The endohedral group-14-based clusters with the encapsulation of transition metal, which are termed as [TM@Em]n- (TM = transition metal, E = group-14 elements), have lots of potential applications and have...

Density functional theory (DFT) calculations were employed to study the stabilities, electronic structures, and vibrational and bonding properties of dianionic pentacarbonyls [TM(CO)5]2- (TM = Cr, Mo, W). A D3h symmetry...

Superelectrophilic monoanions [B 12 (BO) 11 ] À and [B 12 (OBO) 11 ] À , generated from stable dianions [B 12 (BO) 12 ] 2À and [B 12 (OBO) 12 ] 2À , show great potential for binding with noble gases (Ngs). The binding energies, quantum theory of atoms in molecules (QTAIM), natural population analysis (NPA), energy decomposition analysis (EDA), and electron localization function (ELF) were carried out to understand the BÀ Ng bond in [B 12 (BO) 11 Ng] À and [B 12 (OBO) 11 Ng] À . The calculated results reveal that heavier noble gases (Ar, Kr, and Xe) bind covalently with both [B 12 (BO) 11 ] À and [B 12 (OBO) 11 ] À with large binding energies, making them potentially feasible to be synthesized. Only [B 12 (OBO) 11 ] À could form a covalent bond with helium or neon but the small binding energy of [B 12 (OBO) 11 He] À may pose a challenge for its experimental detection.

The coordination of 10-electron diatomic ligands (BF, CO N 2) to iron complexes Fe(CO) 2 (CNAr Tripp2) 2 [Ar Tripp2 = 2,6-(2,4,6-(isopropyl) 3 C 6 H 2) 2 C 6 H 3 ] have been realized in experiments very recently (Science, 2019, 363, 1203-1205). Herein, the stability, electronic structures, and bonding properties of (E 1 E 2)Fe-(CO) 2 (CNAr Tripp2) 2 (E 1 E 2 = BF, CO, N 2 , CN À , NO +) were studied using density functional (DFT) calculations. The ground state of all those molecules is singlet and the calculated geometries are in excellent agreement with the experimental values. The natural bond orbital analysis revealed that Fe is negatively charged while E 1 possesses positive charges. By employing the energy decomposition analysis, the bonding nature of the E 2 E 1-Fe(CO) 2 (CNAr Tripp2) 2 bond was disclosed to be the classic dative bond E 2 E 1 !Fe(CO) 2 (CNAr Tripp2) 2 rather than the electron-sharing double bond. More interestingly, the bonding strength between BF and Fe(CO) 2 (CNAr Tripp2) 2 is much stronger than that between CO (or N 2) and Fe(CO) 2 (CNAr Tripp2) 2 , which is ascribed to the better σ-donation and π back-donations. However, the orbital interactions in CN À !Fe(CO) 2 (CNAr Tripp2) 2 and NO + !Fe (CO) 2 (CNAr Tripp2) 2 mainly come from σ-donation and π backdonation, respectively. The different contributions from σ donation and π donation for different ligands can be well explained by using the energy levels of E 1 E 2 and Fe (CO) 2 (CNAr Tripp2) 2 fragments.

First-principles calculations have been carried out for the 20-electron transition metal complexes (Cp)2TMO and their molecular wires (Cp = C5H5, C5(CH3)­H4, C5(CH3)5; TM = Cr, Mo, W). The calculation results at the BP86/def2-TZVPP level reveal that the ground state is singlet and the optimized geometries are in good agreement with the experimental values. The analysis of frontier molecular orbitals shows that two electrons in the highest occupied molecular orbital HOMO-1 are mainly localized on cyclopentadienyl and oxygen ligands. Furthermore, the nature of the TM–O bond was investigated with the energy decomposition analysis-natural orbitals for chemical valence (EDA-NOCV). The attraction term in the intrinsic interaction energies ΔE int is mainly composed of two important parts, including electrostatic interaction (about 52% of the total attractive interactions ΔE elstat + ΔE orb) and orbital interaction, which might be the major determinant of the stability of these (Cp)2TMO complexes. All of the TM–O bonds should be described as electron-sharing σ single bonds [(Cp)2TM]+–[O]− with the contribution of 53–57% of ΔE orb and two π backdonations from the occupied p orbitals of oxygen ligands into vacant π* MOs of the [(Cp)2TM]+ fragments, which are 35–40% of ΔE orb. The results of bond order and interaction energy from EDA-NOCV calculations suggest the influence of the radius of TM and methyl in the interactions between TM and O in (Cp)2TMO. Additionally, the relativistic effects slightly amplify the strength of bonding with increasing ΔE orb for the EDA-NOCV calculations on three metal complexes (C5H5)2TMO. Finally, the geometries, electronic structures, and magnetics of infinitely extended systems, [(C5H5)­TMO]∞, have also been explored. The results of the density of states (DOS) and band structure revealed that [(C5H5)­CrO]∞ and [(C5H5)­WO]∞ are semiconductors with the narrow bands, whereas [(C5H5)­MoO]∞ behaves as metal.