Sir:We wish to report the synthesis and characterization of the initial examples of a new class of metallocenes, the cationic metal halide complexes of triphenylphosphinium cyclopentadienylide, I.-hPh, -CpPPh, I Stirring 0.2401 g (0.736 mmol) of CpPPh3 with 0.3360 g (0.738 mmol) of mercuric iodide in 50 ml of dry, deoxygenated (N2) tetrahydrofuran (THF) a t room temperature resulted in the formation of a dark yellow precipitate after a few minutes. Upon filtration 0.3155 g (55%) of the 1:l adduct, CpPPh3HgI2, mp 191-192 'C dec, was obtained. More of the product could be precipitated by addition of petroleum ether (60-90 'C), but it was of slightly lesser quality. The complex has been air-stable at room temperature for more than a year.
Scheme I ture) from 9, reacts with the sodium salt of methyl (dimethylphosphinyl)bromoacetate9 in 1,2-dimethoxy ethane to afford 11. Treatment of 11 with m-chloroperoxybenzoic acid gives rise to 12 as a 2:3 mixture of E and Z isomers.Reaction of silyl enol ether 13 (3.5 equiv) at -78 °C in 1,2-dimethoxyethane with methyllithium (2.5 equiv) generates, presumably, enolate 14, which reacts with the esters 12 (-78 °C (30 min) -*• room temperature (1 h)). Chromatography on silica gel afforded three products (Scheme
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