The first planar-chiral stable carbene and its metal complexes

Starting from (S)-S-ferrocenyl-S-4-tolyl sulfoxide the planar-chiral imidazolium salt (R-p)-1- [2-(trimethylsilyl)ferrocenylmethyl]-3-methylimidazolium iodide was synthesized utilizing the directed ortho-metalation strategy. Deprotonation thereof yielded the first planar-chiral carbene, (R-p)-3-methyl-1-[2-(trimethylsilyl)ferrocenylmethyl]imidazolin-2-ylidene, which is stable in tetrahydrofuran at room temperature for several hours. Conversion with sulfur resulted in the formation of the corresponding thiourea derivative. Reaction with the metal precursors [Rh(COD)Cl](2) and Cr(CO)(6) gave air-stable complexes. For the latter product an X-ray structural analysis was conducted.