Mesityl-Phosphorus Compounds. Synthesis of a New Imino(Methylene)phosphorane and Its Dimers.

The reaction of CCl4 with the sterically congested silylamino phosphine Me3Si2NPRCH2SiMe3 compound 1, R double bond 2,4,6-Me3C6H2 unexpectedly yields the 4-membered P2N2 ring system Me3SiCH double bond PR-NSiMe32 compound 2. Heating of the dimer compound 2 under a dynamic vacuum results in distillation of the monomeric, 3-coordinate iminomethylenephosphorane R-Pdouble bond CHSiMe3 double bond NSiMe3 compound 3. Compound 3 exhibits reasonable stability at room temperature but reverts to the dimer compound 2 on standing for a few days. Treatment of compound 3 with methanol affords the stable addition product Me3SiN double bond P R OMeCH2SiMe3 compound 4. Direct bromination of the phosphine compound 1 occurs to give the expected P-bromophosphinimine compound 5 which, by reaction with LiOCH2CF3, is converted to Me3SiN double bond P R OCH2CF3CH2SiMe3 compound 6. When either the dimer compound 2 or the monomer compound 3 is heated in a sealed tube, an isomeric, 4-membered PCPN dimer compound 7 is obtained quantitatively. Proton, 13C, and 31P NMR data are reported for the new compounds and the CCl4 reaction of compound 1 is contrasted to that observed for related systems. Author