29933-65-1Relevant academic research and scientific papers
Ligand-Directed Reactivity in Dioxygen and Water Binding to cis-[Pd(NHC)2(η2-O2)]
Palluccio, Taryn D.,Cai, Xiaochen,Majumdar, Subhojit,Serafim, Leonardo F.,Tomson, Neil C.,Wieghardt, Karl,Cazin, Catherine S. J.,Nolan, Steven P.,Rybak-Akimova, Elena V.,Fernández-González, Miguel ángel,Temprado, Manuel,Captain, Burjor,Hoff, Carl D.
supporting information, p. 264 - 276 (2017/12/15)
Reaction of [Pd(IPr)2] (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) and O2 leads to the surprising discovery that at low temperature the initial reaction product is a highly labile peroxide complex cis-[Pd(IPr)2(η2-O2)]. At temperatures ?-40 °C, cis-[Pd(IPr)2(η2-O2)] adds a second O2 to form trans-[Pd(IPr)2(η1-O2)2]. Squid magnetometry and EPR studies yield data that are consistent with a singlet diradical ground state with a thermally accessible triplet state for this unique bis-superoxide complex. In addition to reaction with O2, cis-[Pd(IPr)2(η2-O2)] reacts at low temperature with H2O in methanol/ether solution to form trans-[Pd(IPr)2(OH)(OOH)]. The crystal structure of trans-[Pd(IPr)2(OOH)(OH)] is reported. Neither reaction with O2 nor reaction with H2O occurs under comparable conditions for cis-[Pd(IMes)2(η2-O2)] (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene). The increased reactivity of cis-[Pd(IPr)2(η2-O2)] is attributed to the enthalpy of binding of O2 to [Pd(IPr)2] (-14.5 ± 1.0 kcal/mol) that is approximately one-half that of [Pd(IMes)2] (-27.9 ± 1.5 kcal/mol). Computational studies identify the cause as interligand repulsion forcing a wider C-Pd-C angle and tilting of the NHC plane in cis-[Pd(IPr)2(η2-O2)]. Arene-arene interactions are more favorable and serve to further stabilize cis-[Pd(IMes)2(η2-O2)]. Inclusion of dispersion effects in DFT calculations leads to improved agreement between experimental and computational enthalpies of O2 binding. A complete reaction diagram is constructed for formation of trans-[Pd(IPr)2(η1-O2)2] and leads to the conclusion that kinetic factors inhibit formation of trans-[Pd(IMes)2(η1-O2)2] at the low temperatures at which it is thermodynamically favored. Failure to detect the predicted T-shaped intermediate trans-[Pd(NHC)2(η1-O2)] for either NHC = IMes or IPr is attributed to dynamic effects. A partial potential energy diagram for initial binding of O2 is constructed. A range of low-energy pathways at different angles of approach are present and blur the distinction between pure side-on or end-on trajectories for oxygen binding.
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.
supporting information, p. 12674 - 12681 (2013/11/19)
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-mediated vibrational energy relaxation from Vaska's complex adducts in binary solvent mixtures
Jones, Brynna H.,Huber, Christopher J.,Massari, Aaron M.
, p. 6150 - 6157 (2013/08/23)
A vibrational pump-probe and FTIR study was performed on two different adducts of Vaska's complex in two different sets of binary solvent mixtures. The carbonyl vibrational mode in the oxygen adduct exhibits solvatochromic shifts of ～10 cm-1 in either benzyl alcohol or chloroform relative to benzene-d6, whereas this vibration is nearly unchanged for the iodine adduct for the same three solvents. The width and center frequency of the carbonyl stretch for each adduct are compared to its vibrational lifetime in binary mixtures of benzene-d6 with either benzyl alcohol or chloroform. In neat solvents, the trends in line width, frequency, and vibrational lifetime are consistent for the two adducts, but complex relationships emerge when the trends in each property are compared as a function of mixed solvent composition. νCO is more sensitive to the solvation environment around the trans ligand, whereas the line width and lifetime depend on the environment around the CO group itself. The carbonyl frequency and width vary nonlinearly across the two binary solvent series, indicating preferential solvation. In contrast, the vibrational lifetime changes linearly with solvent composition and is correlated with the mole fraction of chloroform but anticorrelated with the mole fraction of benzyl alcohol. The results are explained by differences in the densities of solvent modes that affect intermolecular relaxation of the carbonyl mode.
Redetermination of the O-O bond length in the dioxygen-adduct of Vaska's complex
Lebel, Hélène,Ladjel, Chehla,Bélanger-Gariépy, Francine,Schaper, Frank
, p. 2645 - 2648 (2008/12/20)
Solid state structural studies were performed with (Ph3P)2IrCl(CO)(O2) and the O-O length redetermined to be 1.47(1) ? in contrast to results reported earlier.
Synthesis and characterisation of high-nuclearity osmium-silver mixed-metal clusters
Lee, Yui-Bing,Wong, Wing-Tak
, p. 3924 - 3926 (2008/09/21)
The reaction of the triosmium cluster anion, [Os3(μ-H)(CO) 11][PPN] (PPN = [N(PPh3)2]+), with [AgPF6] in the presence of [Ir(PPh3)2(CO)Cl] in THF at room temperature a
Structures of transition states in metal-mediated O2-activation reactions
Lanci, Michael P.,Brinkley, David W.,Stone, Kristie L.,Smirnov, Valeriy V.,Roth, Justine P.
, p. 7273 - 7276 (2007/10/03)
(Chemical Equation Presented) Kinetic isotope effects (KIEs) have been used to probe the mechanism of the binding of O2 to classic inorganic compounds. The intermolecular 18O KIEs decrease with increasing rate constants, and the corr
Reactions of Singlet Oxygen with Organometallic Complexes. 3. Kinetics and Scope of the Oxidative Addition Reaction of Singlet Oxygen with Iridium(I), Rhodium(I), and Platinum(II) Complexes
Selke, Matthias,Karney, William L.,Khan, Saeed I.,Foote, Christopher S.
, p. 5715 - 5720 (2008/10/08)
Photosensitized oxidation of a series of iridium(I) complexes of the type trans-Ir(CO)X(PPh3)2 (X = halogen) leads to the same iridium(III) dioxygen complexes as the reaction with triplet oxygen. The reaction with singlet oxygen is many orders of magnitude faster than the triplet oxygenreactions. In contrast to those for the reaction with triplet oxygen, the rate constants for the (1)O2 reaction and physical deactivation do not vary significantly with different ligands, except for extremely electron-poor complexes, where there is no interaction between the complex andsinglet oxygen. The analogous rhodium(I) complexes show very similar reactivity. The resulting previously unknown rhodium(III) dioxygen complexes are unstable at room temperature. Related square-planar platinum(II) complexes do not show any interaction with singlet oxygen, except for trans-PtHCl(PEt3)2, which gives some physical deactivation of singlet oxygen; however, with this compound, no reaction product could be detected even at low temperature. The results suggest that many metal complexes may react with singlet oxygen to form novel metal-dioxygen complexes.
