Third-row Transition Metal Research Articles

Revised model core potentials for third-row transition–metal atoms from Lu to Hg

We have produced new relativistic model core potentials (spdsMCPs) for the third-row transition–metal atoms from Lu to Hg explicitly treating explicitly 5s and 5p electrons in addition to 5d and 6s electrons in the same manner for the first- and second-row transition–metal atoms given in the previous Letters [Y. Osanai, M.S. Mon, T. Noro, H. Mori, H. Nakashima, M. Klobukowski, E. Miyoshi, Chem. Phys. Lett. 452 (2008) 210; Y. Osanai, E. Soejima, T. Noro, H. Mori, M.S. Mon, M. Klobukowski, E. Miyoshi, Chem. Phys. Lett. 463 (2008) 230]. Using suitable correlating functions with the split-valence MCP functions, we demonstrate that the present MCP basis sets show reasonable performance in describing the electronic structures of atoms and molecules, bringing about accurate excitation energies for atoms and proper spectroscopic constants for Au 2, Hg 2, and AuH.

All-Electron Scalar Relativistic Basis Sets for Third-Row Transition Metal Atoms.

A family of segmented all-electron relativistically contracted (SARC) basis sets for the elements Hf-Hg is constructed for use in conjunction with the Douglas-Kroll-Hess (DKH) and zeroth-order regular approximation (ZORA) scalar relativistic Hamiltonians. The SARC basis sets are loosely contracted and thus offer computational advantages compared to generally contracted relativistic basis sets, while their sufficiently small size allows them to be used in place of effective core potentials (ECPs) for routine studies of molecules. Practical assessments of the SARC basis sets in DFT calculations of atomic (ionization energies) as well as molecular properties (geometries and bond dissociation energies for MHn complexes) confirm that the basis sets yield accurate and reliable results, providing a balanced description of core and valence electron densities. CCSD(T) calculations on a series of gold diatomic compounds also demonstrate the applicability of the basis sets to correlated methods. The SARC basis sets will be of most utility in calculating molecular properties for which the core electrons cannot be neglected, such as studies of electron paramagnetic resonance, Mössbauer and X-ray absorption spectra, and topological analysis of electron densities.

Structural motifs, mixing, and segregation effects in 38-atom binary clusters

Thirty eight-atom binary clusters composed of elements from groups 10 and 11 of the Periodic Table mixing a second-row with a third-row transition metal (TM) (i.e., clusters composed of the four pairs: Pd-Pt, Ag-Au, Pd-Au, and Ag-Pt) are studied through a combined empirical-potential (EP)/density functional (DF) method. A "system comparison" approach is adopted in order to analyze a wide diversity of structural motifs, and the energy competition among different structural motifs is studied at the DF level for these systems, mainly focusing on the composition 24-14 (the first number refers to the second-row TM atom) but also considering selected motifs with compositions 19-19 (of interest for investigating surface segregation effects) and 32-6 (also 14-24 and 6-32 for the Pd-Au pair). The results confirm the EP predictions about the stability of crystalline structures at this size for the Au-Pd pair but with decahedral or mixed fivefold-symmetric/closed-packed structures in close competition with fcc motifs for the Ag-Au or Ag-Pt and Pd-Pt pairs, respectively. Overall, the EP description is found to be reasonably accurate for the Pd-Pt and Au-Pd pairs, whereas it is less reliable for the Ag-Au and Ag-Pt pairs due to electronic structure (charge transfer or directionality) effects. The driving force to core-shell chemical ordering is put on a quantitative basis, and surface segregation of the most cohesive element into the core is confirmed, with the exception of the Ag-Au pair for which charge transfer effects favor the segregation of Au to the surface of the clusters.

High‐Energy X‐ray Absorption Spectroscopy: A New Tool for Structural Investigations of Lanthanoids and Third‐Row Transition Elements

This is the first systematic study exploring the potential of high-energy EXAFS as a structural tool for lanthanoids and third-row transition elements. The K-edge X-ray absorption spectra of the hydrated lanthanoid(III) ions both in aqueous solution and in solid trifluoromethanesulfonate salts have been studied. The K-edges of lanthanoids cover the energy range from 38 (La) to 65 keV (Lu), while the corresponding energy range for the L(3)-edges is 5.5 (La) to 9.2 keV (Lu). We show that the large widths of the core-hole states do not appreciably reduce the potential structural information in the high-energy K-edge EXAFS data. Moreover, for lanthanoid compounds, more accurate structural parameters are obtained from analysis of K-edge than from L(3)-edge EXAFS data. The main reasons are the much wider k range available and the absence of double-electron transitions, especially for the lighter lanthanoids. A comparative K- and L(3)-edge EXAFS data analysis of nonahydrated crystalline neodymium(III) trifluoromethanesulfonate demonstrates the clear advantages of K-edge analysis over conventionally performed studies at the L(3)-absorption edge for structural investigations of lanthanoid and third-row transition metal compounds. The coordination chemistry of the hydrated lanthanoid(III) ions in aqueous solution and solid trifluoromethanesulfonate salts, based on the results of both the K- and L(3)-edge EXAFS data, is thoroughly discussed in the next paper in this series (I. Persson, P. D'Angelo, S. De Panfilis, M. Sandström, L. Eriksson, Chem. Eur. J. 2008, 14, DOI: 10.1002/chem.200701281).

Ion Mobility of Ground and Excited States of Laser-Generated Transition Metal Cations

The application of ion mobility to separate the electronic states of first-, second-, and third-row transition metal cations generated by the laser vaporization/ionization (LVI) technique is presented. The mobility measurements for most of the laser-generated transition metal cations reveal the presence of two or three mobility peaks that correspond to ground and excited states of different electronic configurations. The similarity of the measured reduced mobilities for the metal cations generated by LVI, electron impact, and glow discharge ion sources indicates that the same electronic configurations are produced regardless of the ion source. However, in comparison with electron impact of volatile organometallic compounds, the LVI populates fewer excited states due to the thermal nature of the process. Significant contributions to the production and populations of excited states of Ni+, Nb+, and Pt+ cations have been observed in the presence of argon during the LVI process and attributed to the Penning ionization mechanism. The origin of the mobility difference between the ground and the excited states is mainly due to the different interaction with helium. The ratio of the reduced mobilities of the excited and ground states decreases as one goes from the first- to the second- to the third-row transition metal cations. This trend is attributed to the ion size, which increases in the order 6sd(n-1) > 5sd(n-1) > 4sd(n-1). This work helps to understand the mechanisms by which transition metal cations react in the gas phase by identifying the ground and excited states that can be responsible for their reactivity.

Electronic structure of the d 1 bent-metallocene Cp 2VCl 2: A photoelectron and density functional study

The Cp 2VCl 2 molecule is a prototype for bent-metallocene complexes with a single electron in the metal d shell, but experimental measure of the binding energy of the d electron by photoelectron spectroscopy eluded early attempts due to apparent decomposition in the spectrometer to Cp 2VCl. With improved instrumentation, the amount of decomposition is reduced and subtraction of ionization intensity due to Cp 2VCl from the Cp 2VCl 2/Cp 2VCl mixed spectrum yields the Cp 2VCl 2 spectrum exclusively. The measured ionization energies provide well-defined benchmarks for electronic structure calculations. Density functional calculations support the spectral interpretations and agree well with the ionization energy of the d 1 electron and the energies of the higher positive ion states of Cp 2VCl 2. The calculations also account well for the trends to the other Group V bent-metallocene dichlorides Cp 2NbCl 2 and Cp 2TaCl 2. The first ionization energy of Cp 2VCl 2 is considerably greater than the first ionization energies of the second- and third-row transition metal analogues.

Light Emitting Materials for Organic Electronics

This paper presents the case studies on the syntheses and characterization of three third-row transition metal complexes, all of them are associated with at least one functionalized 2-pyridyl pyrazolate chelates. Each of these complexes possesses distinctive central metal atom and shows highly efficient phosphorescent emission ranging from red, green and blue of the visible spectrum. Their photophysical properties are briefly discussed, including the assignment of their fundamental absorption and emission characteristics. Finally, performance data on fabrication of phosphorescent OLEDs using these complexes as emitters are presented.

Electronic Perturbation in a Molecular Nanowire of [IrCl5(NO)]− Units

The nitrosyl in [IrCl5(NO)]- is probably the most electrophilic known to date. This fact is reflected by its extremely high IR frequency in the solid state, electrochemical behavior, and remarkable reactivity in solution. PPh4[IrCl5(NO)] forms a crystal in which the [IrCl5(NO)]- anions are in a curious wire-like linear arrangement, in which the distance between the N--O moiety of one anion and the trans chloride of the upper one nearby is only 2.8 A. For the same complex [IrCl5(NO)]- but with a different counterion, Na[IrCl5(NO)], the anions are stacked one over the other in a side-by-side arrangement. In this case the electronic distribution can be depicted as the closed-shell electronic structure Ir III-NO+, as expected for any d(6) third-row transition metal complex. However, in PPh4[IrCl5(NO)] an unprecedented electronic perturbation takes place, probably due to NO*-Cl- acceptor-donor interactions among a large number of [IrCl5(NO)]- units, favoring a different electronic distribution, namely the open-shell electronic structure Ir IV-NO*. This conclusion is based on XANES experimental evidence, which demonstrates that the formal oxidation state for iridium in PPh4[IrCl5(NO)] is +4, as compared with +3 in K[IrCl5(NO)]. In agreement, solid-state DFT calculations show that the ground state for [IrCl5(NO)]- in the PPh4+ salt comprises an open-shell singlet with an electronic structure which encompasses half of the spin density mainly localized on a metal-centered orbital, and the other half on an NO-based orbital. The electronic perturbation could be seen as an electron promotion from a metal-chloride to a metal-NO orbital, due to the small HOMO-LUMO gap in PPh4[IrCl5(NO)]. This is probably induced by electrostatic interactions acting as a result of the closeness and wire-like spatial arrangement of the Ir metal centers, imposed by lattice forces due to pi-pi stacking interactions among the phenyl rings in PPh4+. Experimental and theoretical data indicate that in PPh4[IrCl5(NO)] the Ir-N-O moiety is partially bent and tilted.

Porphyrin Framework Solids. Synthesis and Structure of Hybrid Coordination Polymers of Tetra(carboxyphenyl)porphyrins and Lanthanide-Bridging Ions

New types of porphyrin-based framework solids were constructed by reacting meso-tetra(3-carboxyphenyl)porphyrin and meso-tetra(4-carboxyphenyl)metalloporphyrins with common salts of lanthanide metal ions. The large size, high coordination numbers and strong affinity for oxo ligands of the latter, combined with favorable hydrothermal reaction conditions, allowed the formation of open three-dimensional single-framework architectures by coordination polymerization, in which the tetradentate porphyrin units are intercoordinated by multinuclear assemblies of the bridging metal ions. The latter serve as construction pillars of the supramolecular arrays, affording stable structures. Several modes of coordination polymerization were revealed by single-crystal X-ray diffraction. They differ by the spatial functionality of the porphyrin building blocks, the coordination patterns of the lanthanide-carboxylate assemblies, and the topology of the resulting frameworks. The seven new reported structures exhibit periodically spaced 0.4-0.6 nm wide channel voids that perforate the respective crystalline polymeric architectures and are accessible to solvent components. Materials based on the m-carboxyphenyl derivative reveal smaller channels than those based on the p-carboxyphenyl analogues. An additional complex of the former with a smaller third-row transition metal (Co) is characterized by coordination connectivity in two dimensions only. Thermal and powder-diffraction analyses confirm the stability of the lanthanide-TmCPP (TmCPP=tetra(m-carboxyphenyl)porphyrin) frameworks.

Experimental and Theoretical Studies of the Activation of Methane by Ta+

A guided-ion-beam tandem mass spectrometer is used to study atomic tantalum cations reacting with CH4 and CD4. Like other third-row transition metal ions, W+, Os+, Ir+, and Pt+, the dehydrogenation reaction to form TaCH2+ + H2 is exothermic. At higher energies, other products, TaH+, TaCH+, and TaCH3+, are observed with TaH+ dominating the product spectrum. Modeling of the endothermic cross sections provides the 0 K bond dissociation energies (in eV) of D0(Ta +−CH) = 5.82 ± 0.16 and D0(Ta+−CH3) = 2.69 ± 0.14 eV. We also examined the reverse reaction, TaCH2+ + H2 → Ta+ + CH4, and its isotopic equivalent, TaCH2+ + D2. By combining the cross sections for the forward and reverse processes, an equilibrium constant for this reaction is derived, from which D0(Ta +−CH2) = 4.81 ± 0.03 eV is obtained. The Ta +−H and Ta +−CH3 experimental bond energies are in reasonable agreement with density functional calculations at the BHLYP/HW+/6-311++G(3df,3p) level of theory, whereas the Ta +−CH and Ta+−CH2 bond energies are p...

Why [(η5-C5MenH5-n)2Ti]2(μ2,η2,η2-N2) Can Not Add a H2 Molecule to the Side-On-Coordinated N2 while Its Zr and Hf Analogues Can? Insights from Computational Studies

The potential energy surface of the reaction [(eta5-C5MenH5-n)2M]2(micro2,eta2,eta2-N2) + H2 --> [(eta5-C5MenH5-n)2M][(eta5-C5MenH5-n)2MH](micro2,eta2,eta2-NNH) at low-lying singlet and triplet electronic states of the reactants was investigated using density functional methods, for n = 0 and 4, and M = Ti, Zr, and Hf. Ground electronic states of the Ti complexes are found to be triplet states, while that for the corresponding Zr and Hf complexes are singlet states. In their singlet state, all these complexes satisfy known necessary conditions (they have a side-on-coordinated N2 molecule and appropriate frontier orbitals) for successful addition of an H2 molecule to the coordinated N2, and consequently, add of an H2 molecule with a reasonable energy barrier. Hf complexes show slightly higher reactivity than corresponding Zr complexes, and in turn, both are more reactive than their singlet-state Ti counterparts. The calculated trend in reactivity of Zr and Hf complexes is consistent with the latest experimental data (see refs 13 and 16). However, Ti complexes have the ground triplet state that lacks in appropriate frontier orbitals. As a result, H2 addition to the Ti complexes at their triplet ground states requires a larger activation barrier than the singlet state and is endothermic (lacks of driven force for reaction). On the basis of these results, we predict that the [(eta5-C5Me4H)2M]2(micro2,eta2,eta2-N2) and [(eta5-C5H5)2M]2(micro2,eta2,eta2-N2) complexes cannot react with an H2 molecule for M = Ti, while those for M = Zr and Hf can. It was shown that the difference in the B3LYP (hybrid) and PBE (nonhybrid) calculated energy gaps between the lowest closed-shell singlet and triplet states of the present complexes reduces via first- > second- > third-row transition metals; both hybrid and nonhybrid density functionals can be safely used to describe reactivity of the low-lying low-spin and high-spin states of second- and third-row transition metal complexes.

Activation of methane by gold cations: Guided ion beam and theoretical studies

The potential energy surface for activation of methane by the third-row transition metal cation, Au+, is studied experimentally by examining the kinetic energy dependence of this reaction using guided ion beam tandem mass spectrometry. A flow tube ion source produces Au+ primarily in its 1S0 (5d10) electronic ground state level but with some 3D (and perhaps higher lying) excited states that can be completely removed by a suitable quenching gas (N2O). Au+ (1S0) reacts with methane by endothermic dehydrogenation to form AuCH2+ as well as C-H bond cleavage to yield AuH+ and AuCH3+. The kinetic energy dependences of the cross sections for these endothermic reactions are analyzed to give 0 K bond dissociation energies (in eV) of D0(Au+ - CH2) = 3.70 +/- 0.07 and D0(Au+ -CH3) = 2.17 +/- 0.24. Ab initio calculations at the B3LYPHW + /6-311++G(3df,3p) level performed here show good agreement with the experimental bond energies and previous theoretical values available. Theory also provides the electronic structures of the product species as well as intermediates and transition states along the reactive potential energy surface. Surprisingly, the dehydrogenation reaction does not appear to involve an oxidative addition mechanism. We also compare this third-row transition metal system with the first-row and second-row congeners, Cu+ and Ag+. Differences in thermochemistry can be explained by the lanthanide contraction and relativistic effects that alter the relative size of the valence s and d orbitals.

Structure and Stability of Networked Metallofullerenes of the Transition Metals

A DFT investigation of substitutionally doped fullerenes MC59 of second- and third-row transition metals shows that their stability increases toward the right-hand side of the d-block. Whereas the structural deviation from that of C60 depends on the size of the metal atom, stability is governed by electronic properties of the transition metal atom. A range of MC59 compounds of group 6-8 metals are predicted to have sufficient stability for experimental observation.

Why is hafnium so unreactive?: Experimental and theoretical studies of the reaction of Hf + with methane

The reaction of atomic hafnium cations with CH 4 and CD 4 is studied using a guided ion beam tandem mass spectrometer. In contrast to most third-row transition metal ions, the dehydrogenation reaction to form HfCH 2 + + H 2 is endothermic. At higher energies, other products, HfCH +, HfCH 3 +, and HfH +, the latter being the predominant species, are observed. Implicit in the behavior of the cross sections for HfH +, HfCH 2 +, and HfCH 3 + is a H Hf + CH 3 intermediate. Modeling of the endothermic cross sections provides for 0 K bond dissociation energies (in eV) of D 0(Hf + CH) = 5.10 ± 0.15, D 0(Hf + CH 2) = 4.37 ± 0.07, D 0(Hf + CH 3) = 2.12 ± 0.26, and D 0(Hf + H) = 1.97 ± 0.11. These experimental bond energies are in good agreement with density functional calculations at the B3LYP/HW+/6–311 ++ G(3 df,3 p) level of theory. Theoretical calculations reveal the mechanism of the reaction and illustrate the geometric and electronic structures of the individual products and intermediates. Unlike its first and second-row congeners, which have quartet ground states and must change spin to dehydrogenate methane, Hf + retains its ground state doublet configuration throughout the dehydrogenation reaction, demonstrating that spin-restrictions are not responsible for the relatively low reactivity of Hf +. Instead, this can be attributed to the unfavorable doubly occupied 6 s orbital in the 2D ground state of Hf +.

The most reactive third-row transition metal: Guided ion beam and theoretical studies of the activation of methane by Ir +

The potential energy surface for activation of methane by the third-row transition metal cation, Ir +, is studied experimentally by examining the kinetic energy dependence of reactions of Ir + with methane, IrCH 2 + with H 2 and D 2, and collision-induced dissociation of IrCH 2 + with Xe using guided ion beam tandem mass spectrometry. A flow tube ion source produces Ir + in its electronic ground state term and primarily in the ground spin–orbit level. We find that dehydrogenation to form IrCH 2 + + H 2 is exothermic, efficient, and the only process observed at low energies for reaction of Ir + with methane, whereas IrH + dominates the product spectrum at higher energies. We also observe the IrH 2 + product, which provides evidence that methane activation proceeds via a dihydride (H) 2IrCH 2 + intermediate. The kinetic energy dependences of the cross sections for several endothermic reactions are analyzed to give 0 K bond dissociation energies (in eV) of D 0(Ir +–2H) > 5.09 ± 0.07, D 0(Ir +–C) = 6.59 ± 0.05, D 0(Ir +–CH) = 6.91 ± 0.23, and D 0(Ir +–CH 3) = 3.25 ± 0.18. D 0(Ir +–CH 2) = 4.92 ± 0.03 eV is determined by measuring the forward and reverse reaction rates for I r + + C H 4 ⇌ IrC H 2 + + H 2 at thermal energy. Ab initio calculations at the B3LYP/HW+/6-311++G(3df,3p) level performed here show reasonable agreement with the experimental bond energies and with the few previous experimental and theoretical values available. Theory also provides the electronic structures of the product species as well as intermediates and transition states along the reactive potential energy surfaces. We also compare this third-row transition metal system with the first-row and second-row congeners, Co + and Rh +. Differences in reactivity and mechanisms can be explained by the lanthanide contraction and relativistic effects that alter the relative size of the valence s and d orbitals.

Dual Room-Temperature Fluorescent and Phosphorescent Emission in 8-Quinolinolate Osmium(II) Carbonyl Complexes: Rationalization and Generalization of Intersystem Crossing Dynamics

A new series of quinolinolate osmium carbonyl complexes were synthesized and characterized by spectroscopic methods. Single-crystal X-ray diffraction studies indicate that these complexes consist of an octahedral ligand arrangement with one chelating quinolinolate, one tfa or halide ligand, and three mutually orthogonal terminal CO ligands. Variation of the substituents on quinolinolate ligands imposes obvious electronic or structural effects, while changing the tfa ligand to an electron-donating iodide slightly increases the charge density on the central osmium atom. These Os(II) complexes show salient dual emissions consisting of fluorescence and phosphorescence, the spectral properties and relaxation dynamics of which have been studied comprehensively. The results, in combination with the theoretical approaches, lead us to propose that the emission mainly originates from the quinolinolate pi pi* state. Both experimental and theoretical approaches generalize various types of intersystem crossing versus those of the tris(quinolinolate) iridium Ir(Q)3, and their relative efficiencies were accessed on the basis of the associated frontier orbital configurations. Our results suggest that [1d(pi)pi* absolute value(H(so))3 pi pi*] (or [3d(pi)pi* absolute value(H(so))1 pi pi*]) in combination with a smaller deltaE(S1-T1) gap (i.e., increasing the MLCT (d(pi)pi*) character) is the main driving force to induce the ultrafast S1 --> T1 intersystem crossing in the third-row transition metal complexes, giving the strong phosphorescent emission.

Spectral studies, cyclic voltammetry and synthesis of cobalt(II) and ruthenium(III) complexes with symmetric and asymmetric ring containing membered N 2S 2, N 4, and N 5 donor macrocyclic ligands

Reaction of divalent cobalt(II) and trivalent ruthenium(III) salts (NO 3, SCN and SO 4) with macrocyclic ligands L 1, L 2 and L 3 having N 2S 2, N 4 and N 5 core, have been designed and carry out. All these three macrocyclic ligands and their complexes were obtained in pure form. Their structures were investigated by using microanalytical analyses, IR, mass, magnetic moments, electronic and EPR spectral studies. The redox properties of the complexes were also examined by cyclic voltammetry. An interesting feature of complexes is that the relatively large rings of macrocyclic ligands prevent the macrocyclic rings from approaching the metal center as closely as they would, if they were not constrained. So the Ru–N distances are longer than expected due to ring size. Electrochemical studies show that the macrocyclic ligand L 1 is more effective electron donors to ruthenium than of L 2 and L 3. Electronic spectral properties also show that the sulphur donor atom of L 1 weakens the ligand field with respect to ligand-to-metal charge-transfer band. However it is expected that second-row transition metal–ligand bonds tend to be weaker than third-row transition metal–ligand bonds. There are well-established examples of reactions in which decreased of reactivity down a triad of transition metals is not observed. These novelties are usually attributed to π-bonding effects for ligands such as carbon monoxide, solvent effects, or a change in mechanism.

Guided Ion Beam and Theoretical Study of the Reactions of Ir+ with H2, D2, and HD

We present the kinetic energy dependence of reactions of the late third-row transition metal cation Ir(+) with H(2), D(2), and HD measured using a guided ion beam tandem mass spectrometer. A flow tube ion source produces Ir(+) ions in its electronic ground state term and primarily in the ground spin-orbit level. Corresponding state-specific reaction cross sections are obtained. The kinetic energy dependence of the cross sections for forming IrH(+) and IrD(+) are analyzed to give a 0 K bond dissociation energy of D(0)(Ir(+)-H) = 3.12 +/- 0.06 eV. Ab initio calculations at the B3LYP/HW+/6-311+G(3p), BHLYP/HW+/6-311+G(3p), and QCISD(T)/HW+/6-311+G(3p) levels performed here show reasonable agreement with the experimental bond energies and with the previous theoretical values available. Theory also provides the electronic structures of these species and the reactive potential energy surfaces. We also compare this third-row transition metal system with those of the first-row and second-row congeners Co(+) and Rh(+). We find that Ir(+) has a stronger M(+)-H bond, which can be explained by the lanthanide contraction and relativistic effects that alter the relative size of the valence s and d orbitals. Results from reactions with HD provide insight into the reaction mechanisms and indicate that Ir(+) reacts largely via an insertion mechanism, in contrast with the lighter group 9 metal ions Co(+) and Rh(+) which react via direct mechanisms.

Activation of CH4by gas-phase Ni+and the thermochemistry of Ni–ligand complexes

The kinetic energy dependence of the reaction of Ni+ (2D) with methane has been studied using guided ion beam mass spectrometry. Formation of NiH+, NiCH2+ and NiCH3+ are all observed with thresholds near 2 eV, and NiCH+ is observed at higher kinetic energies. The dehydrogenation reaction is shown to proceed over a barrier in excess of the endothermicity by examining the reverse reaction of NiCH2(+) + D2. Collision-induced dissociation of NiCH2+ and NiCH4+ with Xe provides additional information on the products and reaction intermediates. Modeling of the endothermic reaction cross sections yields the 0 K bond dissociation energies (in eV) of D0(Ni( +)-H) = 1.60 +/- 0.08, D0(Ni(+)-CH) = 3.12 +/- 0.12, D0(Ni(+)-CH2) = 3.20 +/- 0.08, D0(Ni(+)-CH3) = 1.76 +/- 0.07, and D0(Ni(+)-CH4) = 1.00 +/- 0.05. The experimental thermochemistry is favorably compared with previous experimental results and density functional theory calculations (B3LYP), which also establish the electronic structures of these species and provide insight into the reaction mechanism. The results for Ni(+) are compared with those for the third-row transition metal congener Pt+ and the differences in behavior and mechanism are discussed.

Probes of spin conservation in heavy metal reactions: experimental and theoretical studies of the reactions of Re+ with H2, D2, and HD.

A guided ion beam tandem mass spectrometer is used to examine the kinetic energy dependence of reactions of the third-row transition metal cation, Re(+), with molecular hydrogen and its isotopologues. A flow tube ion source produces Re(+) in its (7)S(3) electronic ground state. Reaction with H(2), D(2), and HD forms Re H(+)(Re D(+)) in endothermic processes. Modeling of the endothermic reaction cross sections yields the 0 K bond dissociation energy of D(0)(Re(+)-H)=2.29+/-0.07 eV (221+/-6 kJ/mol). The experimental thermochemistry is consistent with ab initio calculations, performed here and in the literature. Theory also provides the electronic structures of these species and is used to examine the reactive potential energy surfaces. Results from reactions with HD provide insight into the reaction mechanisms and indicate that the late metal ion, Re(+), reacts largely via a statistical mechanism. This is consistent with the potential energy surfaces which locate a stable Re H(2) (+)((5)B(2)) complex. Results for this third-row transition metal system are compared with the first-row congener (Mn(+)) and found to have much higher reactivity towards dihydrogen and stronger M(+)-H bonds. These differences can be attributed to efficient coupling among surfaces of different spin along with lanthanide contraction and relativistic effects.