The new iridium N-heterocyclic carbene complexes Cp N Ir(Ii-PrMe)I 2 and CpIr(Ii-PrMe)I 2 (Cp N ) (2-(dimethylamino)ethyl)cyclopentadienyl; Ii-PrMe ) 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) have been synthesized along with Ir(cod)(Ii-PrMe)Cl, Cp N Ir(Ii-PrMe)(η 2 -cod), and CpIr(Ii-PrMe)(η 2 -cod). Facile intramolecular alkyl C-H bond activation reactions of Cp*Ir(Ii-PrMe)Cl 2 (Cp* ) η 5 -pentamethylcyclopentadienyl) and Cp N Ir(Ii-PrMe)I 2 have occurred by treatment with MeONa and AgOTf, respectively.

The series Cp*Ir(NHC) (Cp* ) η 5 -pentamethylcyclopentadienyl; NHC ) N-heterocyclic carbene) complexes, Cp*Ir(IEt)Cl 2 (1a), Cp*Ir(IPr)Cl 2 (1b), and Cp*Ir(IBu)Cl 2 (1c) (IEt ) 1,3-diethylimidazol-2-ylidene; IPr ) 1,3-di-n-propylimidazol-2-ylidene; IBu ) 1,3-di-n-butylimidazol-2-ylidene) have been prepared by the carbene-transfer method using silver salts. The reactions of 1a-c with 1 equiv of i-PrONa in isopropyl alcohol give chloro hydrido complexes Cp*Ir(NHC)(H)(Cl) (2a-c). The reaction of 1a with 2 equiv of i-PrONa in isopropyl alcohol results in the intramolecular C-H activation of the ethyl group in the NHC ligand to give Cp*Ir(IEt′)(H) (3), while the similar reactions of 1b and 1c give dihydrido complexes Cp*Ir(IPr)(H) 2 (4b) and Cp*Ir(IBu)(H) 2 (4c) as main products, respectively. These reactions proceed via alkoxo species, [Cp*Ir(NHC)(Oi-Pr)]Cl and Cp*Ir(NHC)(Oi-Pr)(H), as the key intermediates. Derivation of 3 into the chloro complex Cp*Ir(IEt′)(Cl) (5) and cationic complexes [Cp*Ir(IEt′)(L)]OTf [L ) acetonitrile (6); pyridine (7)] is also described. § Dedicated to the memory of Professor Yoshihiko Ito for his great contribution to organometallic chemistry.

Density functional theory (DFT) calculations were conducted to investigate mechanistic details of ethanol‐to‐butadiene conversion reaction over MgO or ZnO catalyst. We evaluated the Lewis acidity and basicity of MgO and ZnO and found that ZnO had the stronger Lewis acidity and basicity than MgO. Potential energy surfaces of ethanol‐to‐butadiene conversion, which included relevant transition states and intermediates, were computed in detail following the generally accepted mechanism reported in the literature, where such mechanism included ethanol dehydrogenation, aldol condensation, Meerwein‐Pondorf‐Verley reduction, and crotyl alcohol dehydration. DFT results showed that ethanol dehydrogenation was the rate‐limiting step of overall reaction when the reaction was catalyzed by MgO. Also, DFT results showed that ethanol dehydrogenation occurred more easily on ZnO than on MgO, where such a result correlated with the stronger Lewis acidity of ZnO. In addition, we computed ethanol dehydration, which generates ethylene, one of the major undesired side reaction products for butadiene formation. DFT results showed that ZnO favored dehydrogenation over dehydration, while MgO favored dehydration.

The 1,1 0 -disila-4,4 0 -biphenyl species 1, the first molecule bearing directly connected two silaaromatic rings, was synthesized and characterized by its spectroscopic and X-ray crystallographic data. The UV-vis spectrum of 1 showed not only a red shift but also a 6-fold increase in absorbance of the longest absorption maximum in comparison with those of Tbt-substituted silabenzene, indicating that the concept of conjugation through the single bond connecting two aromatic rings is applicable even in the silaaromatic systems.

The ZnO-ZrO2/SiO2 catalyst is very active and selective for the ethanol conversion to 1,3-butadiene (ETB). By probing through varying the method of catalyst preparation we uncovered that there is no...

Novel hydrido(silacyclohexadienyl)chromium complexes bearing a bulky substituent, Tbt (2,4,6-tris[bis(trimethylsilyl)methyl]phenyl), were synthesized using formal insertion reactions of Cr(0) into C-H or Si-H bond. When the reactions of 1-silacyclohexa-2,4-dienes bearing a hydroxy or chloro group on the silicon atom with [Cr(CH 3 CN) 3 (CO) 3 ] were performed, the corresponding hydrido(1-silacyclohexa-2,4-dienyl) complexes were obtained as the sole product. A similar reaction of a hydrosilane having a similar skeleton with [Cr(CH 3 CN) 3 (CO) 3 ] gave an unprecedented type of silacyclohexadienyl complex, hydrido(1-silacyclohexa-1,3-dienyl)chromium bearing a three-center bonding interaction among the silicon, hydrogen, and chromium atoms. These are the first syntheses of silacyclohexadienyl complexes by the formal insertion reaction toward the corresponding silacyclohexadienes. Furthermore, the isolation of the silacyclohexadienyl anion was achieved; it was applied to synthesis of the corresponding sandwich-type iron complex. Structures of the newly obtained complexes were revealed based on their NMR and IR spectroscopic data and X-ray diffraction study.

A key intermediate for the hydration reaction of [Cr(η6-silabenzene)(CO)3], hydrido(η5-silacyclohexadienyl)chromium complex, was successfully synthesized by the reaction of silabenzene complex with 2 mol equiv of H2O. X-ray diffraction study revealed that the hydroxy group on the central silicon atom is located at the endo position to the metal moiety. The treatment of the endo adduct with excess of D2O resulted in the stereoselective formation of 1-silacyclohexa-2,4-diene bearing a deuterium atom at the methylene position.

A mass of codes: Lysine‐rich silaffin proteins from diatoms guide silica formation by self‐assembly processes. Aided by mass spectrometry, the analysis of 28 posttranslationally modified lysine residues in silaffin‐3 from Thalassiosira pseudonana uncovers an amino acid sequence based code selecting the type of modification. This code may be a key element in the genetic control of species‐specific silica architectures.