Trialkylselenonium salts

Gilman noted in 1949 that butyllithium slowly displaces phenyllithium from phenylselenides in ether.134 But it was the work of Krief, who reported in 1974135 that in THF this reaction becomes much faster (complete in 30 min at 0 °C) that gave selenium-lithium exchange synthetic possibilities. The reaction of a dialkylselenide - or a trialkylselenonium salt - with an alkyllithium, displacing the most stable organolithium, is effective, but of rather limited use, and there is insufficient difference in stability between Me and Bu for clean displacement of one by the other ... 

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