Strain-Modulated Reactivity: An Acidic Silane.

Compounds of main-group elements such as silicon are attractive candidates for green and inexpensive catalysts. For them to compete with state-of-the-art transition-metal complexes, new reactivity modes must be unlocked and controlled, which can be achieved through strain. Using a tris(2-skatyl)methylphosphonium ([TSMPH ] ) scaffold, we prepared the strained cationic silane [TSMPSiH] .

Synthesis and Complexation of a Free Germanide Bearing a Tridentate N-Heterocyclic Substituent.

The tris-N-heterocycle germanide (tmim)Ge () (tmimH = tris(3-methylindol-2-yl)methane) was synthesized by nucleophilic substitution for the tmim trianion on GeCl·dioxane. In combination with the previously reported (tmim)Si and (tmim)P analogues, it provides a convenient model for investigating the influence of the central atom on the properties of isoelectronic ligands. Complexation of the germanide (tmim)Ge to CuCl resulted in the dimeric chloro cuprate [(tmim)GeCu(μ-Cl)] , which is prone to dissociation in MeCN to form the neutral, solvated germylcopper (tmim)GeCu(NCMe).

Synthesis of N-Heterocycle Substituted Silyl Ligands within the Coordination Sphere of Iron.

N-Heterocycle-substituted silyl iron complexes have been synthesized by nucleophilic substitution at trichlorosilyl ligands bound to iron. The homoleptic (tripyrrolyl)- and tris(3-methylindolyl)silyl groups were accessed from (ClSi)CpFe(CO) (ClSiFp) by substitution of chloride with pyrrolide or 3-methylindolide, respectively. Analogously, nucleophilic substitution of Cl with pyrrolide on the anionic Fe(0) synthon ClSiFe(CO) generates the (tripyrrolyl)silyl ligand, bound to the iron tetracarbonyl fragment.

A Free Silanide from Nucleophilic Substitution at Silicon(II).

A computationally guided synthetic route to a free silanide derived from tris(3-methylindol-2-yl)methane ([(tmim)Si] ) through nucleophilic substitution on the Si precursor (Idipp)SiCl is reported (Idipp=2,3-dihydro-1,3-bis(2,6-diisopropylphenyl)-1H-imidazol-2-ylidene). This approach circumvents the need for strained tetrahedral silanes as synthetic intermediates. Computational investigations show that the electron-donating properties of [(tmim)Si] are close to those of PMe Experimentally, the [(tmim)Si] anion is shown to undergo clean complexation to the base metal salts CuCl and FeCl , demonstrating the potential utility as a supporting ligand.

Hydrosilylation in Aryliminopyrrolide-Substituted Silanes.

A range of silanes was synthesized by the reaction of HSiCl3 with iminopyrrole derivatives in the presence of NEt3 . In certain cases, intramolecular hydrosilylation converts the imine ligand into an amino substituent. This reaction is inhibited by factors such as electron-donating substitution on Si and steric bulk.

Spectroscopic Characterization of a Monomeric, Cyclopentadienyl-Based Rhenium(V) Dioxo Complex.

Mononuclear, coordinatively unsaturated rhenium(V) dioxo species of the type XReO2 (X = Me, substituted cyclopentadienyl) have long been postulated as intermediates in rhenium-catalyzed deoxydehydration, but their characterization was precluded because of aggregation into dimeric or oligomeric structures. Using the bulky 1,2,4-tri-tert-butylcyclopentadienyl (Cp(ttt)) ligand, the rhenium(V) dioxo species (Cp(ttt))ReO2 could now be observed, in equilibrium with the dimeric form [(Cp(ttt))Re(O)μ-O]2, and characterized by NMR, IR, and UV-vis spectroscopies, as well as electrospray ionization mass spectrometry. (Cp(ttt))ReO2 is shown to be the primary product of reduction of the rhenium(VII) complex (Cp(ttt))ReO3 with PPh3 and demonstrated to react with ethylene glycol significantly faster than its dimeric counterpart, supporting its role as an intermediate in rhenium-catalyzed deoxydehydration reactions.

Tailoring ZnSe-CdSe colloidal quantum dots via cation exchange: from core/shell to alloy nanocrystals.

We report a study of Zn(2+) by Cd(2+) cation exchange (CE) in colloidal ZnSe nanocrystals (NCs). Our results reveal that CE in ZnSe NCs is a thermally activated isotropic process. The CE efficiency (i.