The tetrahedral clusters [EFe(2)Co(CO)(9)](-)(E=Te, I; E=Se, II) were synthesized by reactions of the isostructural complexes E(2)Fe(3)(CO)(9) with [Co(CO)(4)](-), respectively. Reaction of Te2Fe3(CO)(9) with [Mn(CO)(5)](-) gives a Mn(CO)(4) bridging butterfly [Te2Fe2Mn(CO)(10)](-)(III), while treatment of Se2Fe3(CO)(9) with [Mn(CO)(5)](-) produces a square-pyramidal [Se2Fe2Mn(CO)(9)](-)(IV). When Te2Fe3(CO)(9) reacts with Collman’s reagent, [Fe(CO)(4)](2-) the previously characterized [Te6Fe8(CO)(24)](2-) is formed. The similar reaction of Se2Fe3(CO)(9) with [Fe(CO)(4)](2-) generates the known complexes [SeFe3(CO)(9)](2-) and [HSeFe3(CO)(9)](-). The anionic complexes I-IV are fully characterized by infrared spectroscopy, elemental analysis, negative-ion mass, or/and X-ray diffraction methods. Crystals of [Et(4)N]-[II] are tetragonal, space group P4(2)/ncm with a=16.456(3) Angstrom, c=17.925(6) Angstrom, V=4854(2) Angstrom(3), Z=8; R=0.045, and R(w)=0.051 at 25 degrees C. [Et(4)N][III] crystallizes in the triclinic space group P $($) over bar$$ 1 with a=9.343(3) Angstrom, b=12.401(6) Angstrom, c=13.198(2) Angstrom, alpha=77.96(3)degrees, beta=74.36(2)degrees, gamma=69.72(3)degrees, V=1370(1) Angstrom(3), Z=2, R=0.026, and R(w)=0.028 at 25 degrees C. Crystals of [Et(4)N][IV] are monoclinic, space group P2(l)/n with a=9.236(2) Angstrom, b=24.665(6) Angstrom, c=11.870(1) Angstrom, beta=112.62(2)degrees, V=2496(1) Angstrom(3), Z=4, R=0.032, and R(w)=0.039 at 25 degrees C. This paper describes the similarities and differences among these reactions and discusses the effects of the main-group and transition elements on bond formation and cleavage of transition-metal chalcogenide clusters.