SYNTHESIS AND CHARACTERIZATION OF TRANSITION-METAL HYDRIDO/CHALCOGENIDO/CARBONYL CLUSTERS (ETA 5-RC5H4)(CO)2MFE2H(MU 3-E)(CO)6 (M = MO, W; E = S, SE) AND THEIR DERIVATIVES (ETA 5-2,4-(NO2)2C6H3NHNC(ME)C5H4)(CO)2WFE2H(MU 3-S)( CO)6 AND (ETA 5-RC5H4)(CO)2MFECO(MU 3-S)(CO)5(PPH3) GENERATED FROM ISOLOBAL