Selenium-Bridged Clusters. Synthesis and Structural Characterization of the μ₄-Se Twin Cluster [(μ-BuSe)Fe₂(CO)₆]₂(μ₄-Se)

Abstract

The unusual tetranuclear cluster [(µ-BuSe)-Fe 2 (CO) 6 ] 2 (µ 4 -Se) (1) has been obtained from the reaction of a monoanion, derived from Fe 2 (µ-Se 2 )(CO) 6 and n-BuLi, with 1,3-dibromopropane. Compound 1 has been characterized by IR and 1 H, 13 C, and 77 Se NMR spectroscopy. It has been structurally characterized by single-crystal X-ray diffraction methods. The structure consists of two [(µ-BuSe)Fe 2 (CO) 6 ] units bridged by a pseudotetrahedral Se atom.

Synthesis of [(μ-RS)Fe2(CO)6](μ4-S)[(μ-R‘S)Fe2(CO)6] and [(μ-t-BuS)Fe2(CO)6](μ4-Se)[(μ-PhSe)Fe2(CO)6] via Reactions of (μ-RS)(μ-p-MeC6H4SO2S)Fe2(CO)6 with Nucleophiles. Crystal Structure of [(μ-t-BuS)Fe2(CO)6](μ4-S)[(μ-PhC⋮CS)Fe2(CO)6]

“…It is worth pointing out that the reaction of 2 with 4 shown in Scheme provides another new synthetic method for production of symmetrical and asymmetrical μ 4 -S twin clusters. ,, In view of the nucleophilic similarity of the bridged sulfur-centered anions such as in salts 4 with their selenium analogues, it might be expected that reaction of 2 with bridged selenium-centered anions would produce corresponding μ 4 -Se twin clusters. , This has been proved to be true by our experiment, that is, the reaction of 2 (R = t-Bu) with the [MgBr] + salt of the bridged selenium-centered anion [(μ-PhSe)(μ-Se - )Fe 2 (CO) 6 ] (prepared from μ-Se 2 Fe 2 (CO) 6 and PhMgBr) 1 in THF, from −78 °C to room temperature to afford the μ 4 -Se twin cluster [(μ-t-BuS)Fe 2 (CO) 6 ][(μ 4 -Se)(μ-PhSe)Fe 2 (CO) 6 ] ( 6 ), as shown in Scheme .…”

“…For example, for twin clusters 5b − d and 6 , the IR spectra show three to four absorption bands in the range 2082−1983 cm -1 for their terminal carbonyls attached to iron atoms, in addition to the IR spectrum of 5b , showing a weak absorption band at 2172 cm -1 for its C⋮C triple bond. It is well-known that twin clusters 5b − d and 6 could exist, on the basis of the steric repulsion grounds, as only one isomer in which the two substituents are bonded to the bridged S and Se atoms with an equatorial type of bond. ,,, This has been verified by their 1 H NMR spectra; that is, the Et group of 5b displays one triplet at 1.39 ppm and one quartet at 2.49 ppm and the t-Bu group of 5c , d and 6 shows one singlet between 1.44 and 1.52 ppm.…”

“…Interestingly, although some methods are known for preparation of μ 4 -Se twin clusters, , there has been no method reported so far for making a type of μ 4 -Se clusters that contain two different bridging ligands, such as μ-t-BuS and μ-PhSe in cluster 6 .…”

Synthesis of Double and Quadruple Butterfly Fe/S Cluster Complexes via a Novel Type of Reaction of Anions (μ-RS)(μ-S-)[Fe2(CO)6]2(μ4-S) with Succinyl Chloride

“…However, although in 6b the dihedral angle between the two butterfly wings of each subcluster core is almost the same (95.94° and 95.78°), that in 6a is quite different (95.7° for subcluster core Fe(1)Fe(2)S(1)S(3) and 83.6° for Fe(3)Fe(4)S(3)S(4)). It is worth noting that, to our knowledge, 6a and 6b are respectively the first double butterfly Fe/S cluster complex containing a bridging alkylperchalcogenido ligand η 2 -RS 2 and the longest multibutterfly Fe/S cluster complex (nonbonded distance C13···C13* = 0.92 nm) prepared and crystallographically characterized so far, although some single, double, and even triple butterfly Fe/E cluster complexes are prepared and crystallographically studied, such as (μ-EtS) 2 Fe 2 (CO) 6 , [(μ-MeS)Fe 2 (CO) 6 ](μ 4 -S), [(μ-EtS)Fe 2 (CO) 6 ][(μ-PhS)Fe 2 (CO) 6 ](μ 4 -S), [(μ-EtS)Fe 2 (CO) 6 ] 2 (μ 4 -Se),3h [(μ-p-MeC 6 H 4 Se)Fe 2 (CO) 6 ] 2 (μ 4 -Se), [(μ-PhS)Fe 2 (CO) 6 ] 2 [(μ-S−S-μ],3c [(μ-MeS)Fe 2 (CO) 6 ] 2 [μ-S-(m-CH 2 C 6 H 4 CH 2 )-S-μ],3g [(μ-t-BuS)Fe 2 (CO) 6 ] 2 [μ 4 -SFe 2 (CO) 6 -S-μ 4 ],4b and [(μ-n-BuSe)Fe 2 (CO) 6 ] 2 (μ 4 -Se) …”