517865-04-2Relevant academic research and scientific papers
Ancillary ligand control of the regiochemistry of coupling of 3,3-dimethyl-1-butyne at titanium metal centers
Lee, Jongtaik,Fanwick, Phillip E.,Rothwell, Ian P.
, p. 1546 - 1549 (2008/10/08)
The ambient-temperature sodium amalgam (2 Na per Ti) reduction of hydrocarbon solutions of [Cp(ArO)TiCl2] (ArO = 2,3,5,6-tetraphenylphenoxide) (1) in the presence of 3,3-dimethyl-1-butyne yields the 2,5-di(tert-butyl)titanacyclopentadiene compound [Cp(ArO)Ti(C4H2Bu2t-2,5)] (2). An X-ray diffraction study of 2 confirms the regiochemistry and shows carbon - carbon distances of 1.343(3) and 1.492(3) A for the double and single bonds, respectively. In contrast the analogous reaction of either [Cp2TiCl2] or [(ArO)2TiCl2] in the presence of 3,3-dimethyl-1-butyne yields the corresponding 2,4-di(tert-butyl)titanacyclopentadiene compounds. When 2 is heated at 100 °C for a few days in C6D6 solution, isomerization to the more stable 2,4-di(tertbutyl) regioisomer 3 is observed by NMR. An attempt is made to rationalize the regiochemistry of the kinetically formed titanacyclopentadiene in terms of steric factors within the intermediate bis(alkyne) complex.
