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|Title:||Transition metal carbene chemistry. 3:Nucleophilic attachment of 4-nitrophenyl acetonitrile and benzoyl nitromethane anions to Fischer carbene complexes†|
|IPC Code:||Int.Cl 7 C07F11/00|
|Abstract:||Rate constants for the nucleophilic attachment of 4-NO2- PhCH(CN)- and PhCOCHNO2- to Fischer carbene complexes of the type (CO)5M=C(SMe)C6H5 with M = Cr and W in 50% MeCN-50% water (v/v) at 25oC are reported. The acetonitrile anions PhCH(CN)- show much higher reactivity towards these carbene complexes than OH-, primary aliphatic amines (e.g., n- butylamine) or secondary alicyclic amines (e.g., piperidine) but are less reactive than thiolate ions (e.g .,HOCH2CH2S-) and CH(CN)2-. The carbanion PhCOCHNO2- is more reactive than OH- but less reactive than the above-mentioned ions. The reactivity of carbanions towards a particular carbene complex follows the order: CH(CN)2- > 4-NO2-PhCH(CN)- > PhCOCHNO2- for both the carbene complexes. The possible explanation for it comes from the delocalization of negative charge on the carbanion which follows the reverse order. The higher reactivity of 1-W over 1-Cr for all the carbanions fits a pattern observed previously and arises mainly clue to lowering of intrinsic barrier of the tungsten carbene complex than corresponding chromium one.|
|Appears in Collections:||IJC-A Vol.44A(09) [September 2005]|
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