Reaction of lanthanum with Hg(C6F5)2 and bulky N,N'-bis(2,6-diisopropylphenyl)formamidine (HDippForm) in tetrahydrofuran gives [LaF{DippForm}2(THF)] with a rare terminal Ln-F bond, and a high yield of a novel functionalized formamidine, DippForm((CH2)4OC6F4H-o).