ELECTROPHILIC ADDITIONS OF MERCURY AND GOLD SPECIES TO THE ANION CARBIDE CLUSTER [FE5C(CO)(14)](2-) - X-RAY CRYSTAL-STRUCTURES OF (NET4)[FE5C(CO)(14)(MU-HGW(CO)(3)CP)) AND (NET4)(2)[MU(4)-HG(FE5C(CO)(14))(2)]

The reaction of the carbide carbon anion [Fe5C(CO)(14)](2-) with ClHgM in tetrahydrofuran gives the new heptametallic clusters (NEt4)[Fe5C(C o)(14){mu-HgM}] (M= Mo(CO)(3)Cp (1a), W(CO)(3)Cp (1b ), Mn(CO)(5) (1c) , Co(CO)(4) (1d), Fe(CO)(2)Cp (1e)). The spiro species (NEt4)(2)-[mu(4 )-Hg{Fe5C(CO)(14)}(2)] (2) has been isolated by reaction of the pentai ron carbide carbon dianion with Hg(NO3)(2). The structures of 1b and 2 have been determined by X-ray diffraction methods. The anion of 1b ha s an Fe-5 square-pyramidal metal skeleton in which a basal edge is bri dged by the HgW(CO)(3)Cp moiety. For the cluster anion 2, the metal co re consists of a four-coordinate mercury atom bridging the bond edges of two square-based-pyramidal pentairon units. The electrochemical beh avior of these compounds has been investigated by cyclic voltammetry a nd coulometry. The Fe-57 Mossbauer spectroscopy of complexes 1b,e reve als the existence of three and four types of iron sites, respectively. This study has been extended by reacting the new species (NEt4)[Fe5C( Co)(14){mu-HgM}] (1a,b) with AuPPh3+ to give the neutral octametallic clusters [Fe5C(CO)(14){mu-HgM}{mu-AuPPh3}] (M = Mo(CO)(3)Cp (3a), W(CO )(3)Cp (3b)).