Reactivity of the inversely polarized phosphaalkenes RP=C(NMe2)2 (R = tBu, Me3Si, H) towards arylcarbene complexes [(CO)5M=C(OEt)Ar] (Ar = Ph, M = Cr, W; Ar=2-MeC6H4, 2-MeOC6H4, M = W)

The reaction of the arylated Fischer carbene complexes [(CO)(5)M=C(OFt)Ar] (Ar = Ph; M=Cr, W, 2-MeC6H4; 2-MeOC6H4, M = W) with the phosphaalkenes RP C(NMe2)(2) (R=tBu, SiMe3) afforded the novel phosphaalkene complexes [{RP=C(OEt)Ar}M(CO)(5)] in addition to the compounds [{RP-C(NMe2)(2)}M(CO)(5)]. Only in the case of the R = SiMe3 (E/Z) mixtures of the metathesis products were obtained. The bis(ditnethylamino)-methylene unit of the phosphaalkene precursor was incorporated in olefins of the type (Me2N)(2)C=C(OEt)(Ar). Treatment of [(CO)(5)W=C(OEt)(2-MeOC6H4)] with HP=C(NMe2)(2) gave rise to the formation of an E/Z mixture of [{(Me2N)(2)CH-P=C(OEt)-(2-MeOC6H4)}W(CO)(5)] the organophosphorus ligand of which formally results from a combination of the carbene ligand and the phosphanediyl [P-CH(NMe2)(2)]. The reactions reported here strongly depend on an inverse distribution of pi -electron density in the phosphaalkene precursors (P-delta-C-delta+), which renders these molecules powerful nucleophiles.