Divalent carbon transfer reagent. Prepn: D. Seyferth, R. S. Marmor, Tetrahedron Lett. 11, 2493 (1970); and applications in organophosphorus syntheses: D. Seyferth et al., J. Org. Chem. 36, 1379 (1971). Reactions with aldehydes and aryl ketones to form alkynes: J. C. Gilbert, U. Weerasooriya, ibid. 47, 1837 (1982). Improved prepn: D. G. Brown et al., ibid. 61, 2540 (1996).