Dual Reactivity of a Geometrically Constrained Phosphenium Cation
Solomon Volodarsky, Deependra Bawari, Roman Dobrovetsky
Abstract
Abstract A geometrically constrained phosphenium cation in bis(pyrrolyl)pyridine based NNN pincer type ligand ( 1 + ) was synthesized, isolated and its preliminary reactivity was studied with small molecules. 1 + reacts with MeOH and Et 2 NH, activating the O−H and N−H bonds via a P‐center/ligand assisted path. The reaction of 1 + with one equiv. of H 3 NBH 3 leads to its dehydrogenation producing 5 . Interestingly, reaction of 1 + with an excess H 3 NBH 3 leads to phosphinidene (P I ) species coordinating to two BH 3 molecules ( 6 ). In contrast, [ 1 + ][OTf] reacts with Et 3 SiH by hydride abstraction yielding 1‐H and Et 3 SiOTf, while [ 1 + ][B(C 6 F 5 ) 4 ] reacts with Et 3 SiH via an oxidative addition type reaction of Si−H bond to P‐center, affording a new P V compound ( 8 ). However, 8 is not stable over time and degrades to a complex mixture of compounds in matter of minutes. Despite this, the ability of [ 1 + ][B(C 6 F 5 ) 4 ] to activate Si−H bond could still be tested in catalytic hydrosilylation of benzaldehyde, where 1 + closely mimics transition metal behaviour.