Diverse Reactions of o-Carborane-Fused Silylenes with C≡E (E = C, P) Triple Bonds

Silylenes with a Small Chalcogenide Substituent: Tuning Frontier Orbital Energies from O to Te

The general synthesis of heteroleptic acyclic silylenes with a bulky carbazolyl substituent (dtbpCbz) is detailed and a series of compounds with a chalcogenide substituent of the type [(dtbpCbz)SiE16R] (E16R=OtBu, SEt, SePh, TePh) is reported. With the bulky carbazolyl substituent present, the chalcogenide moiety can be very small, as is shown by incorporating groups as small as ethyl, phenyl or tert-butyl. For the first time, the electronic properties of the silylene can be tuned along a complete series of chalcogenide substituents. The effects are clearly visible in the NMR and UV/Vis spectra, and were rationalised by DFT computations. The reactivity of the heaviest chalcogenide-substituted silylenes was probed by reactions with trimethylphosphine selenide and the terphenyl azide TerN3 (Ter=2,6-dimesitylphenyl).

Reactivities of phosphaalkynes towards diverse bis-silylenes

Bis-silylenes do not only act as strong chelating σ-donor ligands, but also exhibit cooperative behaviour in the activation of small molecules. Three different P-Si containing molecules were prepared from the reaction between tBuCP and different bis-silylenes, which are bridged by ferrocenediyl, diaminobenzene, or o-carborane.

Applications of low-valent compounds with heavy group-14 elements

Over the last two decades, the low-valent compounds of group-14 elements have received significant attention in several fields of chemistry owing to their unique electronic properties. The low-valent group-14 species include tetrylenes, tetryliumylidene, tetrylones, dimetallenes and dimetallynes. These low-valent group-14 species have shown applications in various areas such as organic transformations (hydroboration, cyanosilylation, N-functionalisation of amines, and hydroamination), small molecule activation (e.g. P4, As4, CO2, CO, H2, alkene, and alkyne) and materials. This review presents an in-depth discussion on low-valent group-14 species-catalyzed reactions, including polymerization of rac-lactide, L-lactide, DL-lactide, and caprolactone, followed by their photophysical properties (phosphorescence and fluorescence), thin film deposition (atomic layer deposition and vapor phase deposition), and medicinal applications. This review concisely summarizes current developments of low-valent heavier group-14 compounds, covering synthetic methodologies, structural aspects, and their applications in various fields of chemistry. Finally, their opportunities and challenges are examined and emphasized.

Synthesis of SiN/SiS-heterocycles via the reactions of a bis-silylene with isocyanate/isothiocyanate molecules

Reactions of o-carborane-fused bis-silylene 1 with isocyanate/isothiocyanate molecules furnished a series of SiN/SiS-heterocycles, which show distinct styles of cyclization and were theoretically studied.

SiP-heterocycles derived from a bulky phosphanylsilylene

Bis(1-adamantyl)phosphanylsilylene 1 was reacted with ArCCR (Ar = Ph, 4-iPr-C6H4, 3-F-C6H4; R = H, Ph) at 80 °C under microwave irradiation to afford fluorescence-active SiP-heterocycles 3a-d, which may undergo unique isomerizations starting from silirene intermediates. Moreover, the treatment of 1 with AdCP furnished a heavy congener of cyclopentadiene (4), whose formation involves cleavage of the Si(II)-P bond that is rarely observed in silylene chemistry.

Redox-active carborane clusters in bond activation chemistry and ligand design

Icosahedral closo-dodecaboranes have the ability to accept two electrons, opening into a dianionic nido-cluster. This transformation can be utilized to store electrons, drive bond activation, or alter coordination to metal cations. In this feature article, we present cases for each of these applications, wherein the redox activity of carborane facilitates the generation of unique products. We highlight the effects of exohedral substituents on reactivity and the stability of the products through conjugation between the cluster and exohedral substituents. Futher, the utilization of the redox properties and geometry of carborane clusters in the ligand design is detailed, both in the stabilization of low-valent complexes and in the tuning of ligand geometry.