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.

The isolable complex [Os(PHMes*)H(PNP)] (Mes* = 2,4,6-t Bu 3 C 6 H 3 ;P NP = N{CHCHP t Bu 2 } 2 )e xhibits high phosphinyl radical character.T his compound offers access to the phosphinidene complex [Os(PMes*)H(PNP)] by PÀHp roton coupled electron transfer (PCET). The PÀH bond dissociation energy (BDE) was determined by isothermal titration calorimetry and supporting DFT computations.T he phosphinidene product exhibits electrophilic reactivity as demonstrated by intramolecular C À Ha ctivation. : osmium ·p hosphanyl radical ·p hosphinidene · pincer ·p roton coupled electron transfer Scheme 4. Reactivity of phosphinidene complex 6.Scheme 5. Thermochemical square-scheme of 5, 6 and 9.