TRANSITION-METAL SUBSTITUTED ACYLPHOSPHAN ES AND PHOSPHAALKENES .24. DIPOLAR [3-CYCLOADDITIONS AND [2+2]-CYCLOADDITIONS OF CARBONYL ACTIVATED ALKYNES TO (ETA(5)-C-5ME(5))(CO)(2)FE-P=C(NME(2))(2) - SYNTHESIS AND STRUCTURE OF THE 1-PHOSPHA-1,3-BUTADIENE )(CO)(2)FE-P=C(E)-C(E)=C(NME(2))(2)(E=CO(2)ME)(2])

The metallophosphaalkene (eta(5)-C(5)Me(5))(CO)(2)Fe-P=C(NMe(2))(2) (1 ) was converted into the stable metallated 1-phospha-1,3-butadiene, et a(5)-C(5)C(5)Me(5))(CO)(2)Fe-P=C(E)=C(NMe(2))(2) 5a) and the [3+2]-cyc loadduct (5)-C(5)Me(5))(CO)Fe-C(O)-C(E)=C(E)-P=C(NMe(2))(2) (4 a) by t reatment with the alkyne E-C=C-E (E = CO(2)Me). A similar reaction of 1 with Me-C=C-E (E = CO(2)Me) resulted in the formation of the 1,2-dih ydrophosphete (eta(5)-C(5)Me(5))(CO)(2)Fe-PC(=CH2)-C(E)=C-NMe(2) (6). The cycloadduct )Me(5))(CO)Fe-C(O)-C[C(O)tBu]=C(Ph)-P=C(NMe(2))(2) (4c ) was the sole tractable product from the reaction of 1 with the alkyn e Ph-C=C-C(O)tBu. The compounds 4a-c, 5a, b and 6 have been characteri zed by elemental analysis as well as by spectroscopic data (IR, H-1,C- 13, P-31 NMR, MS). The molecular structures of 4a, 5a and 6 have been determined by single crystal X-ray analysis.