Facile synthesis of a stable dihydroboryl {BH2}– anion

While the one-electron reduction of (CAACMe)BH2Br (CAACMe = 1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-ylidene) yields a hydride-shift isomer of the corresponding tetrahydrodiborane, a further reversible reduction leads to the first stable parent boryl anion, [(CAACMe)BH2]–, which acts as a powerful boron nucleophile

Reduction of a dihydroboryl cation to a boryl anion and its air-stable, neutral hydroboryl radical through hydrogen shuttling

The addition of Lewis bases to a cyclic (alkyl)(amino)carbene (CAAC)-supported dihydroboron triflate yields the mixed doubly base-stabilised dihydroboryl cations [(CAAC)BH2L]+. Of these, [(CAAC)2BH2]OTf (OTf = triflate) underwent facile two-electron reduction with KC8 owing to a 1,2-hydride migration from boron to the carbene carbon to yield a stable hydroboryl anion. One-electron oxidation of the latter yielded the first neutral hydroboryl radical, which is bench-stable in the solid state

Intensiv farbige Bor-dotierte Thiazolthiazole durch reduktive Dimerisierung von Borisothiocyanaten

Die Reduktion von (CAAC)BBr2(NCS) (CAAC=cyclisches Alkyl(amino)carben) in der Gegenwart einer Lewis-Base L liefert dreifach koordinierte (CAAC)LB(NCS)-Borylene, die eine reversible (E)/(Z)-Isomerisierung eingehen. Die gleiche Reduktion in Abwesenheit von L führt zu intensiv blauen, bis(CAAC)-stabilisierten, Bor-dotierten, aromatischen Thiazolthiazolen, die aus der Dimerisierung zweifach koordinierter (CAAC)B(NCS)-Borylenintermediate resultieren

Highly colored boron-doped thiazolothiazoles from the reductive dimerization of boron isothiocyanates

Reduction of (CAAC)BBr2(NCS) (CAAC=cyclic alkyl(amino)carbene) in the presence of a Lewis base L yields tricoordinate (CAAC)LB(NCS) borylenes which undergo reversible E/Z‐isomerization. The same reduction in the absence of L yields deep blue, bis(CAAC)‐stabilized, boron‐doped, aromatic thiazolothiazoles resulting from the dimerization of dicoordinate (CAAC)B(NCS) borylene intermediates

Modulation of the Naked-Eye and Fluorescence Color of a Protonated Boron-Doped Thiazolothiazole by Anion-Dependent Hydrogen Bonding

The reaction of a cyclic alkyl(amino)carbene (CAAC)-stabilized thiazaborolo[5,4-d]thiazaborole (TzbTzb) with strong Brønsted acids, such as HCl, HOTf (Tf=O2SCF3) and [H(OEt2)2][BArF4] (ArF=3,5-(CF3)2C6H3), results in the protonation of both TzbTzb nitrogen atoms. In each case X-ray crystallographic data show coordination of the counteranions (Cl−, OTf−, BArF4−) or solvent molecules (OEt2) to the doubly protonated fused heterocycle via hydrogen-bonding interactions, the strength of which strongly influences the 1H NMR shift of the NH protons, enabling tuning of both the visible (yellow to red) and fluorescence (green to red) colors of these salts. DFT calculations reveal that the hydrogen bonding of the counteranion or solvent to the protonated nitrogen centers affects the intramolecular TzbTzb-to-CAAC charge transfer character involved in the S0→S1 transition, ultimately enabling fine-tuning of their absorption and emission spectral features

Ein unsymmetrisches, cyclisches Diboren basierend auf einem chelatisierenden CAAC-Liganden sowie dessen Aktivierung kleiner Moleküle und Umlagerungsreaktionen

Eine Eintopfsynthese eines CAAC-stabilisierten, unsymmetrischen, cyclischen Diborens wurde mittels Zweielektronenreduktion eines CAAC-Addukts von B2Br4(SMe2)2 entwickelt. Theoretische Studien offenbarten, dass dieses Diboren einen signifikant geringeren HOMO-LUMO-Abstand als bisher beschriebene NHC- und Phosphan-stabilisierte Diborene besitzt. Die Komplexierung des Diborens mit [AuCl(PCy3)] lieferte zwei Diboren-AuI-π-Komplexe, während die Reaktion mit DurBH2, P4 und einem terminalen Alkin zur Spaltung der B-H-, P-P- beziehungsweise C-C-π-Bindung führte. Die thermische Umlagerung des Diborens ergab ein elektronenreiches cyclisches Alkylidenboran, welches über die B=C-Doppelbindung direkt an AgI koordiniert werden konnte

Synthese und Reaktivität Pseudohalogenid-substituierter Borane und Borylene

This work involves the synthesis and reactivity of pseudohalide-substituted boranes and borylenes. A series of compounds of the type (CAAC)BR2Y (CAAC = cyclic alkyl(amino)carbene; R = H, Br; Y = CN, NCS, PCO) were prepared first. The two-electron reduction of (CAAC)BBr2Y (Y = CN, NCS) in the presence of a second Lewis base L (L = N-heterocyclic carbene) resulted in the formation of the corresponding doubly Lewis base-stabilized pseudohaloborylenes (CAAC)(L)BY. These borylenes show versatile reactivity patterns, including their oxidation to the corresponding radical cations, coordination via the respective pseudohalide substituent to group 6 metal carbonyl complexes, as well as a boron-centered protonation with Brønsted acids to boronium cations. Reduction of (CAAC)BBr2(NCS) in the absence of a second donor ligand, led to the formation of boron-doped thiazolothiazoles via reductive dimerization of two isothiocyanatoborylenes. These B,N,S-heterocycles possess a low degree of aromaticity as well as interesting photophysical properties and can furthermore be protonated as well as hydroborated. Additionally, CAAC adducts of the parent boraphosphaketene (CAAC)BH2(PCO) could be prepared, which readily reacted with boroles [Ph4BR'] (R' = aryl) via decarbonylation in a ring expansion reaction. The obtained 1,2-phosphaborinines represent B,P-isosteres of benzene and consequently could be coordinated to metal carbonyl complexes of the chromium triade via η6-coordination, resulting in new half-sandwich complexes thereof.Diese Arbeit beinhaltet die Synthese und Reaktivität von Pseudohalogenid-substituierten Boranen und Borylenen. Dabei wurde zunächst eine Reihe an Verbindungen des Typs (CAAC)BR2Y (CAAC = cyclisches Alkyl(amino)carben; R = H, Br; Y = CN, NCS, PCO) dargestellt. Die Zweielektronenreduktion von (CAAC)BBr2Y (Y = CN, NCS) in der Gegenwart einer weiteren Lewis-Base L (L = N-heterocyclisches Carben) resultierte in der Bildung der entsprechenden zweifach Lewis-Basen-stabilisierten Pseudohalogenborylene (CAAC)(L)BY. Diese Borylene zeigen eine vielseitige Folgechemie, wobei sie zu den korrespondierenden Radikalkationen oxidiert, über den jeweiligen Pseudohalogenidsubstituenten an Metallcarbonylkomplexe der Gruppe 6 koordiniert sowie mit Brønsted-Säuren Bor-zentriert zu Boroniumkationen protoniert werden können. Die Reduktion von (CAAC)BBr2(NCS) in Abwesenheit eines weiteren Donorliganden führte über die reduktive Dimerisierung zweier Isothiocyanatoborylene zur Bildung Bor-dotierter Thiazolothiazole. Diese B,N,S-Heterocyclen verfügen über ein geringes Ausmaß an Aromatizität sowie interessante photophysikalische Eigenschaften, und können darüber hinaus protoniert wie auch hydroboriert werden. Des Weiteren konnten CAAC-Addukte des Stammboraphosphaketens (CAAC)BH2(PCO) dargestellt werden, die bereitwillig unter Decarbonylierung in einer Ringerweiterungsreaktion mit Borolen [Ph4BR‘] (R‘ = Aryl) reagieren. Die erhaltenen 1,2-Phosphaborinine stellen B,P-Isostere des Benzols dar und konnten folglich über eine η6-Koordination an Metallcarbonylkomplexe der Chromtriade koordiniert werden, woraus neue Halbsandwichkomplexe dieser resultierten

Decarbonizing Europe's power sector by 2050-Analyzing the economic implications of alternative decarbonization pathways

The European Union aims to reduce greenhouse gas emissions by 80-95% in 2050 compared to 1990 levels. The transition towards a low-carbon economy implies the almost complete decarbonization of Europe's power sector, which could be achieved along various pathways. In this paper, we evaluate the economic implications of alternative energy policies for Europe's power sector by applying a linear dynamic electricity system optimization model in over 36 scenarios. We find that the costs of decarbonizing Europe's power sector by 2050 vary between 139 and 633 (sic)(2010), which corresponds to an increase of between 11% and 44% compared to the total system costs when no CO2 reduction targets are implemented. In line with economic theory, the decarbonization of Europe's power sector is achieved at minimal costs under a stand-alone CO2 reduction target, which ensures competition between all low-carbon technologies. If, however, renewable energies are exempted from competition via supplementary renewable energy (RES-E) targets or if investments in new nuclear and CCS power plants are politically restricted, the costs of decarbonization significantly rise. Moreover, we find that the excess costs of supplementary RES-E targets depend on the acceptance of alternative low carbon technologies. For example, given a complete nuclear phase-out in Europe by 2050 and politically implemented restrictions on the application of CCS to conventional power plants, supplementary RES-E targets are redundant. While in such a scenario the overall costs of decarbonization are comparatively high, the excess costs of supplementary RES-E targets are close to zero. (C) 2013 Elsevier B.V. All rights reserved

Addukte des Stammboraphosphaketens H2_{2}BPCO und deren Insertionsreaktionen mittels Decarbonylierung

Die ersten Beispiele für Lewis-Basen-Addukte des Stammboraphosphaketens H$_{2}$B-PCO und ihre cyclischen Dimere wurden hergestellt. Eines dieser Addukte zeigt unter milden Bedingungen eine Decarbonylierung und anschließende Insertion des Phosphinidens in die B-C-Bindung eines Borols, was in der Bildung sehr seltener Beispiele für 1,2-Phosphaborinine, B,P-Isostere von Benzol, resultiert. Die starken Donoreigenschaften dieser 1,2-Phosphaborinine wurden durch die Synthese ihrer π-Komplexe mit Metallen der Gruppe 6 bestätigt

Adducts of the parent boraphosphaketene H2_2BPCO and their decarbonylative insertion chemistry

The first examples of Lewis base adducts of the parent boraphosphaketene (H$_2$B-PCO) and their cyclodimers are prepared. One of these adducts is shown to undergo mild decarbonylation and phosphinidene insertion into a B−C bond of a borole, forming very rare examples of 1,2-phosphaborinines, B/P isosteres of benzene. The strong donor properties of these 1,2-phosphaborinines are confirmed by the synthesis of their π complexes with the Group 6 metals