C–H bond activation of N-heterocyclic carbene IMes by rare-earth metal alkyl complexes

Excess N-heterocyclic carbene 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) reacted with the tris(trimethylsilylmethyl) rare-earth metal complex [Ln(CH2SiMe3)3(THF)2] (Ln = Y, Lu) in toluene to give a C2-symmetric mono(trimethylsilylmethyl) complex with two IMes’ ligands [Ln(CH2SiMe3)(IMes’)2] (IMes’ = IMes deprotonated at the ortho-methyl group of the mesityl substituent), formed by C–H bond activation of the mesityl substituents’ ortho-methyl groups. With one equivalent of IMes in THF, a mono-activated product [Ln(CH2SiMe3)2(IMes’)(THF)n] is selectively formed. The molecular structure of the lutetium compound [Lu(CH2SiMe3)2(IMes’)(THF)] in the crystal shows a strongly distorted trigonal bipyramid with a strained chelate ligand IMes’.