Abstract The organometallic cation [Cp 2 ZrCH 3 (thf)]+, employed as the tetraphenylborate salt (1), reacts cleanly in 1: 1 stoichiometry with the isocyanates 2 derived from valine methyl ester or valylvaline methyl ester, respectively. In each case addition of the Zr–CH3 group to the isocyanate sp-carbon center is observed with formation of a functionalized zirconocene cation derivative containing a chelating N-metallated N-acetylvaline methyl ester (3a) or N ...