Abstract
Single tucked-in permethyltitanocene 1 reacts with excess of internal alkynes to give 1:1 adducts 3a-3c and 3f-3i arising from insertion of their triple bond into the titanium-methylene bond. Only the simplest 2-butyne inserted two molecules to give the known compound 2, however, at a 1:1 stoichiometric ratio the 1:1 adduct 3j was also smoothly formed. 1,4-Disubstituted conjugated diynes with CMe3 or SiMe3 substituents reacted in the same way by only one triple bond to give 3d and 3e, respectively.
The dimethylsilylene-bridged dialkynes Me2Si(C=CR)2 (R = SiMe3 or CMe3) afforded compounds 3k and 3l with both triple bonds reacting. After insertion of the first triple bond the second one underwent a rearrangement which resulted in substituent shift and formation of a silacyclobutene ring linked to the titanium atom.
The alkynes bearing both bulky substituents CMe3 or SiMe3 were unreactive.