Stable singlet diradicals, polyradicals and carbenes based on boron

INOR 464

Guy Bertrand1, Jean-Baptiste Bourg2, Gad Fuks2, and Yutaka Ishida2. (1) Department of Chemistry, University of California Riverside, UCR/CNRS Joint Research Laboratory, UMR 2282, Riverside, CA 92521-0403, (2) UC Riverside
A very few room temperature stable localized singlet diradicals featuring a four-membered ring skeleton have very recently been isolated. They can be classified into two groups: 6-pi-electron and 2-pi-electron containing species. We have prepared the only known example of a stable diradical belonging to the second category; it features a PBPB core. Catenation of singlet diradicals, via appropriate linkers, is predicted to lead to antiferromagnetic low-spin polymers, in which the half-filled electron bands would confer the capability for metallic conduction without doping. We will discuss compounds featuring two or even three diradical moieties linked by an aryl ring. We have found that carbene analogues of borazines are highly thermally stable. Keeping quasi-identical steric demands, the electronic properties of the carbene can be precisely tuned by varying the nature of the substituents at the boron centers. The catalytic activity of palladium complexes bearing the tunable carbenes as ligand will be discussed.