Lithium‐Aluminate‐Catalyzed Hydrophosphination Applications

Abstract

Synthesized, isolated, and characterized by X‐ray crystallography and NMR spectroscopic studies, lithium phosphidoaluminate iBu3AlPPh2Li(THF)3 has been tested as a catalyst for hydrophosphination of alkynes, alkenes, and carbodiimides. Based on the collective evidence of stoichiometric reactions, NMR monitoring studies, kinetic analysis, and DFT calculations, a mechanism involving deprotonation, alkyne insertion, and protonolysis is proposed for the [iBu3AlHLi]2 aluminate catalyzed hydrophosphination of alkynes with diphenylphosphine. This study enhances further the development of transition‐metal‐free, atom‐economical homogeneous catalysis using common sustainable main‐group metals.

The Road Travelled: After Main‐Group Elements as Transition Metals

“…Interestingly, use of the neutral i Bu 2 Al(TMP) (TMP=2,2,6,6‐tetramethylpiperidinates) was found to efficiently undergo hydroboration reactions, even though it is devoid of an Al−H bond. It was found that this acts as a masked hydride as it undergoes a β‐hydride transfer process for the reduction of benzophenone, indicating new potential catalytic pathways …”

Alkali‐Metal Mediation: Diversity of Applications in Main‐Group Organometallic Chemistry

“…These factors make them attractive and sustainable elements for potential use in a multitude of transformations even though their redox chemistry and the number of oxidation states are limited. A growing number of reports are appearing where the metals of the first main group are used in catalytic applications, for example, hydroboration, [3] intermolecular and intramolecular hydroamination, [4] hydrophosphination/hydrophosphorylation, [5] hydrosilylation, [6] hydrogenation, [7] dehydrogenation (or dehydrocoupling), [8] and Brønsted base catalysed CÀC additions. [9] For the last application, first reports date back to the 1950s from Pine and Wunderlich, who described the addition of alkylbenzenes to styrenes with catalytic amounts Organolithium compounds have been at the forefront of synthetic chemistry for over a century, as they mediate the synthesis of myriads of compounds that are utilised worldwide in academic and industrial settings.…”

Structurally Defined Ring‐Opening and Insertion of Pinacolborane into Aluminium‐Nitrogen Bonds of Sterically Demanding Dialkylaluminium Amides

“…Adding intrigue, DFT calculations suggested that attractive dispersion forces involving alkyl groups on the Al compound are a key feature within the reaction coordinate. It is rare for London dispersion forces to be mentioned in the context of TMP‐aluminate chemistry [33] or TMP's general role in synergistic bimetallic reactions, [34] but as recently highlighted in a seminal review by Liptrot and Power, [35] such weak forces can significantly impact inorganic and organometallic structures involving bulky ligands. Future interrogation or re‐interrogation of TMP and related bimetallic compounds may find that London dispersion forces are more significant than initially evidenced.…”