FUNCTIONALIZATION OF CP4FE4(CO)(4) - CONTRASTS AND COMPARISONS WITH FERROCENE

Thermolysis of a xylene solution of Cp2Fe2(CO)(4) and PPh3 yields prim arily Cp4Fe4(CO)(4) (1) together with smaller amounts of (C5H4Ph)Cp3Fe 4(CO)(4) and Cp3Fe3(CO)(3)(PPh2). Cluster 1 can be alkylated and aryla ted by using organolithium reagents to give the derivatives (C5H4R)Cp3 Fe4(CO)(4). This reaction is competitive with reduction of 1 by the or ganolithium reagent. A more versatile method for functionalizing 1 inv olves its deprotonation with lithium diisopropylamide (LDA) followed b y treatment with electrophiles to give (C5H4X)Cp3Fe4(CO)(4) (X = C(OH) HCH3, CO2H, CHO, SPh, PPh2). An excess of LDA gave increased amounts o f the di- and even trifunctionalized derivatives (C5H4X)(x)Cp4-xFe4(CO )(4) (x = 2, 3). Treatment of (C5H4CHO)Cp3Fe5(CO)(4) with the lithiate d cluster gave the double cluster [(C5H4)Cp3Fe4(CO)(4)](2)CHOH. The us e of the cluster as a ligand was demonstrated by the synthesis of the adducts (C5H4PPh2MLn)Cp3Fe4(CO)(4), where MLn = RuCl2(cymene), IrCl(1, 5-C8H12). Single-crystal X-ray diffraction was employed to characteri ze [(C5H4)Cp3Fe4(CO)(4)](2)CHOH and (C3H4PPh2)Cp3Fe4(CO)(4)RuCl2(cymen e).