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The adenine derivative 8-bromo-9-ethyl-1, N 6-ethenoadenine 3 has been synthesized and oxidatively added to [M0(PPh 3) 4 ] (M = Pd, Pt). Depending on the procedure for the protonation as well as the metal, either the mononuclear complexes trans -[ 4 ]BF 4 and trans -[ 5 ]BF 4 or the dinuclear complex [ 6 ](BF 4) 2 were obtained. [Display omitted] • First NHC complex of 1, N 6-ethenoadenine. • First dinuclear platinum NHC complex of a purine-derived ligand. • Protic NHC complexes of a purine-derived ligand. The 8-bromoadenine derivative 8-bromo-9-ethyl-1, N 6-ethenoadenine 3 was prepared from adenine in three steps. Treatment of 8-bromo-9-ethyl-1, N 6-ethenoadenine 3 with the zero-valent metal precursors [M0(PPh 3) 4 ] (M = Pd, Pt) in the presence of NH 4 BF 4 as proton source gave exclusively the compounds trans -[ 4 ]BF 4 and trans -[ 5 ]BF 4. The obtained complexes bear a modified C8-bound adenine derivative with a protonated endocyclic nitrogen atom N7. A stepwise reaction sequence consisting of an initial oxidative addition of the C8–Br bond of 3 to [Pt0(PPh 3) 4 ] followed by treatment with HBF 4 ·Et 2 O as proton source led to the dinuclear complex [ 6 ]2+ after a reaction time of several days. This complex features two adenine-derived NHC ligands coordinating to two PtII ions in a µ - κ C8: κ N7 bridging fashion. Protonation of the NHC ligands occurred at the nitrogen atom N6 instead of N7 of the purine scaffold. The molecular structures of the three complexes were determined by X-ray diffraction studies. [ABSTRACT FROM AUTHOR]