New potentially tridentate amidinate ligand {o-MeOC6H4NC(Ph)N(SiMe3)}−. Synthesis and molecular structures of amidinate complexes of lithium [{o-MeOC6H4NC(Ph)N(SiMe3)}Li]2 and yttrium [{o-MeOC6H4NC(Ph)N(SiMe3)}YCl2(THF)2]2