Synthesis and characterization of transition-metal hydrido/chalcogenido/carbonyl clusters (eta(5)-RC5H4) (CO)(2)MFe2H(mu(3)-E)(CO)(6) (M = Mo, W; E =S, Se) and their derivatives (eta(5)-2,4-(NO2)(2)C6H3NHNC(Me)C5H4)(CO)(2)WFe2H(mu(3)-S)(CO)(6) and (eta(5)-RC5H4)(CO)(2)MFeCo(mu(3)-S)(CO)(5)(PPh3) generated from isolobal and functional transformation reactions. Crystal structures of (eta(5)-MeCOC5H4)(CO)(2)WFe2H(mu(3)-E)(CO)(6) (E = S, Se) and (eta(5)-MeCOC5H4)(CO)(2)MFeCo(mu(3)-S)(CO)(5)(PPh3) (M

The tetrahedral hydrido/chalcogenido/carbonyl clusters (eta(5)-RC5H4)(CO)(2 )MFe2H(mu(3)-E)(CO)(6) (1-10; R = H, MeCO, MeO2C; M = Mo, W; E = S, Se) wer e synthesized by the isolobal displacement reaction of (eta(5)-RC5H4)(CO)(2 )MCoFe(mu(3)-E)(CO)(6) with NaHFe(CO)(4)/40% H3PO4 in 15-44% yields. A furt her transformation reaction of the acetyl functionality of 5 (M = W, E = S, R = MeCO) with 2,4-(NO2)(2)C6H3NHNH2 gave its phenyl hydrazone derivative (eta(5)-2,4-(NO2)(2)C6H3NHNC(Me)C5H4)(CO)(2)WFe2H(mu(3)-S)(CO)(6) (11) in 4 0% yield, whereas further isolobal reaction of 1-6 (M = Mo, W; E = S; R = H , MeCO, MeO2C) with (PPh3)(3)CoCl afforded the isolobal displacement produc ts (eta(5)-RC5H4)(CO)(2)MFeCo(mu(3)-S)(CO)(5)(PPh3) (12-17; M = Mo, W; R = H, MeCO, MeO2C) in 15-41% yields. All the products were characterized by el emental analysis and IR and H-1 NMR (some by additional MS and Se-77 NMR) s pectroscopy; also, products 5 (R = MeCO, M = W, E = S), 9 (R = MeCO, M = W, E = Se), 13 (M = Mo, R = MeCO), and 16 (M = W, R = MeCO) were characterize d by single-crystal X-ray diffraction analyses. In addition, the mechanisms for the isolobal reactions, which yielded products 1-10 and 12-17, have be en briefly discussed.