Carbonylation of 2-bornenyl(methyl)zirconocene

The reaction of methylzirconocenechloride with 2-bornenyllithium yields (2-bornenyl)methylzirconocene (10a). Carbonylation of 10a takes place exclusively by CO-insertion into the Zr-C(sp²) bond to give Cp₂ZrMe(η²-OC-C₁₀H₁₅) (16a). The corresponding hafnium complex 10b reacts analogously to give 16b. Complex 16a was characterized by X-ray diffraction, and found to contain an η²-acyl ligand bonded to zirconium in the thermodynamically favored “O-inside” arrangement with the following bonding parameters: d Zr-C(acyl) = 2.192(7) Å, d Zr-O(acyl) = 2.258(6) Å, d C=O = 1.246(9) Å, angles O(acyl)---Zr---C(acyl) = 32.5(2)°, Zr---C(acyl)---O(acyl) = 76.7(4)°.