SYNTHESIS OF [FE-2(CO)(6)(MU-SC2H5)(MU-CCR)] (R=CH3 OR C6H5) AND REACTIVITY WITH ELECTRON-RICH MOLECULES, TRIPHENYLPHOSPHINE, DIPHENYLACETYLENE, ETHYLTHIO(PHENYL) ETHYNE AND (DIETHYLAMINO) PROPYNE - PREPARATION OF [FE-2(CO)(6)(MU-SCCC6H5)(MU-CCC6H5)] AND FORMATION OF [FE-4(CO)(12)(MU(4)-S)(MU-CCC6H5)(2)]

Compounds [Fe-2(CO)(6)(mu-SC2H5)(mu-CCR)] with R = CH3 or C6H5, were p repared and allowed to react with triphenylphosphine, diphenylacetylen e, (ethylthio)phenylethyne, 1-(diethylamino)prop-1-yne. These four rea ctants are electron-rich molecules able to attack at the acetylide car bon atoms C-alpha=C(beta)R. The structures of nine complexes were dete rmined by X-ray diffraction. For R = CH3 or P(C6H5)(3) reaction occurr ed at C-beta leading to [Fe-2(CO)6(mu-SC2H5){mu-C=C[P(C6H5)(3)](CH3)}] . In the case of R = C6H5, a monosubstituted complex [Fe-2(CO)(5){P(C6 H5)(3)}(mu-SC2H5)(mu-CCC6H5)] and a disubstituted complex [Fe-2(CO)(4) {P(C6H5)(3)}(2)(mu SC2H5)(mu-CCC6H5)] were obtained. With C6H5C=CC6H5, [Fe-2(CO)(5){mu-S(C2H5)C(R)CC(C6H5)C(C6H5)C(O)}] was obtained (R = CH 3 or C6H5). The opening of the triple bond of the incoming alkyne led to two C-C bonds, one with acetylide C-alpha, one with a carbonyl grou p. The SC2H5 moved around an iron atom from a bridging position to be linked to C-beta. In addition, for R = C6H5 an isomer was obtained the structure of which is based on a nido Fe2C3 framework. It readily tra nsformed into e-2(CO)(5){mu-S(C2H5)C(C6H5)CC(C6H5)C(C6H5)C(O)}]. With C6H5C=CSC2H5 two complexes, e-2(CO)(5){mu-S(C2H5)C(C6H5)CC(C6H5)C(SC2H 5)C(O)}] (80%) and e-2(CO)(5){mu-S(C2H5)C(C6H5)CC(SC2H5)C(C6H5)C(O)}] (20%), were obtained. They are of the same structural type as above. T he major product resulted from the coupling of thioalkyne C-beta with acetylide C-alpha. With CH3C-CN(C2H5)(2) the complex obtained, 2(CO)(6 ){C[C(O)SC2H5]C(C6H5)C(CH3)C[N(C2H5)(2)]}], has a structure based on a ferracyclopentadienyl fragment ligated to a second iron atom by a Fe- Fe bond and by an allylic fragment. An unprecedented CO insertion occu red in a side chain, yielding an ethylthiocarboxy radical. Both CS bon ds were eventually cleaved using S(C=CC6H5)(2) as a starting alkyne. F irst, [Fe-2(CO)(6)(mu-SC=CC6H5)(mu-C=CC6H5)] was prepared. Second, an excess of iron carbonyl yielded [Fe-4(CO)(12)(mu(4)-S)(mu-C=CC6H5)(2)] . The four iron atoms belong to two dinuclear entities and form a tetr ahedron around sulfur.