A Theoretical Study on Divalent Heavier Group 14 Complexes as

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

pubs.acs.org/Organometallics

A Theoretical Study on Divalent Heavier Group 14 Complexes as Promising Donor Ligands for Building Uranium−Metal Bonds Xiao-Wang Chi,†,‡,∥ Qun-Yan Wu,‡,∥ Jian-Hui Lan,‡ Cong-Zhi Wang,‡ Qin Zhang,† Zhi-Fang Chai,‡,§ and Wei-Qun Shi*,‡ †

College of Mining, Guizhou University, Guiyang, 550025, China Laboratory of Nuclear Energy Chemistry, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China § Engineering Laboratory of Advanced Energy Materials, Ningbo Institute of Industrial Technology, Chinese Academy of Sciences, Ningbo, Zhejiang, 315201, China Organometallics Downloaded from pubs.acs.org by ALBRIGHT COLG on 05/01/19. For personal use only.

‡

S Supporting Information *

ABSTRACT: The study of metal−metal bonds is one of the important challenges in organometallic chemistry and of great significance in applied and structural chemistry. We built a series of potential complexes (CpSiMe3)3U-E(NCHMes)2 (E = Si, Ge, Sn, Pb) by constructing two neutral fragments [(CpSiMe3)3U] and [E(NCHMes)2] and investigated their structures with scalar-relativistic theoretical calculations. U−E bonds possess highly polarized U−E interactions and also strong donor−acceptor interactions according to the analyses of MO (molecular orbital), natural charge, QTAIM (quantum theory of atoms in molecules), and ELF (electron localization function). Particularly, the four U−E bonds are mainly composed of U 6d orbitals and E ns orbital, which lead to the nature of donor−acceptor interaction between U and E atoms. These bonds are significantly different from the general uranium−transition-metal and uranium−main-group bonds, Moreover, the U−E bond strengths in the (CpSiMe3)3UE(NCHMes)2 complexes follow the trend of U−Si > U−Sn > U−Ge > U−Pb according to the results of bond orders and EDA (energy decomposed analysis). The binding energies suggest that the four (CpSiMe3)3U-E(NCHMes)2 complexes are thermodynamically accessible. This work indicates that the divalent heavier group 14 complexes are promising donor ligands for building unsupported uranium−metal bonds.

■

INTRODUCTION Since the Re−Re bond was reported,1 the research of metal− metal bonds has become a hot and challenging topic in the field of organometallic chemistry and is of great significance in applied and structural chemistry. The synthesis of unsupported metal−metal bonds is more challenging than the construction of supported metal−metal bonds with bridging ligands.2−5 Research on metal−metal bonds has almost spread throughout the periodic table of elements. Recently, much progress has been made with respect to unsupported metal−metal bonds, such as main-group metals, alkali metals, transition metals, and rareearth metals.6 This regards especially the 5f-element complexes containing actinide−transition-metal (An−M) bonds7−18 and actinide−main-group (An−E) bonds.11,19−32 Some actinide− actinide (An−An)33−41 and An−M bonds42−44 have also been investigated theoretically. For instance, Gagliardi and coworkers explored the bonding nature of actinide− and lanthanide−metal (Ln−M) bonds in heterobimetallic complexes with the DFT method and revealed that the ionic interaction primarily dominates An−M and Ln−M bonds.42 © XXXX American Chemical Society

Recently, we investigated the nature of U−M bonds using the PBE method and showed that the covalency of U(III)−M bonds is higher than that of U(IV)−M bonds.44 The complexes containing An−M bonds have been principally achieved through metathesis or by exploiting coordinative unsaturation.45 The previously reported organoactinide complexes are mainly obtained combining the actinide fragment and the metal fragment by the method of salt or alkane elimination.8,9,11−15,18−20,22,26,30,31 For instance, Porchia et al. reported the first crystal structure [Cp3U-SnPh3] with a U−Sn bond.19 Subsequently, they also obtained the complex [Cp3USiPh3)] with a direct U−Si bond by the reaction of [Cp3UCl] and Li(SiPh3).21 However, complexes (CpSiMe3)3U-MCp* (M = Al, Ga; Cp* = C5Me5) are directly combined with two fragments.25,27 The U(III) atom in the [(CpSiMe3)3U] fragment possesses unoccupied 5f/6d orbitals, which act as electron acceptors. As a donor ligand, Cp*M is a Lewis base Received: January 29, 2019

A

DOI: 10.1021/acs.organomet.9b00059 Organometallics XXXX, XXX, XXX−XXX

Organometallics

■

because the metal atom has a pair of electrons, which is formally isolobal with singlet carbene,46 and the singlet N-heterocyclic carbene complexes of uranium(III) have been reported.23,24 Heavier analogues of singlet carbene are divalent silylenes, germylenes, stannylenes, and plumbylenes, which also possess strong electron donating properties. Most of the isolated metallylenes have “singlet” ground electronic states with the (ns)2(np)2 configuration.47 There are several reports on the direct bonding of uranium and group 14 elements, such as U−C,23,24 U−Si,11,21,22 U− Ge,11,20 and U−Sn11,19,30 bonds, and Cummins et al. reported theoretical calculations for the simplified structures [H3EU(NH2)3] (E = C, Si, Ge, Sn).22 However, the organoactinide complexes obtained by exploiting coordinative unsaturation are still rare. Because [(CpSiMe3)3U] acts as electron acceptor and heavy carbene has a strong electron donating ability, we attempt to construct the potential complexes containing the unsupported uranium−group 14 metal bonds from a theoretical perspective. Generally, the substituents, tertbutyl, 2,6-iPr2C6H3, and 1,3,5-Me3C6H2 (Mes), can stabilize heavy carbene.48 Considering the steric effect of these substituents and the computational demands, we selected a heavy carbene ligand modified by the substituent Mes to construct actinide−metal bonds. Herein, we theoretically investigated the electronic structures, bonding nature, and thermodynamic properties of the (CpSiMe3)3U-E(NCHMes)2 (E = Si, Ge, Sn, Pb) complexes (Scheme 1). This work expands the knowledge on the organoactinide complexes bearing unsupported U−E bonds and paves the way for synthesizing a series of uranium-group 14 complexes.

Article

CALCULATIONAL DETAILS

Kohn−Sham DFT49,50 calculations were performed to explore the electronic structures of the (CpSiMe3)3U-E(NCHMes)2 (E = Si, Ge, Sn, Pb) complexes. The optimizations and the corresponding harmonic vibrational frequencies for the (CpSiMe3)3U-E(NCHMes)2 complexes were carried out with the generalized gradient approximation (GGA) with the pure PBE exchange-correlation method51 using the Gaussian 09 program.52 In general, the PBE method can obtain reliable structures and energies for the heterobimetallic complexes.42 In addition, the B3LYP functional53,54 can evaluate the U−E bonding character in the (CpSiMe3)3U-E(NCHMes)2 complexes, and the hybrid functionals can give more accurate energies than GGA ones.55 The uranium atom used the scalar-relativistic ECP60MWB and the corresponding ECP60MWB-SEG valence basis set,56−58 which provides reliable calculations for actinide complexes.59−64 The LANL08d basis set with effective core potential was applied for Ge, Sn, and Pb.65−68 And the basis set, 6-31G(d), was applied for H, C, N, and Si atoms. To confirm the ground states of the (CpSiMe3)3U-E(NCHMes)2 complexes, four electronic states (2, 4, 6, 8) for each (CpSiMe3)3U-E(NCHMes)2 complex were considered and their electronic energies with PBE and B3LYP functionals are listed in Table S1. It shows that the quartet electronic state is the ground state for the four complexes with both functionals. Moreover, we also found that the energy of the triplet state for the [E(NCHMes)2] monomer is higher than that of the singlet state using PBE and B3LYP methods (Table S2) and revealed that the singlet is the ground state for each monomer. A solvation model based on the density (SMD) model69 was taken into account, and toluene was taken as the solvent. Considering dispersion effects, the electron energies for the (CpSiMe3)3U-E(NCHMes)2 complexes were carried out using Grimme’s DFT-D370−72 with the 6-311G(d, p) basis set in gas phase and toluene solution; the calculated Gibbs free energies were included in the thermal energy correction obtained in the gas phase. Fragment calculations were performed using the ADF2013.01 quantum chemistry code,73 which supplied an energetic decomposition between two fragments. In addition, NBO (natural bond orbital)74 was carried out to explore the interaction between uranium and group 14 atoms in the (CpSiMe3)3U-E(NCHMes)2 complexes. Scalar-relativistic effects employing the zeroth-order regular approximation (ZORA)75 Hamiltonian approach were used. The Slater-type orbital (STO) all-electron basis set, TZ2P,76 was applied for all atoms. Furthermore, the topological analysis for the (CpSiMe3)3U-E(NCHMes)2 complexes was explored with the QTAIM method (quantum theory of atoms in molecules),77,78 which provides useful information on the bonding nature of chemical bonds. Electron localization function (ELF)79−81 and QTAIM were performed using Multiwfn software.82

Scheme 1. Structures of the (CpSiMe3)3U-E(NCHMes)2 (E = Si, Ge, Sn, Pb) Complexes

■

MOLECULAR AND ELECTRONIC STRUCTURES Table 1 presents the geometrical properties of the ground state (CpSiMe3)3U-E(NCHMes)2. Spin contamination for the four structures is negligible with the value of ⟨S2⟩ is close to 3.75. The calculated distance of the U−Si bond is 2.993 Å, which is comparable to the experimental value of 3.0913 Å reported by Cummins and co-workers.22 Moreover, they also theoretically studied electronic structures of the representative model molecules H3E-U(NH2)3 (E = C, Si, Ge, Sn) and obtained U−E bond distances at the PW91/ZORA/V level of theory with Table 1. Spin Contamination ⟨S2⟩ and Bond Distance (Å) for the Ground State (CpSiMe3)3U-E(NCHMes)2 ([U-E], E = Si, Ge, Sn, Pb) Complexes, Delocalization Indices (δ) for U−E Bonds at the PBE/6-31G(d)/RECP-SEG/LANL08d Level of Theory, and Calculated U−E Bond Orders at the B3LYP/ZORA/TZ2P Level of Theory complexes

⟨S2⟩

bond distance

WBO

MBO

GJBO

NMBO

δ

[U-Si] [U-Ge] [U-Sn] [U-Pb]

3.766 3.766 3.766 3.767

2.993 3.079 3.172 3.242

0.817 0.739 0.766 0.654

0.590 0.474 0.538 0.371

0.739 0.617 0.670 0.525

1.049 0.878 0.954 0.759

0.525 0.442 0.483 0.339

B


Article

Organometallics

the HOMO, U−Sn and U−Pb bonds are only σ character according to the NBO analysis as discussed below. U−Sn and U−Pb bonds in the complexes (CpSiMe3)3U-E(NCHMes)2 are different from the U−Ga bond with σ and π character in [(trenTMS)U-Ga(NArCH)2(thf)],26 probably due to the different oxidation state of U. To elucidate the U−E chemical bonding, a qualitative MO correlation diagram between the fragments (CpSiMe3)3U and Ge(NCHMes)2 in the complex (CpSiMe3)3U-Ge(NCHMes)2 as a model is presented in Figure 1. The HOMO diagram in the (CpSiMe3)3U-Ge(NCHMes)2

the values of 2.432, 2.992, 3.018, and 3.202 Å, respectively.22 The calculated U−Sn bond distance (3.172 Å) in the (CpSiMe3)3U-Sn(NCHMes)2 complex is very close to that (3.166 Å) of the [Cp3U-SnPh3] crystal structure,19 and somewhat shorter than that (3.3130(3) Å) in the N(CH2CH2NSi(iPr)3)3U-SnMe3 complex characterized by X-ray diffraction.30 There are no available experimental values for the U−Ge and U−Pb bond distances. The calculated U−Ge and U−Pb bond distances are 3.079 and 3.242 Å, respectively, which are comparable with the values 2.91 (3.14) and 3.16 (3.42) Å, the sum of covalent radii of germanium (plumbum) and uranium proposed by Pyykkö 83,84 and Alvarez,85 respectively. In summary, the calculated U−E (E = Si, Ge, Sn, Pb) bond distances in the (CpSiMe3)3U-E(NCHMes)2 complexes reveal the obvious U−E bonding interactions. In order to evaluate whether the U−E bond distances are sensitive to the dispersion effects, we also performed the optimization at the PBE-D3/631G(d)/RECP-SEG/LANL08d level of theory. There are no significant changes on the U−E bond distances as given in Table S3. Therefore, all results as discussed below are based on the optimized structures at the PBE/6-31G(d)/RECP-SEG/ LANL08d level of theory. Bond orders can assess the strength of the chemical bonds. Four types of U−E bond orders were obtained using Wiberg (WBO),86 Mayer (MBO),87 Gopinatan−Jug (GJBO),88 and Nalewajski−Mrozek bond orders (NMBO)89,90 at the B3LYP/ ZORA/TZ2P level of theory (Table 1). Four types of bond orders for the U−E bonds are almost less than 1 and follow the order of MBO < GJBO < WBO < NMBO. The values of NMBO for the four U−E bonds are about 1, denoting a single U−E bond. The bond strength of four U−E bonds is the trend of U− Si > U−Sn > U−Ge > U−Pb according to the value of bond order. In addition, the delocalization index (δ) can evaluate the bonding nature, which is a measure of bond order.91−93 The values of δ(U−E) are about 0.5, which can also reveal U−E bonds possess a single-bond feature. Figure S1 displays MOs of the four (CpSiMe3)3U-E(NCHMes)2 complexes. It is seen that the SOMOs of the four (CpSiMe3)3U-E(NCHMes)2 complexes display similar characteristics. The electron density of the three SOMOs is predominantly distributed on U with the main U 5f character based on the compositions of MOs in Figure S1, implying the U 5f3 electron configuration in the four complexes. The highest doubly occupied MOs (HOMO/HOMO-1) for the four complexes are shown in Figure S1. Obviously, the diagram of HOMO-1 for the (CpSiMe3)3U-Si(NCHMes)2 complex is very similar to that of HOMO for the complexes (CpSiMe3)3UE(NCHMes)2 (E = Ge, Sn, Pb), while the diagram of HOMO for the former is very similar to that of HOMO-1 for the latter probably due to the nonmetal character of Si atom. HOMO-1 for the (CpSiMe3)3U-Si(NCHMes)2 complex represents the principal U−Si interactions of U (2.87%) and Si (18.37%), and the HOMO for the three (CpSiMe 3 ) 3 U-E(NCHMes) 2 complexes (E = Ge, Sn, Pb) shows the main U−E interactions of U (3.39%) and Ge (19.76%), U (9.79%) and Sn (24.40%), and U (17.14%) and Pb (24.58%), respectively. These MOs indicate the interaction between U and E atoms. It is remarkable that the contribution of uranium dramatically increases from 2.87% to 17.14% with the increasing of heavier group 14 atoms, and the contribution of group 14 atoms gradually increases from 18.37% to 24.58%, implying the increase of the orbital interaction between uranium and group 14 atoms. Although the contribution of Sn and Pb is larger than that of Si and Ge for

Figure 1. Qualitative MO correlation diagram between two fragments (CpSiMe3)3U ([U]) and Ge(NCHMes)2 ([Ge]) in the complex (CpSiMe3)3U-Ge(NCHMes)2 ([U-Ge]) at the B3LYP/6-31G(d)/ RECP-SEG/LANL08d level of theory. The isosurface value of MOs is set to be 0.03 au.

complex is very similar to that of the fragment Ge(NCHMes)2. We also plotted the MO correlation diagram for the interaction based on EDA calculation at the B3LYP/ZORA/DZ level of theory using the ADF in Figure S2. It is clearly seen that the MO correlation diagram obtained with the two programs is similar, though the energy level is different due to the different level of theory. Energy levels of MOs for the four (CpSiMe3)3UE(NCHMes)2 complexes and optimized (CpSiMe3)3U fragment are presented in Figure 2. It shows that the energy levels of the SOMOs of the (CpSiMe3)3U fragment are enhanced in the four (CpSiMe3)3U-E(NCHMes)2 complexes due to ligand field effect of E(NCHMes)2. The energy levels of the corresponding SOMOs gradually decrease when the group 14 atom gets heavier, and the energy level of the same diagram of HOMO for the (CpSiMe3)3U-Si(NCHMes)2 complex and HOMO-1 for the complexes (CpSiMe3)3U-E(NCHMes)2 (E = Ge, Sn, Pb) follows the similar trend. However, the energy level of the same diagram of HOMO-1 for the (CpSiMe3)3U-Si(NCHMes)2 complex and HOMO for the complexes (CpSiMe3)3UE(NCHMes)2 (E = Ge, Sn, Pb) sharply increases, which is the C


Article

Organometallics

value of about 0.63−0.82, clearly indicating the U−E bonds are donor−acceptor character, and also implying divalent group 14 metallylenes ([E(NCHMes)2]) have strong electron donating property. Natural spin density on U and E atoms of the four (CpSiMe3) 3U-E(NCHMes)2 complexes obtained at the B3LYP/ZORA/TZ2P level of theory is listed in Table S5. It is clearly shown that the natural spin densities on uranium in (CpSiMe3)3U-E(NCHMes)2 are about 2.9, which are consistent with electron configuration of U(III), f3. The corresponding natural spin density on the group 14 atom in (CpSiMe3)3UE(NCHMes)2 is approximately zero, which is in line with the singlet states of [E(NCHMes)2] monomers. These results accord with the MO analysis. Table S5 shows that the occupancies of U for the four (CpSiMe3)3U-E(NCHMes)2 complexes are mainly located on the 5f and 6d orbitals, and those of group 14 atoms mainly locate at the s and p orbitals. The 6d occupancies on uranium for the four (CpSiMe3)3UE(NCHMes)2 (E = Si, Ge, Sn, Pb) complexes are about 1.8, which are close to the values (about 1.7) in the [Cp3U-ECp] (E = Al, Ga) complexes27 and much higher than the values (about 1.0) in the complexes LArU-MCp(CO)2 (M = Fe, Ru, Os),44 indicating the 6d subshell for the four (CpSiMe3)3U-E(NCHMes)2 complexes is more prominent in the donor−acceptor bonding type than that of the electron-sharing bonding type. This result is supported by the analysis of NBO as discussed below.

Figure 2. Energy levels of SOMOs and HOMOs for the (CpSiMe3)3U ([U]) and (CpSiMe3)3U-E(NCHMes)2 ([U-E], E = Si, Ge, Sn, Pb) complexes at the B3LYP/6-31G(d)/RECP-SEG/LANL08d level of theory.

similar trend of the Au−E σ and π MOs for the [Au1-NHE] (E = C, Si, Ge, Sn, Pb) complexes.94 These results can be supported by the result of binding energy as discussed below. To evaluate the U−E bonding nature in the (CpSiMe3)3UE(NCHMes)2 complexes, NBO was carried out at the B3LYP/ ZORA/TZ2P level of theory. The natural charges on the uranium and group 14 atoms in the (CpSiMe3)3U-E(NCHMes)2 complexes are displayed in Table 2. The amount of charge

■

U−E BONDING NATURE NBO analysis was performed to explore the nature of the U−E bonds in the (CpSiMe3)3U-E(NCHMes)2 complexes. Only the U−E σ bonding orbital was observed with the B3LYP functional as provided in Figures 3 and S3,which is similar with the U−Ga σ

Table 2. Natural Charges (Q) for U, Si, Ge, Sn, and Pb Atoms in the Complexes (CpSiMe3)3U-E(NCHMes)2 (E = Si, Ge, Sn, Pb) and the Corresponding Charge Difference (ΔQ) between the Complexes and the Isolated Fragments [(CpSiMe3)3U] and [E(NCHMes)2] species

atom

Q

ΔQ

(CpSiMe3)3U-Si(NCHMes)2

U Si U Ge U Sn U Pb

0.477 1.628 0.465 1.643 0.357 1.823 0.439 1.743

0.658 −0.685 0.636 −0.748 0.744 −0.815 0.662 −0.748

(CpSiMe3)3U-Ge(NCHMes)2 (CpSiMe3)3U-Sn(NCHMes)2 (CpSiMe3)3U-Pb(NCHMes)2

transfer can clarify a chemical bonding type. Very recently, Sen et al. reported the bonds between the Si/Ge atom and In atom are classical donor−acceptor bonds by the natural charge analysis.95 Similarly, Arnold et al. reported a dative U−Al bond with a net charge transfer (about 0.1) from Al to U at the B3LYP level.25 In this work, the calculated natural charge on the uranium centers in (CpSiMe3)3U-E(NCHMes)2 spans a range of 0.35−0.48, which is significantly below the formal charge (+3). The corresponding natural charge on the group 14 atoms spans a range of 1.62−1.83, which is close to the formal charge (+2). This result denotes that charge transfer occurs between uranium and group 14 atoms in the (CpSiMe3)3U-E(NCHMes)2 complexes. Natural charges on the U and E atoms for the isolated fragments [(CpSiMe3)3U] and [E(NCHMes)2] are shown in Table S4. The amount for the charge transfer of U atom is close to that of group 14 atom for each complex with the

Figure 3. U−Ge NBO in the (CpSiMe3)3U-Ge(NCHMes)2 complex at the B3LYP/ZORA/TZ2P level of theory. The isosurface value of MOs is set to be 0.03 au.

bond in the [(trenTMS)U-Ga(NArCH)2(thf)] complex at the CASSCF level.42 And no U−E π bonding character was found in these complexes. Figure 3 shows the U−Ge σ bond with highly polarized toward germanium, which can be supported by the composition of NBO in Table 3 with the value of 74.83% for the Ge atom. It is a general phenomenon for metal−metal bonds when the two metals are far apart of the periodic table.96−98 Similar results for the U−Si, U−Sn, and U−Pb NBOs in the (CpSiMe3)3U-E(NCHMes)2 complexes (E = Si, Sn, Pb) are D


Article

Organometallics

Table 3. NBO Compositions of the U−E σ Bonds in the (CpSiMe3)3U-E(NCHMes)2 Complexes at the B3LYP/ZORA/TZ2P Level of Theory U−E

U%

E%

U AOs (%)

E AOs (%)

U−Si U−Ge U−Sn U−Pb

31.79 25.17 27.29 20.61

68.21 74.83 72.71 79.39

7s(14.42)6d(67.58)5f(17.97) 7s(16.41)6d(64.79)5f(18.73) 7s(19.08)6d(63.71)5f(17.08) 7s(19.11)6d(61.90)5f(18.88)

3s(61.84)3p(38.01) 4s(91.42)4p(8.53) 5s(94.34)5p(5.56) 6s(96.87)6p(3.08)

other two ones for the heavier metals, which makes the positive ∇2ρ(r) value.32 In this case, the energy density H(r) can be used as another criterion. H(r) = G(r) + V(r); here G(r) and V(r) are the kinetic and potential energy density, respectively. The values of ∇2ρ(r) and H(r) are negative, denoting covalent bonding character. In the case with slightly positive ∇2ρ(r), negative H(r) suggests the dative or metallic bond, while positive H(r) indicates ionic or van der Waals. All the parameters of the U−E bonds based on the electron density of topological analysis are presented in Table 4. The small ρ(r) and positive ∇2ρ(r) of the

shown in Figure S3 and Table 3, which also reflect highly polarized U−E bonds. The contributions of the atomic orbital of uranium and group 14 atoms to the U−E bonds in the (CpSiMe3)3U-E(NCHMes)2 complexes are also presented in Table 3. The U−E bonds mainly involve U 6d and E ns orbitals, while the contribution of the U 5f orbital to U−E bonds is no more than 20%. It can be explained that the divalent group 14 donor ligands can be significantly stabilized by the interaction with the lower lying and formally empty 6d orbitals on the U(III) ion,27 and the extent of the mixing between the extended U 6d and E ns is larger than that of the more contracted U 5f and E ns,99 which lead to the donor−acceptor nature for the U−E bonds. Whereas for the electron-sharing An−E bonds, they are contributed by the more compact 5f orbitals.31 The contribution of E to U−E bonds is mainly the s orbital. This result is derived from lone pair electrons located on the s orbital for the singlet metallylenes.47 The diagrams of the ground state metallylenes and the E lone pair NBO in the [E(NCHMes)2] monomer are displayed in Figure 4, suggesting that the U−E interaction is a

Table 4. Bond Critical Point Properties (au) of the U−E Bonds in the Four (CpSiMe3)3U-E(NCHMes)2 (E = Si, Ge, Sn, Pb) Complexes U−E

ρ(r)

∇2ρ(r)

G(r)

V(r)

H(r)

U−Si U−Ge U−Sn U−Pb

0.037 0.032 0.031 0.025

0.063 0.058 0.054 0.061

0.022 0.018 0.017 0.015

−0.028 −0.023 −0.022 −0.018

−0.006 −0.004 −0.005 −0.002

U−E BCP indicates that the U−E bonds have no electronsharing interaction. Moreover, H(r) at U−E BCP is slightly negative, revealing that the U−E bonding character is between dative and metallic. The value of ELF ranges from 0 to 1, which provides useful information on chemical bonds. ELF = 1 indicates a completely localized bond, while ELF = 0 shows no localization of electrons. Figure 5 shows electron density (red color) is mainly located on

Figure 4. Ground state of metallylenes and the E lone pair NBO in the [E(NCHMes)2] monomer at the B3LYP/ZORA/TZ2P level of theory. The isosurface value of MOs is set to be 0.03 au.

dative bond. The orbital compositions on the silicon atom in (CpSiMe3)3U-Si(NCHMes)2 are significantly different from the other group 14 atoms in (CpSiMe3)3U-E(NCHMes)2 (E = Ge, Sn, Pb), probably owing to the different bonds (uranium−metal bond and uranium−nonmetal bond). QTAIM analysis provides valuable information about chemical bonds, which is widely used to investigate the bonding nature of f-block complexes.42,100,101 Bonding character is classified based on the values of the electron density [(ρ(r)] and the corresponding Laplacian [∇2ρ(r)] at the BCPs. The ∇2ρ(r) is usually negative, when a chemical bond is a covalent bond. This criterion is usually not suitable for the bonds involving heavier metals. Because ∇2ρ(r) is the sum of three eigenvalues (λ1, λ2, and λ3) of the density Hessian matrix, where only λ3 is not negative. In general, the λ3 term is greater than the sum of the

Figure 5. Two-dimensional ELF contour on the U−Ge−N plane of the (CpSiMe3)3U-Ge(NCHMes)2 complex.

the germanium center, an indication of an obvious electron donating feature between uranium and germanium. Similar results appear in the other three complexes presented in Figure S4. EDA (energy decomposed analysis) was performed to further explore the U−E bonding nature of the four (CpSiMe3)3UE


Article

Organometallics

Table 5. Total Bonding Energy (ΔEint, kcal/mol), Pauli Repulsion (ΔEPauli, kcal/mol), Electrostatic Interaction (ΔEelst, kcal/ mol), Steric Interaction Energy (ΔEsteric, kcal/mol), and Orbital Interaction (ΔEoi, kcal/mol) Obtained from EDA at the PBE/ ZORA/TZ2P Level of Theory species

ΔEint

ΔEPauli

ΔEelst

ΔEsteric

ΔEoi

(CpSiMe3)3U-Si(NCHMes)2 (CpSiMe3)3U-Ge(NCHMes)2 (CpSiMe3)3U-Sn(NCHMes)2 (CpSiMe3)3U-Pb(NCHMes)2

−46.41 −39.43 −42.00 −30.86

73.41 58.40 69.79 55.93

−53.04 −38.73 −43.67 −32.42

20.37 19.67 26.12 23.51

−66.78 −59.10 −68.12 −54.37

E(NCHMes)2 complexes. The (CpSiMe3)3U-E(NCHMes)2 complexes are divided into two parts, [(CpSiMe3)3U] and [E(NCHMes)2]. EDA is based on the transition state method developed by Morokuma102 and Ziegler103 and is a powerful method. In the EDA method, the interaction energy (ΔEint) between two fragments is decomposed into three components: ΔEint = ΔEelst + ΔE Pauli + ΔEoi

Here, the ΔEelst term denotes the electrostatic interaction between the unperturbed charge distributions of two fragments. The Pauli repulsion ΔEPauli is the destabilizing interaction. Therefore, the sum of ΔEPauli and ΔEelst is the steric interaction energy: ΔEsteric = ΔEelst + ΔE Pauli Figure 6. Electrostatic and orbital contributions to the total attractive interaction between two fragments in the (CpSiMe3)3U-E(NCHMes)2 ([U-E], E = Si, Ge, Sn, Pb) complexes.

The term ΔEoi stems from the mixing of orbitals, charge transfer, and polarization between two fragments. The EDA results were obtained at the PBE/ZORA/TZ2P level of theory in Table 5. The U−E (E = Si, Ge, Sn, Pb) bonding energies of the four (CpSiMe3)3U-E(NCHMes)2 complexes are −46.41, −39.43, −42.00, and −30.86 kcal/mol, respectively. Although the total bonding energy does not reflect net bonding between uranium and group 14, it can reflect the relative stability and strength of U−E bonds. The trend of the total bonding energies for the four (CpSiMe3)3U-E(NCHMes)2 complexes is in well agreement with the corresponding bond orders. The absolute total bonding energies of the four (CpSiMe3)3UE(NCHMes)2 complexes are far smaller than those of bimetallic actinide systems in previous works.12−17,26,42−44 There is an exception on the [Cp3U-GaCp*] complex, of which the total energy at the PBE/ZORA/TZ2P level of theory is only −17.8 kcal/mol, because Coulomb interaction between a positively and negatively charged fragment is substantially higher than that between two neutral fragments.42 For the four U−E bonds, the values of the orbital interaction are significantly negative than those of the electrostatic interaction. The contribution of electrostatic and orbital interactions to the total attractive interaction is shown in Figure 6, which shows that the percentage of the orbital interaction is above 55%. This result is obviously different from that of previous works, of which the dominant contribution of the total attractive interaction in the bimetallic actinide systems is electrostatic interaction.12,14,16,17,26,42−44 In general, the orbital interactions should be larger than the electrostatic interactions between two neutral fragments.104 For instance, the orbital interaction is higher than the electrostatic interaction appears in alkali-metal, transitionmetal, and main-group systems with the donor−acceptor bonding mode.105−107 Furthermore, the contribution of the orbital interaction for the four complexes increases with increasing group 14 atomic number.

■

THERMODYNAMICS Formation of the U−E bonds between two neutral fragments [CpSiMe3)3U] and [E(NCHMes)2] can be evaluated according to their binding energy (ΔBE). ΔBE = G[(CpSiMe3)3UE(NCHMes)2] − G[CpSiMe3)3U] − G[E(NCHMes)2]; here G is the corresponding Gibbs free energy (Tables S6 and S7). The binding energies of the (CpSiMe3)3U-E(NCHMes)2 complexes in the gas phase and toluene solution at the PBE/ 6-311G(d, p)/RECP-SEG/LANL08d and B3LYP/6-311G(d, p)/RECP-SEG/LANL08d levels of theory were calculated with the thermal energy correction obtained in the gas phase at the PBE/6-31G(d)/RECP-SEG/LANL08d level of theory. The binding energies become negative in the gas phase after introducing the dispersion effect (Table 6); they get even more negative considering the solvation effect. These results indicate that the binding energies for the (CpSiMe3)3UE(NCHMes)2 complexes are sensitive to the dispersion and solvation effects. Moreover, the four (CpSiMe3)3U-E(NCHMes)2 complexes are accessible based on the negative binding energies, and the absolute binding energies decrease across the group 14 atoms, which are consistent with the energy level of HOMO for the three (CpSiMe3)3U-E(NCHMes)2 (E = Ge, Sn, Pb) complexes and HOMO-1 for the (CpSiMe3)3U-Si(NCHMes)2. Therefore, it is concluded that the complexes bearing donor−acceptor U−E (E = Si, Ge, Sn, Pb) bonds are probably feasible under certain experimental conditions.

■

CONCLUSION In conclusion, a series of potential (CpSiMe3)3U-E(NCHMes)2 (E = Si, Ge, Sn, Pb) complexes are obtained by constructing two neutral fragments [CpSiMe3)3U] and [E(NCHMes)2]. Calculated U−E bond distances in the (CpSiMe3)3U-E(NCHMes)2 F


Article

Organometallics

Table 6. Binding Energy (ΔBE, kcal/mol) of the (CpSiMe3)3U-E(NCHMes)2 Complexes in the Gas Phase and Toluene Solution at the PBE, PBE-D3, B3LYP, B3LYP-D3 Functionals Using the 6-311G(d, p)/LANL08d Basis Seta reactions

ΔBEgas

ΔBEgas-D3

ΔBEtoluene-D3

[(CpSiMe3)3U] + [Si(NCHMes)2] = (CpSiMe3)3U-Si(NCHMes)2 [(CpSiMe3)3U] + [Ge(NCHMes)2] = (CpSiMe3)3U-Ge(NCHMes)2 [(CpSiMe3)3U] + [Sn(NCHMes)2] = (CpSiMe3)3U-Sn(NCHMes)2 [(CpSiMe3)3U] + [Pb(NCHMes)2] = (CpSiMe3)3U-Pb(NCHMes)2

8.59/19.21 11.34/21.59 10.53/20.74 13.46/30.31

−7.27/−4.02 −4.47/−1.57 −3.94/−0.56 −0.69/1.82

−17.41/−14.09 −15.70/−12.79 −14.00/−9.39 −9.53/−7.07

a

.../... denotes the binding energies with PBE and B3LYP, respectively.

■

ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (Grant Nos. 11875058, U1867205), the Major Program of the National Natural Science Foundation of China (21790373), the Science Challenge Project (TZ2016004), and the High-Level of Innovative Talents of Guizhou Province, China (Project [2015]4012). The results described in this work were obtained on the ScGrid of the Supercomputing Center, Computer Network Information Center of the Chinese Academy of Sciences.

complexes are within the covalent radius and show an obvious single-bond feature. The trend of strength of the four bonds follows U−Si > U−Sn > U−Ge > U−Pb, according to the values of bond orders and EDA. Both the MO and natural spin density analyses indicate that the electron configuration of uranium in the (CpSiMe3)3U-E(NCHMes)2 complexes is 5f3. HOMOs containing the U−E interaction denote that the electron density is predominately located on group 14 atoms, indicating there is no electron sharing between uranium and group 14 atoms. Moreover, NBO calculations suggest that the U−E bonds are largely polarized toward the group 14 atoms and consist of U 6d orbitals and E ns orbital with a pair of lone electrons, which are significantly different from the general uranium−transitionmetal and uranium−main-group bonds. Natural charge analyses denote that the U−E bonds possess the donor−acceptor type, that is, dative bonds, which can be confirmed by the analyses of QTAIM and ELF. Additionally, the result of EDA shows that orbital contributions dominate the uranium−group 14 interaction probably due to the dative bonding nature of U−E bonds. Furthermore, the four (CpSiMe3)3U-E(NCHMes)2 complexes are thermodynamically accessible based on the negative binding energies. By and large, divalent group 14 complexes are promising as donor ligands for building new unsupported uranium−metal bonds. This work paves the way for the possible method to synthesize a series of uranium-group 14 complexes.

■

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.9b00059.

■

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) Herberhold, M.; Jin, G. X. Heterodimetallic Complexes with an Unbridged, Polar Metal−Metal Bond. Angew. Chem., Int. Ed. Engl. 1994, 33, 964−966. (3) Friedrich, S.; Memmler, H.; Gade, L. H.; Li, W.-S.; Scowen, I. J.; McPartlin, M.; Housecroft, C. E. Stabilizing Heterobimetallic Complexes Containing Unsupported Ti−M Bonds (M = Fe, Ru, Co): The Nature of Ti−M Donor−Acceptor Bonds. Inorg. Chem. 1996, 35, 2433−2441. (4) Lei, H.; Guo, J.-D.; Fettinger, J. C.; Nagase, S.; Power, P. P. TwoCoordinate First Row Transition Metal Complexes with Short Unsupported Metal−Metal Bonds. J. Am. Chem. Soc. 2010, 132, 17399−17401. (5) Zheng, X.; Wang, X.; Zhang, Z.; Sui, Y.; Wang, X.; Power, P. P. Access to Stable Metalloradical Cations with Unsupported and Isomeric Metal-Metal Hemi-Bonds. Angew. Chem., Int. Ed. 2015, 54, 9084−9087. (6) Liddle, S. T., Ed. Molecular Metal-Metal Bonds: Compounds, Synthesis, Properties; Wiley-VCH: Weinheim, Germany, 2015. (7) Bennett, R. L.; Bruce, M. I.; Stone, F. G. A. Tetrakis(pentacarbonylmanganese)uranium. J. Organomet. Chem. 1971, 26, 355−356. (8) 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. (9) 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. (10) 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 thorium-ruthenium complex. J. Am. Chem. Soc. 1987, 109, 7920−7921. (11) 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. (12) Gardner, B. M.; Mcmaster, J.; Lewis, W.; Liddle, S. T. Synthesis and structure of [{N(CH CH NSiMe) }URe(η-C H) ]: a

Diagrams of frontier molecular orbital, NBO, and ELF, and data of electronic energy, bond orders, natural charges, natural spin density, natural electron configuration, and Gibbs free energies of the (CpSiMe3)3U, E(NCHMes)2, and (CpSiMe3)3U-E(NCHMes)2 complexes (PDF) Optimized Cartesian coordinates of the (CpSiMe3)3U, E(NCHMes)2, and (CpSiMe3)3U-E(NCHMes)2 complexes at the PBE/6-31G(d)/RECP-SEG/LANL08d level of theory (XYZ)

AUTHOR INFORMATION

Corresponding Author

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

Wei-Qun Shi: 0000-0001-9929-9732 Author Contributions ∥

These two authors contributed equally to this work.

Notes

The authors declare no competing financial interest. G


Article

Organometallics heterobimetallic complex with an unsupported uranium−rhenium bond. Chem. Commun. 2009, 17, 2851−2853. (13) 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. (14) 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. (15) 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. (16) 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. (17) Chi, C.; Wang, J.-Q.; Qu, H.; Li, W.-L.; Meng, L.; Luo, M.; Li, J.; Zhou, M. Preparation and Characterization of Uranium−Iron TripleBonded UFe(CO)3− and OUFe(CO)3− Complexes. Angew. Chem. 2017, 129, 7036−7040. (18) Fortier, S.; Aguilarcalderó n , 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. (19) 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. (20) Porchia, M.; Ossola, F.; Rossetto, G.; Zanella, P.; Brianese, N. Synthesis of triscyclopentadienyl (triphenylgermyl) uranium and facile isonitrile insertion into the uranium−germanium bond. J. Chem. Soc., Chem. Commun. 1987, 550−551. (21) Porchia, M.; Brianese, N.; Casellato, U.; Ossola, F.; Rossetto, G.; Zanella, P.; Graziani, R. Tri (η-cyclopentadienyl) uranium (IV) silyl and siloxide compounds. Crystal structure of [U (η 5-C 5 H 5) 3 (OSiPh 3)]. Insertion of lsocyanide into a uranium−silicon bond. J. Chem. Soc., Dalton Trans. 1989, 677−681. (22) 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. (23) Nakai, H.; Hu, X.; Zakharov, L. N.; Rheingold, A. L.; Meyer, K. Synthesis and Characterization of N-Heterocyclic Carbene Complexes of Uranium(III). Inorg. Chem. 2004, 43, 855−857. (24) Mehdoui, T.; Berthet, J.-C.; Thuéry, P.; Ephritikhine, M. The remarkable efficiency of N-heterocyclic carbenes in lanthanide(iii)/ actinide(iii) differentiation. Chem. Commun. 2005, 2860−2862. (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) 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. (28) Hu, H.-S.; Wei, F.; Wang, X.; Andrews, L.; Li, J. Actinide−Silicon Multiradical Bonding: Infrared Spectra and Electronic Structures of the Si(μ-X)AnF3 (An = Th, U; X = H, F) Molecules. J. Am. Chem. Soc. 2014, 136, 1427−1437. (29) Wu, Q.-Y.; Wang, C.-Z.; Lan, J.-H.; Xiao, C.-L.; Wang, X.-K.; Zhao, Y.-L.; Chai, Z.-F.; Shi, W.-Q. Theoretical Investigation on Multiple Bonds in Terminal Actinide Nitride Complexes. Inorg. Chem. 2014, 53, 9607−9614.

(30) 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. (31) Liddle, S.; Rookes, T.; Wildman, E.; Balazs, G.; Gardner, B.; Wooles, A.; Gregson, M.; Tuna, F.; Scheer, M. Actinide-Pnictide (AnPn) Bonds Spanning Non-Metal, Metalloid, and Metal Combinations (An = U, Th; Pn = P, As, Sb, Bi). Angew. Chem., Int. Ed. 2018, 57, 1332− 1336. (32) Su, W.; Pan, S.; Sun, X.; Wang, S.; Zhao, L.; Frenking, G.; Zhu, C. Double dative bond between divalent carbon(0) and uranium. Nat. Commun. 2018, 9, 4997. (33) Pepper, M.; Bursten, B. E. Ab initio studies of the electronic structure of the diuranium molecule. J. Am. Chem. Soc. 1990, 112, 7803−7804. (34) 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. (35) 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. (36) 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. (37) 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. (38) 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. (39) 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. (40) 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 Long-Sought Dimetallic Actinide Endohedral Fullerene. J. Am. Chem. Soc. 2018, 140, 3907−3915. (41) Knecht, S.; Jensen, H. J. A.; Saue, T. Relativistic quantum chemical calculations show that the uranium molecule U2 has a quadruple bond. Nat. Chem. 2019, 11, 40−44. (42) 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. (43) 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. (44) Chi, X.-W.; Wu, Q.-Y.; Hao, Q.; Lan, J.-H.; Wang, C.-Z.; Zhang, Q.; Chai, Z.-F.; Shi, W.-Q. Theoretical Study on Unsupported Uranium−Metal Bonding in Uranium−Group 8 Complexes. Organometallics 2018, 37, 3678−3686. (45) Liddle, S. T.; Mills, D. P. Metal−metal bonds in f-element chemistry. Dalton Trans. 2009, 5592−5605. (46) Gemel, C.; Steinke, T.; Cokoja, M.; Kempter, A.; Fischer, R. A. Transition Metal Chemistry of Low Valent Group 13 Organyls. Eur. J. Inorg. Chem. 2004, 2004, 4161−4176. (47) Mizuhata, Y.; Sasamori, T.; Tokitoh, N. Stable Heavier Carbene Analogues. Chem. Rev. 2009, 109, 3479−3511. (48) Leites, L. A.; Bukalov, S. S.; Aysin, R. R.; Piskunov, A. V.; Chegerev, M. G.; Cherkasov, V. K.; Zabula, A. V.; West, R. Aromaticity of an Unsaturated N-Heterocyclic Stannylene (HCRN)2SnII As Studied by Optical Spectra and Quantum Chemistry. Comparison in the Series (HCRN)2EII, E = C, Si, Ge, Sn (R = t-Bu or Dip). Organometallics 2015, 34, 2278−2286. (49) Hohenberg, P.; Kohn, W. Inhomogeneous Electron Gas. Phys. Rev. 1964, 136, B864−B871. H


Article

Organometallics (50) Kohn, W.; Sham, L. J. Self-Consistent Equations Including Exchange and Correlation Effects. Phys. Rev. 1965, 140, A1133−A1138. (51) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865−3868. (52) 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. (53) Kim, K.; Jordan, K. D. Comparison of Density Functional and MP2 Calculations on the Water Monomer and Dimer. J. Phys. Chem. 1994, 98, 10089−10094. (54) Stephens, P. J.; Devlin, F. J.; Chabalowski, C. F.; Frisch, M. J. Ab Initio Calculation of Vibrational Absorption and Circular Dichroism Spectra Using Density Functional Force Fields. J. Phys. Chem. 1994, 98, 11623−11627. (55) Averkiev, B. B.; Mantina, M.; Valero, R.; Infante, I.; Kovacs, A.; Truhlar, D. G.; Gagliardi, L. How accurate are electronic structure methods for actinoid chemistry? Theor. Chem. Acc. 2011, 129, 657− 666. (56) 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. (57) Cao, X.; Dolg, M.; Stoll, H. Valence basis sets for relativistic energy-consistent small-core actinide pseudopotentials. J. Chem. Phys. 2003, 118, 487−496. (58) Cao, X.; Dolg, M. Segmented contraction scheme for small-core actinide pseudopotential basis sets. J. Mol. Struct.: THEOCHEM 2002, 581, 139−147. (59) 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. (60) 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. (61) Lan, J.-H.; Wang, C.-Z.; Wu, Q.-Y.; Wang, S.-A.; Feng, Y.-X.; Zhao, Y.-L.; Chai, Z.-F.; Shi, W.-Q. A Quasi-relativistic Density Functional Theory Study of the Actinyl(VI, V) (An = U, Np, Pu) Complexes with a Six-Membered Macrocycle Containing Pyrrole, Pyridine, and Furan Subunits. J. Phys. Chem. A 2015, 119, 9178−9188. (62) Wu, Q. Y.; Lan, J. H.; Wang, C. Z.; Cheng, Z. P.; Chai, Z. F.; Gibson, J. K.; Shi, W. Q. Paving the way for the synthesis of a series of divalent actinide complexes: a theoretical perspective. Dalton Trans. 2016, 45, 3102−3110. (63) Wang, C.-Z.; Wu, Q.-Y.; Lan, J.-H.; Chai, Z.-F.; Gibson, J. K.; Shi, W.-Q. Binuclear trivalent and tetravalent uranium halides and cyanides supported by cyclooctatetraene ligands. Radiochim. Acta 2017, 105, 21−32. (64) Wu, Q.-Y.; Cheng, Z.-P.; Lan, J.-H.; Wang, C.-Z.; Chai, Z.-F.; Gibson, J. K.; Shi, W.-Q. Insight into the nature of M−C bonding in the lanthanide/actinide-biscarbene complexes: a theoretical perspective. Dalton Trans. 2018, 47, 12718−12725. (65) 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.

(66) 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. (67) 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. (68) 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. (69) Marenich, A. V.; Cramer, C. J.; Truhlar, D. G. Universal Solvation Model Based on Solute Electron Density and on a Continuum Model of the Solvent Defined by the Bulk Dielectric Constant and Atomic Surface Tensions. J. Phys. Chem. B 2009, 113, 6378−6396. (70) Grimme, S.; Antony, J.; Ehrlich, S.; Krieg, H. A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. J. Chem. Phys. 2010, 132, 154104. (71) Grimme, S.; Ehrlich, S.; Goerigk, L. Effect of the damping function in dispersion corrected density functional theory. J. Comput. Chem. 2011, 32, 1456−1465. (72) Grimme, S. Density functional theory with London dispersion corrections. WIREs. Comput. Mol. Sci. 2011, 1, 211−228. (73) 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. (74) Reed, A. E.; Weinstock, R. B.; Weinhold, F. Natural population analysis. J. Chem. Phys. 1985, 83, 735−746. (75) Lenthe, E. v.; Baerends, E. J.; Snijders, J. G. Relativistic regular two-component Hamiltonians. J. Chem. Phys. 1993, 99, 4597−4610. (76) Van Lenthe, E.; Baerends, E. J. Optimized Slater-type basis sets for the elements 1−118. J. Comput. Chem. 2003, 24, 1142−1156. (77) Bader, R. F. W. A quantum theory of molecular structure and its applications. Chem. Rev. 1991, 91, 893−928. (78) Bader, R. F. W. A Bond Path: A Universal Indicator of Bonded Interactions. J. Phys. Chem. A 1998, 102, 7314−7323. (79) Becke, A. D.; Edgecombe, K. E. A simple measure of electron localization in atomic and molecular systems. J. Chem. Phys. 1990, 92, 5397−5403. (80) Savin, A.; Becke, A. D.; Flad, J.; Nesper, R.; Preuss, H.; von Schnering, H. G. A New Look at Electron Localization. Angew. Chem., Int. Ed. Engl. 1991, 30, 409−412. (81) Savin, A.; Nesper, R.; Wengert, S.; Fässler, T. F. ELF: The Electron Localization Function. Angew. Chem., Int. Ed. Engl. 1997, 36, 1808−1832. (82) Lu, T.; Chen, F. Multiwfn: A multifunctional wavefunction analyzer. J. Comput. Chem. 2012, 33, 580−592. (83) Pyykkö, P.; Atsumi, M. Molecular single-bond covalent radii for elements 1−118. Chem. - Eur. J. 2009, 15, 186−197. (84) Pyykkö, P. Additive Covalent Radii for Single-, Double-, and Triple-Bonded Molecules and Tetrahedrally Bonded Crystals: A Summary. J. Phys. Chem. A 2015, 119, 2326−2337. (85) 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. (86) Wiberg, K. B. Application of the pople-santry-segal CNDO method to the cyclopropylcarbinyl and cyclobutyl cation and to bicyclobutane. Tetrahedron 1968, 24, 1083−1096. (87) Mayer, I. Charge, bond order and valence in the AB initio SCF theory. Chem. Phys. Lett. 1983, 97, 270−274. (88) Gopinathan, M. S.; Jug, K. Valency. I. A quantum chemical definition and properties. Theor. Chim. Acta 1983, 63, 497−509. (89) Nalewajski, R. F.; Mrozek, J. Modified valence indices from the two-particle density matrix. Int. J. Quantum Chem. 1994, 51, 187−200. (90) Nalewajski, R. F.; Mrozek, J.; Michalak, A. Two-electron valence indices from the Kohn-Sham orbitals. Int. J. Quantum Chem. 1997, 61, 589−601. (91) Hlina, J. A.; Pankhurst, J. R.; Kaltsoyannis, N.; Arnold, P. L. Metal−Metal Bonding in Uranium−Group 10 Complexes. J. Am. Chem. Soc. 2016, 138, 3333−3345. I


Article

Organometallics (92) O’Brien, K. T. P.; Kaltsoyannis, N. Computational study of An− X bonding (An = Th, U; X = p-block-based ligands) in pyrrolic macrocycle-supported complexes from the quantum theory of atoms in molecules and bond energy decomposition analysis. Dalton Trans. 2017, 46, 760−769. (93) Bi, Y.-T.; Li, L.; Guo, Y.-R.; Pan, Q.-J. Heterobimetallic Uranium−Nickel/Palladium/Platinum Complexes of Phosphinoaryl Oxide Ligands: A Theoretical Probe for Metal−Metal Bonding and Electronic Spectroscopy. Inorg. Chem. 2019, 58, 1290−1300. (94) Nguyen, T. A. N.; HuynH, T. P. L.; Vo, T. X. P.; Tran, T. H.; TraN, D. S.; Dang, T. H.; Duong, T. Q. Structures, Energies, and Bonding Analysis of Monoaurated Complexes with N-Heterocyclic Carbene and Analogues. ASEAN J. Sci. Technol. Dev. 2015, 32, 1−15. (95) Pahar, S.; Karak, S.; Pait, M.; Raj, K. V.; Vanka, K.; Sen, S. S. Access to Silicon(II)− and Germanium(II)−Indium Compounds. Organometallics 2018, 37, 1206−1213. (96) Wheatley, N.; Kalck, P. Structure and Reactivity of Earlyminus signLate Heterobimetallic Complexes. Chem. Rev. 1999, 99, 3379− 3420. (97) Gade, L. H. Highly polar metal−metal bonds in “early−late” Heterodimetallic complexes. Angew. Chem., Int. Ed. 2000, 39, 2658− 2678. (98) Cooper, B. G.; Napoline, J. W.; Thomas, C. M. Catalytic applications of early/late heterobimetallic complexes. Catal. Rev.: Sci. Eng. 2012, 54, 1−40. (99) Su, J.; Batista, E. R.; Boland, K. S.; Bone, S. E.; Bradley, J. A.; Cary, S. K.; Clark, D. L.; Conradson, S. D.; Ditter, A. S.; Kaltsoyannis, N.; Keith, J. M.; Kerridge, A.; Kozimor, S. A.; Löble, M. W.; Martin, R. L.; Minasian, S. G.; Mocko, V.; La Pierre, H. S.; Seidler, G. T.; Shuh, D. K.; Wilkerson, M. P.; Wolfsberg, L. E.; Yang, P. Energy-Degeneracy-Driven Covalency in Actinide Bonding. J. Am. Chem. Soc. 2018, 140, 17977− 17984. (100) Jones, M. B.; Gaunt, A. J.; Gordon, J. C.; Kaltsoyannis, N.; Neu, M. P.; Scott, B. L. Uncovering f-element bonding differences and electronic structure in a series of 1:3 and 1:4 complexes with a diselenophosphinate ligand. Chem. Sci. 2013, 4, 1189−1203. (101) Kaltsoyannis, N. Transuranic Computational Chemistry. Chem. - Eur. J. 2018, 24, 2815−2825. (102) 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. (103) Ziegler, T.; Rauk, A. On the calculation of bonding energies by the Hartree Fock Slater method. Theor. chim. acta 1977, 46, 1−10. (104) Pandey, K. K.; Power, P. P. Nature of M−E Bonds in Metallosilylenes, -germylenes, -stannylenes, and -plumbylenes [(η5C5H5)(Me3P)(H)2M(EPh)] (M = Fe, Ru, Os; E = Si, Ge, Sn, Pb). Organometallics 2011, 30, 3353−3361. (105) Wu, X.; Zhao, L.; Jin, J.; Pan, S.; Li, W.; Jin, X.; Wang, G.; Zhou, M.; Frenking, G. Observation of alkaline earth complexes M(CO)8 (M = Ca, Sr, or Ba) that mimic transition metals. Science 2018, 361, 912− 916. (106) Pan, S.; Zhao, L.; Dias, H. V. R.; Frenking, G. Bonding in Binuclear Carbonyl Complexes M2(CO)9 (M = Fe, Ru, Os). Inorg. Chem. 2018, 57, 7780−7791. (107) Zhao, L.; Hermann, M.; Holzmann, N.; Frenking, G. Dative bonding in main group compounds. Coord. Chem. Rev. 2017, 344, 163− 204.

J


A Theoretical Study on Divalent Heavier Group 14 Complexes as

Recommend Documents