Nysted reagent
Other names: cyclo-Dibromodi-μ-methylene[μ-(tetrahydrofuran)]trizinc
C6H12Br2OZn3
18/50 
common
The Nysted reagent is a unique organozinc complex used for the methylenation of ketones and aldehydes. Developed in the 1970s, this reagent functions as a powerful Wittig-type olefination agent but with the distinct advantage of being less basic than traditional phosphorus ylides. Its structure features a remarkable zinc cluster with bridging methylene groups and coordinated THF, giving it exceptional stability compared to other organometallic methylenating agents. In its pure form, the Nysted reagent appears as a white to off-white solid that, unlike Tebbe's reagent, can be handled without extreme air-sensitivity precautions, making it particularly valuable for large-scale synthetic applications. This practical advantage has secured its place in the organic chemist's toolkit for the conversion of carbonyls to terminal alkenes in complex molecule synthesis.