On metal coordination of neutral open-shell P-ligands focusing on phosphanoxyls, their electron residence and reactivity

Abstract

This feature article highlights the discovery and development of phosphanoxyl complex chemistry starting from (neutral) low-coordinate phosphorus radicals and the quest of metal ligation effects. We describe synthesis and reactions...

Design of transition metal complexes containing a P–E radical motif

“…, below −30 °C under experimental conditions. 18 The resulting iron radical complex [Fe(CO) 4 ]PPh 2 O˙ ( 1a˙ ) shows a highly localized electron spin density on the Fe(CO) 4 unit (0.94 e ) with only negligible contribution from the terminal oxygen (0.09 e ), and is best represented by OPPh 2 [Fe(CO) 4 ]˙ with a terminal PO double bond rather than a P–O˙ radical, as supported by the computed Wiberg bond index (WBI) of 1.75 for the P–O bond. Interestingly, the complex [Fe(CO) 4 ]PPh 2 S–TEMP ( 1bT ) shows a moderate S–N bond free energy of 20.7 kcal mol −1 , indicating a thermally accessible bond cleavage upon moderate heating.…”

“…16,17 Since then, we have broadened the scope of substitution patterns at phosphorus by establishing various heterophospholidines. 18,19…”

“…16,17 Since then, we have broadened the scope of substitution patterns at phosphorus by establishing various heterophospholidines. 18,19 Raising the question of how the system could be further tuned in particular to reach stable transition metal complexes as useful thermal radical precursors and to explore the chemical space of P-heteroatom radical complexes, we have investigated the generation, stability and reactivity, including rearrangements, of various pentacarbonyl tungsten(0) and tetracarbonyl iron(0) complexes by extensive DFT calculations in the work presented here.…”

Phosphorus radicals and radical ions

“…Very recently, Brehm et al reported a few metal coordinating phosphanoxyl complexes and tried to study the electron density residence across different centers. 42 They primarily used iron (Fe), manganese (Mn) and tungsten (W) metals in the complexes. While 100% electron density was found to be present on the metal centers in the case of Fe and Mn, the W coordinating phosphanoxyl complexes show spin density distribution over W, O and P centers as shown in Scheme 9.…”

Stability of Carbocyclic Phosphinyl Radicals: Effect of Ring Size, Delocalization, and Sterics

“…As our purpose is to scrutinize the stability of phosphinyl radicals, in the following, a selection of the most important examples is presented; however, we note that further derivatives are also known. − ,− …”