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Article Cite This: Organometallics XXXX, XXX, XXX−XXX

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Theoretical Study on Unsupported Uranium−Metal Bonding in Uranium−Group 8 Complexes Xiao-Wang Chi,†,‡ Qun-Yan Wu,† Qiang Hao,§ Jian-Hui Lan,† Cong-Zhi Wang,† Qin Zhang,‡ Zhi-Fang Chai,†,∥ and Wei-Qun Shi*,† †

Laboratory of Nuclear Energy Chemistry, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China College of Mining, Guizhou University, Guiyang, 550025, China § School of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian, 116029, China ∥ School of Radiological and Interdisciplinary Sciences (RAD-X), and Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou, 215123, China

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‡

S Supporting Information *

ABSTRACT: On the basis of the first structurally authenticated LArU− FeCp(CO)2 (LAr = deprotonated p-terphenyl bis(aniline) ligand) complex bearing an unsupported U−Fe bond, we expanded the structures of complexes LArU−MCp(CO)2 (M = Fe, Ru, Os) and systematically investigated the U−M bonding nature by using scalar-relativistic quantum chemical calculations. Theoretical results reveal highly polarized U−M interactions in the three LArU−MCp(CO)2 complexes. Moreover, the three U−M bonds are confirmed to show single bond feature. Topology of electron density reveals predominantly “closed shell” U−M interaction with obvious ionic interaction in the three LArU−MCp(CO)2 complexes. In addition, the negative binding energy suggests that the three LArU− MCp(CO)2 complexes are thermodynamically feasible. This work reveals the bonding nature of the three U−M bonds and expands our knowledge of the unsupported uranium−metal bonding in the heterobimetallic complexes.

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INTRODUCTION The metal−metal bond is a conspicuous feature for a bimetallic complex, which is of great significance in a wide range of structural and applied chemistry. Since Cotton et al. reported the first metal−metal (Re−Re) bond,1 the study of metal−metal bonds has become a hot field. The complexes containing homobimetallic metal−metal bonds have long been recognized to have reactivity, which can be applied to activate organic substrates due to cooperative function in bimetallic centers.2 However, the heterobimetallic compounds may have much more reactivity arising from their bifunctionality and polarity.3−8 The rapid development of experimental, spectroscopic, and computational tools indeed enlightens our understanding of the electronic structure of metal−metal compounds. Besides the potential properties in small molecule activation and catalysis, this evolving perspective of metal− metal bonds also exhibits excellent physical properties such as electrical conductivity, magnetism, and luminescence,9−11 photochemistry,12−14 and bioinorganic chemistry.15,16 Relative to supported metal−metal bonds with bridging ligands, unsupported metal−metal bonds are more active and challenging for synthesis.17 There have been many recent advances on the unsupported metal−metal bonds, such as the alkali metals, the transition metals, and the main group metals, even in the metalloids and rare-earth metals.18 However, the © XXXX American Chemical Society

5f-block compounds bearing metal−metal bonds are relatively rare because of their strong radioactive toxicity and the inherent challenges involved in stabilizing chemical bonds.19 Following the first actinide example of unsupported Th−Ru bond,20 the analogous Cp3U−SnPh321 and a series of An−M (An = Th, U; M = Fe, Ru) complexes22,23 were reported in the late 1980s, and then, the subject on the actinide−metal bonds went through into a period of inactivity with only few reports.24 Until 2008, a compound with an unsupported U−Al bond was reported,25 which has attracted widespread research interest. A number of new unsupported U/Th−metal bonds have been reported.19,26−34 Besides, the first structurally authenticated U−Re complex was reported by Liddle and co-workers,28 who also reported structurally validated series of unsupported uranium−ruthenium (U−Ru) bonds in [(Tren)U−RuCp(CO)2] and [(Ts)(THF)U−RuCp(CO)2] complexes.35 However, the corresponding unsupported U−Fe and U−Os analogues were not obtained. Very recently, Fortier et al. reported a LArU−FeCp(CO)2 (LAr = deprotonated pterphenyl bis(aniline) ligand) complex bearing an unsupported U−Fe bond. DFT and CASPT2 calculations suggest that the LArU−FeCp(CO)2 complex has a quartet ground state, and the Received: June 7, 2018

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DOI: 10.1021/acs.organomet.8b00391 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics

the complexes. The scalar-relativistic small-core pseudopotential (ECP60MWB) and the corresponding ECP60MWB-SEG valence basis set were applied for uranium atom,52−54 which have been shown to provide reliable results for actinide systems.55−58 The LANL2TZ(f) triple-ζ basis set59−61 with effective core potential62,63 was applied for Fe, Ru, and Os. As for other light atoms including C, H, O, and N, the 6-31G(d) basis set was used. Solvation effects were considered by using the solvation model based on density (SMD model) with toluene as the solvent. The electron energies for the three LArU−MCp(CO)2 complexes were carried out using a larger basis set 6-311G(d, p) in gas phase and toluene solution, and the corresponding Gibbs free energies were calculated including the thermal energy correction obtained in the gas phase. To address the multireference character of the wave function for the LArU−FeCp(CO)2 and LArU−RuCp(CO)2 complexes, the 7 electrons in 12 molecular orbitals (seven 5f orbitals on U and five 3d orbitals of Fe/Ru, along with the corresponding number of electrons) complete active space SCF (CASSCF) wave functions were constructed employing the LANL2DZ double-ζ basis set with effective core potential at the DFT optimized geometries. The CASSCF calculation was carried out with Molpro program.64,65 In addition, natural bond orbital (NBO) and energy decomposed analysis (EDA), at the optimized structures, were carried out with PBE method in the ADF code. For these calculations, the scalar-relativistic effects were taken into account using the zeroth-order regular approximation (ZORA) Hamiltonian approach. Slater-type orbital (STO) all-electron basis set TZ2P were used for all atoms. The topological analysis of electron density for the U−M bonds was performed by employing quantum theory of atoms in molecules (QTAIM) method. Within the QTAIM method, a chemical bond is defined by the presence of a line of maximum electron density along a bond path between each atoms pair and BCP (bond critical point).66 Therefore, the topological analysis of electron density can render information about the properties of chemical bonds. The analyses of QTAIM and electron localization function (ELF)67−69 were carried out with Multiwfn software.70

U−Fe bond is highly polarized and shows significant ionic character.36 It can be noted that the nucleophilic metal fragments [FeCp(CO)2]− and [RuCp(CO)2]− were often used to synthesize the unsupported metal−metal bonds in the previous applications.4 This strategy has proved feasible for constructing unsupported An−M (An = Th, U; M = Fe, Ru) bonds.20,22,35,36 In addition, there are also some theoretical studies on the actinide−metal bonds, such as homobimetallic An−An37−44 and heterobimetallic An−M45−47 bonds. Notably, Gagliardi et al. studied the nature of actinide− and lanthanide−metal bonds in heterobimetallic compounds using PBE functional and CASPT2 method, and indicated that An−M and Ln−M bonds are primarily ionic interaction. In addition, they suggested that DFT calculation can quite well describe the interaction between metals.46 Páez-Hernández et al. pointed out that the Th−M interaction contains around 25% covalent character for the [Cp2ThMCp(CO)2]+ complexes based on the energy decomposition analysis.47 These previous works inspired us to study whether the ligand [LArU]− as a new precursor is suitable for forming new uranium−metal bonds. Therefore, we expanded the range of uranium−transition-metal bonds through moving over Fe to Ru and Os based on the structure of LArU−FeCp(CO)2 (Scheme 1). We expect that the orbital contributions to the Scheme 1. Structure of the U−M Complexes LArU− MCp(CO)2 (M = Fe, Ru, Os)

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MOLECULAR AND ELECTRONIC STRUCTURES We optimized the three LArU−MCp(CO)2 (M = Fe, Ru and Os) complexes at the PBE/mbs level of theory. Different spin states (2, 4, 6, 8) of each LArU−MCp(CO)2 complex were considered to obtain the most stable electronic structure. The electronic energies for different spin states are listed in Table S1, and the trends of the relative energies are displayed in Figure 1. It is noted that the quartet state is the lowest in energy for the three complexes, which is consistent with a previous report.36 For LArU−FeCp(CO)2, the dominant contribution to the CASSCF wave function accounts for approximately 90% of the total wave function, which is higher than the previous report (about 70%),36 probably due to the difference in basis set or wave function convergence threshold. In addition, the 7 electrons in 12 molecular orbitals CASSCF single-point calculation is also performed for LArU−RuCp(CO)2 complex, the dominant contribution to the CASSCF wave function is about 96%. These CASSCF calculations demonstrate only small multiconfigurational character; thus, single-reference DFT method is suitable for describing the electronic structure of the LArU−MCp(CO)2 complexes. The electronic and geometrical parameters of the quartet state are

unsupported uranium−metal bonds would vary significantly with different 3d, 4d, and 5d metals. The scalar-relativistic density functional theory (DFT) calculations were carried out to investigate the U−M bonding nature and the structure of the heterobimetallic uranium and group 8. This work expands our understanding of the unsupported uranium−metal bonding in uranium−group 8 complexes.

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CALCULATION DETAILS All DFT calculations were carried out using the pure Perdew− Burke−Ernzerhof (PBE) functional,48 as implemented in Gaussian 09 4 9 and Amsterdam density functional (ADF2013.01)50,51 quantum chemistry codes. Generally, the pure PBE functional gives correct predictions on structure and energy for the heterobimetallic compounds.46 First, optimization of the LArU−FeCp(CO)2 complex was started from the available X-ray structure36 applying the Gaussian 09 program, and analogues LArU−RuCp(CO)2 and LArU−OsCp(CO)2 were constructed by replacing the Fe atom with other group 8 atoms, Ru and Os. Mixed basis sets (mbs) were employed for B


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Organometallics

ZORA/TZ2P and BP86/ZORA/TZP levels of theory, respectively, which is obviously higher than those (0.76− 0.78) in [(Tren)U−RuCp(CO)2] and [(Ts)(THF)U−RuCp(CO)2] at the BP86/ZORA/TZP level of theory given by Liddle.35 The result reveals that the U−Ru bond strength in the LArU−RuCp(CO)2 complex is stronger than those of the series of [(Tren)U−RuCp(CO)2] and [(Ts)(THF)U−RuCp(CO)2] complexes,35 which is also supported by the bonding energy analysis as discussed below. Furthermore, the energy differences between the highest αspin singly occupied molecular orbital (SOMO) and the lowest unoccupied molecular orbital (LUMO), namely, the SOMOLUMO gaps, for the three LArU−MCp(CO)2 complexes are small with the values of about 0.15 eV, which might reflect the nearly degenerate f and d orbitals of the metals. In order to understand the bonding interaction between the uranium and group 8 elements, three high-lying α-spin SOMOs (SOMO, SOMO-1 and SOMO-2) for the LArU− FeCp(CO)2 complex at the PBE/ZORA/TZ2P level of theory are displayed in Figure 2 and the corresponding MOs for the

Figure 1. Relative electronic energies (kcal/mol) of the different spin states at the PBE/mbs level of theory.

presented in Table 1. It shows that the three optimized structures have negligible spin contamination, with ⟨S2⟩ close to the ideal value of 3.75. The calculated U−Fe bond distance is 2.876 Å using the basis set 6-31G(d), which is shorter than the experimental 2.9462(3) Å.36 To evaluate the effect of basis set on the bond distance, 6-311G(d), 6-311G(d, p), and TZVP were selected with the PBE method. The result (Table S2) suggests that the calculated U−Fe bond distance is not sensitive to the size of basis set. The calculated U−Ru bond distance (3.013 Å) in the LArU−RuCp(CO)2 complex is very close to the experimental values (2.989−3.093 Å) in the [(Tren)U−RuCp(CO)2] and [(Ts)(THF)U−RuCp(CO)2] complexes.35 The calculated U−Os bond distance is 3.044 Å with no available experimental value, but it is comparable with the values 3.00 and 3.40 Å, the sum of covalent radii of uranium and osmium proposed by Pyykkö71 and Alvarez,72 respectively. The calculated U−M (M = Fe, Ru, Os) bond distances in LArU−MCp(CO)2 indicate the bonding interactions between uranium and group 8 elements. Mayer (MBO)73 and Nalewajski−Mrozek bond orders (NMBO)74,75 of three U−M bonds were explored. To test the effect of basis set on the bond order, the U−Fe bond order of the LArU−FeCp(CO)2 complex was explored using the basis sets DZP, TZP, and TZ2P. The three NMBO are almost with the value of about 1.0 (Table S3). Therefore, the size of basis set has little effect on bond order of U−M bonds we studied here. In Table 1, NMBO values are larger than those of MBO, but the trend is the same. The NMBO values of the three U− M bonds are close to 1, implying a single U−M bond. It is not hard to note that the U−Ru bond order is a little smaller than those of U−Fe and U−Os bonds. The calculated NMBO values of the U−Ru bond are 0.922 and 0.931 at the PBE/

Figure 2. α-Spin MOs, the corresponding energy level, and the metal compositions for the LArU−FeCp(CO)2 complexes at the PBE/ ZORA/TZ2P level of the theory. The isosurface value of MOs is set to be 0.05 au.

LArU−RuCp(CO)2 and LArU−OsCp(CO)2 complexes are presented in Figure S1. Without exception, the corresponding SOMOs diagrams for the three LArU−MCp(CO)2 complexes show similar character, respectively. The electron density of SOMO, SOMO−1, and SOMO−2 is singularly located on uranium center, which is consistent with the result in previous

Table 1. Spin Contamination ⟨S2⟩ and Bond Distance (Å) for the Quartet Ground State LArU−MCp(CO)2 (M = Fe, Ru, and Os) Complexes at the PBE/mbs Level of Theory and Calculated Mayer Bond Order (MBO), Nalewajski−Mrozek Bond Order (NMBO), and the S-L (SOMO-LUMO) Gap (eV) at the PBE/ZORA/TZ2P Level of Theory species

⟨S2⟩

bond distance

MBO

NMBO

S-L gap

L U−FeCp(CO)2 LArU−RuCp(CO)2 LArU−OsCp(CO)2

3.779 3.776 3.774

2.876/2.9462(3)a 3.013 3.044

0.784 0.721 0.763

0.999 0.922/0.931b 0.997

0.160 0.153 0.154

Ar

a

The experimental bond distance comes from ref 36. bThe value obtained at the BP86/ZORA/TZP level of theory. C


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Table 2. Mulliken Charge (Q, e), Mulliken Spin Density (S), and Natural Electron Configuration on U and TM Atoms for the LArU−MCp(CO)2 Complexes at the PBE/ZORA/TZ2P Level of Theory species LArU−FeCp(CO)2 LArU−RuCp(CO)2 LArU−OsCp(CO)2

atom

Q

S

U Fe U Ru U Os

1.026 −0.461/−0.311a 1.280 −0.610/−0.213a 1.117 −0.420/−0.240a

2.773 −0.082 2.773 −0.065 2.761 −0.052

natural electron configuration 7s 4s 7s 5s 7s 6s

(0.19) (0.38) (0.22) (0.41) (0.22) (0.52)

5f (3.30) 3d (7.90) 5f (3.29) 4d (7.70) 5f (3.29) 5d (7.47)

6d 4p 6d 5p 6d 6p

(0.96) (0.03) (0.93) (0.03) (0.94) (0.03)

7p 4d 7p 5d 7p 6d

(0.02) (0.01) (0.02) (0.03) (0.02) (0.03)

The calculated Mulliken charge on M atom for the isolated [MCp(CO)2]−.

a

Table 3. Bond Critical Point Properties (au) at the U−M Bonds in the Three LArU−MCp(CO)2 (M = Fe, Ru, Os) Complexes U−M

ρ(r)

∇2ρ(r)

G(r)

V(r)

−G(r)/V(r)

H(r)

ELF

U−Fe U−Ru U−Os

0.0460 0.0476 0.0512

0.0474 0.0477 0.0423

0.0229 0.0240 0.0243

−0.0339 −0.0361 −0.0381

0.676 0.665 0.638

−0.0110 −0.0121 −0.0138

0.357 0.361 0.412

work.36 In contrast, Meyer et al.76,77 reported the complexes [((tBuArO)3mes)U] and [((Ad,MeArO)3mes)U], both of which shows some constructive overlap of a U−centered f orbital with a high-lying anti-π orbital of the η6 bound arene ring. SOMO, SOMO−1, and SOMO−2 have predominant U 5f character according to the compositions of MOs in Table S3. The electron configuration of uranium is assigned as 5f3 in the three complexes, supported by the active natural orbital as displayed in Figure S2. The α- and β-spin MOs of the highest doubly occupied MO (HOMO) for three complexes are also presented in Figure S3. It is clearly seen that the diagrams of αand β-spin HOMOs are the same, and the corresponding energy levels are quite similar. Hence, we only take the αHOMO as an example in Figures 2 and S3, which represent the principal U−M interactions of Fe (40.33%) and U (6.11%), Ru (25.79%) and U (3.46%), and Os (11.36%) and U (4.03%) in the three LArU−MCp(CO)2 complexes, respectively. These values show that the transition metals chiefly contribute to the U−M interactions and do not share the electron pair equally with uranium, reflecting highly polarized U−M bonds which are typical in most An−M29,46 and transition M−M78,79 complexes. Moreover, the composition from the transition metal atom decreases with the increasing atomic number, yet the composition of uranium in the LArU−RuCp(CO)2 complex is lower than those of the LArU−FeCp(CO)2 and LArU−OsCp(CO)2 complexes. To further explore the bonding nature of U−M bonds, Mulliken charge, Mulliken spin density, and the natural electron configuration at the bimetallic centers in the three LArU−MCp(CO)2 complexes were calculated at the PBE/ ZORA/TZ2P level of theory. The Mulliken charge, spin density, and electron configuration on U and M atoms are listed in Table 2. It is clearly shown that the Mulliken atomic spin density on uranium and group 8 metal is approximately 2.8 and −0.1, respectively, which accords with the assignment of U(III) and M(0). This result is consistent with the analysis of the SOMOs. It should be noted that for all the metal−metal bonded compounds, charge transfer is a general phenomenon, which is helpful to understand the bonding nature. The Mulliken charge on the uranium center is 1.026, 1.280, and 1.117 for the LArU−FeCp(CO)2, LArU−RuCp(CO)2, and LArU−OsCp(CO)2 complexes, respectively, all of which are less than the formal oxidation state, III. The corresponding Mulliken charge is −0.461 (Fe), −0.610 (Ru) and −0.420

(Os), respectively. In addition, Mulliken charges for the isolated [MCp(CO)2]− fragment is −0.311(Fe), −0.213(Ru), and −0.240(Os), respectively, suggesting charge transfer from the transition metal to uranium atom, especially with a difference of 0.397 between the Ru Mulliken charges. As shown in Table 2, the valence occupancies of uranium atom for the three LArU−MCp(CO)2 complexes, mainly locate on the 5f, 6d, and 7s orbitals, and those of the corresponding transition metals mainly locate at the d and s orbitals, which reveal that these orbitals predominantly participate in the U− M bonds. The d occupancies of the transition metal slightly decrease from Fe and Ru to Os, and a reverse trend is found for the transition metal s orbitals. The natural electron configuration of uranium in the three LArU−MCp(CO)2 complexes is almost the same, which indicates that the valence electron occupancy of U is insensitive to transition metal atoms.

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U−M BONDING NATURE

QTAIM analysis focuses on the topology of electron density and also can quantify chemical concepts. The bonding interactions can be characterized and classified according to the properties of the electron density [(ρ(r)] and its Laplacian [∇2ρ(r)] at these BCPs. At a BCP, the gradient of ρ(r) is 0, while the Laplacian, ∇2ρ(r), is the sum of three eigenvalues of the density Hessian matrix. A positive Laplacian with ρ(r) < 0.10 au means a local depletion of charge with a “closed-shell” interaction, which is consistent with the feature of ionic bond. On the contrary, a negative ∇2ρ(r) value with ρ(r) > 0.20 au reflects a covalent bond. The total energy density H(r) can be used as another classification for a “closed-shell” interaction. H(r) = G(r) + V(r), where G(r) is the kinetic energy density and V(r) is the potential energy. Both the negative ∇2ρ(r) and H(r) values suggest obvious covalent bonds. In this case with slightly positive ∇2ρ(r), if H(r) is negative, then the bond is called dative or metallic. If H(r) is positive, then the bond is ionic or van der Waals. In addition, the value of −G(r)/V(r) may also be another indicator of covalent versus noncovalent interactions. −G(r)/V(r) > 1 shows noncovalent interaction, and −G(r)/V(r) < 0.5 means shared interaction. However, if 0.5< −G(r)/V(r) < 1, then the interaction is partly covalent.80 The calculated parameters at U−M BCPs are presented in Table 3. According to the relevant judgments of the BCPs in the literatures,46,81,82 the values of ρ(r) are about 0.05 with a D


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Organometallics

EDA was carried out to further examine the nature of the U−M bonds in the three LArU−MCp(CO)2 complexes. The LArU−MCp(CO)2 complexes are divided into two fragments, (LArU)+ and [MCp(CO)2]−. EDA is based on the transition state method, adapted by Morokuma and Kitaura.90,91 Thus, the interaction energy ΔEint is decomposed into three physically meaningful terms as follows:

positive Laplacian, indicating all the U−M bonds are predominantly “closed shell” interaction. The slight positive Laplacian (about 0.05) with a negative H(r) (about −0.01) at three U−M BCPs suggest that the U−M bonds are dative or metallic, which would be in line with the complex bearing U(III) and M(0) center. Furthermore, the −G(r)/V(r) value is about 0.65, suggesting that the U−M bonds are partly covalent in nature. The values of −G(r)/V(r) are about 0.75 at U−Ru BCPs for the [Cp3U−RuCp(CO)2], [(Tren)U−RuCp(CO)2], and [(Ts)(THF)U−RuCp(CO)2] complexes,35 which is larger than the corresponding value (0.665) for the LArU−RuCp(CO)2 complex. These results suggest that the covalency of U−Ru bonds in LArU(III)−RuCp(CO)2 is higher than those in [Cp3U(IV)−RuCp(CO)2], [(Tren)U(IV)−RuCp(CO)2], and [(Ts)(THF)U(IV)−RuCp(CO)2], probably due to the different valence state of uranium. Although for most actinide systems where 5f covalency is generally thought to increase with higher oxidation states,83−85 which may be due to the different type of bonds, such as uranium−metal bond, uranium main group bond. In addition, values of the electron localization function (ELF) at U−M BCPs are listed in Table 3 with the corresponding diagrams displayed in Figures 3 and S4. The ELF values fall in the range between 0 and 1.

ΔEint = ΔEelst + ΔE Pauli + ΔEoi

Here, ΔEelst is the electrostatic interaction between the two fragments as they are brought from infinite separation to their final positions in the combined molecule without any change in density. Furthermore, ΔEPauli (Pauli repulsion) represents the destabilizing interaction between the occupied orbitals on two fragments, respectively.92 It is customary to combine ΔEelst and ΔEPauli into the steric interaction energy as follow: ΔEsteric = ΔEelst + ΔE Pauli

Finally, the stabilizing orbital interaction term, ΔEoi, includes the electron pair bonding, charge transfer and orbital polarization due to metal−metal orbital overlap. The results obtained from EDA at the PBE/ZORA/TZ2P level of theory are presented in Table 4. The total bonding energy for the three LArU−MCp(CO)2 complexes becomes more and more negative from Ru and Fe to Os. For the LArU− RuCp(CO)2 complex, the absolute value of electrostatic interaction is higher than those of the LArU−FeCp(CO)2 and LArU−OsCp(CO)2 complexes, while the trend of the orbital interaction is converse. It should be clarified that the total bonding energy is not the net bonding between uranium and metal, while it reflects the relative stability of U−M bonds to a certain extent. In previous works, the Th−Ru bonding energy in the Cp*2(I)Th−RuCp(CO)2 complex at the PBE/ ZORA/TZ2P level of theory is −135 kcal/mol,46 and the U− Ru bonding energy of the homologous structures [(Tren)U− RuCp(CO)2], [(Ts)(THF)U−RuCp(CO)2], and [Cp3U− RuCp(CO)2] at BP86/ZORA/TZP level of theory is −115, −112, and −126 kcal/mol, respectively.35,46 The U−M (M = Fe, Ru, Os) bonding energies of the three LArU−MCp(CO)2 complexes at the PBE/ZORA/TZ2P level of theory are −154.27, −153.21, and −157.77 kcal/mol, respectively. In addition, in order to compare with previous works35,46,47 at the same level of theory, we also calculated the U−Ru bonding energy (−148.99 kcal/mol) of the LArU−RuCp(CO)2 complex at the BP86/ZORA/TZP level of theory. These results indicate that the stability of the U−M bonds in the three LArU−MCp(CO)2 complexes is higher than that of the An−Ru (An = Th, U) bonds in the Cp*2(I)Th−RuCp(CO)2, [(Tren)U−RuCp(CO)2], [(Ts)(THF)U−RuCp(CO)2], and [Cp3U−RuCp(CO)2] complexes, which is consistent with the bond order analysis. For the three U−M bonds, the electrostatic and orbital contributions reach about 65 and

Figure 3. Two-dimensional ELF contour on the U−Fe−N plane containing the U−Fe interaction of the LArU−FeCp(CO)2 complex.

ELF = 0 represents no localization of electron, while ELF = 1 shows a completely localized situation,67,68 which can give valuable information on chemical bonds.86−89 The ELF values (about 0.36−0.41) of U−M bonds for the LArU−MCp(CO)2 complexes indicate that the U−M bonds possess modest covalent character, which is consistent with the analysis of QTAIM.

Table 4. Total Bonding Energy (ΔEint, kcal/mol), Pauli Repulsion (ΔEPauli, kcal/mol), Electrostatic Interaction (ΔEelst, kcal/ mol), and Orbital Interactions (ΔEoi, kcal/mol) Obtained from Energy Decomposition Analysis at the PBE/ZORA/TZ2P Level of Theory species

ΔEint

ΔEPauli

ΔEelst

ΔEoi

%ΔEelst

%ΔEoi

LArU−FeCp(CO)2 LArU−RuCp(CO)2 LArU−OsCp(CO)2

−154.27 −153.21/−148.99a −157.77

139.94 141.56 138.39

−188.81 −192.65 −190.99

−105.40 −102.12 −105.17

64.18 65.36 64.49

35.82 34.64 35.51

a

The value obtained at the BP86/ZORA/TZP level of theory. E


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decreasing oxidation state of uranium, which differs from previous reports.83−85 Moreover, based on the analyses of bond order and EDA, the simulation results suggest that the strength of U−M bonds is probably dominated by the different valence state of uranium, while the ligands and metal center with the same valence state have little effect on the orbital contribution. Additionally, the three L Ar U−MCp(CO) 2 complexes are thermodynamically feasible according to the binding energies. With the exception of unsupported U−Fe and U−Ru bonds, complexes with direct heterobimetallic U− Os bond have not been reported experimentally. This work expands our knowledge of the unsupported uranium−metal bonding in the heterobimetallic complexes.

35%, respectively, indicating these bonds are mainly ionic. The U−Ru bonds in the [(Tren)U−RuCp(CO)2], [(Ts)(THF)U−RuCp(CO)2], and [Cp3U−RuCp(CO)2] complexes have about 26% orbital contribution at BP86/ZORA/TZP level of theory in previous work.35 The orbital interaction of U−M bonds in the three LArU(III)−MCp(CO)2 complexes is higher than those in the [(Tren)U(IV)−RuCp(CO)2], [(Ts)(THF)U(IV)−RuCp(CO)2], and [Cp3U(IV)−RuCp(CO)2], probably owing to the different valence states of uranium. The ligand has little effect for the orbital contribution of the U−M bonds. In addition, the orbital interaction of the Th−M (M = Fe, Ru, Os) bonds in the [Cp 2 Th(IV)−MCp(CO) 2 ] + complexes contributes 23−25% of the total bonding energy at the BP86/ZORA/TZ2P level of theory,47 and the Th−Ru orbital contribution for the Cp*2(I)Th(IV)−RuCp(CO)2 complex is 27% at the PBE/ZORA/TZ2P level of theory.46 Unlike the expected, these results indicate that these 3d, 4d, and 5d metal centers in the same valence state make similar contributions to the covalency of the U−M bond.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.8b00391.

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Total electronic energy, U−Fe bond distance and bond order, the binding energy, diagrams of molecular orbital and ELF for the three LArU−MCp(CO)2 (M = Fe, Ru, and Os) complexes (PDF)

THERMODYNAMICS The binding energy is defined as ΔBE = G(LArU−MCp(CO)2 ) − G([LArU]+ )

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− G([MCp(CO)2 ]− )

where G is the Gibbs free energy (Table S4). The binding energies for these three LArU−MCp(CO)2 complexes in the gas and toluene solution are listed in Table 5. It shows that all

Corresponding Author

*E-mail: [email protected]. Tel.: 86-10-88233968. ORCID

Wei-Qun Shi: 0000-0001-9929-9732

Ar

Table 5. Binding Energy (ΔBE, kcal/mol) of the L U− MCp(CO)2 Complexes in the Gas Phase and Toluene Solution at the PBE/6-311G(d, p)/RECP-SEG Level of Theory reactions Ar

+

−

Ar

[L U] + [FeCp(CO)2] = L U−FeCp(CO)2 [LArU]+ + [RuCp(CO)2]− = LArU−RuCp(CO)2 [LArU]+ + [OsCp(CO)2]− = LArU−OsCp(CO)2

ΔBEgas

ΔBEtoluene

−87.69 −85.54 −91.02

−37.60 −36.89 −41.73

AUTHOR INFORMATION

Author Contributions

X.-W.C. and Q.-Y.W. contributed equally to this work. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (Grant Nos. 21477130, 21471152, 11875058), the Major Program of National Natural Science Foundation of China (21790373) and the Science Challenge Project (TZ2016004). The results described in this work were obtained on the ScGrid of Supercomputing Center, Computer Network Information Center of Chinese Academy of Sciences.

values of the binding energies are negative and similar, indicating that the LArU−RuCp(CO)2 and LArU−OsCp(CO)2 complexes are thermodynamically feasible. Since the unsupported U−Fe and U−Ru complexes have been experimentally obtained,22,24,35,36 and the U−Os bond shows similar properties and strength to U−Fe and U−Ru bonds, we conclude that complexes containing U−Os bond are also available under certain conditions.

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REFERENCES

(1) Cotton, F. A.; Curtis, N. F.; Harris, C. B.; Johnson, B. F. G.; Lippard, S. J.; Mague, J. T.; Robinson, W. R.; Wood, J. S. Mononuclear and Polynuclear Chemistry of Rhenium (III): Its Pronounced Homophilicity. Science 1964, 145, 1305−1307. (2) Sevin, A.; Hengtai, Y.; Chaquin, P. Theoretical semi-empirical study of concerted oxidative additions to dinuclear complexes. J. Organomet. Chem. 1984, 262, 391−405. (3) Wheatley, N.; Kalck, P. Structure and Reactivity of Earlyminus signLate Heterobimetallic Complexes. Chem. Rev. 1999, 99, 3379− 3420. (4) Gade, L. H. Highly polar metal−metal bonds in “early−late” Heterodimetallic complexes. Angew. Chem., Int. Ed. 2000, 39, 2658− 2678. (5) Ritleng, V.; Chetcuti, M. J. Hydrocarbyl ligand transformations on heterobimetallic complexes. Chem. Rev. 2007, 107, 797−858. (6) Cooper, B. G.; Napoline, J. W.; Thomas, C. M. Catalytic applications of early/late heterobimetallic complexes. Catal. Rev.: Sci. Eng. 2012, 54, 1−40.

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CONCLUSION In summary, we have systematically studied the structures of the heterobimetallic uranium and group 8 elements in the three LArU−MCp(CO)2 (M = Fe, Ru, Os) complexes and the bonding nature of U−M bonds using scalar-relativistic density functional theory. MO analyses suggest that the electron configuration of the three LArU−MCp(CO)2 complexes is 5f3, and the strong polarized interactions occur between U and M. These U−M bond orders are close to 1.0 indicating a significant single-bond feature. Moreover, the three U−M bonds are predominantly “closed shell” interaction and are confirmed to be dominated by ionic interaction with minor covalent character based on QTAIM analysis. It is worth noting that the covalency of the U−M bonds increases with F


Article

Organometallics (7) Bodio, E.; Picquet, M.; Le Gendre, P. “Early−Late” Heterobimetallic Catalysis and Beyond. In Homo-and Heterobimetallic Complexes in Catalysis; Springer, 2015; pp 139−186. (8) Powers, I. G.; Uyeda, C. Metal−metal bonds in catalysis. ACS Catal. 2017, 7, 936−958. (9) Sculfort, S.; Braunstein, P. Intramolecular d10−d10 interactions in heterometallic clusters of the transition metals. Chem. Soc. Rev. 2011, 40, 2741−2760. (10) Yam, V. W.-W.; Au, V. K.-M.; Leung, S. Y.-L. Light-emitting self-assembled materials based on d8 and d10 transition metal complexes. Chem. Rev. 2015, 115, 7589−7728. (11) Shieh, M.; Yu, C.-C.; Miu, C.-Y.; Kung, C.-H.; Huang, C.-Y.; Liu, Y.-H.; Liu, H.-L.; Shen, C.-C. Semiconducting Coordination Polymers Based on the Pre-Designed Ternary Te-Fe-Cu Carbonyl Cluster and Conjugation-Interrupted Dipyridyl Linkers. Chem. - Eur. J. 2017, 23, 11261−11271. (12) Powers, D. C.; Hwang, S. J.; Anderson, B. L.; Yang, H.; Zheng, S.-L.; Chen, Y.-S.; Cook, T. R.; Gabbaï, F. P.; Nocera, D. G. Stereoelectronic Effects in Cl2 Elimination from Binuclear Pt (III) Complexes. Inorg. Chem. 2016, 55, 11815−11820. (13) Corcos, A. R.; Pap, J. z. S.; Yang, T.; Berry, J. F. A Synthetic Oxygen Atom Transfer Photocycle from a Diruthenium Oxyanion Complex. J. Am. Chem. Soc. 2016, 138, 10032−10040. (14) Das, A.; Reibenspies, J. H.; Chen, Y.-S.; Powers, D. C. Direct Characterization of a Reactive Lattice-Confined Ru2 Nitride by Photocrystallography. J. Am. Chem. Soc. 2017, 139, 2912−2915. (15) Cotton, F. A.; Murillo, C. A.; Walton, R. A. Multiple Bonds between Metal Atoms; Springer Science & Business Media, 2005. (16) Lindahl, P. A. Metal−metal bonds in biology. J. Inorg. Biochem. 2012, 106, 172−178. (17) Herberhold, M.; Jin, G. X. Heterodimetallic Complexes with an Unbridged, Polar Metal−Metal Bond. Angew. Chem., Int. Ed. Engl. 1994, 33, 964−966. (18) Liddle, S. T. Molecular Metal−Metal Bonds: Compounds, Synthesis, Properties; John Wiley & Sons, 2015. (19) Rookes, T.; Wildman, E.; Balazs, G.; Gardner, B.; Wooles, A.; Gregson, M.; Tuna, F.; Scheer, M.; Liddle, S. T. Electron-Precise Actinide-Pnictide (An−Pn) Bonds Spanning Non-Metal, Metalloid, and Metal Combinations (An = U, Th; Pn = P, As, Sb, Bi). Angew. Chem., Int. Ed. 2018, 57, 1332−1336. (20) Sternal, R. S.; Brock, C. P.; Marks, T. J. Metal-metal bonds involving actinides. Synthesis and characterization of a complex having an unsupported actinide to transition metal bond. J. Am. Chem. Soc. 1985, 107, 8270−8272. (21) Porchia, M.; Casellato, U.; Ossola, F.; Rossetto, G.; Zanella, P.; Graziani, R. Synthesis and crystal structure of triscyclopentadienyl (triphenyltin) uranium. The first example of a uranium−tin bond. J. Chem. Soc., Chem. Commun. 1986, 1034−1035. (22) Sternal, R. S.; Marks, T. J. Actinide-to-transition metal bonds. Synthesis, characterization, and properties of metal-metal bonded systems having the tris (cyclopentadienyl) actinide fragment. Organometallics 1987, 6, 2621−2623. (23) Sternal, R. S.; Sabat, M.; Marks, T. J. Metal-metal bonds involving actinides. Functionalization of activated carbon-hydrogen bonds and unusual oligomerization chemistry mediated by a thoriumruthenium complex. J. Am. Chem. Soc. 1987, 109, 7920−7921. (24) Nolan, S. P.; Porchia, M.; Marks, T. J. Organo-f-element thermochemistry. Actinide-group 14 element and actinide-transitionelement bond disruption enthalpies and stoichiometric/catalytic chemical implications thereof in heterobimetallic tris (cyclopentadienyl) uranium (IV) compounds. Organometallics 1991, 10, 1450− 1457. (25) Minasian, S. G.; Krinsky, J. L.; Williams, V. A.; Arnold, J. A Heterobimetallic Complex With an Unsupported Uranium (III)− Aluminum (I) Bond:(CpSiMe3) 3U− AlCp*(Cp*= C5Me5). J. Am. Chem. Soc. 2008, 130, 10086−10087. (26) Liddle, S. T.; McMaster, J.; Mills, D. P.; Blake, A. J.; Jones, C.; Woodul, W. D. σ and π donation in an unsupported uranium−gallium bond. Angew. Chem., Int. Ed. 2009, 48, 1077−1080.

(27) Roesky, P. W. Compounds with low-valent group 13 metals as ligands for electron poor main group and transition metals. Dalton Trans 2009, 1887−1893. (28) Gardner, B. M.; Mcmaster, J.; Lewis, W.; Liddle, S. T. Synthesis and structure of [{N(CH2CH2NSiMe3)3}URe(η5-C5H5)2]: a heterobimetallic complex with an unsupported uranium−rhenium bond. Chem. Commun. 2009, 17, 2851−2853. (29) Liddle, S. T.; Mills, D. P. Metal−metal bonds in f-element chemistry. Dalton Trans 2009, 5592−5605. (30) Minasian, S. G.; Krinsky, J. L.; Rinehart, J. D.; Copping, R.; Tyliszczak, T.; Janousch, M.; Shuh, D. K.; Arnold, J. A Comparison of 4 f vs 5 f Metal− Metal Bonds in (CpSiMe3) 3M− ECp*(M= Nd, U; E= Al, Ga; Cp*= C5Me5): Synthesis, Thermodynamics, Magnetism, and Electronic Structure. J. Am. Chem. Soc. 2009, 131, 13767−13783. (31) Gardner, B. M.; Mcmaster, J.; Moro, F.; Lewis, W.; Blake, A. J.; Liddle, S. T. An Unsupported Uranium-Rhenium Complex Prepared by Alkane Elimination. Chem. - Eur. J. 2011, 17, 6909−6912. (32) Patel, D.; King, D. M.; Gardner, B. M.; Mcmaster, J.; Lewis, W.; Blake, A. J.; Liddle, S. T. Structural and theoretical insights into the perturbation of uranium-rhenium bonds by dative Lewis base ancillary ligands. Chem. Commun. 2011, 47, 295−297. (33) Patel, D.; Moro, F.; Mcmaster, J.; Lewis, W.; Blake, A. J.; Liddle, S. T. A formal high oxidation state inverse-sandwich diuranium complex: a new route to f-block-metal bonds. Angew. Chem., Int. Ed. 2011, 50, 10388−10392. (34) Winston, M. S.; Batista, E. R.; Yang, P.; Tondreau, A. M.; Boncella, J. M. Extending Stannyl Anion Chemistry to the Actinides: Synthesis and Characterization of a Uranium−Tin Bond. Inorg. Chem. 2016, 55, 5534−5539. (35) Gardner, B. M.; Patel, D.; Cornish, A. D.; Mcmaster, J.; Lewis, W.; Blake, A. J.; Liddle, S. T. The Nature of Unsupported Uranium− Ruthenium Bonds: A Combined Experimental and Theoretical Study. Chem. - Eur. J. 2011, 17, 11266−11273. (36) Fortier, S.; Aguilarcalderón , J. R.; Vlaisavljevich, B.; Mettamagaña, A. J.; Goos, A. G.; Botez, C. E. An N-Tethered Uranium(III) Arene Complex and the Synthesis of an Unsupported U−Fe Bond. Organometallics 2017, 36, 4591−4599. (37) Pepper, M.; Bursten, B. E. Ab initio studies of the electronic structure of the diuranium molecule. J. Am. Chem. Soc. 1990, 112, 7803−7804. (38) Roos, B. O.; Malmqvist, P. A.; Gagliardi, L. Exploring the Actinide−Actinide Bond: Theoretical Studies of the Chemical Bond in Ac2, Th2, Pa2, and U2. J. Am. Chem. Soc. 2006, 128, 17000− 17006. (39) Wu, X.; Lu, X. Dimetalloendofullerene U(2)@C(60) has a U− U multiple bond consisting of sixfold one-electron-two-center bonds. J. Am. Chem. Soc. 2007, 129, 2171−2177. (40) Infante, I.; Gagliardi, L.; Scuseria, G. E. Is Fullerene C60 Large Enough to Host a Multiply Bonded Dimetal? J. Am. Chem. Soc. 2008, 130, 7459−7465. (41) Wang, C. Z.; Gibson, J. K.; Lan, J. H.; Wu, Q. Y.; Zhao, Y. L.; Li, J.; Chai, Z. F.; Shi, W. Q. Actinide (An = Th-Pu) dimetallocenes: promising candidates for metal-metal multiple bonds. Dalton Trans 2015, 44, 17045−17053. (42) Su, D. M.; Zheng, X. J.; Schreckenbach, G.; Pan, Q. J. Highly Diverse Bonding between Two U3+ Ions When Ligated by a Flexible Polypyrrolic Macrocycle. Organometallics 2015, 34, 5225−5232. (43) Hu, H. S.; Kaltsoyannis, N. The shortest Th-Th distance from a new type of quadruple bond. Phys. Chem. Chem. Phys. 2017, 19, 5070−5076. (44) Zhang, X.; Wang, Y.; Moralesmartínez, R.; Zhong, J.; de Graaf, C.; Rodríguezfortea, A.; Poblet, J. M.; Echegoyen, L.; Feng, L.; Chen, N. U2@Ih(7)-C80: Crystallographic Characterization of a LongSought Dimetallic Actinide Endohedral Fullerene. J. Am. Chem. Soc. 2018, 140, 3907−3915. (45) Diaconescu, P. L.; Odom, A. L.; Agapie, T.; Cummins, C. C. Uranium− Group 14 Element Single Bonds: Isolation and Characterization of a Uranium (IV) Silyl Species. Organometallics 2001, 20, 4993−4995. G


Article

Organometallics (46) Vlaisavljevich, B.; Miró, P.; Cramer, C. J.; Gagliardi, L.; Infante, I.; Liddle, S. T. On the nature of actinide- and lanthanide-metal bonds in heterobimetallic compounds. Chem. - Eur. J. 2011, 17, 8424−8433. (47) Canterolópez, P.; Le Bras, L.; Páezhernández, D.; Arratiaperez, R. The role of the [CpM(CO)2]- Chromophore in the Optical properties of the [Cp2ThMCp(CO)2]+ complexes, where M = Fe, Ru and Os. Theoretical View. Dalton Trans 2015, 44, 20004−20010. (48) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865−3868. (49) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, O.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09, revision D.01; Gaussian, Inc.: Wallingford, CT, 2009. (50) Fonseca Guerra, C.; Snijders, J. G.; te Velde, G.; Baerends, E. J. Towards an order-N DFT method. Theor. Chem. Acc. 1998, 99, 391− 403. (51) te Velde, G.; Bickelhaupt, F. M.; Baerends, E. J.; Fonseca Guerra, C.; van Gisbergen, S. J. A.; Snijders, J. G.; Ziegler, T. Chemistry with ADF. J. Comput. Chem. 2001, 22, 931−967. (52) Küchle, W.; Dolg, M.; Stoll, H.; Preuss, H. Energy-adjusted pseudopotentials for the actinides. Parameter sets and test calculations for thorium and thorium monoxide. J. Chem. Phys. 1994, 100, 7535− 7542. (53) Cao, X.; Dolg, M.; Stoll, H. Valence basis sets for relativistic energy-consistent small-core actinide pseudopotentials. J. Chem. Phys. 2003, 118, 487−496. (54) Cao, X.; Dolg, M. Segmented contraction scheme for smallcore actinide pseudopotential basis sets. J. Mol. Struct.: THEOCHEM 2002, 581, 139−147. (55) Lan, J. H.; Shi, W. Q.; Yuan, L. Y.; Li, J.; Zhao, Y. L.; Chai, Z. F. Recent advances in computational modeling and simulations on the An(III)/Ln(III) separation process. Coord. Chem. Rev. 2012, 256, 1406−1417. (56) Wang, C. Z.; Lan, J. H.; Zhao, Y.-L.; Chai, Z. F.; Wei, Y. Z.; Shi, W. Q. Density Functional Theory Studies of UO22+ and NpO2+ Complexes with Carbamoylmethylphosphine Oxide Ligands. Inorg. Chem. 2013, 52, 196−203. (57) Wu, Q. Y.; Lan, J. H.; Wang, C. Z.; Xiao, C. L.; Zhao, Y. L.; Wei, Y. Z.; Chai, Z. F.; Shi, W. Q. Understanding the Bonding Nature of Uranyl Ion and Functionalized Graphene: A Theoretical Study. J. Phys. Chem. A 2014, 118, 2149−2158. (58) Wu, Q. Y.; Lan, J. H.; Wang, C. Z.; Zhao, Y. L.; Chai, Z. F.; Shi, W. Q. Terminal U≡E (E = N, P, As, Sb, and Bi) Bonds in Uranium Complexes: A Theoretical Perspective. J. Phys. Chem. A 2015, 119, 922−930. (59) Hay, P. J.; Wadt, W. R. Ab initio effective core potentials for molecular calculations. Potentials for K to Au including the outermost core orbitals. J. Chem. Phys. 1985, 82, 299−310. (60) Ehlers, A. W.; Böhme, M.; Dapprich, S.; Gobbi, A.; Höllwarth, A.; Jonas, V.; Köhler, K. F.; Stegmann, R.; Veldkamp, A.; Frenking, G. A set of f-polarization functions for pseudo-potential basis sets of the transition metals Sc-Cu, Y-Ag and La-Au. Chem. Phys. Lett. 1993, 208, 111−114. (61) Roy, L. E.; Hay, P. J.; Martin, R. L. Revised Basis Sets for the LANL Effective Core Potentials. J. Chem. Theory Comput. 2008, 4, 1029−1031.

(62) Hay, P. J.; Wadt, W. R. Ab initio effective core potentials for molecular calculations. Potentials for the transition metal atoms Sc to Hg. J. Chem. Phys. 1985, 82, 270−283. (63) Wadt, W. R.; Hay, P. J. Ab initio effective core potentials for molecular calculations. Potentials for main group elements Na to Bi. J. Chem. Phys. 1985, 82, 284−298. (64) Werner, H. J.; Knowles, P. J.; Knizia, G.; Manby, F. R.; Schütz, M. Molpro: a general-purpose quantum chemistry program package. WIREs. Comput. Mol. Sci. 2012, 2, 242−253. (65) Werner, H.-J.; Knowles, P. J.; Knizia, G.; Manby, F. R.; Schütz, M. MOLPRO, a package of ab initio programs, version 2015.1; Molpro, 2015. http://www.molpro.net. (66) Bader, R. F. W. Bond Paths are Not Chemical Bonds. J. Phys. Chem. A 2009, 113, 10391−10396. (67) Becke, A. D.; Edgecombe, K. E. A simple measure of electron localization in atomic and molecular systems. J. Chem. Phys. 1990, 92, 5397−5403. (68) Savin, A.; Nesper, R.; Wengert, S.; Fässler, T. F. ELF: The Electron Localization Function. Angew. Chem., Int. Ed. Engl. 1997, 36, 1808−1832. (69) Bader, R. F. W. A Bond Path: A Universal Indicator of Bonded Interactions. J. Phys. Chem. A 1998, 102, 7314−7323. (70) Lu, T.; Chen, F. Multiwfn: A multifunctional wavefunction analyzer. J. Comput. Chem. 2012, 33, 580−592. (71) Pyykkö, P.; Atsumi, M. Molecular single-bond covalent radii for elements 1−118. Chem. - Eur. J. 2009, 15, 186−197. (72) Cordero, B.; Gomez, V.; Platero-Prats, A. E.; Reves, M.; Echeverria, J.; Cremades, E.; Barragan, F.; Alvarez, S. Covalent radii revisited. Dalton Trans 2008, 21, 2832−2838. (73) Mayer, I. Charge, bond order and valence in the AB initio SCF theory. Chem. Phys. Lett. 1983, 97, 270−274. (74) Nalewajski, R. F.; Mrozek, J. Modified valence indices from the two-particle density matrix. Int. J. Quantum Chem. 1994, 51, 187−200. (75) Nalewajski, R. F.; Mrozek, J.; Michalak, A. Two-electron valence indices from the Kohn-Sham orbitals. Int. J. Quantum Chem. 1997, 61, 589−601. (76) Bart, S. C.; Heinemann, F. W.; Anthon, C.; Hauser, C.; Meyer, K. A new tripodal ligand system with steric and electronic modularity for uranium coordination chemistry. Inorg. Chem. 2009, 48, 9419− 9426. (77) La Pierre, H. S.; Scheurer, A.; Heinemann, F. W.; Hieringer, W.; Meyer, K. Synthesis and characterization of a uranium(II) monoarene complex supported by δ backbonding. Angew. Chem., Int. Ed. 2014, 53, 7158−7162. (78) Eisenhart, R. J.; Rudd, P. A.; Planas, N.; Boyce, D. W.; Carlson, R. K.; Tolman, W. B.; Bill, E.; Gagliardi, L.; Lu, C. C. Pushing the Limits of Delta Bonding in Metal-Chromium Complexes with Redox Changes and Metal Swapping. Inorg. Chem. 2015, 54, 7579. (79) Dunn, P. L.; Carlson, R. K.; Gagliardi, L.; Tonks, I. A. Structure and bonding of group 4-nickel heterobimetallics supported by 2(diphenylphosphino)pyrrolide ligands. Dalton Trans 2016, 45, 9892. (80) Ziółkowski, M.; Grabowski, S. J.; Leszczynski, J. Cooperativity in hydrogen-bonded interactions: ab initio and “atoms in molecules” analyses. J. Phys. Chem. A 2006, 110, 6514−6521. (81) Cremer, D.; Kraka, E. Chemical Bonds without Bonding Electron Density  Does the Difference Electron-Density Analysis Suffice for a Description of the Chemical Bond? Angew. Chem., Int. Ed. Engl. 1984, 23, 627−628. (82) Bianchi, R.; Gervasio, G.; Marabello, D. Experimental electron density analysis of Mn2(CO)10: metal-metal and metal-ligand bond characterization. Inorg. Chem. 2000, 39, 2360−2366. (83) Lukens, W. W.; Edelstein, N. M.; Magnani, N.; Hayton, T. W.; Fortier, S.; Seaman, L. A. Quantifying the σ and π Interactions between U(V) f Orbitals and Halide, Alkyl, Alkoxide, Amide and Ketimide Ligands. J. Am. Chem. Soc. 2013, 135, 10742−10754. (84) Kaltsoyannis, N. Does covalency increase or decrease across the actinide series? Implications for minor actinide partitioning. Inorg. Chem. 2013, 52, 3407−3413. H


Article

Organometallics (85) Neidig, M. L.; Clark, D. L.; Martin, R. L. Covalency in felement complexes. Coord. Chem. Rev. 2013, 257, 394−406. (86) Silvi, B.; Savin, A. Classification of chemical bonds based on topological analysis of electron localization functions. Nature 1994, 371, 683−686. (87) Atanasov, M.; Daul, C. A.; Fowe, E. P. Chemical bonding in molecules and complexes containing d-elements based on DFT. Monatsh. Chem. 2005, 136, 925−963. (88) Petit, L.; Joubert, L.; Maldivi, P.; Adamo, C. A comprehensive theoretical view of the bonding in actinide molecular complexes. J. Am. Chem. Soc. 2006, 128, 2190−2191. (89) Di Santo, E.; Michelini, M. d. C.; Russo, N. Methane C− H bond activation by gas-phase Th+ and U+: reaction mechanisms and bonding analysis. Organometallics 2009, 28, 3716−3726. (90) Morokuma, K. Molecular orbital studies of hydrogen bonds. III. C= O··· H−O hydrogen bond in H2CO··· H2O and H2CO··· 2H2O. J. Chem. Phys. 1971, 55, 1236−1244. (91) Kitaura, K.; Morokuma, K. A new energy decomposition scheme for molecular interactions within the Hartree-Fock approximation. Int. J. Quantum Chem. 1976, 10, 325−340. (92) Ziegler, T.; Rauk, A. On the calculation of bonding energies by the Hartree Fock Slater method. Theor. Chim. Acta 1977, 46, 1−10.

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