Synthesis and Structure of Cubane-Type Tetrairon Clusters Possessing μ₃-Isonitrile Ligands. Reductive Coupling of Two Isonitriles on Redox-Responsive Tetrairon Reaction Sites

Abstract

A 3:1 molar ratio mixture of [(η5-C5H4Me)4Fe4(HCCBr)2](PF6) (1a) and [(η5-C5H4Me)4Fe4(HCCH)(BrCCBr)](PF6) (1b) was converted to [(η5-C5H4Me)4Fe4(μ3-CH)2(μ3-CNPh)2](PF6)2 (2) upon treatment with aniline, followed by N i Pr2Et and finally [Cp2Fe](PF6). The X-ray diffraction analysis revealed that 2 can be described as a cubane-type tetrairon cluster possessing two μ3-CH and two μ3-isonitrile ligands. Treatment of 2 with 2.5 equiv of [Cp2Co] gave the neutral form 3, formulated as [(η5-C5H4Me)4Fe4(HCCH)2(μ3-CNPh)2]. The redox reactions were chemically reversible; treatment of 3 with [Cp2Fe](PF6) reproduced 2 quantitatively. The structure of 3 was determined by X-ray diffraction analysis. The molecule exhibits a butterfly geometry resulting from the scission of one of the iron–iron bonds of the tetrahedron in 2. In accordance with the conversion of the core structure from tetrahedron to butterfly, the coupling of two μ3-CH ligands occurs to form an acetylene ligand. Further treatment of 3 with LiAlH4 followed by air-oxidation resulted in reductive coupling of two isonitrile ligands to give a bis(acetylene) cluster, [(η5-C5H4Me)4Fe4(HCCH)2](PF6) (6).

Bond Forming Reactions Involving Isocyanides at Diiron Complexes

“…Coupling of isocyanide ligands involving dinuclear complexes is far less common [93][94][95]. Thus, the CNR coupling shown in Scheme 12 has a distinctive character for two reasons: It involves a diiron complex, which is rather uncommon [96], and it provides an example of isocyanide coupling taking place via C-N bond formation, which is rarely observed [62,95], with respect to the predominant C-C coupling mode.…”

Nonaqueous capillary gel electrophoretic analysis of metal nanoclusters in polymeric–DMSO–Li+ systems

“…Five tetrairon clusters (Fig. 1) were synthesized according to the previous reports [21][22][23]. BGEs were prepared by dissolving the polymers and lithium ions in DMSO at 60°C.…”

Covalent Metal–Metal-Bonded Mn4 Tetrahedron Inscribed within a Four-Coordinate Manganese Cubane Cluster, As Evidenced by Unexpected Temperature-Independent Diamagnetism

“…The M–M distances in 1 + represent some of the shortest within a transition-metal heterocubane cluster type, of which there are thousands of structures . In contrast to the high-valent, weak-field coordination environment of 1 + , previously reported simple heterocubane cluster types with M–M distances equal to or less than those of 1 + involve low-valent, strong-field coordination environments induced by cyclopentadienyl − or π-accepting ligands like NO, CO, , phosphine, , and, in one report, olefinic agostic ligands . In some of these complexes, very small hydride- , or boron-based − core-bridging ligands permit further contraction of the M 4 core.…”