The reactions of the boraquanidinato germylene (i-Pr)2NB(NDmp)2Ge (1) (Dmp = 2,6-Me2C6H3) with RN3 and RNCS produced rare examples of Ge2N and Ge3S rings, while the treatment of 1 with RNCO led to an insertion into the N-Ge bond leading to a novel type of germylene stabilized within a six membered ring, i.e. [N(R)C(O)N(Dmp)B(N(i-Pr)2)N(Dmp)]Ge (R = t-Bu or Ad).