Evidence for Iron‐Catalyzed α‐Phosphinidene Elimination with Phenylphosphine

Abstract

The ubiquitous half-sandwich iron complex [CpFe(CO) Me] (Cp=η -C H ) appears to be a catalyst for α-phosphinidene elimination from primary phosphines. Dehydrocoupling reactions provided initial insight into this unusual reaction mechanism, and trapping reactions with organic substrates gave products consistent with an α elimination mechanism, including a rare example of a three-component reaction. The substrate scope of this reaction is consistent with generation of a triplet phosphinidene. In all, this study presents catalytic phosphinidene transfer to unsaturated organic substrates.

A Commercially Available Ruthenium Compound for Catalytic Hydrophosphination

“…Indeed, our main objective in investigating ruthenium was the potential for observing α-phosphinidene elimination with a heavier metal that may promote singlet-like phosphinidene chemistry rather than the triplet-like phopshinidene transfer promoted by 1. [11] The absence of phosphinidene transfer with 2 and the observation of hydrophosphination instead is consistent with our developing hypothesis that greater reactivity with unsaturated substrates diminishes transfer of low-valent fragments. [12] In any case, comparison of the same phosphine and unsaturated substrates for both catalysts is important for benchmarking hydrophosphination catalysis.…”

“…The comparative study for 1 and 2 is limited to diphenylphosphine because compound 1 is so poorly effective in hydrophosphination with primary phosphine substrates. Indeed, our main objective in investigating ruthenium was the potential for observing α‐phosphinidene elimination with a heavier metal that may promote singlet‐like phosphinidene chemistry rather than the triplet‐like phopshinidene transfer promoted by 1 . The absence of phosphinidene transfer with 2 and the observation of hydrophosphination instead is consistent with our developing hypothesis that greater reactivity with unsaturated substrates diminishes transfer of low‐valent fragments .…”

A Commercially Available Ruthenium Compound for Catalytic Hydrophosphination

“…Indeed, our main objective in investigating ruthenium was the potential for observing -phosphinidene elimination with a heavier metal that may promote singlet-like phosphinidene chemistry rather than the triplet-like phopshinidene transfer promoted by 1. [11] The absence of phosphinidene transfer with 2 and the observation of hydrophosphination instead is consistent with our developing hypothesis that greater reactivity with unsaturated substrates diminishes transfer of low-valent fragments. [12] In any case, comparison of the same phosphine and unsaturated substrates for both catalysts is important for benchmarking hydrophosphination catalysis.…”

Organoiron- and Fluoride-Catalyzed Phosphinidene Transfer to Styrenic Olefins in a Stereoselective Synthesis of Unprotected Phosphiranes

“…12 Hallmarks of good substrates for group-transfer chemistry feature stable, neutral leaving groups, such as N 2 or iodobenzene. 1 In the case of phosphorus, only a limited number of catalytic group transfer reactions are known, generally involving activation of P–H bonds of primary phosphines in reactions disclosed by the groups of Waterman 13 and Layfield. 14…”

“…12 Hallmarks of good substrates for group-transfer chemistry feature stable, neutral leaving groups, such as N 2 or iodobenzene. 1 In the case of phosphorus, only a limited number of catalytic group transfer reactions are known, generally involving activation of P−H bonds of primary phosphines in reactions disclosed by the groups of Waterman 13 and Layfield. 14 We have developed dibenzo-7-phosphanorbornadiene compounds (RPA, A = anthracene, C 14 H 10 , Scheme 1), readily available from RPCl 2 and MgA•3THF, 15 as useful synthetic equivalents for phosphinidenes.…”