Contributions to the chemistry of phosphorus. 243 - On the oxocyclotetraphosphanes (PBut)(4)O1-4

Under suitable conditions, the reaction of tetra-tert-butylcyclotetraphosph ane. (PBut)(4), with dry atmospheric oxygen gives rise to the corresponding monoxide (PBut)(4)O (1) which has been isolated by column chromatography. The reaction with hydrogen peroxide furnishes a mixture of oxocyclotetrapho sphanes (PBut)(4)O1-4 consisting of two constitutionally isomeric dioxides (PBut)(4)O-2 (2a, 2b), the trioxide (PBut)(4)O-3 (3), and the tetraoxide (P But)(4)O-4 (4), in addition to 1. According to the P-31 NMR parameters the oxygen atoms are exclusively exocyclically bonded to the phosphorus four-me mbered ring. Which of the P atoms are present as lambda (5)-phosphorus foll ows from the different low-field shifts of the individual P nuclei compared with the starting compound. Accordingly, 1 is 1,2,3,4-Tetra-tert-butyl-1-o xocyclotetraphosphane, 2a and 2b are 1,2,3,4-Tetra-tert-butyl-1,2-dioxo- an d -1,3-dioxocyclotetraphosphane, respectively, 3 is 1,2,3,4-Tetra-tert-buty l-1,2,3-trioxocyclotetraphosphane, and 4 is 1,2,3,4-Tetra-tert-butyl-1,2,3, 4-tetraoxocyclotetraphosphane. When the oxidation reaction proceeds a fissi on of the P-4 ring takes place.