REGIOSELECTIVE ADDITION OF MIXED-CHALCOGENIDE IRON CARBONYL CLUSTERS FE-2(CO)(6)(MU-EE') (E-NOT-EQUAL-E', E, E'=S, SE, TE) TO A CARBON-CARBON TRIPLE BOND ACTIVATED BY A METAL CARBENE FRAGMENT - STRUCTURAL CHARACTERIZATION OF NEW TRIMETALLIC ADDUCTS FE-2(CO)(6)(MU-SC(PH)=C(TE)[(OET)C=CR(CO)(5)]), FE-2(CO)(6-) (MU-SC(PH)=C(SE)[(OET)C=W(CO)(5)]), ANDFE-2(CO)(6)(MU-SEC(PH)=C(TE)[(OET)C=W(CO)(5)])

From the room-temperature reaction of the transition-metal alkynyl Fis cher carbene complexes (CO)(5)M=C(OEt)(C=CPh) (M = Cr, W) with the mix ed-chalcogenide compounds Fe-2(CO)(6)(mu-EE') (E not equal E', E, E' = S, Se, Te), the following new trimetallic adducts were obtained: Fe-2 (CO)(6){mu-EC(Ph)=C(E')[(OEt)C=M(CO)(5)]} 1-6 (1, 85%, E = S, E' = Se, M = Cr; 2, 82%, E = S, E' = Se, M = W; 3, 84%, E = S, E' = Te, M = Cr ; 4, 80%, E = S, E' = Te, M = W; 5, 83%, E = Se, E' = Te, M = Cr; 6, 8 1%, E = Se, E' = Te, M = W). In addition, trace amounts of the corresp onding alkenyl Fischer carbene complexes (CO)(5)M=C(OEt){(CH=C(OMe)Ph} 7-8 (7, M = Cr; 8, M = W) were also formed in each case. Compounds 1- 6 were characterized by IR and H-1, C-13, Se-77, and Te-125 NMR spectr oscopy. Crystallographic analyses of the compounds 2, 3, and 6 were ca rried out. The structures of 2, 3, and 6 can be described as Fe2EE' (E , E' = S, Se, Te) tetrahedral butterfly cores containing the alkynyl F ischer carbene as a bridge between the two wingtip chalcogens with thr ee terminally bonded carbonyl groups on each Fe atom.