REACTIVITY OF (PHOSPHAALKENYL)METAL SPECIES - TRANSMETALATIONS AND REACTIONS WITH CARBONYL-COMPOUNDS

The (phosphaalkenyl)lithium carbenoid (Z)-MesP=CClLi (2; Mes* = super mesityl = 2,4,6-tri-tert-butylphenyl) was transmetalated with MgBr2, Z nCl2, and HgCl2 to furnish the new (phosphavinylidene)metal carbenoids MesP=CClMX ((Z)-5a, MX = MgBr; (E)-5b, MX = ZnCl; (E)-5c, MX = HgCl) , while with 0.5 equiv of the metal halide, the bis(phosphaalkenyl)met al carbenoids (MesP=CCl)(2)M((Z,Z)-6a, M = Mg; (E,E)-6b, M = Zn; (E,E )-6c, M = Hg) were formed. Compounds 2 and 5a were reacted with carbon yl compounds under 1,2-addition, leading to the B-phosphaallyl alcohol s 7-10. Bromine-lithium exchange at -90 degrees C between (Z)-MesP=CB rSiMe(3) ((Z)-14) and n-butyllithium furnished (E)-/(Z)MesP=CLiSiMe(3 ) ((E)-/(Z)-16; E:Z = 1:1. Transmetalation of (E)-/(Z)-16 with MgBr2 o r ZnCl2 furnished only the trans-metal isomer of MesP=CMXSiMe(3) ((Z) -18a, MX = MgBr; (E)-18b, MX = ZnCl). From (E)-/(Z)-16, a new access t o the phosphaallene MesP=C=CPh(2) (20) was obtained by reaction with benzophenone.