Reaction of tetramethylimidazol-2-ylidene with (TptBu,Me)YbE(thf) (E = I, CH2SiMe3): simple adduct and a hydrocarbyl tethered carbene ligand

Treatment of (TptBu,Me)YbE(thf) (E = I (1), CH2SiMe3 (2)) with tetramethylimidazol-2-ylidene (ImMe4) resulted in very different outcomes depending on the nature of the anionic ligand E. ImMe4 acts as a simple Lewis base toward 1 resulting in substitution of the thf (tetrahydrofuran) ligand and formation of (TptBu,Me)YbI(ImMe4) (3). However, reaction with 2, in addition to displacement of thf, proceeded by metalation of one of the N–CH3 substituents of ImMe4 and gave (TptBu,Me)Yb(ImMe4)(CH2N(C(CH3)C(CH3)N(CH3)C) (4), featuring a hydrocarbyl tethered carbene ligand. The X-ray structures of 3 and 4 are reported.