Titanium complexes with imido groups

Bis(cyclopentadienyl) titanium complexes with imido groups, 4, 419-420 with indenyls, 4, 428... 

Whereas Groups 5-7 metals form numerous complexes with M=E double bonds, this feature has been less prominent in Group 4. However, an increasing number of titanium imido compounds have recently been prepared 41... 

The first hydroaminations by this mechanism were reported by Bergman with zircono-cene complexes and by Livinghouse with monocyclopentadienyl titanium and zirconium complexes. Bergman reported the intermolecular addition of a hindered aniline to an alkyne. The hindrance of the aniline was important to prevent formation of stable dimeric complexes containing bridging imido groups. Livinghouse reported intramolecular reactions that occurred at lower temperatures over shorter times. The intramolecularity of this process allows the [2+2] cycloaddition of the imido complex with the alkyne to be faster than the dimerization. 

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