Transition Metal Carbon Bonds Research Articles

Adiabatic ionization energies of RuC, RhC, OsC, IrC, and PtC.

The ionization energies (IEs) of RuC, RhC, OsC, IrC, and PtC are assigned by the measurement of their two-photon ionization thresholds. Although late transition metal-carbon bonds are of major importance in organometallic chemistry and catalysis, accurate and precise fundamental thermochemical data on these chemical bonds are mainly lacking in the literature. Based on their two-photon ionization thresholds, in this work, we assign IE(RuC) = 7.439(40) eV, IE(RhC) = 7.458(32) eV, IE(OsC) = 8.647(25) eV, IE(IrC) = 8.933(74) eV, and IE(PtC) = 9.397(32) eV. These experimentally derived IEs are further confirmed through quantum chemical calculations using coupled-cluster single double perturbative triple methods that are extrapolated to the complete basis set limit using a three-parameter mixed Gaussian/exponential extrapolation scheme and corrected for spin-orbit effects using a semiempirical method. The electronic structure and chemical bonding of these MC species are discussed in the context of these ionization energy measurements. The IEs of RuC, RhC, OsC, and IrC closely mirror the IEs of the corresponding transition metal atoms, suggesting that for these species, the (n + 1)s electrons of the transition metals are not significantly involved in chemical bonding.

Enthalpy-Controlled Insertion of a "Nonspectator" Tricoordinate Phosphorus Ligand into Group 10 Transition Metal-Carbon Bonds.

Insertion of a tricoordinate phosphorus ligand into late metal-carbon bonds is reported. Metalation of a P^P-chelating ligand (L1), composed of a nontrigonal phosphorous (i.e., P(III)) triamide moiety, P(N(o-N(Ar)C6H4)2, tethered by a phenylene linker to a -PiPr2 anchor, with group 10 complexes L2M(Me)Cl (M = Ni, Pd) results in insertion of the nontrigonal phosphorus site into the metal-methyl bond. The stable methylmetallophosphorane compounds thus formed are characterized spectroscopically and crystallographically. Metalation of L1 with (cod)PtII(Me)(Cl) does not lead to a metallophosphorane but rather to the standard bisphosphine chelate (κ2-L1)Pt(Me)(Cl). These divergent reactivities within group 10 are rationalized by reference to periodic variation in M-C bond enthalpies.

Transition Metal—Carbon Bond Enthalpies as Descriptor for the Electrochemical Stability of Transition Metal Carbides in Electrocatalytic Applications

Transition metal carbides are used for various applications such as hard coating, heterogeneous catalysis, catalyst support material or coatings in fuel cell applications. However, little is known about the stability of their electrochemically active surface in aqueous electrolytes. Herein, the transition metal—carbon bond enthalpy is proposed as stability criterion for various transition metal carbides. The basis is an oxidation mechanism where the rate determining step is the metal—carbon bond cleavage under acidic conditions which was supported by a detailed corrosion study on hexagonal tungsten carbide. In situ flow cell measurements that were coupled to an inductively coupled plasma mass spectrometer corroborated experimentally the linear dependency of the oxidation overpotential on the transition metal—carbon bond enthalpy. The proposed model allows the estimation of the activation overpotential for electrochemical carbide oxidation resulting in a maximized stabilization for carbides in the 4th group (Ti, Zr, Hf). Together with the calculated thermodynamic oxidation potentials, TiC and VC exhibit the highest experimental oxidation potentials (0.85 VRHE). The model can be used for preselecting possible carbide materials for various electrochemical reactions.

Cobalt-Catalyzed Borylation of Fluorinated Arenes: Thermodynamic Control of C(sp2)-H Oxidative Addition Results in ortho-to-Fluorine Selectivity.

The mechanism of C(sp2)-H borylation of fluorinated arenes with B2Pin2 (Pin = pinacolato) catalyzed by bis(phosphino)pyridine (iPrPNP) cobalt complexes was studied to understand the origins of the uniquely high ortho-to-fluorine regioselectivity observed in these reactions. Variable time normalization analysis (VTNA) of reaction time courses and deuterium kinetic isotope effect measurements established a kinetic regime wherein C(sp2)-H oxidative addition is fast and reversible. Monitoring the reaction by in situ NMR spectroscopy revealed the intermediacy of a cobalt(I)-aryl complex that was generated with the same high ortho-to-fluorine regioselectivity associated with the overall catalytic transformation. Deuterium labeling experiments and stoichiometric studies established C(sp2)-H oxidative addition of the fluorinated arene as the selectivity-determining step of the reaction. This step favors the formation of ortho-fluoroaryl cobalt intermediates due to the ortho fluorine effect, a phenomenon whereby ortho fluorine substituents stabilize transition metal-carbon bonds. Computational studies provided evidence that the cobalt-carbon bonds of the relevant intermediates in (iPrPNP)Co-catalyzed borylation are strengthened with increasing ortho fluorine substitution. The atypical kinetic regime involving fast and reversible C(sp2)-H oxidative addition in combination with the thermodynamic preference for forming cobalt-aryl bonds adjacent to fluorinated sites are the origin of the high regioselectivity in the catalytic borylation reaction.

Formation, characterization, structure and bonding analysis of the metal–carbon bond OM-(η6-C6H6) (M = Sc, Ti) complexes in solid matrix: Infrared spectroscopic and theoretical study

The reactions of ScO and TiO molecules with benzene have been studied in solid argon with infrared absorption spectroscopy combining with theoretical calculations. Laser-evaporation of bulk higher oxide targets prepared the scandium and titanium monoxide molecules. The scandium and titanium monoxide molecules reacted with benzene to form the typical transition metal–carbon bond (MCB) complexes, OM-(η6-C6H6) (M = Sc, Ti), which have been identified on the basis of isotopic infrared studies and density functional calculations. The theoretical calculation results illustrate the deformation of the planar carbon skeleton of benzene takes place and the bond lengths of M–O are largely elongated upon OM-(η6-C6H6) (M = Sc, Ti) complexes. The population results illustrate the OM-(η6-C6H6) are determined to have 2A1 and 1A1 electronic ground state both with C2v symmetry arising from 2Δ and 1∑− of excited-state ScO and TiO reaction with benzene, respectively. The OSc-(η6-C6H6) and OTi-(η6-C6H6) are both stable d–pπ coordination compounds and can also not be photoisomerized by UV irradiation under low temperature in solid argon matrix. Natural bond orbital analyses conclude that the OTi-(η6-C6H6) system includes two equivalent Ti–C single bonds with strong binding bond energies.

ChemInform Abstract: Carbene Insertion into Transition Metal—Carbon Bonds: A New Tool for Catalytic C—C Bond Formation.

AbstractReview: 92 refs.

Carbene insertion into transition metal–carbon bonds: a new tool for catalytic C–C bond formation

In this perspective we highlight the applicability of migratory carbene insertion reactions into TM–C bonds as a new tool for catalytic C–C bond formation. In Section 1 we introduce the reaction, wherein we also discuss the applicability of transition metal carbene formation from reactive carbene precursors. In Section 2 we summarise the available mechanistic information about this elementary step derived from stoichiometric model reactions. In Section 3 we review the available catalytic examples, with a focus on new developments in palladium mediated cross-coupling reactions (thus expanding the substrate scope with carbene precursors) and carbene polymerisation (allowing the synthesis of highly functionalised stereoregular polymers that are difficult to prepare otherwise). Recent developments in these fields in combination with the close analogy of carbene insertion reactions with CO (and alkene) insertions open up new possibilities for the development of interesting new reactions based on carbene insertions.

Reactions of Early Transition Metal – Carbon Bonds with N-Heterocycles

Heterocycles are ubiquitous in biological compounds and methods to functionalize them have been of long standing interest. Reactions of early transition metal-carbon bonds with heterocycles are important in two major areas: (1) activation and functionalization of heterocycles and (2) ring-opening of aromatic heterocycles. In the first area, metalcarbon bonds determine ortho-metalation and insertion of unsaturated substrates to yield functionalized heterocycles. In the latter area, metal-element multiple bonds become important and provide the driving force for ring-opening reactions. This review will focus on reactions of nitrogen-containing heterocycles. Early transition metals are defined as elements belonging to groups III-V, the lanthanides, and the actinides; the reactivity of complexes featuring the metal in its highest oxidation state (d0fn electron count) and a carbon-based ligand will be described. Keywords: Transition Metal, N-Heterocycles, ortho-metalation, lanthanides, oxidation state, ligand, Complexes

Katalizatory i proces koordynacyjnej polimeryzacji etylenu - eksperyment i teoria

Experimental and theoretical studies of coordination polymerization of ethylene have been performed in the presence of precursors - the complexes of Ti, Zr, Hf, V halides with organic Lewis bases, magnesium support [MgCl2(THF)2] and organoaluminium compounds. It was found the correlation between a nature of halide in precursor and vanadium catalyst activity (Table 1, Figs. 1-3). The energetic profiles of insertion (Table 2) and termination [beta-elimination (Fig. 4) or hydrogen transfer (Table 3)] reactions have been computed. Calculated values of insertion barriers as well as of ethylene and active center bond energy correspond well with polymerizations results. Agostic interactions found in the active center, assist in stabilisation of transition metal carbon bond. In the titanium-magnesium catalysts, containing oxygen-donor ligands [tetrahydrofurfurol - Formula (I), its anion - Formula (II) or ethylene glycol dimethyl ether - Formula (III)], the possibility of transformation of O,O'-bidentate ligands into dangling monodentate ones was shown. This may play a crucial role in the catalyst activity. The structures of active centers in catalysts investigated have been proposed (Fig. 7) and has been demonstrated by theoretical way.

Mass selective photodetachment photoelectron spectroscopy: small transition metal (Fe, Ni) carbon hydrogen compounds

Photodetachment photoelectron spectra of chemical products, due to reactions between transition metals and acetylene, have been measured. These products existed as negative ions which have been mass selected in a time-of-flight analyser prior to laser photodetachment. The photoelectron spectra supply values for the electron affinity as well as energies for neutral excited electronic states and vibrations. The following complexes have been investigated: FeC 2H x ( x=0, 1, 2, 3), FeC 4H x ( x=2, 3), Fe 2H x ( x=1, 2), NiC 2H x ( x=1, 3) and NiC 4H 3. These isolated transition metal-containing complexes may correspond to surface bound intermediates during catalytic reactions of hydrocarbons on transition metal surfaces or deliver information about relevant transition metal carbon and transition metal hydrogen bonds.

Preparation of substituted transition-metal (η 1-propargyl complexes and their [3+2] cycloaddition reactions with sulfur dioxide and disulfur monoxide. Transition-metal–carbon bond cleaving reactions of the cycloadducts which yield oxathiolene oxides and dithiolene oxides

The preparations of several new cyclopentadienyl iron dicarbonyl η 1-2-alkynyl complexes are reported. Their [3+2] cycloaddition reactions with sulfur dioxide and disulfur monoxide yielded transition-metal substituted 1,2-oxathiolene-2-oxides and 1,2-dithiolene-1-oxides, respectively. The transition-metal was cleaved from the oxathiolene-oxide and dithiolene-oxide containing complexes to produce new sulfur heterocycles.

Schrock type transition metal complex formation of push–pull substituted phosphanyl-carbenes, a quantum chemical investigation by density-functional methods

The formation of coordination compounds of phosphanyl carbenes with a transition metal in a high oxidation state (Schrock type) is evaluated by density functional theory. In the Schrock type carbene complexes the transition metalcarbon bond possesses a multiple bond character. If one of the ligands at the carbene center possesses a leaving ability, e.g. as the diaminophosphenium unit, a facile distortion to a new type of an anionic metallaalkylidene donor-acceptor complex with a diaminophosphenium cation is predicted.

Reactions of transition-metal η 1-propargyl complexes with sulfur dioxide and sulfur trioxide: transition-metal–carbon bond cleaving reactions of the cycloadducts which yield 1,2-oxathiole-2-oxides and -2,2-dioxides

The preparation of several cyclopentadienyl iron dicarbonyl and triphenylphosphine manganese tetracarbonyl η 1-2-alkynyl complexes are reported. The [3+2] cycloaddition reactions of these complexes with sulfur dioxide and sulfur trioxide yielded transition-metal substituted 1,2-oxathiolene-2-oxides and 1,2-oxathiolene-2,2-dioxides, respectively. One of the η 1-propargyl complex SO 3 cycloadducts has been characterized by X-ray crystallography. The transition metal can subsequently be cleaved from the oxathiole-oxide and dioxide containing complexes to produce a variety of new sulfur containing heterocycles.

Heisenberg model for radical reactions. Part 3. Direct exchange coupling between transition metal ions and triplet methylene

Ab initio UHF calculations have been carried out for naked transition metal-methylene ions. The low-spin open-shell states are found to be the ground states of these ions, in accord with the GVB-CI results. The low-spin transition metal-methylene ions are regarded as direct exchange-coupled systems formed from high-spin transition metal ions and the triplet monocentric diradical. The direct exchange couplings between these species can be described on the basis of the Heisenberg model. The CASSCF calculations using UHF natural orbitals (UNOs) have been carried out for low-spin states, showing that UNOs and their occupation numbers are good trials. However, they provide poor binding energies for the transition metal-carbon double bonds and indicate the necessity for dynamical correlation corrections. The approximate spin-projected UHF Møller-Plesset and UHF coupled-cluster methods provide reasonable binding energies for the transition metal-methylene ions, which are close to those of modified coupled-pair functional (CPF) and average CPF methods.

Quasi-living character of ethylene polymerization by hafnium alkoxide catalysts

Ethylene was polymerized in the presence of soluble catalysts prepared from hafnium alkoxides and an equimolar mixture of triethylaluminium and diethylmonochloroaluminium. These systems show lower productivity than analogous systems based on titanium, but give polymer with high molecular weight, increasing with time and conversion. The kinetic analysis carried out according to the traditional steady-state kinetic model indicates the partial living character of the polymerization. This behaviour is more evident with the bidentate 1,1′-bis-2-naphtholate ligand, which further stabilizes the transition metal-carbon bond towards chain transfer.

Intrinsic transition metal-carbon double bond dissociation energies: periodic trends in M+-CH2 bond strengths

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTIntrinsic transition metal-carbon double bond dissociation energies: periodic trends in M+-CH2 bond strengthsP. B. Armentrout, L. S. Sunderlin, and Ellen R. FisherCite this: Inorg. Chem. 1989, 28, 25, 4436–4437Publication Date (Print):December 1, 1989Publication History Published online1 May 2002Published inissue 1 December 1989https://doi.org/10.1021/ic00324a004RIGHTS & PERMISSIONSArticle Views155Altmetric-Citations48LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (273 KB) Get e-Alerts Get e-Alerts

The mechanism of organometallic migration reactions. A configuration mixing (CM) approach

The configuration mixing (CM) model is applied to the migratory insertion of carbon monoxide into a transition metalcarbon bond. A qualitative reaction profile for the reaction is constructed using an energy plot of the three electronic configurations, which describe the reactant, the product, and the five-coordinate intermediate. The model provides a simple picture of reactivity trends in these systems, as well as indicating the way in which a mechanistic spectrum, encompassing both step-wise and concerted pathways, is generated. The model analyzes the effect of modifications of the migrating group, the acceptor group, and the entering ligand. Migratory insertion assisted by either prior oxidation or reduction of the starting metal complex is also considered. The conclusions are supported by experimental and computational data.

Transition metalcarbon bonds: LV. Cyclometallation and other reactions of PBu t2Bu i and PPh 2Bu i with platinum(II) and palladium(II)

The new phosphine, PBu t 2Bu i (L), was prepared from Bu t 2PCl and LiBu i. PPh 2Bu i (L′) was prepared from Ph 2PCl and LiBu i. Treatment of [PtCl 2(NCBu t) 2] with L′ gives [PtCl 2L′ 2] which does not cyclometallate even on prolonged boiling in 2-methoxyethanol. In contrast, [PtCl 2(NCBu t) 2] reacts with PBu t 2Bu i in boiling 2-methoxyethanol to give the cyclometallated complex [ Pt 2Cl 2(PBu t 2CH 2-CHMeCH 2) 2] (II, X = Cl). The corresponding bromide, iodide and acetylacetonate were prepared. With PPh 3 II (X = Cl) gives [ PtCl(PBu t 2CH 2CHMeCH 2)(PPh 3)] which with NaBH 4 gives [ PtH(PBu t 2CH 2CHMeC H 2)(PPh 3)]. Na 2PdCl 4 with L (2 mol equivalents) gave trans-[PdCl 2L 2], which was converted into trans-[Pd(NCS) 2-L 2] by metathesis with KSCN. Treatment of Na 2PdCl 4 with L (1 mol equivalent) gave [Pd 2Cl 4L 2], which on heating in 2-methoxyethanol gave [ Pd 2Cl 2(PBu t 2CH 2-CHMeCH 2) 2], as a mixture of syn- and anti-isomers. The complexes trans-[PdCl 2-L′ 2] and [Pd 2Cl 4L′ 2] were also prepared. 1H- and 31P NMR data are given.

ChemInform Abstract: STERIC EFFECTS OF TERTIARY PHOSPHINES ON NUCLEOPHILE‐INDUCED INSERTION OF CARBON MONOXIDE INTO TRANSITION METAL‐CARBON BONDS

Chemischer InformationsdienstVolume 14, Issue 5 Organoelement Compounds ChemInform Abstract: STERIC EFFECTS OF TERTIARY PHOSPHINES ON NUCLEOPHILE-INDUCED INSERTION OF CARBON MONOXIDE INTO TRANSITION METAL-CARBON BONDS J. D. COTTON, J. D. COTTONSearch for more papers by this authorR. D. MARKWELL, R. D. MARKWELLSearch for more papers by this author J. D. COTTON, J. D. COTTONSearch for more papers by this authorR. D. MARKWELL, R. D. MARKWELLSearch for more papers by this author First published: February 1, 1983 https://doi.org/10.1002/chin.198305292AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume14, Issue5February 1, 1983 RelatedInformation

Steric effects of tertiary phosphines on nucleophile-induced insertion of carbon monoxide into transition metal-carbon bonds

Rate constants associated with the tertiary phosphine-induced formation of the metal acyls, [(η 5-C 5H 5)(CO)(PR 3)FeCOCH 2Cy] and [(η 5-C 5H 5)(CO) 2(PR 3)MoCOCH 2Ph], show no correlation with the electronic properties of the phosphine, but exhibit a marked dependence on steric effects. Rates decrease slightly with increase in phosphine cone angles in the lower ranges, but drop very rapidly at higher cone angles. The behaviour is consistent with the concept of a pocket of limited size around the metal centre, with large intermolecular effects arising when the sizes of the tertiary phosphine and the pocket become comparable.