0000000000651678
AUTHOR
James Fettinger
Isolation of a Stable, Acyclic, Two-Coordinate Silylene
The synthesis and characterization of a stable, acyclic two-coordinate silylene, Si(SArMe6)2, (ArMe6 = C6H3-2,6(C6H2-2,4,6-Me3)2) by reduction of Br2Si(SArMe6)2 with a magnesium(I) reductant is described. It features a v-shaped silicon coordination with a S-Si-S angle of 90.519(2)° and an average Si-S distance of 2.158(3) Å. Although it reacts readily with an alkyl halide, it does not react with hydrogen under ambient conditions probably as a result of the ca. 4.3 eV energy difference between the frontier silicon lone pair and 3p orbitals. peerReviewed
A Germanium Isocyanide Complex Featuring (n → π*) Back-Bonding and Its Conversion to a Hydride/Cyanide Product via C-H Bond Activation under Mild Conditions
Reaction of the diarylgermylene Ge(ArMe6)2 [ArMe6 = C6H3-2,6-(C6H2-2,4,6-(CH3)3)2] with tert-butyl isocyanide gave the Lewis adduct species (ArMe6)2GeCNBut, in which the isocyanide ligand displays a decreased C–N stretching frequency consistent with an n → π* back-bonding interaction. Density functional theory confirmed that the HOMO is a Ge–C bonding combination between the lone pair of electrons on the germanium atom and the C–N π* orbital of the isocyanide ligand. The complex undergoes facile C–H bond activation to produce a new diarylgermanium hydride/cyanide species and isobutene via heterolytic cleavage of the N–But bond. peerReviewed
Mechanistic Study of Stepwise Methylisocyanide Coupling and C-H Activation Mediated by a Low-Valent Main Group Molecule
An experimental and DFT investigation of the mechanism of the coupling of methylisocyanide and C–H activation mediated by the germylene (germanediyl) Ge(ArMe6)2 (ArMe6 = C6H3-2,6(C6H2-2,4,6-Me3)2) showed that it proceeded by initial MeNC adduct formation followed by an isomerization involving the migratory insertion of the MeNC carbon into the Ge–C ligand bond. Addition of excess MeNC led to sequential insertions of two further MeNC molecules into the Ge–C bond. The insertion of the third MeNC leads to methylisocyanide methyl group C–H activation to afford an azagermacyclopentadienyl species. The X-ray crystal structures of the 1:1 (ArMe6)2GeCNMe adduct, the first and final insertion produc…
Dispersion Forces and Counterintuitive Steric Effects in Main Group Molecules: Heavier Group 14 (Si-Pb) Dichalcogenolate Carbene Analogues with Sub-90° Interligand Bond Angles
The synthesis and spectroscopic and structural characterization of an extensive series of acyclic, monomeric tetrylene dichalcogenolates of formula M(ChAr)2 (M = Si, Ge, Sn, Pb; Ch = O, S, or Se; Ar = bulky m-terphenyl ligand, including two new acyclic silylenes) are described. They were found to possess several unusual features—the most notable of which is their strong tendency to display acute interligand, Ch–M–Ch, bond angles that are often well below 90°. Furthermore, and contrary to normal steric expectations, the interligand angles were found to become narrower as the size of the ligand was increased. Experimental and structural data in conjunction with high-level DFT calculations, in…