Synthetic and Structural Investigations on Double- and Single-Butterfly Fe/E (E = S, Se) Cluster Complexes Containing Diselenolate Ligands

The first examples of diselenolate ligand-containing butterfly Fe/E (E = S, Se) complexes are now
reported. When ca. 1 equiv of dilithium reagent 4-LiC6H4C6H4Li-4‘ containing n-BuBr (prepared from
1 equiv of 4,4‘-dibromobiphenyl and n-BuLi) was treated with 2 equiv of elemental selenium and Fe3(CO)12 followed by treatment with excess CS2 and MeI, both double-butterfly complex (4-μ-SeC6H4C6H4Se-μ-4‘)[(μ-SCSMe)Fe2(CO)6]2 (4) and single-butterfly complex (4-n-BuSeC6H4C6H4Se-μ-4‘)[(μ-SCSMe)Fe2(CO)6] (4*) were produced in 11% and 20% yields, respectively. However, when ca. 1 equiv
of dilithium reagent 4-LiC6H4C6H4Li-4‘ without n-BuBr (n-BuBr was removed by evaporation of the
initially prepared dilithium reagent containing n-BuBr) reacted with 2 equiv of elemental selenium and
Fe3(CO)12 followed by treatment with excess CS2 and MeI, only the double-butterfly complex 4 was
obtained in a higher yield (21%) without any single-butterfly complex being isolated. Other double-butterfly complexes, such as (4-μ-SeC6H4C6H4Se-μ-4‘)[(μ-SCSR)Fe2(CO)6]2 (5, R = Et; 6, PhCH2; 7,
PhCNPh; 8, Cp(CO)2Fe), (4-μ-SeC6H4C6H4Se-μ-4‘)[(μ-SePh)Fe2(CO)6]2 (9), and (4-μ-SeC6H4C6H4Se-μ-4‘)[(μ-CH2SMe)Fe2(CO)6]2 (10), could be similarly prepared via the latter method by using electrophiles
CS2/EtBr, CS2/PhCH2Br, CS2/PhC(Cl)NPh, CS2/Cp(CO)2FeI, PhSeBr, and MeSCH2Cl instead of CS2/MeI, respectively. A possible pathway for production of the double- and single-butterfly complexes 4−10
and 4* has been proposed, in which the versatile two-μ-CO-containing double-butterfly dianion (4-μ-SeC6H4C6H4Se-μ-4‘)[(μ-CO)Fe2(CO)6]22- (3) and the one-μ-CO-containing single-butterfly monoanion
(4-n-BuSeC6H4C6H4Se-μ-4‘)[(μ-CO)Fe2(CO)6]- (3*) are involved. All the new complexes were fully
characterized by elemental analysis and spectroscopy, as well as by X-ray crystallography for 4* and 10.