33541-67-2Relevant articles and documents
Using: Para hydrogen induced polarization to study steps in the hydroformylation reaction
Guan, Dexin,Godard, Cyril,Polas, Stacey M.,Tooze, Robert P.,Whitwood, Adrian C.,Duckett, Simon B.
supporting information, p. 2664 - 2675 (2019/02/27)
A range of iridium complexes, Ir(η3-C3H5)(CO)(PR2R′)2 (1a-1e) [where 1a, PR2R′ = PPh3, 1b P(p-tol)3, 1c PMePh2, 1d PMe2Ph and 1e PMe3] were synthesized and their reactivity as stoichiometric hydroformylation precursors studied. Para-hydrogen assisted NMR spectroscopy detected the following intermediates: Ir(H)2(η3-C3H5)(CO)(PR2R′) (2a-e), Ir(H)2(η1-C3H5)(CO)(PR2R′)2 (4d-e), Ir(H)2(η1-C3H5)(CO)2(PR2R′) (10a-e), Ir(H)2(CO-C3H5)(CO)2(PR2R′) (11a-c), Ir(H)2(CO-C3H7)(CO)2(PR2R′) (12a-c) and Ir(H)2(CO-C3H5)(CO)(PR2R′)2 (13d-e). Some of these species exist as two geometric isomers according to their multinuclear NMR characteristics. The NMR studies suggest a role for the following 16 electron species in these reactions: Ir(η3-C3H5)(CO)(PR2R′), Ir(η1-C3H5)(CO)(PR2R′)2, Ir(η1-C3H5)(CO)2(PR2R′), Ir(CO-C3H5)(CO)2(PR2R′), Ir(CO-C3H7)(CO)2(PR2R′) and Ir(CO-C3H5)(CO)(PR2R′)2. Their role is linked to several 18 electron species in order to confirm the route by which hydroformylation and hydrogenation proceeds.
New perspectives in hydroformylation: A para-hydrogen study
Godard, Cyril,Duckett, Simon B.,Henry, Celine,Polas, Stacey,Toose, Robert,Whitwood, Adrian C.
, p. 1826 - 1827 (2007/10/03)
NMR studies on the reaction of Ir(CO)(PPh3)2(η 3-C3H5) with para-H2 and CO enable the complete mapping of the hydroformylation mechanism for an iridium monohydride catalyst via the detection of species which include iridium acyl and alkyl dihydride intermediates.
Iridium- and rhodium-silanol complexes: Synthesis and reactivity
Goikhman, Roman,Aizenberg, Michael,Shimon, Linda J.W.,Milstein, David
, p. 4020 - 4024 (2008/10/08)
Methods of metallo-silanol synthesis have been developed. The Ir(I) complex (Et3P)2Ir(C2H4)Cl (1) oxidatively adds secondary silanols R2SiHOH (R = iPr, tBu) to yield the iridium-silanol complexes [(Et3P)2Ir(H)(Cl)(SiR2OH)] (R = iPr, 2; R = tBu, 3). The crystal structure of 2 exhibits a trigonal-bipyramidal geometry, and intermolecular Si-O-H- - -Cl hydrogen bonding is present. Deprotonation of 2 results in the highly thermodynamically stable metallo-silanolate [(Et3P)2Ir(H)(Cl) (SiiPr2OLi)]2 (4). Compound 4 has an almost planar core, consisting of two atoms each of iridium, silicon, chlorine, oxygen, and lithium. Upon treatment of (Et3P)3RhCl with HSiiPr2OH, the first Rh-silanol complex, trans-[(Et3P)2Rh(H)(Cl)(iPrSi2OH)], is formed in an equilibrium with the starting complex (Keq = 4 × 10-3); hence, the reaction is dependent on the concentration of the silanol and Et3P, an excess of the latter shifting the equilibrium to the starting compounds. Reaction of the bis-phosphine complex [(Et3P)2RhCl]2 with the silanol, which does not generate free phosphine, results in 96% conversion to the adduct. On the other hand, the chelating bis-phosphine complex [(bis-(diisopropylphosphino)propane)RhCl]2 does not add the silanol even in the presence of a 10-fold excess of the silanol, indicating that the cis-phosphine configuration in the adduct is unfavorable. In contrast to the Et3P-containing Ir complex, and similarly to the Rh complex, (PPh3)3Ir(CO)H reacts with iPr2SiHOH reversibly, leading to 60% conversion to the metallosilanol (PPh3)2Ir(CO)(H)2(SiiPr2O H) (6). A stable PPh3-containing Ir-silanol was prepared by starting from (PPh3)2Ir(CO)(H)2(Si(SEt)3). Following reaction with Et3SiOSO2CF3 to exchange one SEt substituent with OSO2CF3, reaction with NaOH generates the stable silanol complex (PPh3)2Ir(CO)(H)2(Si(SEt)2OH) (14).
Oxidative addition and reductive elimination reactions of trans-[Ir(PPh3)2(CO)(NC4H4)] and trans,cis-[Ir(PPh3)2(H)2(CO)(NC 4H4)], including N-H bond-forming reductive elimination of pyrrole
Driver, Michael S.,Hartwig, John F.
, p. 1134 - 1143 (2008/10/08)
The complex trans-(PPh3)2(CO)Ir(NC4H4) (1) has been synthesized and is an analogue of metal-aryl complexes, but with a nitrogen of the heteroaromatic group covalently bonded to the transition metal. Compound 1 readily undergoes initial reaction with a variety of substrates at the metal center rather than at the pyrrolyl nitrogen, allowing for the study of reactions between the pyrrolyl group and accompanying covalent ligands. These reactions ultimately produce N-substituted pyrroles, X-NC4H4 (X = C(O)CH3, C(O)C6H4CH3, H, SnMe3, SiMe3, SiEt3, Bcat). Compound 1 undergoes oxidative addition of H2 to form the stable Ir-(III) product (PPh3)2(CO)Ir(H)2(NC4H4) (2). When pure 2 is heated, it undergoes simple elimination of H2 to regenerate 1; however, if 2 is heated for longer times under H2 in the presence of PPh3, it undergoes reductive elimination of pyrrole and forms (PPh3)3(CO)Ir(H). Qualitative analysis of the mechanism of this reaction suggests that it occurs by either direct reductive elimination from the octahedral complex or rate-determining ligand dissociation, followed by rapid reductive elimination of pyrrole. Reductive elimination of pyrrole from 2 was also observed to occur photochemically by initial irreversible dissociation of a dative ligand.
Decomposition of iridium alkoxide complexes trans-ROIr(CO)(PPh3)2 (R = Me, n-Pr, and l-Pr): Evidence for β-elimination
Bernard, Karen A.,Rees, Wayne M.,Atwood, Jim D.
, p. 390 - 391 (2008/10/08)
Decomposition of trans-ROIr(CO)(PPh3)2 in the presence of PPh3 leads to HIr(CO)(PPh3)3 for R = Me, n-Pr, and i-Pr. For R = H, t-Bu, or Ph, this decomposition is not observed. For R = i-Pr similar quantities of acetone and 2-propanol are observed with total yield of 90% based on starting iridium complex. Propanal is formed for R = n-Pr. The reaction between trans-i-PrOIr(CO)(PPh3)2 and HIr(CO)(PPh3)3 readily yields 2-propanol. Thus a β-hydrogen abstraction to yield organic carbonyl and HIr(CO)(PPh3)3 is indicated with 2-propanol possibly formed by a binuclear reaction between trans-i-PrOIr(CO)(PPh3)2 and HIr(CO)(PPh3)3.
Complexes of the Platinum Metals. Part 30. Fragmentation Reactions of Rhodium and Iridium Trichloro- and Tribromo-acetates
Boyar, Esther B.,Robinson, Stephen D.
, p. 2113 - 2120 (2007/10/02)
The nitrosyl complexes (M = Rh or Ir) react readily with trichloroacetic acid in acetone solution at ambient temperature to afford the dichloro-complexes in excellent yield.The rhodium-based reaction performed at ca. 0 deg C and quickly worked-up affords the carboxylate complex which is stable in pure acetone, but rapidly converts to the dichloride when free trichloroacetic acid and triphenylphosphine are introduced to the solution.The complexes , , mer-, and also react with trichloroacetic acid to form trichloroacetates which undergo similar ligand fragmentation reactions.Reaction pathways involving formation of CCl3(1-), Cl(1-), :CCl2, and CO2 fragments are outlined; hydrolysis of dichlorocarbene affords carbonyl ligands.Similar reactions have been observed with tribromoacetic acid.
Insertion and other reactions of some hydroolefin complexes of iridium(I)
Drouin, Michel,Harrod, John F.
, p. 353 - 360 (2007/10/02)
A family of complexes IrH(CO)(Ph3P)2(ol), where ol is a monosubstituted ethylene, has been synthesized.Under an inert atmosphere the acrylonitrile complex undergoes clean decomposition to produce C2H5CN, half of the necessary hydrogen for the ligand reduction apparently being furnished by the phosphine ligand.The first step in the hydrogenation is insertion of of the unsaturated ligand into the Ir-H bond.The alkyl product is unstable but may be trapped by O2, to give the alkyl dioxygen complex, or by excess acrylonitrile to give the α-cyanoethyl acrylonitrile complex.Other ligands, such as CO and phosphines, displace the olefinic ligand more rapidly than insertion occurs.When ol=styrene, the complex is very unstable with respect to styrene dissociation and very little insertion is observed.Under O2, the styrene complex gives the first known hydridodioxygen complex IrH(CO)(PPh3)2(O2).The methyl acrylate complex exhibits behavior intermediate between that of the styrene and acrylonitrile analogues.
ELECTROCHEMISTRY OF COORDINATION COMPOUNDS. XX. ELECTROGENERATED Rh(CO)(PPh3)3 AND Ir(CO)(PPh3)3
Zotti, Gianni,Zecchin, Sandro,Pilloni, Giuseppe
, p. 61 - 72 (2007/10/02)
The redox behaviour of the d8 complexes + (M=Rh, Ir) was studied on platinum electrode in 1,2-dimethoxyethane by cyclic voltammetry, differential pulse voltammetry, and potentiostatic coulometry.The complexes show two reversible one-electron reductions consistent with the formation of the rare zerovalent M(CO)(PPh3)3 and the anionic - derivatives, respectively.The reduced species were characterized by ESR and IR spectroscopy.A significant feature is that the one-electron reduced intermediates, in spite of their radical nature, react very easily with molecules capable of reacting as proton rather than H-atom sources to give the hydride species HM(CO)(PPh3)3.A tentative interpretation of this behaviour is suggested.
Preparation and interconversion of two isomeric iridium trihydrides
Harrod,Yorke
, p. 1156 - 1159 (2008/10/08)
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.
