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]

Abstract

The reaction of the carbide carbon anion [Fe5C(CO)14]2- with ClHgM in tetrahydrofuran gives the new heptametallic clusters (NEt4)[Fe5C(CO)14{μ-HgM}] (M = Mo(CO)3Cp (1a), W(CO)3Cp (1b), Mn(CO)5 (1c), Co(CO)4 (1d), Fe(CO)2Cp (1e)). The spiro species (NEt4)2[μ4-Hg{Fe5C(CO)14}2] (2) has been isolated by reaction of the pentairon 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 has an Fe5 square-pyramidal metal skeleton in which a basal edge is bridged by the HgW(CO)3Cp 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 57Fe 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 (NEt4)[Fe5C(CO)14{μ-HgM}] (1a,b) with AuPPh3 + to give the neutral octametallic clusters [Fe5C(CO)14{μ-HgM}{μ-AuPPh3}] (M = Mo(CO)3Cp (3a), W(CO)3Cp (3b)).

Selective Additions of Group 11 and 12 Metal Fragments to the Fe4C and Fe5C Units

“…The isomer shift of Fe(2,3) atoms is more positive than that of Fe(1,4), which indicates that the 4s electron density at the iron nucleus of the former is less than for the latter . This fact could be related to the high electrophilic character attributable to the HgM + compared with that of the M‘PPh 3 + fragment and corroborates well with the ν(CO) shifts observed in IR spectra of each type of iron carbonyl compound. − ,,− …”

“…Reactions with [Fe 5 C(CO) 14 {HgM}] - . In a recent work, we examined the tendency of the [Fe 5 C(CO) 14 -{HgM}] - anion to add AuPPh 3 + fragments by giving mixed Au/Hg/Fe clusters . The new cluster [Fe 5 C(CO) 14 {HgM(CO) 3 Cp}{AuPPh 3 }] (M = Mo, W) was obtained and fully characterized.…”

Cobalt/Mercury Carbide Clusters Based on Trigonal-Prismatic or Octahedral Co6C Skeletons − X-ray Crystal Structure of (NEt4)2[Co6C(CO)12{HgW(CO)3Cp}2]

“…Despite the fact that [Co 6 C(CO) 13 {HgW(CO) 3 Cp}] Ϫ bears one negative charge and, consequently, is relatively inert to symmetrization processes, with high nuclearity clusters a spontaneous albeit slow symmetrization occasionally takes place. [15,16] The failure to isolate 6 precluded its spectroscopic characterization. However, it was thought that the addition of four electrons to its polyhedral skeleton, by reaction with carbon monoxide, would facilitate skeletal arrangement to the trigonalprismatic [Co 6 C(CO) 15 {HgW(CO) 3 Cp}] Ϫ (3a), which has been characterized previously.…”