Preparation of a Compound with a SiII -SiIV -SiII Bonding Arrangement.

Herein, we report the synthesis of a rare bis-silylene, 1, in which two SiII atoms are bridged by a SiIV atom. Compound 1 contains an unusual SiII -SiIV -SiII bonding arrangement with SiII -SiIV bond distances of 2.4212(8) and 2.4157(7) Å. Treatment of 1 with Fe(CO)5 afforded a dinuclear Fe0 complex 2 with two unusually long Si-Si bonds (2.4515(8) and 2.4488(10) Å). We have also carried out a detailed computational study to understand the nature of the Si-Si bonds in these compounds. Natural bond orbital (NBO) and energy decomposition analysis-natural orbital for chemical valence (EDA-NOCV) analyses reveal that the Si-Si bonds in 1 and 2 are of an electron-sharing nature.

Computationally rational design of metal-involving halogen bonds with π-covalency: Structures and bonding analysis.

Traditional π-covalent interactions have been proved in the non-metal halogen bond adducts formed by chloride and halogenated triphenylamine-based radical cations. In this study, we have rationally designed two metal-involving halogen bond adducts with π-covalency property, such as [L1-Pd···I-PTZ]+ (i.e., 1) and [L2-Pd···I-PTZ]+ (i.e., 2), in which the square-planar palladium complexes serve as halogen bond acceptor and 3,7-diiodo-10H-phenothiazine radical cation (i.e., [I-PTZ]•+ ) acts as halogen bond donor. Noncovalent interaction analysis and quantum theory of atoms in molecules analysis revealed that there are notable halogen bond interactions along the Pd···I direction without genuine chemical bond formed in both designed adducts. Energy decomposition analysis together with natural orbital for chemical valence calculations were performed to gain insight into their bonding nature, which demonstrated the presence of remarkable π-covalent interactions and σ-covalent interactions in both 1 and 2. We therefore proposed a new strategy for building the metal-involving halogen bonds with π-covalency property, which will help the further development of new types of halogen bonds.

Dative quadruple bonds between d10 transition metals and beryllium in BeM(PMe3 )2 and BeM(CO)2 (M = Ni, Pd, and Pt) complexes: Transition metal fragments as six-electron donor and two-electron acceptor.

The structure, chemical bonding, and reactivity of neutral 16 valence electrons (VE) transition metal complexes of beryllium, BeM(PMe3 )2 (1M-Be) and BeM(CO)2 (2M-Be, M = Ni, Pd, and Pt) were studied. The molecular orbital and EDA-NOCV analysis suggest dative quadruple bonds between the transition metal and beryllium, viz., one Be→M σ bond, one Be←M σ bond, and two Be←M π bonds. The strength of these bonding interactions varies based on the ligands coordinated to the transition metal. The Be←M σ bond is stronger than the Be→M σ bond when the ligand is PMe3, whereas the reverse order is observed when the ligand is CO. This is attributed to the higher π acceptor strength of CO as compared to PMe3 . Since these complexes have M-Be dative quadruple bonds, the beryllium center is susceptible to ambiphilic reactivity, as indicated by high proton and hydride affinity values.

Theoretical investigation of the effect of O⋯M={Ti,Zr,Hf} interactions on the sensitivity of energetic N-nitro compounds.

This paper outlines the role of intermolecular interactions involving group 4 transition metals in stabilising the N-NO2 trigger bonds. Minimising sensitivity is the foremost priority in designing energetic compounds. A quantitative analysis with Molecular Electrostatic Potential (MEP) evidenced anomalies arising from the marked depletion of negative charge distribution of RDX and HMX. The Energy Decomposition Analysis with Natural Orbitals for Chemical Valence (EDA-NOCV) results reveal that the electrostatic and orbital contributions are the dominant factors driving the assembly of the M={Ti,Zr,Hf}-based complexes. Sensitivity of the N-NO2 trigger bonds is investigated by using the Quantum Theory of Atoms in Molecules (QTAIM). The QTAIM topological analysis showed that the O⋯M={Ti,Zr,Hf} interaction strengthens these trigger bonds, revealing an increased stability to decomposition. This effect is more marked in the Hf- and Zr-based complexes. Finally, the results based on Interaction Indicator Region (IRI) are fully consistent with those generated from QTAIM analysis.