An asymmetric bis(silyl) niobocene hydride complex, namely, bis(η5-cyclopentadienyl)(fluorodimethylsilyl)hydrido(iododimethylsilyl)niobium, [Nb(C5H5)2(C2H6FSi)(C2H6ISi)H] or Cp2NbH(SiIMe2)(SiFMe2), has been studied to determine the effect of the silyl ligand on the position of the hydride attached to the Nb atom. It has been shown that when a Group 17 atom is substituted onto one of the silyl ligands, there is a greater interaction between the hydride and this ligand, as demonstrated by a shorter Si...H distance. In the present work, we have investigated the effect when the silyl ligands are substituted by different Group 17 atoms. We present here the structure and DFT calculations of Cp2NbH(SiIMe2)(SiFMe2), showing that the position of the hydride is located between the two silyl ligands. The results from our investigation show that the hydride is closer to the silyl ligand that is substituted by fluorine.

PhI(OTf)2 and related ArI(OTf)2 species have been incorrectly invoked as intermediates in oxidation reactions for many years. We recently established that such compounds did not yet exist but remain an attractive target. Here we describe the synthesis, isolation, and structural characterization of NO2 -PhI(OTf)2, which is resistant to decomposition and more reactive than PhI(OTf)(OAc), the species previously misidentified as PhI(OTf)2 .

The dynamic and reversible changes of coordination numbers between five and six in solution and solid states, based on hypervalent tin(IV)-fused azobenzene (TAz) complexes, are reported. It was found that the TAz complexes showed deep-red emission owing to the hypervalent bond composed of an electron-donating three-center four-electron (3c-4e) bond and an electron-accepting nitrogen-tin (N-Sn) coordination. Furthermore, hypsochromic shifts in optical spectra were observed in Lewis basic solvents because of alteration of the coordination number from five to six. In particular, vapochromic luminescence was induced by attachment of dimethyl sulfoxide (DMSO) vapor to the coordination point at the tin atom accompanied with a crystal-crystal phase transition. Additionally, the color-change mechanism and degree of binding constants were well explained by theoretical calculation. To the best of our knowledge, this is the first example of vapochromic luminescence by using stable and variable coordination numbers of hypervalent bonds.

The activation of a single C-F bond in di- and trifluoromethyl groups by frustrated Lewis pairs (FLPs) has been computationally explored by means of Density Functional Theory calculations. It is found that in this activation reaction the FLP partners exhibit a peculiar cooperative action, which is markedly different from related FLP-mediated processes, and where non-covalent interactions established between the Lewis base and the substrate play a decisive role. In addition, the process proceeds through the intermediacy of a hypervalent species featuring a pentacoordinate carbon atom, which is rare in the chemistry of FLPs. The physical factors controlling this process as well as the bonding situation of these hypervalent intermediates have been quantitatively analyzed in detail by using state-of-the-art computational methods to not only rationalize the mechanism of the transformation but also to guide experimentalists towards the realization of these so far elusive hypervalent systems.

PhI(OTf)2 has been used for the past 30 years as a strong I(III) oxidant for organic and inorganic transformations. It has been reported to be generated in situ from the reactions of either PhI(OAc)2 or PhI=O with two equivalents of trimethylsilyl trifluoromethanesulfonate (TMS-OTf). In this report it is shown that neither of these reactions generate a solution with spectroscopic data consistent with PhI(OTf)2 , with supporting theoretical calculations, and thus this compound should not be invoked as the species acting as the oxidant for transformations that have been associated with its use.

Stannylation of calcium carbide followed by Sn-hypervalent iodine(III) exchange reaction cleanly afforded the electrophilic ethynylating agent ethynyl(phenyl)-λ3-iodane in high yield. This two-step method uses very inexpensive materials and is readily operable without any special precautions.

Although oxidative addition (OA) and reductive elimination (RE) are exceedingly important processes in organometallic chemistry, such processes are still extremely rare for main-group element species. Herein, we report a theoretical study on the reaction of phosphine-stabilized silylenes with silanes that proceeds through reversible OA/RE at room temperature. Of particular interest is that this theoretical approach highlights the important role of the ligand, which can greatly affect the kinetics and energy balance of the reaction. Indeed, in contrast to the case of free aminosilylenes, the reaction of ligand-supported silylenes proceeds in an unsynchronized manner and starts with the silylene→silane charge transfer (CT). Suitably electron-donating ligands, such as phosphines or N-heterocyclic carbenes, enhancing the CT at the transition state (TS), significantly decrease the Gibbs activation energy and the exergonic nature of the reaction, which promote the OA/RE processes. In the same way, silanes with electron-withdrawing groups also favor the CT and thus stabilize the TS. It was also computationally predicted that phosphine-stabilized silylenes should be able to activate the C-Si bond of trimethoxy(ethynyl)silane (HC≡C-Si(OMe)3 ) and that the reaction should proceed in a reversible manner under mild conditions.

Three new saccharin-based hypervalent iodine compounds were prepared by the reaction of saccharine with (diacetoxyiodo)arenes or acetoxybenziodoxole. Structures of these new imidoiodanes were established by X-ray crystallography. The saccharin-based μ-oxo-bridged imidoiodane readily reacts with silyl enol ethers under mild conditions to give the corresponding α-aminated carbonyl compounds in moderate yields.

The direct synthesis of N-arylated carbazoles through a palladium-catalyzed amination of cyclic iodonium salts with anilines is described. In particular, electron-poor aniline derivatives reacted smoothly with only 5 mol % of Pd(OAc)2 as catalyst to give the desired products in up to 71% yield. Furthermore, the reactivity of cyclic iodonium salts is compared with the reactivity of the corresponding cyclic bromonium analogues.