The thermally unstable compounds Hg(CN)P(CF3)(2) and Hg[P(CF3)(2)](2) were obtained by reactions of mercury cyanide and bis(trifluoromethyl)phosphane in solution and characterized by multinuclear NMR spectroscopy. An increase in thermal stability is observed when the products form 18 valence electron complexes. The compounds [Hg{P(CF3)(2)}(2)(dppe)] (dppe = 1,2-bis(diphenylphosphanyl)ethane) and [Hg{P(CF3)(2)}(2)(Me3P)(2)] have been isolated in almost quantitative yield by reacting [Hg(CN)(2)(dppe)] or [Hg(CN)(2)(Me3P)(2)] With HP(CF3)(2). [Hg{P(CF3)(2)}(2)(dppe)] crystallizes in the triclinic space group P (1) over bar. The mercury atom is coordinated in a distorted tetrahedral fashion. The Hg-P(CF3)(2) bonds, ca. 250 pm, are significantly longer than those of the mercury bis(phosphanides) Hg(PR2)(2) With R = t-BU, 245 pm, or SiMe3, 241 pm. These easily accessible compounds [Hg{P(CF3)(2)}(2)(dppe)] and [Hg{P(CF3)(2)}(2)(Me3P)(2)] act as nucleophilic bis(trifluoromethyl)phosphane group transfer reagents.