ADDITION OF INORGANIC AND ORGANIC NUCLEOPHILES TO THE VINYLIDENE LIGAND OF THE CLUSTER FECO2(CO)9(MU-3-C=CH2)

The C = CH2 ligand of the cluster FeCo2(CO)9(mu-3-C = CH2) (1) is electrophilic at the terminal C atom. Soft inorganic nucleophiles [Nu = PR3, (CH3)2SO, CN-, SCN-] are added to form the zwitterionic complexes FeCo2(CO)9(mu-3-C-CH2-Nu) (4, 7, 8), as proved by the structure determination of FeCo2(CO)9(mu-3-C-CH2-PMe3) (4a). The products are of low thermal stability. Upon heating, the PR3 derivatives rearrange to the CO substitution products FeCo2(CO)8(PR3)(mu-3-C = CH2) (5, 6). C - C coupling is achieved by addition of malonic ester anion derivatives [X - CH - CO2Me]- (X = MeO2C, CN, Br). The anionic addition product for X = MeO2C (10a) can be protonated to form HFeCo2(CO)9(mu-3-C - CH2 - CH(COOMe)2] (11) which liberates H-2 upon warming resulting in FeCo2(CO)9[mu-3-C = CH - CH(COOMe)2] (12). Thus, a substitution of a vinylidene H atom has been performed by an HX addition/H-2 elimination sequence. Phosphorus ylides R3P = CHX [X = H, SiMe3, Cl, CHO, C(O)Ph, COOR] are also added with C - C coupling to yield the complexes FeCo2(CO)9(mu-3-C - CH2 - CHX - PR3) (15, 16). The structure determination of the compound with X = EtO2C and R = Ph (16c) proves that these complexes differ from the complexes 4 just by insertion of one methylene unit.