ISOLATION AND CHARACTERIZATION OF SE-2(MU-(CO)(3)CR(ETA(5)-C-5(H)(CH2PH)(PH)(OET))], [(CO)(6)FE-2(MU-EC(PH)=C(E')C(H)(OET))](2) AND [(CO)(6)FE-2(MU-SC(H)(PH)C(TE)=C(H)(OET))] FROM THE THERMOLYSIS OF FISCHER CARBENE ADDUCTS [(CO)(6)FE2EE'(MU-C(PH)=C-C(OET)=CR(CO)(5))] (E, E' = SEAND E = S, E' = TE)

Thermolysis of the trimetallic adducts [(CO)(6)Fe2EE'{mu-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: [Fe-2(CO)(6)EE' {mu-(CO)(3)Cr(eta(5 )-C-5(H)(CH2Ph)(Ph)(OEt)}], (2: E = E' = Se); [(CO)(6)Fe-2{mu-EC(Ph)=C (E')C(H)(OEt)}](2), (3a: E = E' = Se; 3b: E = S, E' = Te) and [(CO)(6) Fe-2{mu-EC(H)(Ph)C(E')=C(H)(OEt)}], (4: E = S, E' = Te), where the pro duct formation depends on the nature of chalcogen atoms present in the trimetallic adducts 1a and 1b. All products have been characterized b y IR and H-1-,C-13-, Se-77- and Te-125-NMR spectroscopy and structural types were unequivocally established by X-ray crystallographic analys is of compounds 3a and 4. (C) 1998 Elsevier Science S.A. All rights re served.