10060-40-9Relevant academic research and scientific papers
Chemistry of Polynuclear Metal Complexes with Bridging Carbene or Carbyne Ligands. Part 88. Carbaboranetungsteniridium Compounds; Crystal Structure of the Complex 5-C2B9H9Me2)>
Jeffery, John C.,Ruiz, Miguel A.,Sgerwood, Paul,Stone, F. Gordon A.
, p. 1845 - 1854 (1989)
The reaction between the compounds (cod = cyclo-octa-1,5-diene) and CR)(CO)2(η5-C2B9H9Me2)> (R = C6H4Me-4) in thf (tetrahydrofuran) at room temperature affords the complex 5-C2B9H9Me2)>.The triphenylphosphine groups in the latter can be displaced with PEt3, P(OPh)3, or P(OMe)3 to give the compounds 5-C2B9H9Me2)> .In solution several of these products exist as isomeric mixtures.An X-ray diffraction study was carried out on an isomer of 5-C2B9H9Me2)>.The W-Ir bond is spanned by the p-tolylmethylidyne group .The nido-icosahedral fragment C2B9H9Me2 is η5-co-ordinated to the tungsten, but the central boron CCBBB in the pentagonal face of the ligand is attached to the iridium via a two-electron three-centre B-HIr bond.The tungsten atom also carries two terminal CO groups, and the two PEt3 ligands are bonded to the iridium.The co-ordination environment of the iridium is such that the plane defined by the atoms IrP2 is perpendicular to that containing the atoms W, μ-C, and B-HIr, and the midpoint of the cage C-C bond.The reaction between 5-C2B9H9Me2)> and P(OMe)3 also affords the compounds 5-C2B9H8Me2)(CO)32> and 5-CH(R)(C2B9H7Me2)>(CO)24>.Similarly PMe3 displaces the PPh3 groups in the precursor to give 5-C2B9H8Me2)(CO)2(PMe3)3> and 5-CH(R)(C2B9H7Me2)>(CO)2(PMe3)4>.The reactions between 2(cod)> (L2 = Ph2PCH2CH2PPh2 or 2,2'-bipyridine) and CR)(CO)2(η5-C2B9H9Me2)> yield tungsten-iridium complexes 5-C2B9H8Me2)(CO)3L2> with terminal Ir-H bonds, and ? B-Ir linkages to the carbaborane group ligating the tungsten.N.m.r. data (1H, 13C-, 31P-, and 11B-) for the new compounds are reported and discussed.
Cationic (η3-allyl)metal complexes part XIV. Catalytic oligomerisation of ethylene: A very selective dimerisation catalyst prepared from [(η3-methallyl)Ni(cod)]PF6 and a tris(3-sulphophenyl)-phosphine salt
Brunet,Sivade,Tkatchenko
, p. 291 - 302 (1989)
The influence of a tris(3-sulfophenyl)phosphine salt on the oligomerization of ethylene catalyzed by [(η3-methallyl)Ni(cod)]PF6 has been investigated. Introduction of this particular ligand slightly lowers the catalytic activity of the cationic nickel complex, but always results in increased selectivity for dimerization at the expense of the formation of trimers. Selectivities in butenes up to 96% could be obtained.
Synergy between Experimental and Computational Chemistry Reveals the Mechanism of Decomposition of Nickel-Ketene Complexes
Staudaher, Nicholas D.,Arif, Atta M.,Louie, Janis
, p. 14083 - 14091 (2016)
A series of (dppf)Ni(ketene) complexes were synthesized and fully characterized. In the solid state, the complexes possess η2-(C,O) coordination of the ketene in an overall planar configuration. They display similar structure in solution, except in some cases, the η2-(C,C) coordination mode is also detected. A combination of kinetic analysis and DFT calculations reveals the complexes undergo thermal decomposition by isomerization from η2-(C,O) to η2-(C,C) followed by scission of the C=C bond, which is usually rate limiting and results in an intermediate carbonyl carbene complex. Subsequent rearrangement of the carbene ligand is rate limiting for electron poor and sterically large ketenes, and results in a carbonyl alkene complex. The alkene readily dissociates, affording alkenes and (dppf)Ni(CO)2. Computational modeling of the decarbonylation pathway with partial phosphine dissociation reveals the barrier is reduced significantly, explaining the instability of ketene complexes with monodentate phosphines.
Isolation of a Bimetallic Cobalt(III) Nitride and Examination of Its Hydrogen Atom Abstraction Chemistry and Reactivity toward H2
Sengupta, Debabrata,Sandoval-Pauker, Christian,Schueller, Emily,Encerrado-Manriquez, Angela M.,Metta-Maga?a, Alejandro,Lee, Wen-Yee,Seshadri, Ram,Pinter, Balazs,Fortier, Skye
, p. 8233 - 8242 (2020)
Room temperature photolysis of the bis(azide)cobaltate(II) complex [Na(THF)x][(ketguan)Co(N3)2] (ketguan = [(tBu2CN)C(NDipp)2]-, Dipp = 2,6-diisopropylphenyl) (3a) in THF cleanly forms the binuclear cobalt nitride Na(THF)4{[(ketguan)Co(N3)]2(μ-N)} (1). Compound 1 represents the first example of an isolable, bimetallic cobalt nitride complex, and it has been fully characterized by spectroscopic, magnetic, and computational analyses. Density functional theory supports a CoIII═N═CoIII canonical form with significant π-bonding between the cobalt centers and the nitride atom. Unlike other group 9 bridging nitride complexes, no radical character is detected at the bridging N atom of 1. Indeed, 1 is unreactive toward weak C-H donors and even cocrystallizes with a molecule of cyclohexadiene (CHD) in its crystallographic unit cell to give 1·CHD as a room temperature stable product. Notably, addition of pyridine to 1 or photolyzed solutions of [(ketguan)Co(N3)(py)]2 (4a) leads to destabilization via activation of the nitride unit, resulting in the mixed-valent Co(II)/Co(III) bridged imido species [(ketguan)Co(py)][(ketguan)Co](μ-NH)(μ-N3) (5) formed from intermolecular hydrogen atom abstraction (HAA) of strong C-H bonds (BDE ～100 kcal/mol). Kinetic rate analysis of the formation of 5 in the presence of C6H12 or C6D12 gives a KIE = 2.5 ± 0.1, supportive of a HAA formation pathway. The reactivity of our system was further probed by photolyzing benzene/pyridine solutions of 4a under H2 and D2 atmospheres (150 psi), which leads to the exclusive formation of the bis(imido) complexes [(ketguan)Co(μ-NH)]2 (6) and [(ketguan)Co(μ-ND)]2 (6-D), respectively, as a result of dihydrogen activation. These results provide unique insights into the chemistry and electronic structure of late 3d metal nitrides while providing entryway into C-H activation pathways.
Kinetics of the substitution of the cyclooctadiene ligand in β-diketonatocyclooctadienerhodium(I) complexes by triphenylphosphite
Leipoldt, Johann G.,Lamprecht, Gert J.,Steynberg, E.C.
, p. 239 - 244 (1990)
The reaction between complexes and triphenylphosphite was studied for various β-diketones in a dichloroethane medium.The observed rate law is R = k.The reaction rate increases in the order acac A good linear free energy relationship was obtained.The large negative values for the entropy of activation, as well as the order of reactivity of the different β-diketone complexes, point towards an associative mechanism.
A Combined Spectroscopic and Protein Crystallography Study Reveals Protein Interactions of RhI(NHC) Complexes at the Molecular Level
Daubit, Isabelle M.,Sullivan, Matthew P.,John, Milena,Goldstone, David C.,Hartinger, Christian G.,Metzler-Nolte, Nils
, p. 17191 - 17199 (2020)
While most Rh-N-heterocyclic carbene (NHC) complexes currently investigated in anticancer research contain a Rh(III) metal center, an increasing amount of research is focusing on the cytotoxic activity and mode of action of square-planar [RhCl(COD)(NHC)] (where COD = 1,5-cyclooctadiene) which contains a Rh(I) center. The enzyme thioredoxin reductase (TrxR) and the protein albumin have been proposed as potential targets, but the molecular processes taking place upon protein interaction remain elusive. Herein, we report the preparation of peptide-conjugated and its nonconjugated parent [RhCl(COD)(NHC)] complexes, an in-depth investigation of both their stability in solution, and a crystallographic study of protein interaction. The organorhodium compounds showed a rapid loss of the COD ligand and slow loss of the NHC ligand in aqueous solution. These ligand exchange reactions were reflected in studies on the interaction with hen egg white lysozyme (HEWL) as a model protein in single-crystal X-ray crystallographic investigations. Upon treatment of HEWL with an amino acid functionalized [RhCl(COD)(NHC)] complex, two distinct rhodium adducts were found initially after 7 d of incubation at His15 and after 4 weeks also at Lys33. In both cases, the COD and chlorido ligands had been substituted with aqua and/or hydroxido ligands. While the histidine (His) adduct also indicated a loss of the NHC ligand, the lysine (Lys) adduct retained the NHC core derived from the amino acid l-histidine. In either case, an octahedral coordination environment of the metal center indicates oxidation to Rh(III). This investigation gives the first insight on the interaction of Rh(I)(NHC) complexes and proteins at the molecular level.
Malodorogenic Sensing of Carbon Monoxide
Bergmann, Marvin,Egert, Meike,Plenio, Herbert
, p. 13328 - 13331 (2017)
A thin film of poly-([IrCl(cod)(NHC-onbe)]n-(propyl-onbe)m) (onbe=oxanorbornene) coated on filter paper reacts quantitatively with CO to yield 1,5-cyclooctadiene, the unpleasant smell of which can be detected by the human olfactory system with very high sensitivity. Odorless, but toxic CO is thus “translated” into the distinct smell of 1,5-cyclooctadiene. Based on malodorogenic sensing it is possible to smell the presence of CO.
Platinum ω-Alkenyl Compounds as Chemical Vapor Deposition Precursors: Synthesis and Characterization of Pt[CH2CMe2CH2CH═CH2]2and the Impact of Ligand Design on the Deposition Process
Liu, Sumeng,Zhang, Zhejun,Gray, Danielle,Zhu, Lingyang,Abelson, John R.,Girolami, Gregory S.
, p. 9316 - 9334 (2020)
We describe the synthesis and characterization of three platinum(II) ω-alkenyl complexes of stoichiometry Pt[CH2CMe2(CH2)xCH═CH2]2 where x is 0, 1, or 2, as well as some related platinum(II) compounds formed as byproducts during their synthesis. The ω-alkenyl ligands in all three complexes, cis-bis(η1,η2-2,2-dimethylbut-3-en-1-yl)platinum (2), cis-bis(η1,η2-2,2-dimethylpent-4-en-1-yl)platinum (3), and cis-bis(η1,η2-2,2-dimethylhex-5-en-1-yl)platinum (4), bind to Pt by means of a Pt-alkyl sigma bond at one end of the ligand chain and a Pt-olefin pi interaction at the other; the olefins reversibly decomplex from the Pt centers in solution. The good volatility of 3 (10 mTorr at 20 °C), its ability to be stored for long periods without decomposition, and its stability toward air and moisture make it an attractive platinum chemical vapor deposition (CVD) precursor. CVD of thin films from 3 shows no nucleation delay on several different substrates (SiO2/Si, Al2O3, and VN) and gives films that are unusually smooth. At 330 °C in the absence of a reactive gas, the precursor deposits platinum containing 50% carbon, but in the presence of a remote oxygen plasma, the amount of carbon is reduced to below the Rutherford backscattering spectroscopy (RBS) detection limit without affecting the film smoothness. Under hot wall CVD conditions at 250 °C in the absence of a co-reactant, 72% of the carbon atoms in 3 are released as hydrogenated products (largely 4,4-dimethylpentenes), 22% are released as dehydrogenated products (all of which are the result of skeletal rearrangements), and 6% remain in the film. Some conclusions about the CVD mechanism are drawn from this product distribution.
Rotaxane synthesis exploiting the M(i)/M(III) redox couple
Emerson-King, Jack,Knighton, Richard C.,Gyton, Matthew R.,Chaplin, Adrian B.
, p. 11645 - 11655 (2017)
In the context of advancing the use of metal-based building blocks for the construction of mechanically interlocked molecules, we herein describe the preparation of late transition metal containing [2]rotaxanes (1). Capture and subsequent retention of the interlocked assemblies are achieved by the formation of robust and bulky complexes of rhodium(iii) and iridium(iii) through hydrogenation of readily accessible rhodium(i) and iridium(i) complexes [M(COD)(PPh3)2][BArF4] (M = Rh, 2a; Ir, 2b) and reaction with a bipyridyl terminated [2]pseudorotaxane (3·db24c8). This work was underpinned by detailed mechanistic studies examining the hydrogenation of 1p;:p;1 mixtures of 2 and bipy in CH2Cl2, which proceeds with disparate rates to afford [M(bipy)H2(PPh3)2][BArF4] (M = Rh, 4a[BArF4], t = 18 h @ 50 °C; Ir, 4b[BArF4], t 2Cl2 (1 atm H2). These rates are reconciled by (a) the inherently slower reaction of 2a with H2 compared to that of the third row congener 2b, and (b) the competing and irreversible reaction of 2a with bipy, leading to a very slow hydrogenation pathway, involving rate-limiting substitution of COD by PPh3. On the basis of this information, operationally convenient and mild conditions (CH2Cl2, RT, 1 atm H2, t ≤ 2 h) were developed for the preparation of 1, involving in the case of rhodium-based 1a pre-hydrogenation of 2a to form [Rh(PPh3)2]2[BArF4]2 (8) before reaction with 3·db24c8. In addition to comprehensive spectroscopic characterisation of 1, the structure of iridium-based 1b was elucidated in the solid-state using X-ray diffraction.
Heats of reaction of triphenylphosphine with compounds of the type hexafluoroacetylacetonato(olefin)silver(I)
Partenheimer, Walter,Johnson, Earl H.
, p. 1274 - 1278 (1973)
Characterization of and heats of the following reactions are reported where hfacac is the conjugate base of hexafluoioace-[Ag(hfacac)(olefin)] + P(C6H5)3 →CH2Cl2 [Ag(hfacac)(P(C6H5)3/
