The "pogo stick" complex [FeCp*{N(SiMe)}]: spin state properties, adduct formation with Lewis bases, and reactivity towards weakly Brønsted acidic protonated NHCs.

[FeCp*{N(SiMe)}] is a high-spin complex with four unpaired electrons according to SQUID magnetometry and Mößbauer spectroscopy. Its reactions with 4-dimethylaminopyridine (DMAP) and NPrX (X = Cl, Br) respectively afford [FeCp*{N(SiMe)}(DMAP)] (6), NBu[FeCp*Cl{N(SiMe)}] (7), and NPr[FeCp*Br{N(SiMe)}] (8). 7 and 8 react with formamidinium tetrafluoroborates fc[(NCHR)CH][BF] (fc = 1,1'-ferrocenylene; R = Ph, Mes) at room temperature in THF to furnish [FeCp*X{fc[(NCHR)C]}] (4: X = Cl, R = Mes; 10: X = Br, R = Mes; 11: X = Cl, R = Ph; 12: X = Br, R = Ph), which contain a ferrocene-based NHC ligand.

Imidazolium-benzimidazolates as convenient sources of donor-functionalised normal and abnormal N-heterocyclic carbenes.

Imidazolium-benzimidazolates are readily available conjugated mesomeric betaines, whose carbenic tautomers can form C,N-metal chelates containing amino-functionalised normal or abnormal NHC ligands, depending on the degree of steric congestion. Deprotonation of the amino moiety gives rise to imine-functionalised C,N-metal chelates, whose N atom can be easily utilised for the construction of heteronuclear complexes.