Carbene analogues

Highly reactive dipolar bis(tnfluoromethyl)-subsmtuted heterodienes are excellent traps for one-skeleton-atom species , even when these are short lived The hetero-1,3-dienes add electron nch and electron poorcarbenes[/2,, 125,126,127,128 129,130], carbene complexes [131], carbene analogues [SnClj, Sn(C< H, )2, GeCl2, Gey [132, 133], isonitriles [128], etc, to give [4-t-l] cycloadducts (equation 29)... 

A number of close carbene analogues - silylenes and germylenes - have also been generated, stabilized in inert matrices and studied using the IR spectroscopic technique. 

Structure 3 Generic representation of the structures of IV-heterocyclic carbene analogues... 

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. 

Elimination — The reverse of an addition reaction or transformation. In an elimination two groups (called eliminands) are lost most often from two different centers (1/2/elimination or 1/3/elimination, etc.) with concomitant formation of an unsaturation in the molecule (double bond, triple bond) or formation of a new ring. If the groups are lost from a single center (a-elimination, 1/1/elimination) the resulting product is a carbene or a carbene analogue . 

The carbene analogues, ER2, have been intensively investigated. Their stability increases with an increase in the atomic weight of the element. Silenes (also referred... 

A series of thermally stable, homoleptic, and bulky phosphanyl-substituted carbene analogues of germanium, tin, and lead have been prepared150 by the following method ... 

When such an (SiF2) polymer (or oligomer) mechanism was cited in the literature, one could not but wonder whether difluorosilylene behaved as a carbene analogue at all. With considerable foresight, Gaspar and Herold stated more than a decade ago (39), in view of the poor Si—Si n interaction and the relative weakness of Si—Si single bond, it is very likely that characteristic reactions of difluorosilylene other than polymerization will be found in the near future. ... 

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