Zwitterionic and biradicaloid heteroatomic cyclopentane derivatives containing different group 15 elements

The formal cyclopentane-1,3-diyl derivatives [E(1)(μ-NTer)(2)({E(2)C} = NDmp)] (Ter = 2,6-dimesityl-phenyl, Dmp = 2,6-dimethylphenyl) were prepared by 1,1-insertion of CNDmp into the N–E(2) bond of [E(1)(μ-NTer)(2)E(2)] (E(1) = N, P; E(2) = P, As). The insertion does not occur for E(1) = E(2) = As or E(2) = Sb. Dependent on the choice of formal radical centres E, either a biradicaloid or a zwitterion was obtained. The biradicaloid features a P and an As radical center and its biradical character was established by computations as well as characteristic reactivity with respect to the formation of a housane derivative and the activation of molecules bearing multiple bonds, which was demonstrated using the example of PC(t)Bu. In contrast, the formally N,As- and N,P-centered biradicaloids are better regarded as zwitterionic species in accord with computations and diminished reactivity, as neither housane formation nor activation of multiple bonds could be observed.