Metal-metal Bond Energies Research Articles

Guided ion beam studies of the reactions of Con+ (n=1–18) with N2: Cobalt cluster mononitride and dinitride bond energies

The reactions of Con+ (n=1–18) with N2 are measured as a function of kinetic energy over a range of 0–15eV in a guided ion beam tandem mass spectrometer. A variety of Com+, ComN+, and ComN2+ (m⩽n) product ions are observed, all in endothermic processes, with collision-induced dissociation dominating the products for all clusters. Bond dissociation energies for both cobalt cluster nitrides and dinitrides are derived from threshold analysis of the energy dependence of the endothermic reactions using several different approaches. These values show only a mild dependence on cluster size over the range studied, although the Co13+–N bond energy is relatively weak. The bond energies of Con+–N for larger clusters suggest that a reasonable value for the desorption energy of atomic nitrogen from bulk phase cobalt is 6.3±0.2eV, which is somewhat lower than the only available value in the literature, an estimate based on the enthalpy of formation of bulk cobalt nitride. The trends in the cobalt nitride thermochemistry are also compared to previously determined metal-metal bond energies, D0(Con+–Co), and to D0(Fen+–N). Implications for catalytic ammonia production using cobalt versus iron are discussed.

Design of Density Functionals by Combining the Method of Constraint Satisfaction with Parametrization for Thermochemistry, Thermochemical Kinetics, and Noncovalent Interactions.

We present a new hybrid meta exchange-correlation functional, called M05-2X, for thermochemistry, thermochemical kinetics, and noncovalent interactions. We also provide a full discussion of the new M05 functional, previously presented in a short communication. The M05 functional was parametrized including both metals and nonmetals, whereas M05-2X is a high-nonlocality functional with double the amount of nonlocal exchange (2X) that is parametrized only for nonmetals. In particular, M05 was parametrized against 35 data values, and M05-2X is parametrized against 34 data values. Both functionals, along with 28 other functionals, have been comparatively assessed against 234 data values: the MGAE109/3 main-group atomization energy database, the IP13/3 ionization potential database, the EA13/3 electron affinity database, the HTBH38/4 database of barrier height for hydrogen-transfer reactions, five noncovalent databases, two databases involving metal-metal and metal-ligand bond energies, a dipole moment database, a database of four alkyl bond dissociation energies of alkanes and ethers, and three total energies of one-electron systems. We also tested the new functionals and 12 others for eight hydrogen-bonding and stacking interaction energies in nucleobase pairs, and we tested M05 and M05-2X and 19 other functionals for the geometry, dipole moment, and binding energy of HCN-BF3, which has recently been shown to be a very difficult case for density functional theory. We tested eight functionals for four more alkyl bond dissociation energies, and we tested 12 functionals for several additional bond energies with varying amounts of multireference character. On the basis of all the results for 256 data values in 18 databases in the present study, we recommend M05-2X, M05, PW6B95, PWB6K, and MPWB1K for general-purpose applications in thermochemistry, kinetics, and noncovalent interactions involving nonmetals and we recommend M05 for studies involving both metallic and nonmetallic elements. The M05 functional, essentially uniquely among the functionals with broad applicability to chemistry, also performs well not only for main-group thermochemistry and radical reaction barrier heights but also for transition-metal-transition-metal interactions. The M05-2X functional has the best performance for thermochemical kinetics, noncovalent interactions (especially weak interaction, hydrogen bonding, π···π stacking, and interactions energies of nucleobases), and alkyl bond dissociation energies and the best composite results for energetics, excluding metals.

Density Functionals for Inorganometallic and Organometallic Chemistry

We present a database of 21 bond dissociation energies for breaking metal-ligand bonds. The molecules in the metal-ligand bond energy database are AgH, CoH, CoO+, CoOH+, CrCH3+, CuOH2+, FeH, Fe(CO)5, FeO, FeS, LiCl, LiO, MgO, MnCH3NiCH2+, Ni(CO)4, RhC, VCO+, VO, and VS. We have also created databases of metal-ligand bond lengths and atomic ionization potentials. The molecules used for bond lengths are AgH, BeO, CoH, CoO+, FeH, FeO, FeS, LiCl, LiO, MgO, RhC, VO, and VS and the ionization potentials are for the following atoms: C, Co, Cr, Cu, Ni, O, and V. The data were chosen based on their diversity and expected reliability, and they are used along with three previously developed databases (transition metal dimer bond energies and bond lengths and main-group molecular atomization energies) for assessing the accuracy of several kinds of density functionals. In particular, we report tests for 42 previously defined functionals: 2 local spin density approximation (LSDA) functionals, 14 generalized gradient approximation (GGA) methods, 13 hybrid GGA methods, 7 meta GGA methods, and 8 hybrid meta GGA methods. In addition to these functionals, we also examine the effectiveness of scaling the correlation energy by testing 13 functionals with scaled or no gradient-corrected correlation energy, and we find that functionals of this kind are more accurate for metal-metal and metal-ligand bonds than any of the functionals already in the literature. We also present a readjusted GGA and a hybrid GGA with parameters adjusted for metals. When we consider these 57 functionals for metal-ligand and metal-metal bond energies simultaneously with main-group atomization energies, atomic ionization potentials, and bond lengths we find that the most accurate functional is G96LYP, followed closely by MPWLYP1M (new in this article), XLYP, BLYP, and MOHLYP (also new in this article). Four of these five functionals have no Hartree-Fock exchange, and the other has only 5%. As a byproduct of this work we introduce a convenient diagnostic, called the B1 diagnostic, for ascertaining the multireference character in a bond.

Guided ion-beam studies of the kinetic-energy-dependent reactions of Con+(n=2–16) with D2: Cobalt cluster-deuteride bond energies

The kinetic-energy-dependent cross sections for the reactions of Co(n)+ (n = 2-16) with D2 are measured as a function of kinetic energy over a range of 0-8 eV in a guided ion-beam tandem mass spectrometer. The observed products are Co(n) D+ for all clusters and Co(n)D2+ for n = 4,5,9-16. Reactions for the formation of Co(n)D+ (n = 2-16) and Co9D2+ are observed to exhibit thresholds, whereas cross sections for the formation of Co(n)D2+ (n = 4,5,10-16) exhibit exothermic reaction behavior. The Co(n)+-D bond energies as a function of cluster size are derived from the threshold analysis of the kinetic-energy dependence of the endothermic reactions and are compared to previously determined metal-metal bond energies, D0(Co(n)+-Co). The bond energies of Co(n)+-D generally increase as the cluster size increases, and roughly parallel those for Co(n)+-Co for clusters n > or = 4. These trends are explained in terms of electronic and geometric structures for the Co(n)+ clusters. The bond energies of Co(n)+-D for larger clusters (n > or = 10) are found to be very close to the value for chemisorption of atomic hydrogen on bulk-phase cobalt. The rate constants for D2 chemisorption on the cationic clusters are compared with the results from previous work on cationic and neutral cobalt clusters.

On some fundamental factors in the effect of alloying elements on passivation of alloys

Passsivity promoters and dissolution moderators are identified among metallic elements and classified by considering two fundamental properties, which are the metal-oxygen bond strength and the metal-metal bond strength. Passivity promoters are elements which combine a high metal-oxygen bond strength (high heat of adsorption of oxygen or OH ( ΔH ads(ox)) with a low metal-metal bond energy ( ε M-M), because the transition from adsorbed O or OH overlayer to 3D oxide requires the breaking of metal-metal bonds. In contrast, dissolution moderators are expected to be elements with a high metal-metal bond energy. Groups of metals appear clearly in a diagram of ΔH ads (oxygen) and ε M-M.

Direct solution calorimetric measurements of enthalpies of proton and electron transfer reactions for transition metal complexes. Thermochemical study of metal-hydride and metal-metal bond energies

Enthalpies of reaction with sodium amalgam, sodium benzophenone ketyl, and metal carbonyl anions of organometallic complexes in THF solution have been measured. Relative to reduction with Na metal, the following enthalpies of reduction (kcal mol −1) are reported: benzophenone = −38.5, Cr(CO) 2(PEt 3)C 5H 5 = −54.3, Cr(CO) 2(PPh 3)C 5H 5 = −59.8, 1/2[Mo(CO) 3C 5Me 5] 2 = −59.9, 1/2[W(CO) 3C 5H 5] 2 = −61.7, 1/2[Mo(CO) 3C 5H 5] 2 = −63.5, Cr(CO) 2(P(OMe) 3)C 5H 5 = −64.4, 1/2[C 5H 5(CO) 3Mo-Cr(CO) 3C 5H 5] = −66.1, 1/2[Cr(CO) 3C 5H 5] 2 = −68.2, Cr(CO) 3C 5Me 5 = −72.3, Cr(CO) 3C 5H 5 = −75.6, 1/2Co 2(CO) 8 = −77.9. The value for the enthalpy of reduction of benzophenone is 14.5 kcal mol −1 more exothermic than recent literature data. The enthalpies of electron transfer and proton transfer between NaCr(CO) 2C 5H 5 and other chromium radicals and hydrides have been measured and span about 20 kcal mol −1. These measurements are used in thermochemical cycles to calculate enthalpies of H atom transfer. The role of substituents in determining enthalpies of reaction relevant to electrochemical and p K a measurement enthalpies of reaction is discussed. The heat of hydrogenation of Mn 2(CO) 10 has been determined using calorimetrically determined enthalpies of H atom transfer. The heat of hydrogenation, +4 kcal mol −1 in THF, allows estimation of the MnH bond strength = 68 kcal mol −1.

The dependence of the pitting potentials of aluminum alloys on the solid-state cohesion of the alloying metals

It is shown that the pitting potentials of aluminum alloys reported by Inturi and Szklarska-Smialowska [ Corros Sci. 34, 705 (1993)] can be causatively correlated with the metal-metal bond energy, b(M-M), values of the alloying elements: high b(M-M) values raise the pitting potentials towards nobler values and vice versa. This has been interpreted as resulting from pitting being nothing but active dissolution of the bare metal sites in the micro-fissures and defects of the oxide covering the alloy, in accordance with the pioneering studies of Richardson and Wood [ Corros. Sci. 10, 313 (1970)] and Galvele et al. [U. R. Evans Conf. on Localized Corrosion, Williamsburg Dec 1971)]. Further, interpretations of pitting phenomenon being controlled by the pH of the surface oxide in relation to pH of the electrolyte solution as proposed by Natishan et al. [ J. electrochem. Soc. 135, 321 (1988)], cannot be sustained by a further analysis: such relationships between pitting potentials and pH pzc can arise because of the correlation between b(M-M) and pH pzc. Quantitatively, the slope of the correlative line between the pitting potentials of aluminum alloys and the b(M-M) values of the alloying elements has been found to be unity: no theoretical significance can be attributed to this slope at the present time, however.

A Mössbauer effect and Fenske-Hall molecular orbital study of the bonding in a series of organoiron-copper clusters

The electronic properties of a series of organoiron-copper clusters, Na 2[Cu 6Fe 4(CO) 16] ( I), Na 3[Cu 5Fe 4(CO) 16] ( II), Na 3[Cu 3-Fe 3(CO) 12] ( III), [Cu(P(CH 3) 3) 4] 2[Fe 3(CO) 12Cu 4(P(CH 3) 3) 2] ( IV), [((C 6H 11) 3PCu) 2Fe(CO) 4] ( V), [((Ph 3P) 2Cu) 2Fe(CO) 4] ( VI), [(Ph 3P) 2CuFe(CO) 3(NO)] ( VII), and [((NH 3) 2Cu) 2Fe(CO) 4] ( VIII), have been investigated experimentally by the Mössbauer effect and theoretically by Fenske- Hall molecular orbital calculations. The Mössbauer effect hyperfine parameters are sensitive to the variety of bonding situations found in these clusters. The Mössbauer effect isomer shifts observed for these clusters range from −0. 141 to −0.037 mm/s at 78 K. The expected increase in the isomer shift with a decrease in the iron 4s Mulliken atomic orbital population, and a decrease in the Clementi effective nuclear charge experienced by the iron 4s electrons is observed. The electric field gradients at the iron sites have been calculated and compared with the experimental quadrupole splittings which range from 0.191 to 2.497 mm/s at 78K. The valence contribution was found to be the major component of the electric field gradient and is directly related to the symmetry of the iron electronic environment. The calculated values of the electric field gradients are also used to confirm the Mössbauer effect spectral assignments in II. The calculated metal-metal bond energy decreases as the cluster metal-metal bond length increases. The major bonding in these clusters is the iron-copper bond in which the iron 3d atomic orbitals overlap the copper 4s and 4p atomic orbitals.

Dissociative chemistry of ionic transition metal cluster fragments

The ionic fragments formed by collision-induced dissociation of Mn2(CO) + ions (y=1–10) are reported. The ratio of product ions formed by metal-metal vs. metal-ligand bond cleavage are discussed in terms of the dependence of the metal-metal bond energy on the metal-to-ligand ratio. The collision-induced dissociation data indicate that the metal-metal bond energy of Mn2(CO) 5 + and Mn2(CO) 10 + is less than that for Mn2(CO) + (y=1–4 and 6–9). The product ions arising by metal-metal and metal-ligand bond cleavage reactions for collision-induced dissociation and photodissociation are compared. On the basis of this data and the known photochemistry/photophysics of Mn2(CO)10, it is proposed that the difference in collision-induced dissociation and photodissociation product ion branching ratios is attributable to spin-orbit transitions of the activated ions.

The pitting corrosion potentials of metals and surface alloys in relation to their solid state cohesion

Recent data on the pitting potentials of metals in chloride ion solutions, as well as on the pitting potentials of surface alloys (prepared by ion implantation) of aluminum in solutions containing chloride ions, are examined in relation to the solid state cohesion of corresponding metals and alloys. Consistent with our previous proposal, it is shown that low metal-metal bond energies, b(M-M), herald less noble pitting potentials both for metals and alloys. These observations are interpreted as a support for the suggestion of Richardson and Wood [1], and, Galvelle et al. [2] that pitting is the active dissolution of the bare metal sites in the micro-fissures and defects of the oxide, under attack by the aggressive anions such as the halide. The oxide itself is concluded to play an inert role and the events postulated by Natishan and coworkers [6] invoking anion adsorption on, and penetration through, the oxide surface to initiate pitting have been found to be less solidly based in experimental facts.

Electrochemical mechanism for the lattice atomization of metal oxides in hydrogen-atom-containing plasmas

The recent data of Vinckier et al. [React. Solids, 1 (1986) 275] on lattice atomization observed on reduction of metal oxides by atomic hydrogen produced in the afterglows of a hydrogen-argon microwave-induced plasma are considered. It is suggested that a possible mechanism for the lattice atomization of the metal layer produced by the oxide reduction is through an electrochemical “dissolution” path appropriate to the metal-plasma interface existing in this situation. Further, it is pointed out that lower metal-metal bond energies tend to indicate pronounced tendencies towards lattice atomization and vice versa.

A theoretical study on the strength of multiple metal-metal bonds in binuclear complexes and transition-metal dimers by a non-local density functional method

The strength of multiple metal-metal bonds in the metal dimers M 2 (M = Cr, Mo or W) and binuclear complexes M 2(OH) 6 (M = Cr, Mo or W), M 2Cl 4(PH 3) 4 M = V, Cr, Mn, Nb, Mo, Tc, Ta, W or Re) has been studied by a non-local density functional theory. The method employed here provides metal-metal bond energies [ D(M-M)] in good accord with experiments for Cr 2 and Mo 2, and predicts that W 2 of the three dimers M 2 (M = Cr, Mo or W) has the strongest metal-metal bond with D(W-W) = 426 kJ mol −1 and R(W-W) = 2.03 Å. Among the binuclear complexes studied here we find the 3 d elements to form relatively weak metal-metal bonds (40–100 kJ mol −1), compared to the 4 d and 5 d elements with bonding energies ranging from 250 to 450 kJ mol −1. The metal-metal bond for a homologous series is calculated to be up to 100 kJ mol −1 stronger for the 5 d complex, than for the 4 d complex. An energy decomposition of D(M-M) revealed that the σ-bond is somewhat stronger than each of the π-bonds, and one order of magnitude stronger than the δ-bond. For the same transition metal we find D(M-M) to be larger for M 2(PH 3) 4Cl 4 (M = Cr, Mo or W) than for M 2(OH) 6 (M = Cr, Mo or W), and attribute this to a stronger π-interaction in the former series. While many of the findings here are in agreement with previous HFS studies, the order of stability D(3 d-3 d) « D(4 d-4 d) < D(5 d-5 d) differs from the order D(3 d-3 d) « D(5 d-5 d) < D(4 d-4 d) obtained by the HFS method, and the present method provides in general more modest values for D(M-M) than the HFS scheme.

Photocalorimetry. 5. Enthalpies of reaction of M2(CO)10 (M = Mn, Re) compounds with iodine in cyclohexane solution at 25.degree.C

Enthalpies of reaction of Mn/sub 2/(CO)/sub 10/, Re/sub 2/(CO)/sub 10/, and MnRe(CO)/sub 10/ with iodine in cyclohexane solution are reported for 25 /sup 0/C, as obtained by the method of photocalorimetry. The photochemical reactions give the M(CO)/sub 5/I products cleanly with quantum yields of 0.41 +/- 0.01 (436 nm), 0.57 +/- 0.02 (366 nm), and 0.42 +/- 0.05 (366 nm) for the above systems, respectively, in good agreement with literature values. The ..delta..H/sub s,298/ values (s denoting solution) are -44.9 +/- 2.0 kcal for Mn/sub 3/(CO)/sub 10/(s) + I/sub 2/(s) = 2Mn(CO)/sub 5/I(s), -37.6 +/- 3.8 kcal for the analogous reaction of Re/sub 2/(CO)/sub 10/, and -55.7 +/- 3.0 kcal for MnRe(CO)/sub 10/(s) + I/sub 2/(s) = Mn(CO)/sub 5/I(s) + Re(CO)/sub 5/I(s). Also reported are the heats of solution of Mn/sub 2/(CO)/sub 10/(c) (c denoting crystalline state), Re/sub 2/(CO)/sub 10/(c), and Re(CO)/sub 5/I(c) in cyclohexane at 25 /sup 0/C, the respective values being 8.6 +/- 0.5, 8.2 +/- 0.5, and 8.3 +/- kcal mol/sup -1/. In the case of the manganese system, comparison of ..delta..H/sub c//sup 0/ (obtained by correcting ..delta..H/sub s,298/ for heats of solution) with that obtained from the literature values of ..delta..H/sub f//sup 0//sub 298/ of Mn/submore » 2/(CO)/sub 10/(c) and of Mn(CO)/sub 5/I(c) shows a discrepancy amounting to a correction of 9.6 kcal mol/sup -1/ if assigned entirely to the former ..delta..H/sub f//sup 0//sub 298/ value and of -4.6 kcal mol/sup -1/ if assigned entirely to the latter one. Combination of the ..delta..H/sub s,298/ values indicates that the Mn-Re bond in MnRe(CO)/sub 10/ is weaker by 15 kcal than the average of the corresponding metal-metal bond energies in Mn/sub 2/(CO)/sub 10/ and Re/sub 2/(CO)/sub 10/. The result contrasts considerably with that derived from bond energy values obtained from literature reports of ionization and appearance potentials.« less

ChemInform Abstract: COMPARISON OF METAL‐METAL BOND ENERGIES IN THE CHROMIUM(II) AND COPPER(II) ACETATE DIMERS

Chemischer InformationsdienstVolume 12, Issue 40 Physical Organic Chemistry ChemInform Abstract: COMPARISON OF METAL-METAL BOND ENERGIES IN THE CHROMIUM(II) AND COPPER(II) ACETATE DIMERS R. D. CANNON, R. D. CANNONSearch for more papers by this author R. D. CANNON, R. D. CANNONSearch for more papers by this author First published: October 6, 1981 https://doi.org/10.1002/chin.198140071Read the full textAboutPDF 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 onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume12, Issue40October 6, 1981 RelatedInformation

Comparison of metal-metal bond energies in the chromium(II) and copper(II) acetate dimers

Comparison of metal-metal bond energies in the chromium(II) and copper(II) acetate dimers

Some fundamental factors determining the degree of passivity of common metals in aggressive electrolyte media: Interpretations in terms of solid state science

Some aspects of the passivation tendencies of Zr, Ti, Ta, Nb, Al, Cr, Be, Mo, Mg, Ni, Co, Fe, Mn, Zn, Cd, Sn, Pb and Cu in chloride ion solutions have been analyzed in terms of solid state concepts. It is shown that highly passivating metals (Zr, Ti, Ta, Nb, Al, Cr, Be, Mo and Mg) have either high metal-metal bond energies or possess high magnitudes of the (exothermic) heats of formation per equivalent values of the oxides, or both; the less passivating metals (Ni, Co, Fe, Mn, Zn, Cd, Sn, Pb and Cu) tend to show the reverse trend. An attempt is made to analyse the significance of these observations.

Comparative tendencies for metal loss by abrasive wear, impact erosion and arc erosion

It has been shown that metals exhibit similar relative tendencies to metal loss by abrasive wear, impact erosion or arc erosion. High metal-metal bond energies in metals indicate high resistance to metal loss by any of these three processes.

Metal-metal and metal-carbon bond energy terms for the rhodium carbonyl clusters Rh 4(CO) 12 and Rh 6(CO) 16

Alternative ways of obtaining metal-metal and metal-carbon bond energy terms, E(M-M) and E(M-C), from published thermochemical data for the clusters Rh 4(CO) 12 and Rh 6(CO) 16 are outlined. One gives average bond energy terms for the two clusters of E(M-M) = 86±11 and E(M-C) = 178±8 kJ.mol −1. The other, which makes allowance for the greater length, and presumably lower strength, of the metal-metal bonds of Rh 6(CO) 16, gives E(M-M) = 89±11 kJ.mol −1 for this cluster, 91±11 kJ.mol −1 for Rh 4(CO) 12, and E(M-C) = 175±8 kJ.mol −1.

The Engel-Brewer theory and related physical properties of the Hume-Rothery's Class-I metals

The densities of electrons (number of valency electrons per unit volume), of solid metals were calculated from the Engel Theory on the electronic distribution in the pure solid-state metallic elements. The metallic valence electron concentration was correlated with the elastic bulk moduli, cohesive energy, metal-metal single bond energy, atomic volume, heat of fusion and fusion temperature of the Hume-Rothery's Class-I metals. Although all these plots reveal fair linear relations, the plot against the bulk modulus on a log scale exhibits the best correlation, regardless of the structural characteristics, the group and the period of the metals. The plots of electron concentration vs atomic volume and atomic volume vs bulk modulus, reveal the discrete linear periodic dependency on the Group-Number of the metals. These two are related to the log scale correlation between the electron concentration vs bulk modulus. It is attempted to explain the linear dependency of the bulk modulus on the electron density through the free electron theory of metals.

Some factors determining the rates of electrochemical dissolution-deposition reactions on metallic surfaces

The nature of factors that determine the electrochemical activities of metals for the M z+ + ze - ⇌ M reaction have been investigated. High activities of metals for this reaction are inversely related to their metal-metal bond energies and to their electrocatalytic activities for the hydrogen evolution reaction. The significance of these observations is discussed in relation to many other relevant factors, such as the electronic structure of metals, the ligand-field theory, the complex-forming affinities of metal ions, the activation energy for the exchange of water molecules from the first coordination sphere of the metal ions, the heat of hydration of M z+ ions and the mechanism of pitting potentials of metals. Correlative trends that permit some generalizations regarding the electrochemical activities of metals for the M z+ + ze - ⇌ M reaction have been shown to exist and are discussed.