Terminal Molybdenum Phosphides with d Electrons: Radical Character Promotes Coupling Chemistry

A terminal Mo phosphide was prepared via group transfer of both P- and Cl-atoms from chloro-substituted dibenzo-7λ^3-phosphanorbornadiene. This compound represents the first structurally characterized terminal transition metal phosphide with valence d electrons. In the tetragonal ligand field, these electrons populate an orbital of d_(xy) parentage, an electronic configuration that accommodates both metal d-electrons and a formal M≡P triple bond. Single electron oxidation affords a transient open shell terminal phosphide cation with significant spin density on P, as corroborated by CW and pulsed EPR characterization. Facile P-P bond formation occurs from this species via intermolecular phosphide coupling.