Round 13: Tossup 12

A derivative of this ligand binds at multiple sites in metal centers on tuck-in complexes. Methyl·aluminoxane is used to activate a class of catalysts named for Walter Kaminsky that possess this ligand, emulating Ziegler–Natta catalysts. (-5[1])An NMR peak in this ligand (10[1])that splits into three peaks at low temperatures is evidence for a fluxional “whizzing” mechanism. A derivative (-5[1])of this ligand (-5[1])in a manganese complex was the main early replacement for tetra·ethyl·lead (10[1])as an antiknocking agent. Two of these ligands are linked (10[1]-5[1])in a class of compounds denoted with the prefix ansa-. Fischer (10[2])and Wilkinson won the 1973 Chemistry Nobel for showing the “double-cone” (10[1])shape of an iron compound containing (10[2])two (-5[1])of these ligands. (10[2])For 10 points, metallocenes like (-5[1])ferrocene contain (10[1])two instances (-5[1])of what ligand with a five-member (10[1]-5[1])aromatic (-5[1])carbon (10[1])ring? ■END■ (10[2]0[12])

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