An unusual way of formation of spirophosphoranes during the oxidative addition of hexafluoroacetone to sigma P-5-sigma P-3-diphosphorus compounds, and in the reaction of 2-chloro-1,2-dimethyl-3-phenyl-2-phenylseleno-1,3,5 sigma(5)-diazaphosphetidin-4-one with bis(2-chloroethyl)amine hydrochloride/triethylamine

The reaction of (chloromethyl)dichlorophosphine 1 with N,N'-dimethyl N,N'-bis(trimethylsilyl)urea 2 furnished the sigma(5)P-sigma(3)P-diphosphorus compound 3. The reaction of 3 with hexafluoroacetone proceeded in an unusual fashion, with the rupture of the P-P bond, resulting in 4,4-bis(trifluoromethyl)-3-chloro-2-hexafluoroisopropoxy-2-oxo-1,2-oxaphosphetane 7 and the spirophosphorane 4-chloromethyl-1,3,5,7-tetramethyl-1,3,5,7-tetraaza-4 sigma(5)-phosphaspiro[3.3]heptan-2,6-dione 8. The reaction of 2-chloro-1,2-dimethyl-3-phenyl-2-phenylseleno-1,3,2 sigma(5)-diazaphosphetidin-4-one 9 with bis(2-chloroethyl)amine hydrochloride/triethylamine 10 also proceeded in an unexpected fashion, leading to the spirophosphorane 11 as the only identified product. Single-crystal X-ray structure analyses of compounds 8 and 11 were conducted. The coordination geometry at phosphorus in both compounds shows a large deviation from idealized forms. This distortion arises mainly from the presence of the four-membered rings.