Synthesis and Reactivity of Bora‐ and Borata‐Benzenes

Abstract

Since their discovery almost 50 years ago, boratabenzenes have become widely studied systems at the interface of organic, inorganic, and materials chemistry, mainly due to their use as stabilizing ligands for organometallic complexes. Together with their neutral analogues, the borabenzenes, this chapter provides a comprehensive and structured overview of the various synthetic methods for their construction. In addition, the conceptually different approaches to their corresponding metal complexes receive detailed review. The second part addresses the multifaceted reactivity of these aromatic boron heterocycles by outlining differences between the metal‐free and ‐bound forms.

Azaborinine

“…Tauscht man eines der Kohlenstoffatome des Benzols formal durch Bor aus, so wird Borabenzol ( 8 ) erhalten. Dieses kann nicht als einzelnes Molekül ohne stabilisierende Gruppen isoliert werden [2]. Wie ist das zu erklären?…”

Stabile zweibeinige Klavierstuhl‐Carbonyl‐ und gemischte Diborabenzol‐E4 (E=P, As) Sandwichkomplexe der Gruppe 8

“…[36] Die Substitution endocyclischer Kohlenstoffatome in einem Benzolring durch elektropositivere Boratome führt zur Aufhebung der Entartung der höchsten besetzten Molekülorbitale (MOs) und zur Destabilisierung der MOs, an denen die 2p-Orbitale des Bors beteiligt sind. [37][38][39][40][41][42] Dadurch sind Borabenzole erheblich bessere Elektrondonoren als ihre isoelektronischen organischen Pendants. Unsere Gruppe berichtete über die Synthese und Koordinationschemie des doppelt cyclisch Alkyl(amino)carben (CAAC)-stabilisierten 1,4-Diborabenzols (DBB) 1 (Schema 1).…”

Ligation of Boratabenzene and 9-Borataphenanthrene to Coinage Metals

“…The bonding of unsaturated organic species to transition metals has been known since the pioneering synthesis of [PtCl 3 (C 2 H 4 )] − in 1831 [ A (Figure )]. , The advent of metallocene chemistry is marked by the synthesis of ferrocene ( B ) in 1951, − and since these foundational discoveries, the bonding of unsaturated hydrocarbons with transition metals has been extensively studied. − Substituting a carbon atom for boron in benzene results in a six-membered anionic species, boratabenzene ( C ), that contains six π-electrons and can be considered a boron-containing hybrid of benzene and cyclopentadienide . Cobalt boratabenzene complex D was disclosed by Herberich in 1970, and these anionic BC 5 heteroarenes have been investigated as ligands for transition metals with complexes having diverse applications, including single-ion magnets as well as olefin polymerization and hydrogenation catalysts. − …”