SYNTHESIS OF THE NOVEL THIOLATO-BRIDGED AND OXO-CAPPED TRIMETALLIC CLUSTERS (ETA 5-R'C5H4)(CO)2MFE2(MU 3-O)-(MU -RS)(CO)6 VIA REACTIONS OF ET3NH(MU -R S)(MU -CO)-FE2(CO)6 WITH TRIPLY BONDED DIMERS (ETA 5-R'C5H4)(CO)2M2 (M = MO , W) AND SUBSEQUENT TREATMENT WITH AIR. CRYSTAL STRUCTURES OF (ETA 5-MEO2CC