117916-67-3Relevant academic research and scientific papers
Synthesis of group 4 metallocene-substituted ylides and their reactions with ketones
Erker, Gerhard,Czisch, Peter,Mynott, Richard
, p. 91 - 108 (1987)
A new method has been developed to synthezise group 4 metallocene ylides.Ph3P=CH2 reacts with in situ generated (η2-ethene)MCp2 (M = Zr, Hf), (η2-aryne)MCp2 (M = Ti, Zr), or with (η4-conjugated diene)MCp2 (M = Zr, Hf) via intramolecular hydrogen transfer to form metallocene ylides Cp2M(R)CH=PPh3.In some cases competitive methylene transfer occurs leading to four-membered metallacycles.The metallocene ylides all exhibit a substantial metal to carbon ?-interaction, increasing in strength on going from hafnium to titanium as the central metal atom.Ylide reactivity is greatly reduced.With a non-enolizable ketone, Cp2Zr(CH2CH=CHCH3)CH=PPh3 reacts via the reverse of metallocene ylide forming reaction.With enolizable ketones, zirconocene or hafnocene ylides serve as bases and form metal enolates.The resulting enolate (E)/(Z) ratio strongly depends on the group R of the metallocene ylide base Cp2Zr(R)CH=PPh3.
