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A bent metallocene with a side-on η3-bound trimethylenemethane (tmm) ligand is observed in the crystal structure of the title compound 1 (shown on the right). The Zr[BOND]Cl and Zr[BOND]C2 bond lengths indicate that two strong σ bonds link Zr to the terminal C atoms of the tmm ligand. The distance between Zr and the central atom C 3 is typical for a weak σ bond. Reactions of 1 with reagents that contain polar double bonds, for example methyl formate and tert-butyl isocyanate, yield insertion products with six-membered rings.