P = dppma has been characterized by crystallography as Ru2-(CO)3(μ-PPh2)(μ-Ph2PNMePPh2). The kinetics of the displacement of CO from Ru(CO)4(η1-(P-P)) in n-heptane are characterized by ΔH? values that are lower by up to 9 kcal mol-1 than those of their monodentate P-donor analogues. ΔS? values range from quite positive to slightly negative and suggest a trend from purely dissociative to appreciably associative mechanisms along the series P-P = dpp-benzene 4L complexes when L = monodentate P-donor ligands.
Structure and reactivity of the zero-valent ruthenium complex Ru(1,2-bis(diphenylphosphino)ethane)(CO)3 and the dicationic ruthenium dimer [Ru2(1,2-bis(diphenylphosphino)ethane)2(CO) 6]2+
Skoog, Steven J.,Jorgenson, Amy L.,Campbell, John P.,Douskey, Michelle L.,Munson, Eric,Gladfelter, Wayne L.
, p. 13 - 28 (2007/10/03)
The structure of Ru(dppe)(CO)3 was characterized by single crystal X-ray diffraction [monoclinic crystal system, space group P21/n, a=12.2353(2) A, b=16.0803(3) A, c=14.2451(3) A, β=111.109(1)°, V=2614.62(9) A3, Z=4] and found to be intermediate between trigonal bipyramidal and square pyramidal. One electron oxidation of Ru(dppe)(CO)3 using [(η5-C5H5)2Fe][PF6] produced [Ru2(dppe)2(CO)6][PF6]2. The dicationic complex was fully characterized by solution spectroscopic methods and by single crystal X-ray diffraction [trigonal crystal system, space group P3121, a=20.566(2) A, c=13.871(2) A, V=5080.7(8) A3, Z=3] and found to have a dimeric structure with two octahedral units sharing a common apex via a Ru(I)-Ru(I) single bond. One octahedral unit is rotated approximately 45° relative to the other, and the chelating phosphine ligand occupies sites cis and trans to the Ru(I)-Ru(I) bond. All of the carbonyl ligands were found to be terminal. The dimer was fluxional in solution and line-shape analysis of the 31P{1H} and 13C{1H} variable-temperature NMR spectra was used to investigate the exchange mechanism and evaluate the rate constants. The mechanism involved an intramolecular, two-site exchange involving pairwise bridging carbonyls and had activation parameters of 11.8±0.15 kcal mol-1 and -6.7±0.6 eu for ΔH? and ΔS? respectively. The dimer exhibited similar thermal and photochemical reactivity patterns; disproportionation occurred in CH3CN and halogen atom abstraction occurred in halogenated solvents.
Homogeneous catalytic carbonylation of nitroaromatics. 8. Kinetic and mechanistic studies of the carbon-nitrogen bond and product forming steps from Ru(Ph2PCH2CH2PPh2)(CO) 2[C(O)OCH3]2: The turnover limiting reactions in the catalytic cycle
Gargulak, Jerry D.,Gladfelter, Wayne L.
, p. 3792 - 3800 (2007/10/02)
Mechanistic studies of the reaction of (OC-6-32)-dicarbonylbis(methoxycarbonyl)[1,2-bis(diphenylphosphino)-ethane] ruthenium(II) with p-toluidine to form N,N'-di-p-tolylurea are presented. The overall reaction was studied from 22 to 103°C and was found to be first order with respect to each reactant. Spectroscopic and kinetic studies between 22 and 52°C showed that the reaction proceeds through a species, Ru(dppe)(CO)2[C(O)OCH3] [C(O)-NH(p-tolyl)], which is in equilibrium with Ru(dppe)(CO)2[C(O)OCH3]2. The mechanism of the C-N bond forming step is proposed to involve nucleophilic attack on a coordinated Ru-CO moiety with subsequent cleavage of the C(O)-OMe bond. The methoxycarbonyl-carbamoyl complex decomposes in a unimolecular fashion to liberate CH3OH, the starting catalyst Ru(dppe)(CO)3, and p-tolyl isocyanate, which is immediately scavenged by excess amine to form N,N'-di-p-tolylurea. Studies of the analogous bis(isopropylcarbamoyl) complex provided supporting evidence for isocyanate elimination. Thermolysis of (OC-6-32)-dicarbonylbis(isopropylcarbamoyl)[1,2-bis(diphenylphosphino)-ethane] ruthenium(II) yields isopropylamine, the starting catalyst Ru(dppe)(CO)3, and isopropyl isocyanate, which reacts with isopropylamine over time to form diisopropylurea. The kinetics obtained from all of the stoichiometric reactions were combined into a suitable expression and found to lie on the same Arrhenius activation energy plot as the overall rate of the catalytic reaction.
