|In this thesis, reactions of the singlet biradicaloids [P(µ-NTer)]2 and [As(µ-NTer)]2 are presented. An essential aspect of this work is the preparation of new cyclic group 15 biradicaloids. A new general synthetic approach to biradicaloids with distinguishable radical centres could be developed. Thus, several biradicaloids of the type [E1(µ-NTer)2E2] (E = N, P, As, Sb) became accessible. By a ring expansion reaction the the cyclobutane-1,3-diyl derivates the first preparative access to stable cyclopentane-1,3-diyls was found.