Preparation and properties of fluorenylidenephosphines bearing an electron-donating substituent, 2-alkoxy-4,6-di-t-butylphenyl or 2-(alkoxymethyl)-4,6-di-t-butylphenyl

Fluorenylidenephosphines having a 2,4-di-t-butyl-6-methoxyphenyl, 2,4-di-t-butyl-6-(methoxymethyl)phenyl or 2,4-di-t-butyl-6-(phenoxymethyl)phenyl group were prepared. 31P NMR chemical shifts of the fluorenylidenephosphines indicated that electron-donating effects through space are not so strong between the alkoxy group and the double-bonded phosphorus atom. The structure of a tungsten carbonyl complex of [2,4-di-t-butyl-6-(phenoxymethyl)phenyl](fluorenylidene)phosphine was analyzed by X-ray crystallography.