The scope of N-atom transfer from the electrophilic ruthenium(VI) nitrido containing polyoxometalate [(PW11O39RuN)-N-VI](4-) has been extended to the N-heterocyclic carbene {CH2(Mes)N}(2)C and the coupling product {CH2(Mes)N}(2)CNH2+ characterized by H-1 NMR and high-resolution mass spectrometry. Because guanidines display many fields of applications ranging from biology to supramolecular chemistry, this could afford an original route to the synthesi:s of cyclic guanidines. This also enlarges the potential of nitrido complexes in the synthesis of heterocycles, mainly illustrated in the literature through the formation of aziridines through N-atom transfer to alkenes. In the course of the reaction, the ruthenium(III)-containing polyoxometallic intermediate [PW11O39RuIII{NC {N(Mes)CH2}(2)}](5-) has been thoroughly characterized by continuous-wave and pulsed electron paramagnetic resonance, which nicely confirms the presence of the organic moiety on the polyoxometallic framework, Ru K-edge X-ray absorption near-edge structure, and electrochemistry.