TRANSITION-METAL-SUBSTITUTED ACYLPHOSPHANES AND PHOSPHAALKENES .26. SYNTHESIS AND STRUCTURE OF THE 2-METALLO-1,2,3-DIAZAPHOSPHOLES A(5)-C(5)ME(5))(CO)(2)FE-N-P=C(NME(2))-C(CO(2)R)=N (R=ET, TBU)

Treatment of the metallophosphaalkene (eta(5)C(5)Me(5))(CO)(2)Fe-P=C(N Me(2))(2) with diazoacetates N(2)CHCO(2)R (R = Et, tBu) afforded the n ovel N-metalated 1,2,3-diazaphospholes ta(5)-C(5)Me(5))(CO)(2)Fe-N-P=C (NMe(2))C(CO(2)R)=N (R = Et, tBu) as the formal result of a dipolar [3 + 2] cycloaddition which is followed by the elimination of dimethylam ine and a sigmatropic 1,2-shift of the metal fragment from phosphorus to nitrogen. The molecular structure of one representative (R = tBu) w as established by a single-crystal X-ray analysis. The combination of reactive sites in metallophosphaalkenes such as (eta(5)-C(5)Me(5))(CO) (2)Fe-P=CR(1)R(2) (R(1) = R(2) = SiMe(3),2 NMe(2)(3)) renders them ver satile as useful building blocks in organometallic synthesis. Thus, th e compound (eta(5)-C(5)Me(5))(CO)(2)Fe-P=C(NMe(2))(2) (1) was convenie ntly converted into 1-metallo-1,2-dihydrophosphetes I-3 and IV4 when r eacted with fumarodinitrile and dimethyl fumarate or methyl butynoate, respectively.