Main-Group Metallomimetics: Transition Metal-like Photolytic CO Substitution at Boron

Braunschweig, Holger; Krummenacher, Ivo; Légaré, Marc‐André; Matler, Alexander; Radacki, Krzysztof; Ye, Qing

doi:10.1021/jacs.6b13047

Cited by 156 publications

(173 citation statements)

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“…Althoughr epeated attempts to isolate any of these CÀH activation products failed, the specieso bserved at d 11B À13 ppm most likely results from the intramolecular insertion of ab orylene into aC ÀHb ond of an ortho-methyl group on I Mes .S uch intramolecular CÀHa ctivation products have been repeatedly observed when attempting to reduce particularly sterically encumbered boranes presenting pendant Mes or Dip groups, [29] or when heating sterically encumberedi solated borylenes. [30] For the dibromoborane precursors, monitoring of the reactions by 11 BNMR spectroscopy indicated nearly full consumption of the borane within one hour,a fter which the suspension was promptly filtered to remove remaining KC 8 and the KBr byproduct. This was done to avoid side reactions such as CÀH activations, which increased upon longerr eaction times, as the concentration of borylene monomersdecreased, favoring intramolecular reactions over dimerization.…”

Section: Resultsmentioning

confidence: 99%

Increasing the Reactivity of Diborenes: Derivatization of NHC‐Supported Dithienyldiborenes with Electron‐Donor Groups

Auerhammer

Arrowsmith

Bissinger

et al. 2017

Chemistry A European J

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As eries of NHC-supported 1,2-dithienyldiborenes was synthesized from the corresponding (dihalo)thienylborane NHC precursors. NMR and UV/Vis spectroscopicd ata, as well as X-ray crystallographic analyses, wereu sed to assess the electronic and steric influences on the B=Bd ouble bond of various NHCs and electron-donating substituents on the thienyl ligands. Crystallographic data showedt hat the degree of coplanarity of the diborene core and thienyl groups is highly dependento nt he sterics of the substituents. Furthermore, any increase in the electron-donating ability of the substituents resulted in the destabilization of the HOMO and greateri nstability of the resulting diborenes.

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Section: Resultsmentioning

confidence: 99%

Increasing the Reactivity of Diborenes: Derivatization of NHC‐Supported Dithienyldiborenes with Electron‐Donor Groups

Auerhammer

Arrowsmith

Bissinger

et al. 2017

Chemistry A European J

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“…[18] This shift is also reminiscent of that of the 1,2-bis(borylene) species [(CAAC)(OC)BB(CO)(CAAC)] (δB -22), [19] as well as other compounds containing the monovalent [-B(CO)(CAAC)] fragment. [20] The C-O (1.157 (2) (2); B-C: 1.469(2) Å) [17] Strong, sharp signals at 1987 and 1777 cm -1 were found in the solid-state IR spectrum of 5. Similar to that of 3, the band at 1777 cm -1 can be assigned to the carboxyl C=O double bond of 5, while the band at 1987 cm -1 can be comfortably assigned to the stretching mode of the boraketene C=O unit.…”

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CO₂ Binding and Splitting by Boron–Boron Multiple Bonds

et al. 2018

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[3] whose combination of nucleophilic and electrophilic sites are well-suited to combine with the carbon and oxygen atoms of CO2, respectively ( Figure 1A). Another common mechanism of main-group-based CO2 activation is the (initial) 2+2 cycloaddition of one C=O bond of CO2 with another E-E multiple bond, e.g. P=N (i.e. the Aza-Wittig reaction), Si=O, Si=N, Ge=O, Sn=O, and B=N bonds ( Figure 1B). [4] To our knowledge, no CO2 fixation or activation has been observed by solely utilizing a nonpolar multiple bond, despite the fact that a range of highly reactive compounds with E-E multiple bonds are known.[5] However, in 2011 Kato and Baceiredo reported [6] the reaction of CO2 with a disilyne bisphosphine adduct, a compound thought to possess some multiple bonding character between its two silicon atoms despite the clearly non-planar geometry around the silicon atoms. Herein we present fixation and splitting reactions of CO2 through its interaction with distinctly non-polar multiple bonds of two significantly different diboron species:[5c,d,e] a doubly basestabilized diborene [5,7] with tricoordinate boron atoms and a B=B double bond, and a linear diboryne species bearing strongly π-acidic cyclic (alkyl)(amino)carbene (CAACs) donors, [8] effectively a diboracumulene [9] species with a B-B bond order between two and three. Interestingly, in the reaction of CO2, we were also able to isolate the thermally unstable 2+2 (C=O + B=B) cycloaddition product, which slowly undergoes cleavage of one C=O bond. The apparently facile reaction of CO2 with B-B multiply bound species is attributed to the high reactivity of the latter, which is able to overcome the lack of polarity in the bond and effect the initial cycloaddition step. Dibromodiborenes (L(Br)B=B(Br)L), very few of which exist in the literature, [10,11] were chosen as candidates for CO2 binding due to their sterically unhindered B=B bonds and thus presumed high reactivity. Upon treatment with one atmosphere of CO2 at room temperature, after 7 min the 11 B NMR spectroscopic signal of diborene 1 [10] (dB 20) was found to have completely disappeared, replaced by two broad signals (dB ca. 0, -10). Removal of the solvent from this mixture and extraction of the residue into hexane provided a solution from which orange crystals (2) were grown. The solid-state structure of 2 (Figure 2, middle) confirms the combination of the diborene 1 with CO2 to form a dibora-b-lactone structure in which the two boron atoms form a slightly puckered four-membered B-B-C-O ring with one carbon and one oxygen atom of the CO2 unit. The remaining oxygen atom is part of a carbonyl group with a short C-O distance of 1.20(1) Å but a relatively wide O-C-B angle (136.2(8)º). Interestingly, the endocyclic B-B-C angle is strongly acute (73.7(8)º). The NHC and Br groups are each oriented in a trans fashion with respect to the ring.

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“…[61] Während ersteres als Quelle fürein [(CAAC)BPh]-Borylen Fragment nach Zweielektronenreduktion fungiert, [59] handelt es sich bei dem zweiten Edukt um eine lçsliche monomere Al I -Verbindung sowie um ein Reduktionsmittel, wie kürzlich durch unsere Gruppe berichtet. [57][58][59] Weiterhin sind sterische Einschränkungen zwischen dem CAAC-und dem Cp 3t -Rest vorhanden, die wahrscheinlich die B-Al-Interaktion schwächen. Hierbei bildeten sich Komplexe mit Mehrfachbindungscharakter, aufgrund der M-Al-p-Rückbindung,v ergleichbar mit Carbonylliganden.…”

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“…Diese wird aufgrund der vor-ausgegangenen Arbeiten in der Borylenchemie postuliert, [57][58][59] und geht von einer Assoziation eines kurzlebigen Borylens mit dem Al I -Komplex aus.B eide Edukte liegen in einem Singulettgrundzustandv or. Diese wird aufgrund der vor-ausgegangenen Arbeiten in der Borylenchemie postuliert, [57][58][59] und geht von einer Assoziation eines kurzlebigen Borylens mit dem Al I -Komplex aus.B eide Edukte liegen in einem Singulettgrundzustandv or.…”

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Heterodiatomare Mehrfachbindung zwischen Elementen der Gruppe 13: Ein Komplex mit B‐Al‐π‐Bindung reduziert CO₂

et al. 2019

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Verbindungen mit heterodiatomarer Mehrfachbindung zwischen Gruppe-13-Elementen sind bislang unbekannt. In dieser Zuschrift berichten wir über eine Darstellungsmethode von [(CAAC)PhB = AlCp 3t ]( 1), einem Komplex, bei dem zwei Singulettfragmente nachAssoziation eine p-Bindung zwischen Bor und Aluminium bilden. Neben den Eigenschaften dieser Mehrfachbindung wird die Reaktivitätv on 1 gegenüber CO 2 präsentiert. Diese führt über eine ungewçhnliche Metathesereaktion zu einer B-CO-Verbindung.

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Main-Group Metallomimetics: Transition Metal-like Photolytic CO Substitution at Boron

Cited by 156 publications

References 41 publications

Increasing the Reactivity of Diborenes: Derivatization of NHC‐Supported Dithienyldiborenes with Electron‐Donor Groups

Increasing the Reactivity of Diborenes: Derivatization of NHC‐Supported Dithienyldiborenes with Electron‐Donor Groups

CO₂ Binding and Splitting by Boron–Boron Multiple Bonds

Heterodiatomare Mehrfachbindung zwischen Elementen der Gruppe 13: Ein Komplex mit B‐Al‐π‐Bindung reduziert CO₂

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Main-Group Metallomimetics: Transition Metal-like Photolytic CO Substitution at Boron

Cited by 156 publications

References 41 publications

Increasing the Reactivity of Diborenes: Derivatization of NHC‐Supported Dithienyldiborenes with Electron‐Donor Groups

Increasing the Reactivity of Diborenes: Derivatization of NHC‐Supported Dithienyldiborenes with Electron‐Donor Groups

CO2 Binding and Splitting by Boron–Boron Multiple Bonds

Heterodiatomare Mehrfachbindung zwischen Elementen der Gruppe 13: Ein Komplex mit B‐Al‐π‐Bindung reduziert CO2

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CO₂ Binding and Splitting by Boron–Boron Multiple Bonds

Heterodiatomare Mehrfachbindung zwischen Elementen der Gruppe 13: Ein Komplex mit B‐Al‐π‐Bindung reduziert CO₂