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

A terminal Mo phosphide was prepared through the group transfer of both P and Cl atoms from chloro-substituted dibenzo-7 lambda(3)-phosphanorbornadiene. This compound represents the first structurally characterized terminal transitionmetal 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 continuous wave (CW) and pulse electron paramagnetic resonance (EPR) characterization. Facile P-P bond formation occurs from this species through intermolecular phosphide coupling.