Thermolysis of the trimetallic adducts [(CO)6Fe2EE′μ-C(Ph)=C-C(OEt)=Cr(CO) 5] 1a,b (1a: E=E′=Se; 1b: E=S, E′=Te) in refluxing THF yield the following complexes: [Fe2(CO)6EE′μ-(CO)3Cr(η 5-C5(H)(CH2Ph)(Ph)(OEt)], (2: E=E′=Se); [(CO)6Fe2μ-EC(Ph)=C(E′)C(H)(OEt)]2, (3a: E=E′=Se; 3b: E=S, E′=Te) and [(CO)6Fe2μ-EC(H)(Ph)C(E′)=C(H)(OEt)], (4: E=S, E′=Te), where the product formation depends on the nature of chalcogen atoms present in the trimetallic adducts 1a and 1b. All products have been characterized by IR and 1H-, 13C-, 77Se- and 125Te-NMR spectroscopy and structural types were unequivocally established by X-ray crystallographic analysis of compounds 3a and 4.