Interconversion of Phosphinyl Radical and Phosphinidene Complexes by Proton Coupled Electron Transfer

Abstract

The isolable complex [Os(PHMes*)H(PNP)] (Mes*=2,4,6‐ t Bu 3 C 6 H 3 ; PNP=N{CHCHP t Bu 2 } 2 ) exhibits high phosphinyl radical character. This compound offers access to the phosphinidene complex [Os(PMes*)H(PNP)] by P−H proton coupled electron transfer (PCET). The P−H bond dissociation energy (BDE) was determined by isothermal titration calorimetry and supporting DFT computations. The phosphinidene product exhibits electrophilic reactivity as demonstrated by intramolecular C−H activation.

A Terminal Iridium Oxo Complex with a Triplet Ground State

“…The slightly exothermic (Δ r H o HAT =−3.83±0.05 kJ mol −1 ) and endergonic (Δ r G o HAT =+0.0162±0.087 kJ mol −1 ) reaction allowed for estimating BDE IrO−H THF ( 5 )=350±2 kJ mol −1 and BDFE IrO−H THF ( 5 )=325±6 kJ mol −1 , which is slightly lower compared with a recently reported cobalt(III) hydroxo complex, [Co(OH){PhB( t BuIm) 3 }] (BDFE CoO−H MeCN =356 kJ mol −1 ) . The reaction entropy for Equation (1) (Δ r S o HAT =−13±18 J mol −1 K −1 ) is in line with small contributions from both the HAT reagent ( S o Mes*O ≈ S o Mes*OH ) and the hydroxo/oxo couple 5 / 8 . Minor changes in vibrational and electronic entropies can be expected for 5d metal complexes with energetically well‐separated electronic ground states, such as 5 and 8 (Figure a, b)…”

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

“…Perhaps one reason for the underdevelopment of catalytic phosphinidene transfer reactions stems from the lack of availability of appropriate precursors, a limitation recently articulated by de Bruin and Schneider. 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.…”

“…Perhaps one reason for the underdevelopment of catalytic phosphinidene transfer reactions stems from the lack of availability of appropriate precursors, a limitation recently articulated by de Bruin and Schneider . Hallmarks of good substrates for group-transfer chemistry feature stable, neutral leaving groups, such as N 2 or iodobenzene .…”

The Metaphosphite (PO2−) Anion as a Ligand

“…The EPR spectrum of 2 K at room temperature in solution (Figure 3) exhibits a 6‐line signal, which could be satisfactorily simulated with g iso =2.046 and large hyperfine interaction (HFI) with a single low‐spin rhenium(II) ion ( A iso ( 185/187 Re)=770 MHz) [20] . The absence of resolved 31 P HFI suggests little spin delocalization onto the metaphosphite ligand [21, 22] . DFT computations confirm this notion locating the spin density mainly at the rhenium (59 %) and pincer nitrogen (30 %) atoms (Figure 3).…”