A Stable Two-Coordinate Acyclic Silylene

Abstract

Simple two-coordinate acyclic silylenes, SiR(2), have hitherto been identified only as transient intermediates or thermally labile species. By making use of the strong σ-donor properties and high steric loading of the B(NDippCH)(2) substituent (Dipp = 2,6-(i)Pr(2)C(6)H(3)), an isolable monomeric species, Si{B(NDippCH)(2)}{N(SiMe(3))Dipp}, can be synthesized which is stable in the solid state up to 130 °C. This silylene species undergoes facile oxidative addition reactions with dihydrogen (at sub-ambient temperatures) and with alkyl C-H bonds, consistent with a low singlet-triplet gap (103.9 kJ mol(-1)), thus demonstrating fundamental modes of reactivity more characteristic of transition metal systems.

Dispersion Forces and Counterintuitive Steric Effects in Main Group Molecules: Heavier Group 14 (Si–Pb) Dichalcogenolate Carbene Analogues with Sub-90° Interligand Bond Angles

“…17c The MSeAr Pr i 4 (M = Li, K) salts were prepared by addition of either LiBu n or K metal to the air-stable triselenine, Se(SeAr Pr i 4 )2 (see Supporting Information). 19 1 H and 13 C NMR spectra were recorded on either a Varian 300 MHz, 400 MHz or a 600 MHz instrument and referenced internally to either protio benzene or trace silicone grease (δ = 0.29 in C6D6). 29 Si NMR spectra were acquired on a…”

Diborane heterolysis: breaking and making B–B bonds at magnesium

“…A reaction of compound 8 with B 2 pin 2 was performed under identical conditions to those employed in the synthesis of compounds 10 and 11. Initial inspection of the resultant 1 H and 11 B NMR spectra indicated the generation of a single reaction product (12), which was anticipated to be the result of formal n-BuB(hex) elimination to form a magnesium complex of the catenated [ pinB(Bpin)B(hex)] − anion. Work up and crystallisation of compound 12, however, revealed that this process had produced an isomeric form of the anticipated triborane anion (Scheme 4).…”

The Nature of the Active Site in Ziegler–Natta Olefin Polymerization Catalysis Systems – A Computational Investigation

“…However, a barrier height of 22.0 kcal/mol is not formidable, especially as the ZN catalysis is usually performed at temperatures greater than 60°C [63,64] (it is well established that reactions with barriers of 20.0-25.0 kcal/mol occur readily at room temperature). [65][66][67] What is more pertinent is the result that the insertion process becomes significantly more preferred in comparison to termination, by more than 12.0 kcal/mol, for every donor case that has been considered. The reason for this marked preference can be understood by a comparison of the insertion and termination transition states.…”