Phosphonium-substituted Diphosphaindenylide (PPI): Exploration of Biradical Character and Ligand Properties.

Starting from C H (PCl ) and the TMS-substituted ylide (TMS) C=PR (TMS=trimethylsilyl, R=p-tolyl), the phosphonium-substituted diphosphaindenylide PPI was prepared in two steps. CASSCF calculations as well as the reactivity toward diphenyl acetylene suggest a notable biradical character in PPI. Reaction with [Cr(CO) (MeCN) ] affords the complex [Cr(CO) (η -PPI)] (5). This complex was employed to explore the ligand properties of PPI, which demonstrates considerable potential through the combination of strong metal-ligand interactions and the possibility of a pronounced indenyl effect.