A Phosphorus(V)‐Centered Porphyrin Having Redox‐ and Air‐Stable Axial P–H Bonds

Phosphorus(V)-centered porphyrins (P(V)-porphyrins) are an important class of functional dyes in many fields of research, and axial ligands on the phosphorus atom affect the electronic properties of P(V)-porphyrins and add functions. Herein, we report on the synthesis and characterization of a hitherto unknown P(V)-porphyrin having hydrogen atoms as axial ligands (1+·PF6 -, PF6 - is a counter anion). Synthesis of 1+·PF6 - was achieved by treatment of dichloro-derivative (2+·Cl-) with LiAlH4 followed by AgPF6 via hydride reduction accompanied by one-electron reduction and one-electron oxidation. The porphyrin core of 1+·PF6 - is nonplanar but considerably ruffled. The cyclic voltammogram of 1+·PF6 - exhibits two reversible waves, which indicates redox couples among 1+, neutral radical 1•, and 1-. Compound 1+·PF6 - is tolerant toward air despite its PH2 moiety due to the energetically low-lying HOMO (highest occupied molecular orbital) and σ(P-H) orbitals.