Synthesis, structure, and reactivity of mixed-sandwich zirconacarborane methyl complex (η5-C5Me5)[η1:η5-(Me2NCH2CH2)C2B9H10]ZrMe

• Synthesis and structural characterization of new mixed-sandwich zirconacarborane methyl complex.
• Diverse reactivity patterns of ZrC bond toward terminal and internal alkynes as well as nitriles.
• X-ray structures of new complexes.

A neutral mixed-sandwich zirconacarborane methyl complex (η5-Cp*)[η1:η5-(Me2NCH2CH2)C2B9H10]Zr(Me) (1) (Cp* = C5Me5) was prepared via methane elimination reaction of 7-Me2N(H)CH2CH2-7,8-C2B9H11 with (η5-Cp*)ZrMe3. It underwent intramolecular CH activation at 70 °C to afford [η1:σ:η5-{MeN(CH2)CH2CH2}C2B9H10]Zr(η5-Cp*) (2) and eliminate CH4. This complex reacted with internal alkynes to give the ZrC σ bond mono-insertion products, in which both electronic and steric factors played a role in controlling the regioselectivity of the insertion process. In the case of terminal alkynes, both insertion and acid-base reaction products were obtained, dependent upon the substituents. On the other hand, complex 1 reacted with alkyl nitriles at room temperature to give the mono-insertion zirconacarborane imide complexes, whereas high temperature was required to promote the insertion reaction with aryl nitrile, generating a different type of insertion product, zirconacarborane amide. All new complexes were characterized by NMR spectroscopy and elemental analyses. Most of them were further confirmed by single-crystal X-ray analyses.

A new mixed-sandwich zirconacarborane methyl complex was prepared via methane elimination reaction and structurally characterized. Its reactivity patterns toward alkynes and nitriles were studied.Figure optionsDownload as PowerPoint slide