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{μ-HgW(CO)3Cp}] and (NEt4)2[μ4-Hg{Fe5C(CO)14}2]

The reaction of the carbide carbon anion [Fe 5 C(CO) 14 ] 2 - with ClHgM in tetrahydrofuran gives the new heptametallic clusters (NEt 4 )[Fe 5 C(CO) 14 {μ-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 (NEt 4 ) 2 [μ 4 -Hg{Fe 5 C(CO) 14 } 2 ] ( 2 ) has been isolated by reaction of the pentairon carbide carbon dianion with Hg(NO 3 ) 2 . The structures of 1b and 2 have been determined by X-ray diffraction methods. The anion of 1b has an Fe 5 square-pyramidal metal skeleton in which a basal edge is bridged by the HgW(CO) 3 Cp moiety. For the cluster anion 2, the metal core consists of a four-coordinate mercury atom bridging the bond edges of two square-based-pyramidal pentairon units. The electrochemical behavior of these compounds has been investigated by cyclic voltammetry and coulometry. The 57 Fe Mössbauer spectroscopy of complexes 1b, e reveals the existence of three and four types of iron sites, respectively. This study has been extended by reacting the new species (NEt 4 )[Fe 5 C(CO) 14 {μ-HgM}] ( 1a, b ) with AuPPh 3 + to give the neutral octametallic clusters [Fe 5 C(CO) 14 {μ-HgM}{μ-AuPPh 3 }] (M = Mo(CO) 3 Cp ( 3a ), W(CO) 3 Cp ( 3b )).