Reactivity of the Inversely Polarized Phosphaalkenes RP=C(NMe 2 ) 2 (R= t Bu, Me 3 Si, H) towards Arylcarbene Complexes [(CO) 5 M=C(OEt)Ar] (Ar=Ph, M=Cr, W; Ar=2‐MeC 6 H 4 , 2‐MeOC 6 H 4 , M=W)

The reaction of the arylated Fischer carbene complexes [(CO) 5 M=C(OEt)Ar] (Ar=Ph; M=Cr, W; 2‐MeC 6 H 4 ; 2‐MeOC 6 H 4 ; M=W) with the phosphaalkenes RP=C(NMe 2 ) 2 (R= t Bu, SiMe 3 ) afforded the novel phosphaalkene complexes [{RP=C(OEt)Ar}M(CO) 5 ] in addition to the compounds [{RP=C(NMe 2 ) 2 }M(CO) 5 ]. Only in the case of the R=SiMe 3 ( E / Z ) mixtures of the metathesis products were obtained. The bis(dimethylamino)methylene unit of the phosphaalkene precursor was incorporated in olefins of the type (Me 2 N) 2 C=C(OEt)(Ar). Treatment of [(CO) 5 W=C(OEt)(2‐MeOC 6 H 4 )] with HP=C(NMe 2 ) 2 gave rise to the formation of an E / Z mixture of [{(Me 2 N) 2 CH‐P=C(OEt)(2‐MeOC 6 H 4 )}W(CO) 5 ] the organophosphorus ligand of which formally results from a combination of the carbene ligand and the phosphanediyl [P−CH(NMe 2 ) 2 ]. The reactions reported here strongly depend on an inverse distribution of π‐electron density in the phosphaalkene precursors (P δ − C δ + ), which renders these molecules powerful nucleophiles.