ANNULATION REACTIONS OF FISCHER CARBENE COMPLEXES TETHERED ON A CHALCOGEN-STABILIZED IRON CARBONYL CLUSTER - DEPENDENCE OF REACTION PATHWAYON CHALCOGEN ATOM

When a benzene solution containing the Fischer carbene complex [(CO)(6 )Fe2Se2{mu-C(Ph)= C-C(OEt)=Cr(CO)(5)}] (6) and phenylacetylene, diphen ylacetylene, 1-hexyne, or 3-hexyne is subjected to reflux, the substit uted cyclopentadienylchromium complexes )(6)Se-2{mu-(Co)(3)Cr(eta(5)-C -5(R)(R')(Ph)(OEt)}] (8a R = H, R' = Ph; 8b R, R' = Ph; 8c R = H, R' = (CH2)(3)-CH3; and 8d R, R' = C2H5) are formed in 72-79% yield. The co rresponding SSe analogue [(Co)(6)Fe2SSe{mu-C(Ph)=C-C(OEt)=Cr(CO)(5)}] (7) reacts with phenylacetylene or diphenylacetylene to form SSe{mu-C( H)C(O)C(H)=C(eta(6)-C6H6Cr(CO)(3))C(Ph)}] (9a) or Se{mu-C(H)C(O)C(Ph)= C(eta(6)-C6H5Cr(CO)(3))C(PhP}] (9b) in high yields (82% and 85%). All new compounds have been characterized by IR and H-1, C-13, and Se-77 N MR spectroscopy, and structural types were unequivocally established b y crystallographic analysis of compounds 8b and 9b.