Heavy Tetrel Clusters Based on the Bicyclobutane Framework: Bicyclo[1.1.0]butanes, [1.1.1]Propellanes, and Tricyclo[2.1.0.02,5 ]pentanes

In this review, the current state of affairs in the novel field of the group 14 element clusters based on the bicyclo[1.1.0]butane framework, namely, bicyclo[1.1.0]butane, [1.1.1]propellane, and tricyclo[2.1.0.02,5 ]pentane derivatives, are overviewed. Structural similarities and differences between these three classes of highly strained polycyclic compounds are considered from the viewpoint of the critically important nature of their bridgehead bonds. Synthetic strategies towards bicyclo[1.1.0]butanes, [1.1.1]propellanes, and tricyclo[2.1.0.02,5 ]pentanes, as well as their peculiar structural and bonding features, and specific reactivity, are also presented and discussed in this review.

Pyramidanes: newcomers to the anti-van't Hoff-Le Bel family

In this feature article, an overview of the chemistry of pyramidanes, as a novel class of main group element clusters, is given. A general introduction sets the scene, briefly presenting the non-classical pyramidal geometry of tetracoordinate carbon, as opposed to the classical tetrahedral configuration. Pyramidanes, as the simplest organic compounds possessing a pyramidal carbon atom, are then discussed from both computational and experimental viewpoints, to show the theoretical predictions on the stability and thus the feasibility of pyramidanes has finally culminated in the isolation of the first stable representatives of the pyramidane family featuring heavy main group elements at the apex of the square pyramid. Synthetic strategies towards pyramidanes, as well as their peculiar structural features, non-classical bonding situations, and specific reactivity, are presented and discussed in this review.

Titanium Germylidenes

Two novel 18-electron titanium germylene complexes, Cp₂ Ti(L)=Ge[Si₃ (SiMe^t Bu₂ )₄ ] 3 b (L=Me₃ P) and 3 c (L=XylNC), were synthesized, isolated, and structurally characterized. The length of the titanium-germanium bonds of 2.5387(3) Å and 2.5276(3) Å (in 3 b and 3 c, respectively) well match those expected for the double bond, which was further supported by the DFT study. Based on their structural characteristics, as well as their atomic charges calculations which revealed Ti(δ+)=Ge(δ-) bond polarization, both 3 b and 3 c are classified as the Schrock-type titanium germylidenes, as the germanium analogues of the widely known titanium alkylidenes. By contrast, germylene complexes of the group 6 metals 8 a (M=Mo) and 8 b (M=W) are better described as Fischer-type germylene complexes.

Electronic structure and magnetic properties of the triangular nanographenes with radical substituents: a DFT study

DFT modeling of triangular polycyclic hydrocarbons bearing radicals provided insights into dependence of electronic ground states on their structural peculiarities

Tuning Philicity of Dichlorosilylene: Nucleophilic Behavior of the Dichlorosilylene-NHC Complex Cl2Si-IPr

Novel unsaturated four-membered ring disilene, 3,3-dichloro-1,2,4,4-tetrakis[di-tert-butyl(methyl)silyl]-¹Δ-1,2,3,4-trisilagermetene, was synthesized by the ring expansion reaction of the three-membered ring 1-disilagermirene with the silylene-NHC complex Cl₂Si-IPr. The mechanism of the unexpected formation of this compound was verified by high-level density functional theory computations, which revealed n_Si:(HOMO)-π_Si=Si(LUMO) ^* as the dominant orbital interaction.

Arsagermene, a compound with an –AsGe double bond

Arsagermene, a stable compound featuring an AsGe double bond, was synthesized, isolated, and structurally characterized for the first time.

Bis(stibahousene)

Strained hydrocarbons constitute one of the most prominent classes of organic compounds. Among them, bicyclo[2.1.0]pentene ("housene") derivatives represent a highly challenging and very attractive class. Although organic housenes have been known for more than five decades, there are still very few of them containing heavier main group elements. In this paper, we report on the two housene-type structures, novel monomeric stibahousene and dimeric bis(stibahousene). The bonding natures of both compounds were approached from both experimental and computational directions to reveal their peculiar structural features.

Germanium, carbon-germanium, and silicon-germanium triangulenes

A series of germanium-containing triangular molecules have been studied by density functional theory (DFT) calculations. The triangulene topology of the compounds provides for their high-spin ground states and strong sign alternation of spin density and atomic charge distributions. High values of the exchange coupling constants witness ferromagnetic ordering of electronic structures of all studied triangulenes. The compounds bearing more electronegative atoms in a-positions of the triangular networks possess higher aromatic character and stronger ferromagnetic ordering.