110901-95-6Relevant academic research and scientific papers
Preparation and interconversion of two isomeric iridium trihydrides
Harrod,Yorke
, p. 1156 - 1159 (1981)
The preparation, separation, and structural characterization of a,b,c-trihydrido-f-carbonylbis(triphenylphosphine)iridium(III) and a,b,f,-trihydrido-d-carbonylbis(triphenylphosphine)iridium(III) are described. The kinetics of interconversion of the two isomers and of the displacement of H2 from both isomers by triphenylphosphine have been measured and indicate that interconversion occurs via reversible reductive elimination/oxidation sequence. Both the isomerization and substitution reactions are postulated to involve the intermediate IrH(CO)P2. The relationship of the present results to other studies of the stereochemistry of oxidative additions to square-planar iridium(I) complexes is discussed.
Determination of Metal-Hydride and Metal-Ligand (L = CO, N2) Bond Energies Using Photoacoustic Calorimetry
Belt, Simon T.,Scaiano, J. C.,Whittlesey, Michael K.
, p. 1921 - 1925 (1993)
Photoacoustic calorimetry has been used to determine the M-H mean bond dissociation energies in Ru(dmpe)2H2 (dmpe = Me2PCH2CH2PMe2) and H2IrCl(CO)(PPh3)2 (63.5 +/- 2.0 and 64.0 +/- 1.0 kcal mol-1, respectively).The quantum yield for loss of H2
Photoinduced Cobalt(III)?Trifluoromethyl Bond Activation Enables Arene C?H Trifluoromethylation
Harris, Caleb F.,Kuehner, Christopher S.,Bacsa, John,Soper, Jake D.
, p. 1311 - 1315 (2018)
Visible-light capture activates a thermodynamically inert CoIII?CF3 bond for direct C?H trifluoromethylation of arenes and heteroarenes. New trifluoromethylcobalt(III) complexes supported by a redox-active [OCO] pincer ligand were prepared. Coordinating solvents, such as MeCN, afford green, quasi-octahedral [(SOCO)CoIII(CF3)(MeCN)2] (2), but in non-coordinating solvents the complex is red, square pyramidal [(SOCO)CoIII(CF3)(MeCN)] (3). Both are thermally stable, and 2 is stable in light. But exposure of 3 to low-energy light results in facile homolysis of the CoIII?CF3 bond, releasing .CF3 radical, which is efficiently trapped by TEMPO. or (hetero)arenes. The homolytic aromatic substitution reactions do not require a sacrificial or substrate-derived oxidant because the CoII by-product of CoIII?CF3 homolysis produces H2. The photophysical properties of 2 and 3 provide a rationale for the disparate light stability.
Vibrational Couplings in Hydridocarbonyl Complexes: A 2D-IR Perspective
Fernández-Terán, Ricardo,Hamm, Peter,Ruf, Jeannette
, (2020)
Hydridocarbonyl complexes, a class of industrially relevant catalysts, contain both the M-H and M-CO moieties. Here, using two-dimensional infrared spectroscopy, we examine the coupling of the typically weak M-H stretching mode and the intense M(CO) mode. By studying a series of Ir(I)- and Ir(III)-based hydridocarbonyl complexes, we show that the arrangement of the H and CO ligands in a trans configuration leads to strong vibrational coupling and mode delocalization. In contrast, a cis arrangement leads to no coupling, with the localized M-H mode having a much larger anharmonicity. These results highlight a promising strategy for enhancing the M-H vibration by intensity borrowing from the strong CO modes in a trans configuration, allowing for direct determination by infrared spectroscopy of both the oxidation (by frequency shifts) and the protonation state (via vibrational coupling) of the complex, in mechanistic studies of proton-coupled electron transfer reactions.
Kinetic Isotope Effect Associated with the Dissociative Addition of Dihydrogen to trans-Ir(CO)Cl(Ph3P)2
Zhou, Peng,Vitale, Arturo A.,San Filippo, Joseph,Saunders, William H.
, p. 8049 - 8054 (1985)
The temperature dependence of the kinetic isotope effect for the dissociative addition of dihydrogen and dideuterium to trans-Ir(CO)(Cl)(Ph3P)2 in toluene has been determined between 0 and 30 deg C.Model calculations based on these data suggest that the transition state for dissociation is best formulated as triangular with reactant-like character and involves substantial hydrogen tunneling.The weak KIE (kH/kD ca. 1-2) generally observed for the dissociative addition of dihydrogen to transition-metal complexes is seen to be a consequence of the product of an unusually large MMI factor, a moderately inverse EXC term and a substantially inverse ZPE factor.Only the tunnel correction prevents the overall KIE from being inverse.
Synthesis and reactivity of new bis(N-heterocyclic carbene) iridium(I) complexes
Nelson, David J.,Truscott, Byron J.,Slawin, Alexandra M. Z.,Nolan, Steven P.
, p. 12674 - 12681 (2013)
New complexes of the type trans-[IrCl(η2-COE)(NHC) 2] (COE = cis-cyclooctene; NHC = N-heterocyclic carbene) have been prepared in one step from the reaction of ca. 4 equiv of NHC or [AgCl(NHC)] with [IrCl(η2-COE)2/su
Solvent effect for oxidative addition of hydrogen in solvents from toluene to water: Reaction of H2 with trans-[Ir(CO)Cl{PPh2(C6H4SO 3K-m)}2]
Paterniti, David P.,Roman Jr., Paul J.,Atwood, Jim D.
, p. 2659 - 2660 (1996)
A significant enhancement in the rate of oxidative addition of H2 to square-planar iridium(II) complexes in water is observed; kinetic studies of the addition of H2 to trans-[Ir(CO)Cl(PPh3)2] in toluene and of H2 to trans-[Ir-(CO)Cl{PPh2(C6H4SO 3K-m)}2] in water show a factor of 45 increase in rate constant in water; this solvent effect is shown to be general for the solvents toluene, chlorobenzene, N,N-dimethylformamide, dimethyl sulfoxide and water, and has important ramifications for catalysis in water.
Transition state characterization for the reversible binding of dihydrogen to bis(2,2′-bipyridine)rhodium(I) from temperature- and pressure-dependent experimental and theoretical studies
Fujita, Etsuko,Brunschwig, Bruce S.,Creutz, Carol,Muckerman, James T.,Sutin, Norman,Szalda, David,Van Eldik, Rudi
, p. 1595 - 1603 (2006)
Thermodynamic and kinetic parameters for the oxidative addition of H 2 to [RhI(bpy)2]+ (bpy = 2,2′-bipyridine) to form [RhIII(H)2(bpy) 2]+ were determined from either the UV-vis spectrum of equilibrium mixtures of [RhI(bpy)2]+ and [RhIII(H)2(bpy)2]+ or from the observed rates of dihydride formation following visible-light irradiation of solutions containing [RhIII(H)2(bpy)2] + as a function of H2 concentration, temperature, and pressure in acetone and methanol. The activation enthalpy and entropy in methanol are 10.0 kcal mol-1 and -18 cal mol-1 K-1, respectively. The reaction enthalpy and entropy are -10.3 kcal mol-1 and -19 cal mol-1 K-1, respectively. Similar values were obtained in acetone. Surprisingly, the volumes of activation for dihydride formation (-15 and -16 cm3 mol-1 in methanol and acetone, respectively) are very close to the overall reaction volumes (-15 cm3 mol-1 in both solvents). Thus, the volumes of activation for the reverse reaction, elimination of dihydrogen from the dihydrido complex, are approximately zero. B3LYP hybrid DFT calculations of the transition-state complex in methanol and similar MP2 calculations in the gas phase suggest that the dihydrogen has a short H-H bond (0.823 and 0.810 A, respectively) and forms only a weak Rh-H bond (1.866 and 1.915 A, respectively). Equal partial molar volumes of the dihydrogenrhodium(I) transition state and dihydridorhodium(III) can account for the experimental volume profile found for the overall process.
Comparative reactivity of triorganosilanes, HSi(OEt)3 and HSiEt3, with IrCl(CO)(PPh3)2. Formation of IrCl(H)2(CO)(PPh3)2 or Ir(H)2(SiEt3)(CO)(PPh3
Nishihara, Yasushi,Takemura, Miwa,Osakada, Kohtaro
, p. 2951 - 2956 (2009/10/01)
Reaction of HSi(OEt)3 with IrCl(CO)(PPh3)2 (5:1 molar ratio) at room temperature for 1 h gives IrCl(H){Si(OEt)3}(CO)(PPh3)2 (1), which is observed by the 1H and 31P{s
Bridging the gap between homogeneous and heterogeneous catalysis: Ortho/para H2 conversion, hydrogen isotope scrambling, and hydrogenation of olefins by Ir(CO)Cl(PPh3)2
Matthes, Jochen,Pery, Tal,Gruendemann, Stephan,Buntkowsky, Gerd,Sabo-Etienne, Sylviane,Chaudret, Bruno,Limbach, Hans-Heinrich
, p. 8366 - 8367 (2007/10/03)
Some transition metal complexes are known to catalyze ortho/para hydrogen conversion, hydrogen isotope scrambling, and hydrogenation reactions in liquid solution. Using the example of Vaska's complex, we present here evidence by NMR that the solvent is no
