Metalloles tautomerism

No tautomeric forms of l//-germoles or stannoles are as yet known. In these metalloles, it is likely that the carbene analogue isomer (like 9) should be more stable than the 2H-or 3//-forms. 

Studies in the chemistry of group 14 metalloles over the past few years have been numerous. Mention should be made of the synthesis of the C-unsubstituted l//-silole the structures of the product itself, as well as of its tautomeric forms and dimer, have been established. Progress has also been made in developing new synthetic routes. By way of a transmetallation reaction from zirconacyclopentadiene, the synthesis of group 14 hete-rocyclopentadiene derivatives was considerably facilitated. On the other hand, though the method is limited to 3,4-diphenylsiloles, a further noticeable contribution was a general and versatile synthesis of the corresponding 2,5-difunctional derivatives. 

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