Filtern
Volltext vorhanden
- ja (28)
Gehört zur Bibliographie
- ja (28)
Dokumenttyp
Schlagworte
- boron (17)
- diborenes (7)
- carbenes (3)
- density functional calculations (3)
- diborane (3)
- inorganic chemistry (3)
- Bor (2)
- borylenes (2)
- chemical bonding (2)
- diborynes (2)
- diradicals (2)
- heterocycles (2)
- main group elements (2)
- radicals (2)
- 1,2-additions (1)
- Anorganische Chemie (1)
- Arylborylene Complexes (1)
- Boron (1)
- Borylation (1)
- B−H activation (1)
- CO2 fixation (1)
- Carbene (1)
- DFT-Rechnungen (1)
- Decarbonylierung (1)
- Diboran (1)
- Diboryne (1)
- Dihydroboranes (1)
- Festkörperstrukturen (1)
- Halogene (1)
- Heterocyclen (1)
- Hydroarylation (1)
- Ketene (1)
- N ligands (1)
- N-heterocyclic carbenes (1)
- OLEDs (1)
- Phosphor (1)
- Ruthenium (1)
- \(\pi\) interactions (1)
- ab initio calculations (1)
- alkylideneborane (1)
- antiaromaticity (1)
- aromaticity (1)
- beryllium (1)
- bond theory (1)
- boranes (1)
- borohydrides (1)
- boron chains (1)
- boron tetraiodide (1)
- boron-bound hydrogen (1)
- boryl anion (1)
- borylation (1)
- carbene (1)
- carbene donor (1)
- carbene ligands (1)
- carbon dioxide (1)
- catenation (1)
- chalcogens (1)
- chemistry (1)
- computational chemistry (1)
- cumulene (1)
- decarbonylation (1)
- dehydrocoupling (1)
- density functional theory (1)
- diboranes (1)
- diboration (1)
- diborene (1)
- electrolytes (1)
- halides (1)
- hydroarylation (1)
- hydroboration (1)
- hydrogen (1)
- iodine (1)
- ketenes (1)
- ligands (1)
- low-valent main-group species (1)
- multiple bonding (1)
- multiple bonds (1)
- naphthyridine (1)
- nucleophile (1)
- nucleophilic addition (1)
- nucleophilic substitution (1)
- oligomerization (1)
- organometallic chemistry (1)
- oxidation (1)
- phosphorus (1)
- phosphorus heterocycles (1)
- pi-conjugation (1)
- pincer ligand (1)
- potassium reagent (1)
- ruthenium (1)
- s-block metals (1)
- sigma boranes (1)
- small HOMO-LUMO gap (1)
- small-molecule activation (1)
- solid-state NMR (1)
- solid-state sturcture (1)
- steric effects (1)
- thermal rearrangement (1)
- transition metal (1)
- triple bonds (1)
Institut
Sonstige beteiligte Institutionen
The reaction of [(cAAC\(^{Me}\))BH\(_{3}\)] (cAAC\(^{Me}\) = 1-(2,6-iPr\(_{2}\)C\(_{6}\)H\(_{3}\))-3,3,5,5-tetramethylpyrrolidin-2-ylidene) with a range of organolithium compounds led to the exclusive formation of the corresponding (dihydro)organoborates, Li\(^{+}\)[(cAAC\(^{Me}\)H)BH\(_{2}\)R]− (R = sp\(^{3}\)-, sp\(^{2}\)-, or sp-hybridised organic substituent), by migration of one boron-bound hydrogen atom to the adjacent carbene carbon of the cAAC ligand. A subsequent deprotonation/salt metathesis reaction with Me3SiCl or spontaneous LiH elimination yielded the neutral cAAC-supported mono(organo)boranes, [(cAAC\(^{Me}\)H)BH\(_{2}\)R]− (R]. Similarly the reaction of [cAAC\(^{Me}\))BH\(_{3}\)] with a neutral donor base L resulted in adduct formation by shuttling one boron-bound hydrogen to the cAAC ligand, to generate [(cAAC\(^{Me}\)H)BH\(_{2}\)L], either irreversibly (L = cAAC\(^{Me}\)) or reversibly (L = pyridine). Variable-temperature NMR data and DFT calculations on [(cAAC\(^{Me}\)H)BH\(_{2}\)(cAAC\(^{Me}\))] show that the hydrogen on the former carbene carbon atom exchanges rapidly with the boron-bound hydrides.
The diborene 1 was synthesized by reduction of a mixture of 1,2-di-9-anthryl-1,2-dibromodiborane(4) (6) and trimethylphosphine with potassium graphite. The X-ray structure of 1 shows the two anthryl rings to be parallel and their π(C\(_{14}\)) systems perpendicular to the diborene π(B=B) system. This twisted conformation allows for intercalation of the relatively high-lying π(B=B) orbital and the low-lying π* orbital of the anthryl moiety with no significant conjugation, resulting in a small HOMO-LUMO gap (HLG) and ultimately an unprecedented anthryl B–B bond hydroarylation. The HLG of 1 was estimated to be 1.57 eV from the onset of the long wavelength band in its UV–vis absorption spectrum (THF, λ\(_{onset}\) = 788 nm). The oxidation of 1 with elemental selenium afforded diboraselenirane 8 in quantitative yield. By oxidative abstraction of one phosphine ligand by another equivalent of elemental selenium, the B–B and C\(^1\)–H bonds of 8 were cleaved to give the cyclic 1,9-diboraanthracene 9.
The self-stabilizing, tetrameric cyanoborylene [(cAAC)B(CN)]4 (I, cAAC = 1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-ylidene) and its diborene relative, [(cAAC)(CN)B=B(CN)(cAAC)] (II), both react with disulfides and diselenides to yield the corresponding cAAC-supported cyanoboron bis(chalcogenides). Furthermore, reactions of I or II with elemental sulfur and selenium in various stoichiometries provided access to a variety of cAAC- stabilized cyanoboron-chalcogen heterocycles, including a unique dithiaborirane, a diboraselenirane, 1,3-dichalcogena-2,4-diboretanes, 1,3,4-trichalcogena- 2,5-diborolanes and a rare six-membered 1,2,4,5-tetrathia-3,6-diborinane. Stepwise addition reactions and solution stability studies provided insights into the mechanism of these reactions and the subtle differences in reactivity observed between I and II.
CO\(_2\) is found to undergo room-temperature, ambient- pressure reactions with two species containing boron-boron multiple bonds, leading to incorporation of either one or two CO\(_2\) molecules. In one case, a thermally-unstable intermediate was structurally characterized, indicating the operation of an initial 2+2 cycloaddition mechanism in the reaction.
Molecules containing multiple bonds between atoms—most often in the form of olefins—are ubiquitous in nature, commerce, and science, and as such have a huge impact on everyday life. Given their prominence, over the last few decades, frequent attempts have been made to perturb the structure and reactivity of multiply-bound species through bending and twisting. However, only modest success has been achieved in the quest to completely twist double bonds in order to homolytically cleave the associated π bond. Here, we present the isolation of double-bond-containing species based on boron, as well as their fully twisted diradical congeners, by the incorporation of attached groups with different electronic properties. The compounds comprise a structurally authenticated set of diamagnetic multiply-bound and diradical singly-bound congeners of the same class of compound.
sp\(^2\)–sp\(^3\) diborane species based on bis(catecholato)diboron and N-heterocyclic carbenes (NHCs) are subjected to catechol/bromide exchange selectively at the sp\(^3\) boron atom. The reduction of the resulting 1,1-dibromodiborane adducts led to reductive coupling and isolation of doubly NHC-stabilized 1,2-diboryldiborenes. These compounds are the first examples of molecules exhibiting pelectron delocalization over an all-boron chain.
Molecules containing multiple bonds between atoms—most often in the form of olefins—are ubiquitous in nature, commerce, and science, and as such have a huge impact on everyday life. Given their prominence, over the last few decades, frequent attempts have been made to perturb the structure and reactivity of multiply-bound species through bending and twisting. However, only modest success has been achieved in the quest to completely twist double bonds in order to homolytically cleave the associated π bond. Here, we present the isolation of double-bond-containing species based on boron, as well as their fully twisted diradical congeners, by the incorporation of attached groups with different electronic properties. The compounds comprise a structurally authenticated set of diamagnetic multiply-bound and diradical singly-bound congeners of the same class of compound.
A set of diboryldiborenes are prepared by the mild, catalyst-free, room-temperature diboration of the B–B triple bonds of doubly base-stabilized diborynes. Two of the product diboryldiborenes are found to be air- and water-stable in the solid state, an effect that is attributed to their high crystallinity and extreme insolubility in a wide range of solvents.
The lability of B=B, B-P and B-halide bonds is combined in the syntheses of the first diiododiborenes. In a series of reactivity tests, these diiododiborenes demonstrate cleavage of all six of their central bonds in different ways, leading to products of B=B hydrogenation and dihalogenation as well as halide exchange.