N-Heterocyclic carbene ligands (NHC) were metalated with Pd(OAc) 2 or [Ni(CH 3 CN) 6 ](BF 4 ) 2 by in situ deprotonation of imidazolium salts to give the N-olefin functionalized biscarbene complexes [MX 2 (NHC) 2 ] 3–7 (3: M=Pd, X=Br, NHC=1,3-di(3-butenyl)imidazolin-2-ylidene; 4: M=Pd, X=Br, NHC=1,3-di(4-pentenyl)imidazolin-2-ylidene; 5: M=Pd, X=I, NHC=1,3-diallylimidazolin-2-ylidene; 6: M=Ni, X=I, NHC=1,3-diallylimidazolin-2-ylidene; 7: M=Ni, X=I, NHC=1-methyl-3-allylimidazolin-2-ylidene). Molecular structure determinations for 4–7 revealed that square-planar complexes with cis (5) or trans (4, 6, 7) coordination geometry at the metal center had been obtained. Reaction of nickelocene with imidazolium bromides afforded the η 5 -cyclopentadienyl (η 5 -Cp) monocarbene nickel complexes [NiBr(η 5 -Cp)(NHC)] 8 and 9 (8: NHC=1-methyl-3-allylimidazolin-2-ylidene; 9: NHC=1,3-diallylimidazolin-2-ylidene). The bromine abstraction in complexes 8 and 9 with silver tetrafluoroborate gave complexes [NiBr(η 5 -Cp)(η 3 -NHC)] 10 and 11. The X-ray structure analysis of 10 and 11 showed a trigonal-pyramidal coordination geometry at the nickel(II) center and coordination of one N-allyl substituent.