Synthesis and Structures of One- and Two-Electron Oxidized Forms of Bis(acetylene)tetrairon Clusters Cp‘₄Fe₄(HCCH)₂ (Cp‘ = Cp, η⁵-C₅H₄Me)

Abstract

Air-oxidation of Cp'(4)Fe(4)(HCCH)(2) (Cp' = Cp (1a), C(5)H(4)Me (1b)) in an NH(4)PF(6)/CH(3)CN solution afforded the one-electron oxidized clusters [Cp'(4)Fe(4)(HCCH)(2)](PF(6)). Oxidation of 1a with excess AgBF(4) in THF afforded [1a](BF(4)), while that of 1b with excess AgBF(4) gave [1b](BF(4))(2). The X-ray crystal structure analysis of [1a](BF(4)) revealed that the monocationic cluster retains the butterfly-type Fe(4)(mu4-eta(2):eta(2):eta(1):eta(1)-HCCH)(2) framework similar to that of the neutral cluster. The average Fe-Fe bond length is shorter by 0.029 A than that in the neutral cluster. Electrochemical oxidation of 1a and 1b in 0.1 M NH(4)PF(6)/CH(3)CN solution at +0.30 and +0.25 V versus Ag/10 mM AgNO(3), respectively, afforded the two-electron oxidized clusters [1a](PF(6))(2) and [1b](PF(6))(2). The X-ray crystal structure analysis for [1b](BF(4))(2) shows that the butterfly-type cluster core is retained but shrinks more of those of neutral and monocationic clusters. The four Fe-Fe bonds in [1b](BF(4))(2) are unequivalent: one Fe-Fe bond (2.397(1) A) is apparently shorter than the others (2.439(2)-2.461(2) A).

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

“…The 1 H and 13 C NMR signals were observed at δ( 1 H) 11.58 and δ( 13 C) 212.1. These chemical shifts lie in the region expected for the acetylene ligand bridging the butterfly-type tetrairon cores …”

Stepwise Bromination of Two Acetylene Molecules on a Butterfly-Type Tetrairon Core and Reactivity of the Resulting Bromoacetylene Fragment toward Nucleophiles

“…A dichloromethane solution (20 mL) of [2](OTf) (102 mg, 0.124 mmol) was treated with NBS (22 mg, 0.12 mmol) at room temperature. After the solution was stirred at room temperature for 2 h, the mixture was concentrated to dryness under reduced pressure.…”

“…A round-bottomed flask equipped with a greaseless vacuum valve was charged with [2](PF 6 ) (46 mg, 0.056 mmol) and acetonitrile (5 mL), followed by the introduction S-6 of pyridine (27 mg, 0.34 mmol) into the tube under high vacuum by the trap-to-trap-transfer technique.…”

“…13 C{ 1 H} NMR (75.5 MHz, CD 3 CN) δ 8.9, 17.6, 23.8 (C 5 H 4 Me), 75.1, 80.8, 92.4, 98.7, 106.7, 116.1, 123.5, 127.3, 127.5, 128.8, 134.8 (C 5 H 4 Me). [2](PF 6 ) and [2](TFPB) were obtained by the similar methods, using [1](PF 6 ) (500 mg, 0.679 mmol) and NBS (121 mg, 0.680 mmol) and [1]…”

20 Organometallic chemistry of bi- and poly-nuclear complexes

“…The bond length of the coordinated C-C bonds remain almost unchanged with oxidation. 48 Cluster-mediated hydro-silation reactions have been studied for both iron, 49 and ruthenium 50 scaffolds.…”