Ternary antimony–chalcogen iron carbonyl complexes and their derivatives: Syntheses, structures, reactivities, and low-energy-gap characteristics

A novel series of ternary antimony–chalcogen iron carbonyl clusters, [{SbTeFe₃(CO)₉}{Te₂Fe₃(CO)₉}]^– (1), [{SbSeFe₃(CO)₉}{Se₂Fe₂(CO)₆}]^– (2), and [{SbSFe₃(CO)₉}{SFe₃(CO)₉}]^– (3), were synthesized in moderate yields from reactions of [EFe₃(CO)₉]^2– (E = Te, Se, S) with SbCl₃. X-ray analyses revealed that complexes 1–3 each can be viewed as a square pyramidal geometry [SbEFe₃(CO)₉] (E = Te, Se, S), where the Sb atom was further coordinated with pendant cluster fragments [Te₂Fe₃(CO)₉], [Se₂Fe₂(CO)₆], and [SFe₃(CO)₉], respectively. Interestingly, the oxidation state of the Sb atom in complexes 1–3 was 0, which was evidenced by XPS and XANES. Complexes 1–3 showed high electrophilicity toward a series of metal carbonylates, which produced transmetallated products, the “spiked” square pyramidal complexes [{SbEFe₃(CO)₉}{M(CO)_x}] [M(CO)_x = Fe(CO)₄, E = Te, 1-Fe; Se, 2-Fe; S, 3-Fe; M(CO)_x = Cr(CO)₅, Se, 2-Cr; S, 3-Cr] and the Mn(CO)₄-bridged di-ESbFe₃(CO)₉-based clusters [{SbEFe₃(CO)₉}₂Mn(CO)₄]^– (E = Se, 2-Mn; S, 3-Mn). Furthermore, the diffuse reflectance spectra showed that these ternary and quaternary antimony-chalcogenide metal carbonyl clusters possessed low energy gaps of 0.84–1.48 eV, suggesting possible electron transports within the frameworks, which was supported by crystal packings and DFT calculations.