Coordination Behavior and Reactivity of alpha-Heterosubstituted Trimethylsilylalkynes at Titano- and Zirconocene

The coordination behavior of the a-donor-atom-substituted (trimethylsilyl) alkynes OC4H8N-C C-SiMe3 (2), EtO-C C-SiMe3 (3), and Me2P-C C-SiMe3 (4) towards group 4 metallocene generators [Cp2Ti(eta(2)-btmsa)] (1a), [Cp2Zr(py)(eta(2)-btmsa)] (1b), and [Cp-2*Ti(eta(2)-btmsa)] (1c) [Cp = eta(5)-cyclo-pentadienyl; btmsa = bis(trimethylsilyl)acetylene; py = pyridine; Cp* = eta(5)-pentamethylcyclopentadienyl] was investigated. By using 1a and 1b, metallacyclopropenes were obtained for alkyne 2, a titanacyclopentadiene for alkyne 3, and dimeric-stabilized metallacyclopropenes for alkyne 4. Employing the sterically demanding metallocene 1c resulted in monomeric metallacyclopropenes for alkynes 3 and 4. The reactivity of the obtained complexes towards CO2 and acetone was explored as well, thus leading to regioselective formation of metallafuranones and metalladihydrofurans.