1,720,987 research outputs found
An Aluminum Dihydride Working as a Catalyst in Hydroboration and Dehydrocoupling
No full textThe well-defined aluminum dihydride LAlH2 (L = HC(CMeNAr)(2), Ar = 2,6-Et2C6H3) (1) operates in catalysis like a transition metal complex. The catalytic activity of 1 for hydroboration of terminal alkynes was investigated. Furthermore, catalyst 1 effectively initiated the dehydrocoupling of boranes with amines, thiols, and phenols, respectively, to form compounds with B-E bonds (E = S, O) under elimination of H-2. Quantum mechanical calculations indicate that hydroboration and dehydrocoupling reactions occur via three consecutive cycloaddition reactions involving the activation of the X-H (X = Al, B, C, and O) sigma-bonds
An Aluminum Hydride That Functions like a Transition-Metal Catalyst
No full textThe reaction of [LAlH2] (L= HC(CMeNAr)(2), Ar= 2,6-iPr(2)C(6)H(3)) with MeOTf (Tf= SO2CF3) resulted in the formation of [LAlH(OTf)] (1) in high yield. The triflate substituent in 1 increases the positive charge at the aluminum center, which implies that 1 has a strong Lewis acidic character. The excellent catalytic activity of 1 for the hydroboration of organic compounds with carbonyl groups was investigated. Furthermore, it was shown that 1 effectively initiates the addition reaction of trimethylsilyl cyanide (TMSCN) to both aldehydes and ketones. Quantum mechanical calculations were carried out to explore the reaction mechanism
Stabilization of a Two-Coordinate Mononuclear Cobalt(0) Compound
No full textCompound (Me-2-cAAC:)(2)Co-0 (2; Me-2-cAAC:=cyclic (alkyl) amino carbene; :C(CH2)(CMe2)(2)N-2,6-iPr(2)C(6)H(3)) was synthesized by the reduction of the precursor (Me-2-cAAC:)(2)(CoCl)-Cl-I (1) with KC8 in THF. The cyclic voltammogram of 1 exhibited one-electron reduction, which suggests that synthesis of a bent 2-metallaallene (2) from 1 should be possible. Compound 2 contains one cobalt atom in the formal oxidation state zero, which is stabilized by two Me-2-cAAC: ligands. Bond lengths from X-ray diffraction are 1.871(2) and 1.877(2) angstrom with a C-Co-C bond angle of 170.12(8)degrees. The EPR spectrum of 2 exhibited a broad resonance attributed to the unique quasi-linear structure, which favors near degeneracy and gives rise to very rapid relaxation conditions. The cAAC-Co bond in 2 can be considered as a typical Dewar-Chatt-Duncanson type of bonding, which in turn retains 2.5 electron pairs on the Co atom as nonbonding electrons.Deutsche Forschungsgemeinschaft (DFG) [RO 224/60-I]; DS
A C2Linked Bis-silene Formed without Using Metals and the Transformation into the Bis-silyl and Bis-silylium C4Cumulenes
No full textA functionalized Ge3-compound with a dual character of the central germanium atom
Full text linkDeutsche Forschungs gemeinschaft [RO 224/60-1]; China Scholarship Council (CSC)(cAAC) Ge(GeL)(2) (1) (cAAC = cyclic alkyl(amino) carbene; L = PhC-(tBuN)(2)), a functionalized Ge-3-compound was prepared. Quantum mechanical studies on 1 show a reciprocal relationship between the electronic state of the central tri-coordinated Ge atom and its reactivity towards protons, viz. tetravalent Ge(0) in terms of bonding and divalent Ge(0) in terms of reactivity. Thus the central Ge atom can be considered as having a hidden but highly reactive lone pair of electrons. However, the terminal Ge atoms can be considered as tri-coordinated divalent Ge(I) with an active lone pair of electrons
One‐Pot Catalytic Synthesis of <i>gem</i> ‐Diazides and Their Direct Conversion into Safe Materials
No full textCommercial availability and storage issues have left reactivity studies of gem-diazides underdeveloped, in contrast to the relatively abundant chemistry of monoazides. The present study uses triflic acid (0.1 mol-%) as a catalyst for the quantitative production of gem-diazides from the reaction of aldehydes with trimethylsilyl azide. The diazides could be isolated in high yields by simple evaporation of the Me3Si-O-SiMe3 byproduct. In a one-pot synthesis, the diazide was directly treated with an N-heterocyclic carbene to obtain a gem-bis(triazabutadiene). Reaction of the diazide with triphenylphosphane followed by triflic acid yielded n N,N'-bis(triphenylphosphane) adduct
Excellent yield of a variety of silicon-boron radicals and their reactivity
No full textHerein we report stable silicon-boron radicals of composition LSi(NMe2)–B(Br)Tip (1), LSi(NMe2)–B(I)Tip (2) LSi(tBu)–B(I)Tip (3) [L = PhC(NtBu)2]. They were prepared in high yield using a one pot reaction of LSiR, X2BTip and KC8 in a 1 : 1 : 1 molar ratio (R = tBu, NMe2; X = Br, I). The reaction of the silicon–boron radical with Br2 and Se affords the dihalogenated compound LSi(tBu)–B(Br2)Tip (4) and oxidative addition product LSi(tBu)[double bond, length as m-dash]Se (5). All the compounds were characterized by single-crystal X-ray structural analysis, electron paramagnetic resonance (EPR) analysis, elemental analysis, multinuclear NMR spectroscopy, and mass spectrometry. Quantum chemical calculations show that the B-centered radicals 1–3 are stabilised by hyperconjugative interactions.Danmarks Grundforskningsfond https://doi.org/10.13039/501100001732Fonds der Chemischen Industrie https://doi.org/10.13039/100018992National Institute of Technology Calicut https://doi.org/10.13039/501100015063Science and Engineering Research Board https://doi.org/10.13039/50110000184
Multiple Cycloaddition Reactions of Ketones with a β‐Diketiminate Al Compound
No full textA beta-diketiminate Al compound (1) with an exocyclic double bond reacts with two equivalents each of benzophenone and 2-benzoylpyridine in a [4+2] cycloaddition to generate bicyclic and tricyclic compounds 2 and 3, respectively. Compound 2 consists of six-and eight-membered aluminium rings, whereas 3 has two five-and one eight-membered ring. Compounds 2 and 3 were characterized by a number of analytical tools including single-crystal X-ray diffraction. The quantum mechanical calculations suggest that the dissociation of the solvent molecule from 1 would lead to an active species 1A having two 1,4-dipolar 4 pi electron moieties, in which the electrophilic site is the Al atom and the nucleophilic positions are polarized exocyclic and endocyclic C=C pi bonds. The detailed mechanistic study shows that the dipolarophiles, benzophenone, and 2-benzoylpyridine undergo double cycloaddition with two 1,4-dipolar 4 pi electron moieties of 1A. Herein, the addition of one molecule of the dipolarophile promotes the addition of the second one
- …
