A series of imidazolium-based synthetic routes to imidazolium cyclopentadienides are reported. The 2:1 reaction of imidazolium (1) with [Cp 2 Ti III Cl] 2 gives [NHC Dipp H] + [Cp 2 Ti III Cl 2 ] − (NHC Dipp = 2,6-diisopropylphenyl-substituted N-heterocyclic carbene) (2). The "inverse sandwich" imidazolium cyclopentadienide (3) is obtained as a crystalline solid via reaction of 1 with both [Cp 2 Ti III Cl] 2 and cyclopentadienyllithium (CpLi) (in a molar ratio of 2:1:1) in THF/toluene at elevated temperature. Notably, the 1:1 reaction of 1 with CpLi leads to the isolation of "multidecker" 4 in the solid state, while the corresponding 1:2 reaction of 1 with CpLi gives the crystals of CpLi-bound cyclopentadienylimidazolium complex 5. While compounds 3, 4, and 5 have been structurally characterized using single-crystal X-ray diffraction, in solution these complexes dissociate due to the conversion of [NHC Dipp H] + [Cp] − to both cyclopentadiene and NHC Dipp through intramolecular proton transfer. The equilibrium of the acid−base conversion between [NHC Dipp H] + Cp − and the 1:1 mixture of NHC Dipp and cyclopentadiene is probed by theoretical methods.

Lithiation of an imidazole-based monothiolate, 2, by excess n-butyllithium gives a white powder containing both a lithiated product and an nBuLi contaminant (in a ca. 1:1 molar ratio). This white powder not only reacts with TMEDA in toluene to give 4, a C5-lithiated-imidazole-based monothiolate dimer but also cleaves THF to give a pair of enantiomers of 5 (as a result of “capturing” the LiOCHCH2 fragment by a C5-lithiated-imidazole-based monothiolate monomer). Further reaction of the lithiated product of 2 with selenium results in the first dimeric (7) and monomeric (8) selenothiolates. The nature of the bonding in 7 and 8 was further probed by DFT computations.

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