Importance of energy level matching for bonding in Th(3+)-Am(3+) actinide metallocene amidinates, (C(5)Me(5))(2)[(i)PrNC(Me)N(i)Pr]An

The synthesis of a rare trivalent Th(3+) complex, (C(5)Me(5))(2)[(i)PrNC(Me)N(i)Pr]Th, initiated a density functional theory analysis on the electronic and molecular structures of trivalent actinide complexes of this type for An = Th, Pa, U, Np, Pu, and Am. While the 6d orbital is found to accommodate the unpaired spin in the Th(3+) species, the next member of the series, Pa, is characterized by an f(2) ground state, and later actinides successively fill the 5f shell. In this report, we principally examine the evolution of the bonding as one advances along the actinide row. We find that the early actinides (Pa-Np) are characterized by localized f orbitals and essentially ionic bonding, whereas the f orbitals in the later members of the series (Pu, Am) exhibit significant interaction and spin delocalization into the carbon- and nitrogen-based ligand orbitals. This is perhaps counter-intuitive since the f orbital radius and hence metal-ligand overlap decreases with increasing Z, but this trend is counter-acted by the fact that the actinide contraction also leads to a stabilization of the f orbital manifold that leads to a near degeneracy between the An 5f and cyclopentadienyl π-orbitals for Pu and Am, causing a significant orbital interaction.     

Spin-orbit coupling in O2(upsilon)+O2 collisions: I. Electronic structure calculations on dimer states involving the X 3Sigmag-, a 1Deltag, and b 1Sigmag+ states of O2

The importance of vibrational-to-electronic (V-E) energy transfer mediated by spin-orbit coupling in the collisional removal of O2(X 3Sigmag-,upsilon>or=26) by O2 has been reported in a recent communication [F. Dayou, J. Campos-Martinez, M. I. Hernandez, and R. Hernandez-Lamoneda, J. Chem. Phys. 120, 10355 (2004)]. The present work provides details on the electronic properties of the dimer (O2)2 relevant to the self-relaxation of O2(X 3Sigmag-,upsilon>0) where V-E energy transfer involving the O2(a 1Deltag) and O2(b 1Sigmag+) states is incorporated. Two-dimensional electronic structure calculations based on highly correlated ab initio methods have been carried out for the potential-energy and spin-orbit coupling surfaces associated with the ground singlet and two low-lying excited triplet states of the dimer dissociating into O2(X 3Sigmag-)+O2(X 3Sigmag-), O2(a 1Deltag)+O2(X 3Sigmag-), and O2(b 1Sigmag+)+O2(X 3Sigmag-). The resulting interaction potentials for the two excited triplet states display very similar features along the intermolecular separation, whereas differences arise with the ground singlet state for which the spin-exchange interaction produces a shorter equilibrium distance and higher binding energy. The vibrational dependence is qualitatively similar for the three studied interaction potentials. The spin-orbit coupling between the ground and second excited states is already nonzero in the O2+O2 dissociation limit and keeps its asymptotic value up to relatively short intermolecular separations, where the coupling increases for intramolecular distances close to the equilibrium of the isolated diatom. On the other hand, state mixing between the two excited triplet states leads to a noticeable collision-induced spin-orbit coupling between the ground and first excited states. The results are discussed in terms of specific features of the dimer electronic structure (including a simple four-electron model) and compared with existing theoretical and experimental data. This work gives theoretical insight into the origin of electronic energy-transfer mechanisms in O2+O2 collisions.     

Reactions of Th and U atoms with C2H2: infrared spectra and relativistic calculations of the metallacyclopropene, actinide insertion, and ethynyl products

Reactions of laser-ablated Th and U atoms with C(2)H(2) during condensation with excess argon at 7 K give several new product species. The metallacyclopropene, inserted hydride, and actinide ethynyl are identified from isotopic frequencies and relativistic DFT calculations. The higher-energy vinylidine isomer was not observed. These actinide metallacyclopropenes exhibit substantially stronger bonding interactions than found recently for the Pd and Pt metals. In the case of Th(C(2)H(2)) the argon matrix interaction is strong enough to reverse the computed order of states (MR-CISD) in favor of a triplet ground state for the (Ar)(n)(Th(C(2)H(2))) complex. The nature of the electronic interactions between various metal atoms and acetylene is compared and the origin of the particularly strong interaction for U and Th is traced to the higher energy of their 6d orbitals. The ThCCH and UCCH actinide ethynyl products are also observed and characterized by C[triple bond]C stretching modes 38+/-2 cm(-1) lower than acetylene itself.     

Photoelectron imaging of I2- at 5.826 eV

We report the anion photoelectron spectrum of I2- taken at 5.826 eV detachment energy using velocity mapped imaging. The photoelectron spectrum exhibits bands resulting from transitions to the bound regions of the X 1Sigmag+(0g+), A' 3Piu(2u), A 3Piu(1u), and B 3Piu(0u+) electronic states as well as bands resulting from transitions to the repulsive regions of several I2 electronic states: the B' 3Piu(0u-), B" 1Piu(1u), 3Pig(2g), a 3Pig(1g), 3Pig(0g-), and C 3Sigmau+(1u) states. We simulate the photoelectron spectrum using literature parameters for the I2- and I2 ground and excited states. The photoelectron spectrum includes bands resulting from transitions to several high-lying excited states of I2 that have not been seen experimentally: 3Pig(0g-), 1Pig3(1g), 1 3Sigmag-3(0g+), and the 1Sigmag-3(0u-) states of I2. Finally, the photoelectron spectrum at 5.826 eV allows for the correction of a previous misassignment for the vertical detachment energy of the I2 B 3Piu(0u+) state.     

Bond characterization on a Cr-Cr quintuple bond: a combined experimental and theoretical study

A combined experimental and theoretical charge density study on a quintuply bonded dichromium complex, Cr(2)(dipp)(2) (dipp = (Ar)NC(H)N(Ar) and Ar = 2,6-i-Pr(2)-C(6)H(3)), is performed. Two dipp ligands are bridged between two Cr ions; each Cr atom is coordinated to two N atoms of the ligands in a linear fashion. The Cr atom is in a low oxidation state, Cr(I), and in low coordination number condition, which stabilizes a metal-metal multiple bond, in this case, a quintuple bond. Indeed, it gives an ultrashort Cr-Cr bond distance of 1.7492(1) ? in the complex. The bond characterization of such a quintuple bond is undertaken both experimentally by high-resolution single-crystal X-ray diffraction and theoretically by density functional calculation (DFT). Electron densities are depicted via deformation density and Laplacian distributions. Bond characterizations of the complex are presented in terms of topological properties, Fermi hole function, source function (SF), and natural bonding orbital (NBO) analysis. The electron density at the Cr-Cr bond critical point (BCP) is 1.70 e/?(3), quite a high value for metal-metal bonding and mainly contributed from the metal ion itself. The quintuple bond is confirmed with one σ, two π, and two δ interactions by NBO analysis and Fermi hole function. The molecular orbitals (MOs) illustrate that five bonding orbitals are predominantly contributed from the 3d orbitals of the Cr(I) ion. The effective bond order from NBO analysis is 4.60. The detail comparison between experiment and theory will be given. Additionally, three closely related complexes are calculated for systematic comparison.     

Analysis of the putative Cr-Cr quintuple bond in Ar'CrCrAr' (Ar' = C6H3-2,6(C6H3-2,6-Pr(i)2)2 based on the combined natural orbitals for chemical valence and extended transition state method

The nature of the putative Cr-Cr quintuple bond in Ar'CrCrAr' (Ar' = C(6)H(3)-2,6(C(6)H(3)-2,6-Pr(i)(2))(2)) is investigated with the help of a newly developed energy and density decomposition scheme. The new approach combines the extended transition state (ETS) energy decomposition method with the natural orbitals for chemical valence (NOCV) density decomposition scheme within the same theoretical framework. The results show that in addition to the five bonding components (σ(2)π(2)π'(2)δ(2)δ'(2)) of the Cr-Cr bond, the quintuple bond is augmented by secondary Cr-C interactions involving the Cr-ipso-carbon of the flanking aryl rings. The presence of isopropyl groups (Pr(i)) is further shown to stabilize Ar'CrCrAr' by 20 kcal/mol compared to the two Ar'Cr monomers through stabilizing van der Waals dispersion interactions.     

Actinide sulfides in the gas phase: experimental and theoretical studies of the thermochemistry of AnS (An = Ac, Th, Pa, U, Np, Pu, Am and Cm)

The gas-phase thermochemistry of actinide monosulfides, AnS, was investigated experimentally and theoretically. Fourier transform ion cyclotron resonance mass spectrometry was employed to study the reactivity of An(+) and AnO(+) (An = Th, Pa, U, Np, Pu, Am and Cm) with CS(2) and COS, as well as the reactivity of the produced AnS(+) with oxidants (COS, CO(2), CH(2)O and NO). From these experiments, An(+)-S bond dissociation energies could be bracketed. Density functional theory studies of the energetics of neutral and monocationic AnS (An = Ac, Th, Pa, U, Np, Pu, Am and Cm) provided values for bond dissociation energies and ionization energies; the computed energetics of neutral and monocationic AnO were also obtained for comparison. The theoretical data, together with comparisons with known An(+)-O bond dissociation energies and M(+)-S and M(+)-O dissociation energies for the early transition metals, allowed for the refining of the An(+)-S bond dissociation energy ranges obtained from experiment. Examination of the reactivity of AnS(+) with dienes, coupled to comparisons with reactivities of the AnO(+) analogues, systematic considerations and the theoretical results, allowed for the estimation of the ionization energies of the AnS; the bond dissociation energies of neutral AnS were consequently derived. Estimates for the case of AcS were also made, based on correlations of the data for the other An and the electronic energetics of neutral and ionic An. The nature of the bonding in the elementary molecular actinide chalcogenides (oxides and sulfides) is discussed, based on both the experimental data and the computed electronic structures. DFT calculations of ionization energies for the actinide atoms and the diatomic sulfides and oxides are relatively reliable, but the calculation of bond dissociation energies is not uniformly satisfactory, either with DFT or CCSD(T). A key conclusion from both the experimental and theoretical results is that the 5f electrons do not substantially participate in actinide-sulfur bonding. We emphasize that actinides form strikingly strong bonds with both oxygen and sulfur.     

Study of the An–Cl bond contraction in actinide trichlorides

The variation of the An–Cl bond distance in ground-state actinide trichloride (AnCl₃) molecules has been studied by density functional theory calculations using the B3LYP exchange–correlation functional in conjunction with small-core relativistic energy-consistent pseudopotentials for the actinides. The ground electronic states and the ground-state molecular properties of the trichlorides of heavy actinides (An = Bk–Lr) are reported in this paper the first time. Extending the present results with literature data on the light actinide trichlorides (AnCl₃, An = Th–Cm), the trend in the bond distance has been evaluated for the whole actinide row. The contraction is well manifested in the major part of the actinide row (An = U–Fm). The deviations at the beginning (Th, Pa) and end of the row (Md, No) have been explained by minor differences in the bonding interactions.     

Computed vibrational frequencies of actinide oxides AnO(0/+/2+) and AnO2(0/+/2+) (An = Th, Pa, U, Np, Pu, Am, Cm)

The vibrational frequencies of the actinide oxides AnO and AnO(2) (An = Th, Pa, U, Np, Pu, Am, Cm) and of their mono- and dications have been calculated using advanced quantum chemical techniques. The stretching fundamental frequencies of the monoxides have been determined by fitting the potential function to single-point energies obtained by relativistic CASPT2 calculations along the stretching coordinate and on this basis solving numerically the ro-vibrational Schro?dinger equation. To obtain reliable fundamental frequencies of the dioxides, we developed an empirical approach. In this approach the harmonic vibrational frequencies of the AnO(2)(0/+/2+) species were calculated using eight different exchange-correlation DFT functionals. On the basis of the good correlation found between the vibrational frequencies and computed bond distances, the final frequency values were derived for the CASPT2 reference bond distances from linear regression equations fitted to the DFT data of each species. As a test, the approach provided excellent agreement with accurate experimental data of ThO, ThO(+), UO, and UO(+). The joint analysis of literature experimental and our computed data facilitated the prediction of reliable gas-phase molecular properties for some oxides. They include the stretching frequencies of PuO, ThO(2), UO(2), and UO(2)(+) and the bond distance of PuO (1.818 ?, being likely within 0.002 ? of the real value). Also the derived equilibrium bond distances of ThO(2), UO(2), and UO(2)(+) (1.896, 1.790, and 1.758 ?, respectively) should approximate closely the (yet unknown) experimental values. On the basis of the present results, we suggest that the ground electronic state of PuO(2) in Ar and Kr matrices is probably different from that in the gaseous phase, similarly to UO(2) observed previously.     

Electronic structure and luminescence of [AuS2PPh(OCH2CHCH2)]2 complex

The complex [AuS₂PPh(OCH₂CHCH₂)]₂ (1) presents an Au(I)–Au(I) intramolecular and intermolecular bonding with luminescence properties. To understand the nature of these features, fully optimized geometries were obtained by three computational methods, DFT/B3LYP, MPW1B95 and MP2. An Au(I)–Au(I) intramolecular bond was found in the ground state, at the three levels of theory, exhibiting an aurophilic interaction between the two gold atoms. Two molecules of the complex were optimized using DFT/B3LYP, in order to analyze the intermolecular interaction between them. The resulting intermolecular bonding distance between the two adjacent gold atoms on each molecule is 3.16 Å, indicating a strong aurophilic attraction. Time dependent calculations indicate that the first excited state with nonzero oscillator strength is a singlet, with an excitation energy equal to 3.16 eV. This should correspond to the absorption band seen experimentally at 3.10 eV. The lowest energy emission of (1) was obtained at 2.73 eV, which corresponds to the emission peak resulting from phosphorescence and located at 2.53 eV. This transition comes from an excited electron on the p orbitals of the ligands that is transferred to the d orbitals of the gold atoms on the HOMO. This interaction may be attributed to Ligand to Ligand–Metal Charge Transfer (LL–MCT).     

Gas-phase reactions of the bare Th2+ and U2+ ions with small alkanes, CH4, C2H6, and C3H8: experimental and theoretical study of elementary organoactinide chemistry

The gas-phase reactions of two dipositive actinide ions, Th(2+) and U(2+), with CH(4), C(2)H(6), and C(3)H(8) were studied by both experiment and theory. Fourier transform ion cyclotron resonance mass spectrometry was employed to study the bimolecular ion-molecule reactions; the potential energy profiles (PEPs) for the reactions, both observed and nonobserved, were computed by density functional theory (DFT). The experiments revealed that Th(2+) reacts with all three alkanes, including CH(4) to produce ThCH(2)(2+), whereas U(2+) reacts with C(2)H(6) and C(3)H(8), with different product distributions than for Th(2+). The comparative reactivities of Th(2+) and U(2+) toward CH(4) are well explained by the computed PEPs. The PEPs for the reactions with C(2)H(6) effectively rationalize the observed reaction products, ThC(2)H(2)(2+) and UC(2)H(4)(2+). For C(3)H(8) several reaction products were experimentally observed; these and additional potential reaction pathways were computed. The DFT results for the reactions with C(3)H(8) are consistent with the observed reactions and the different products observed for Th(2+) and U(2+); however, several exothermic products which emerge from energetically favorable PEPs were not experimentally observed. The comparison between experiment and theory reveals that DFT can effectively exclude unfavorable reaction pathways, due to energetic barriers and/or endothermic products, and can predict energetic differences in similar reaction pathways for different ions. However, and not surprisingly, a simple evaluation of the PEP features is insufficient to reliably exclude energetically favorable pathways. The computed PEPs, which all proceed by insertion, were used to evaluate the relationship between the energetics of the bare Th(2+) and U(2+) ions and the energies for C-H and C-C activation. It was found that the computed energetics for insertion are entirely consistent with the empirical model which relates insertion efficiency to the energy needed to promote the An(2+) ion from its ground state to a prepared divalent state with two non-5f valence electrons (6d(2)) suitable for bond formation in C-An(2+)-H and C-An(2+)-C activated intermediates.     

Agostic interaction in the methylidene metal dihydride complexes H2MCH2 (M=Y, Zr, Nb, Mo, Ru, Th, or U)

Multiconfigurational quantum chemical methods (complete active space self-consistent field (CASSCF)/second-order perturbation theory (CASPT2)) have been used to study the agostic interaction between the metal atom and H(C) in the methylidene metal dihydride complexes H2MCH2, where M is a second row transition metal or the actinide atoms Th or U. The geometry of some of these complexes is highly irregular due to the formation of a three center bond CH...M, where the electrons in the CH bond are delocalized onto empty or half empty orbitals of d- or f-type on the metal. No agostic interaction is expected when M=Y, where only a single bond with methylene can be formed, or when M=Ru, because of the lack of empty electron accepting metal valence orbitals. The largest agostic interaction is found in the Zr and U complexes.     

Understanding structure and bonding in early actinide 6d(0)5f0 MX6q (M = Th-Np; X = H, F) complexes in comparison with their transition metal 5d0 analogues

The relationship between structure and bonding in actinide 6d(0)5f(0) MX(6)(q)() complexes (M = Th, Pa, U, Np; X = H, F; q = -2,-1, 0, +1) has been studied, based on density functional calculations with accurate relativistic actinide pseudopotentials. The detailed comparison of these prototype systems with their 5d(0) transition metal analogues (M = Hf, Ta, W, Re) reveals in detail how the 5f orbitals modify the structural preferences of the actinide complexes relative to the transition metal systems. Natural bond orbital analyses on the hydride complexes indicate that 5f orbital involvement in sigma-bonding favors classical structures based on the octahedron, while d orbital contributions to sigma-bonding favor symmetry lowering. The respective roles of f and d orbitals are reversed in the case of pi-bonding, as shown for the fluoride complexes.     

Spectroscopy of the ground and low-lying excited states of ThO+

The ThO(+) cation is of interest as it is a useful prototype for experimental and theoretical studies of bonding in a simple actinide compound. Formally the ground state of ThO(+) has the configuration Th(3+)(7s)O(2-), where there is a single unpaired electron associated with a closed-shell Th(4+)-ion core. The first tier of excited states above the X (2)Sigma(+) ground state is expected to be 1 (2)Delta, 1 (2)Pi, and 2 (2)Sigma(+) derived from the Th(3+)(6d)O(2-) configuration. Spectroscopic observations of ThO(+) using the pulsed field ionization-zero kinetic-energy photoelectron technique are reported here. Rotationally resolved spectra were recorded for the X (2)Sigma(+), 1 (2)Delta, and 1 (2)Pi states. Extensive vibrational progressions were observed. Surprisingly, it was found that ionization of ThO decreases the dissociation energy, while increasing the vibrational frequency and decreasing the bond length. Accurate values for the ionization energies of ThO [53 253.8(2) cm(-1)] and Th [50 868.71(8) cm(-1)] were determined as part of this investigation.     

Ab Initio Analysis of Metal–Ligand Bonding in An(COT)2 with An=Th,U in Their Ground- and Core-Excited States

Relativistic multireference ab initio wave function calculations with the restricted active space second-order perturbation theory (RASPT2) were performed on thorocene and uranocene to determine the actinide N_4,5-edge and carbon K-edge X-ray absorption near-edge structure (XANES) intensities and the metal–ligand orbital mixing in the ground state and core-excited states. Calculated spectral intensities show very good agreement with the experiments and therefore allow detailed and unambiguous assignment of the observed spectral features. φ-type covalent bonding or antibonding interactions are observed for thorocene in the core-excited states, though not in the ground state. This is because the molecular orbital of φ symmetry, which is the in-phase combination of the ligand L_φ and the Th 5f_φ orbitals, can be populated with electrons in core-excited states, whereas it is essentially unoccupied in the ground state. For uranocene, the XANES spectra do not reveal much information beyond multiplet broadening, despite the presence of distinct peaks in the spectra. Every core-excited peak is best characterized by its own set of bond orbitals, as the excited state covalency is clearly different from the ground state covalency.     

Dissociation energy of ekaplutonium fluoride E126F: the first diatomic with molecular spinors consisting of g atomic spinors

Our ab initio all-electron fully relativistic Dirac-Fock (DF) and nonrelativistic (NR) Hartree-Fock (HF) self-consistent field (SCF) calculations predict the superheavy diatomic ekaplutonium fluoride E126F to be bound with the calculated dissociation energy of 7.44 and 10.46 eV at the predicted E126-F bond lengths of 2.03 and 2.18 Angstroms, respectively. The antibinding effects of relativity to the dissociation energy of E126F are approximately 3 eV. The predicted dissociation energy with both our NR HF and relativistic DF SCF wave functions is fairly large and is comparable to that for very stable diatomics. This is the first case, where in a diatomic, an atom has g orbital (l = 4) occupied in its ground state electronic configuration and such superheavy diatomics would have occupied molecular spinors (orbitals) consisting of g atomic spinors (orbitals). This opens up a whole new field of chemistry where g atomic spinors (orbitals) may be involved in electronic structure and chemical bonding of systems of superheavy elements with Z> or =122.     

GVVPT2 multireference perturbation theory description of diatomic scandium, chromium, and manganese

With relatively simple model spaces derived from valence bond models, a straightforward zero-order Hamiltonian, and the use of moderate-sized Dunning-type correlation consistent basis sets (cc-pVTZ, aug-cc-pVTZ, and cc-pVQZ), the second order generalized Van Vleck perturbation theory (GVVPT2) method is shown to produce potential energy curves (PECs) and spectroscopic constants close to experimental results for both ground and low-lying excited electronic states of Sc(2), Cr(2) and Mn(2). In spite of multiple quasidegeneracies (particularly for the cases of Sc(2) and Mn(2)), the GVVPT2 PECs are smooth with no discontinuities. Since these molecules have been identified as ones that widely used perturbative methods are inadequate for describing well, due to intruder state problems, unless shift parameters are introduced that can obfuscate the physics, this study suggests that the conclusion about the inadequacy of multireference perturbation theory be re-evaluated. The ground state of Sc(2) is predicted to be X(5)∑(u)(-), and its spectroscopic constants are close to the ones at the MRCISD level. Near equilibrium geometries, the 1(3)∑(u)(-) electronic state of Sc(2) is found to be less stable than the quintet ground state by 0.23 eV. The Cr(2) PEC has several features of the Rydberg-Klein-Rees (RKR) experimental curve (e.g., the pronounced shelf at elongated bond lengths), although the predicted bond length is slightly long (R(e) = 1.80 ? with cc-pVQZ compared to the experimental value of 1.68 ?). The X(1)∑(g)(+) ground state of Mn(2) is predicted to be a van der Waals molecule with a long bond length, R(e), of 3.83 ? using a cc-pVQZ basis set (experimental value = 3.40 ?) and a binding energy, D(e), of only 0.05 eV (experimental value = 0.1 eV). We obtained R(e) = 3.40 ? and D(e) = 0.09 eV at the complete basis set (CBS) limit for ground state Mn(2). Low lying excited state curves have also been characterized for all three cases (Cr(2), Mn(2), and Sc(2)) and show similar mathematical robustness as the ground states. These results suggest that the GVVPT2 multireference perturbation theory method is more broadly applicable than previously documented.     

Infrared spectroscopic and theoretical investigations of the OUF2 and OThF2 molecules with triple oxo bond character

The terminal oxo species OUF(2) and OThF(2) have been prepared via the spontaneous and specific OF(2) molecule reactions with laser ablated uranium and thorium atoms in solid argon and neon. These isolated molecules are characterized by one terminal M-O and two F-M-F (M = U or Th) stretching vibrational modes observed in matrix isolation infrared spectra, which are further supported by density functional frequency calculations and CASPT2 energy and structure calculations. Both molecules have pyramidal structures with singlet (Th) and triplet (U) ground states. The molecular orbitals and metal-oxygen bond lengths for the OUF(2) and OThF(2) molecules indicate triple bond character for the terminal oxo groups, which are also substantiated by NBO analysis at the B3LYP level and by CASPT2 molecular orbital calculations. Dative bonding involving O(2p) → Th(6d) and U(df) interactions is clearly involved in these oxoactinide difluoride molecules. Finally, the weak O-F bond in OF(2) as well as the strong U-O, U-F and Th-O, Th-F bonds make reaction to form the OUF(2) and OThF(2) molecules highly exothermic.     

Guided ion beam and theoretical study of the reactions of Au+ with H2, D2, and HD

Reactions of the late third-row transition metal cation Au(+) with H(2), D(2), and HD are examined using guided ion beam tandem mass spectrometry. A flow tube ion source produces Au(+) in its (1)S (5d(10)) electronic ground state level. Corresponding state-specific reaction cross sections for forming AuH(+) and AuD(+) as a function of kinetic energy are obtained and analyzed to give a 0 K bond dissociation energy of D(0)(Au(+)-H) = 2.13 ± 0.11 eV. Quantum chemical calculations at the B3LYP∕HW+∕6-311+G(3p) and B3LYP∕Def2TZVPP levels performed here show good agreement with the experimental bond energy. 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 previous results for analogous reactions of the first-row and second-row congeners, Cu(+) and Ag(+). We find that Au(+) 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 mechanism and indicate that ground state Au(+) reacts largely via a direct mechanism, in concordance with the behavior of the lighter group 11 metal ions, but includes more statistical behavior than these metals as well.