TY - JOUR A1 - Härterich, Marcel A1 - Matler, Alexander A1 - Dewhurst, Rian D. A1 - Sachs, Andreas A1 - Oppel, Kai A1 - Stoy, Andreas A1 - Braunschweig, Holger T1 - A step-for-step main-group replica of the Fischer carbene synthesis at a borylene carbonyl JF - Nature Communications N2 - The Fischer carbene synthesis, involving the conversion of a transition metal (TM)-bound CO ligand to a carbene ligand of the form [=C(OR’)R] (R, R’ = organyl groups), is one of the seminal reactions in the history of organometallic chemistry. Carbonyl complexes of p-block elements, of the form [E(CO)n] (E = main-group fragment), are much less abundant than their TM cousins; this scarcity and the general instability of low-valent p-block species means that replicating the historical reactions of TM carbonyls is often very difficult. Here we present a step-for-step replica of the Fischer carbene synthesis at a borylene carbonyl involving nucleophilic attack at the carbonyl carbon followed by electrophilic quenching at the resultant acylate oxygen atom. These reactions provide borylene acylates and alkoxy-/silyloxy-substituted alkylideneboranes, main-group analogues of the archetypal transition metal acylate and Fischer carbene families, respectively. When either the incoming electrophile or the boron center has a modest steric profile, the electrophile instead attacks at the boron atom, leading to carbene-stabilized acylboranes – boron analogues of the well-known transition metal acyl complexes. These results constitute faithful main-group replicas of a number of historical organometallic processes and pave the way to further advances in the field of main-group metallomimetics. KW - chemical bonding KW - ligands Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-357270 VL - 14 ER - TY - JOUR A1 - Lu, Wei A1 - Jayaraman, Arumugam A1 - Fantuzzi, Felipe A1 - Dewhurst, Rian D. A1 - Härterich, Marcel A1 - Dietz, Maximilian A1 - Hagspiel, Stephan A1 - Krummenbacher, Ivo A1 - Hammond, Kai A1 - Cui, Jingjing A1 - Braunschweig, Holger T1 - An unsymmetrical, cyclic diborene based on a chelating CAAC ligand and its small-molecule activation and rearrangement chemistry JF - Angewandte Chemie International Edition N2 - A one-pot synthesis of a CAAC-stabilized, unsymmetrical, cyclic diborene was achieved via consecutive two-electron reduction steps from an adduct of CAAC and B\(_2\)Br\(_4\)(SMe\(_2\))\(_2\). Theoretical studies revealed that this diborene has a considerably smaller HOMO–LUMO gap than those of reported NHC- and phosphine-supported diborenes. Complexation of the diborene with [AuCl(PCy\(_3\))] afforded two diborene–Au\(^I\) π complexes, while reaction with DurBH\(_2\), P\(_4\) and a terminal acetylene led to the cleavage of B−H, P−P, and C−C π bonds, respectively. Thermal rearrangement of the diborene gave an electron-rich cyclic alkylideneborane, which readily coordinated to Ag\(^I\) via its B=C double bond. KW - inorganic chemistry KW - thermal rearrangement KW - alkylideneborane KW - carbene KW - diborene Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256576 VL - 61 IS - 3 ER - TY - JOUR A1 - Cui, Jingjing A1 - Dietz, Maximilian A1 - Härterich, Marcel A1 - Fantuzzi, Felipe A1 - Lu, Wei A1 - Dewhurst, Rian D. A1 - Braunschweig, Holger T1 - Diphosphino-Functionalized 1,8-Naphthyridines: a Multifaceted Ligand Platform for Boranes and Diboranes JF - Chemistry—A European Journal N2 - A 1,8-naphthyridine diphosphine (NDP) reacts with boron-containing Lewis acids to generate complexes featuring a number of different naphthyridine bonding modes. When exposed to diborane B\(_{2}\)Br\(_{4}\), NDP underwent self-deprotonation to afford [NDP-B\(_{2}\)Br\(_{3}\)]Br, an unsymmetrical diborane comprised of four fused rings. The reaction of two equivalents of monoborane BBr\(_{3}\) and NDP in a non-polar solvent provided the simple phosphine-borane adduct [NDP(BBr\(_{3}\))\(_{2}\)], which then underwent intramolecular halide abstraction to furnish the salt [NDP-BBr\(_{2}\)][BBr\(_{4}\)], featuring a different coordination mode from that of [NDP-B\(_{2}\)Br\(_{3}\)]Br. Direct deprotonation of NDP by KHMDS or PhCH2K generates mono- and dipotassium reagents, respectively. The monopotassium reagent reacts with one or half an equivalent of B\(_{2}\)(NMe\(_{2}\))\(_{2}\)Cl\(_{2}\) to afford NDP-based diboranes with three or four amino substituents. KW - pincer ligand KW - potassium reagent KW - diborane KW - naphthyridine KW - boron Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256994 VL - 27 IS - 63 ER - TY - THES A1 - Härterich, Marcel T1 - Synthese und Reaktivität niedervalenter borhaltiger Verbindungen der Oxidationsstufe +1 T1 - Synthesis and reactivity of low-valent boron-containing compounds in the oxidation state +1 N2 - Die vorliegende Arbeit befasst sich mit der Synthese und Reaktivitat niedervalenter borhaltiger Verbindungen der Oxidationsstufe +I, sowie der Darstellung eines neuen zweizähnigen Carbens. Von zentraler Bedeutung waren dabei Verbindungen aus der Substanzklasse der cAACs, die sowohl als stabilisierende Lewis-Basen der Diborene und Borylene zum Einsatz kamen, als auch das Grundgerüst des neuen Carbens bilden. Zunächst stand die Synthese eines neuen Diborens im Fokus, wobei Cyclohexylsubstituenten am Pyrrolidingerust des cAACs verwendet wurden. Die Reaktivitätsstudien wurden anschließend am Diboren mit dem methylsubstituierten cAAC-Derivat durchgeführt. Dabei konnte neben der 1,2-Addition von Wasser die Insertion von Acetylen in die BB-Bindung, sowie die Spaltung durch die Reaktion mit diversen Aziden beobachtet werden. Darüber hinaus gelingt die vollständige Separierung beider Boratome in zwei getrennte Moleküle bei der Umsetzung mit Kohlenstoffdioxid in einer Reaktionssequenz aus [2+2]-Cycloaddition und -reversion. Das dabei erhaltene Hydroborylen wurde im zweiten Teil der Arbeit hinsichtlich seiner Reaktivität untersucht. Gerade die Carbonylfunktionalität erlaubte hierbei den Zugang zu vielfältigen Reaktionsprodukten. Unter anderen kann der Carbonylsubstituent in ein Alkin oder ein Nitril überführt werden. Zudem kann die, aus der Übergangsmetall-Carbonylchemie bekannte, Fischer-Carben Synthese am Borylen reproduziert werden und stellt somit ein metallomimetisches Verhalten der Borylene zur Schau. Der letzte Teil befasst sich mit der Darstellung eines zweizähnigen Carbenliganden, wobei der Nachweis des freien Carbens indirekt mittels Abfangreaktionen gelang. N2 - The present work deals with the synthesis and reactivity of low-valent boron-containing compounds of oxidation state +I, as well as the preparation of a new bidentate carbene. Compounds from the substance class of cAACs were of central importance, since they were used both as stabilizing Lewis bases of the diborenes and borylenes and also represent the generic framework of the newly synthesised. Firstly, this work focused on the synthesis of a new diborene using cyclohexyl substituents on the pyrrolidine residue of the cAAC. Reactivity studies were then performed on the diborene with the methyl-substituted cAAC. In addition to the 1,2-addition of water, the insertion of acetylene into the BB bond as well as the bond cleavage upon treatment with various azides was observed. Moreover, the complete separation of both boron atoms into two separate molecules succeeds upon reaction with carbon dioxide in a reaction sequence of [2+2]-cycloaddition and -reversion. The hydroborylene obtained from the reaction with CO2 was investigated in the second part of the work with respect to its reactivity. The carbonyl functionality in particular allowed access to a wide range of structural motifs. Among others, the carbonyl substituent can be converted into an alkyne or a nitrile. In addition, the Fischer-Carben synthesis, known from transition metal carbonyl chemistry, can be reproduced on the borylene, thus exhibiting a metallomimetic behavior of the borylene. The last part deals with the preparation of a bidentate carbene ligand, where the detection of the free carbene was achieved indirectly by means of trapping reactions. KW - Bor KW - Doppelbindung KW - Borylene KW - Carbene KW - Reaktivität KW - Diboren KW - Borylen KW - Carben KW - Niedervalent Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-317605 ER -