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 Fe-3( CO)(12) followed by treatment with excess CS2 and MeI, both double-butterfly complex (4-mu-SeC6H4C6H4Se- mu-4')[(mu-S=CSMe) Fe-2(CO)(6)](2) ( 4) and single-butterfly complex (4-n-BuSeC6H4C6H4Se-mu-4')[(mu-S= CSMe) Fe-2(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 Fe-3(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-mu-SeC6H4C6H4Se-mu-4')[(mu-S=CSR) Fe-2(CO)(6)](2) (5, R = Et; 6, PhCH2; 7, PhC=NPh; 8, Cp(CO)(2)Fe), (4-mu-SeC6H4C6H4Se-mu-4')[(mu-SePh) Fe-2(CO)(6)](2) ( 9), and (4-mu-SeC6H4C6H4Se-mu-4')[(mu-CH2SMe) Fe-2(CO)(6)](2) (10), could be similarly prepared via the latter method by using electrophiles CS2/EtBr, CS2/PhCH2Br, CS2/PhC(Cl = dNPh, CS2/Cp(CO)(2)FeI, 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-mu-CO-containing double-butterfly dianion (4-mu-SeC6H4C6H4Se-mu-4')[(mu-CO) Fe-2(CO)(6)](2)(2-) (3) and the one-mu-CO-containing single-butterfly monoanion (4-n-BuSeC6H4C6H4Se-mu-4')[(mu-CO) Fe-2(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.