Compared to the abundance of papers concerning N-heterocyclic carbenes (NHCs) in coordination  chemistry and organocatalysis, much less attention has been placed on their isovalent group 15 analogues,  N-heterocyclic  phosphenium cations (NHPs). Instead of being strong s-donors and weak p-acceptors  like NHCs, the excellent p-acceptor and poor s-donor nature of NHPs suggests  different catalytic activities and applications. In an effort to impart stability to transition metal NHP complexes and protect the NHP unit  from nucleophilic attack, we have incorporated an NHP cation into a multidentate framework. The coordination chemistry of the NHP  containing tridentate pincer ligand to late transition metals will be presented, revealing an unusual pyramidal NHP coordination mode suggestive of formal  two-electron oxidation of the transition metal center and a phosphido  (rather than phosphenium) description. Likewise, the ability of NHPs to  cooperatively promote redox activity will be explored and discussed with a focus on applications toward s bond activation.

Metal complexes of a tridentate pincer-type ligand featuring a central N-heterocyclic phosphenium donor

243rd National Meeting (2012)

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