Thermolysis of a xylene solution of Cp2Fe2(CO)4 and PPh3 yields primarily Cp4Fe4(CO)4 (1) together with smaller amounts of (C5H4Ph)Cp3Fe4(CO)4 and Cp3Fe3(CO)3(PPh2). Cluster 1 can be alkylated and arylated by using organolithium reagents to give the derivatives (C5H4R)Cp3Fe4(CO)4. This reaction is competitive with reduction of 1 by the organolithium reagent. A more versatile method for functionalizing 1 involves its deprotonation with lithium diisopropylamide (LDA) followed by treatment with electrophiles to give (C5H4X)Cp3Fe4(CO)4 (X = C(OH)HCH3, CO2H, CHO, SPh, PPh2). An excess of LDA gave increased amounts of the di- and even trifunctionalized derivatives (C5H4X) x Cp4 - x Fe4(CO)4 (x = 2, 3). Treatment of (C5H4CHO)Cp3Fe4(CO)4 with the lithiated cluster gave the double cluster [(C5H4)Cp3Fe4(CO)4]2CHOH. The use of the cluster as a ligand was demonstrated by the synthesis of the adducts (C5H4PPh2ML n )Cp3Fe4(CO)4, where ML n = RuCl2(cymene), IrCl(1,5-C8H12). Single-crystal X-ray diffraction was employed to characterize [(C5H4)Cp3Fe4(CO)4]2CHOH and (C3H4PPh2)Cp3Fe4(CO)4RuCl2(cymene).

Toluene solutions of C(60) react upon UV irradiation with Fe(2)S(2)(CO)(6) to give C(60)[S(2)Fe(2)(CO)(6)](n)() where n = 1-6. C(60)[S(2)Fe(2)(CO)(6)](n)() where n = 1-3 have been isolated and characterized. Crystallographic studies of C(60)S(2)Fe(2)(CO)(6) show that the S-S bond of the Fe(2) reagent is cleaved to give a dithiolate with idealized C(2)(v)() symmetry. The addition occurred at a 6,6 fusion, and the metrical details show that the Fe(2) portion of the molecule resembles C(2)H(4)S(2)Fe(2)(CO)(6). IR spectroscopic measurements indicate that the Fe(2)(CO)(6) subunits in the multiple-addition species (n > 1) interact only weakly. UV-vis spectra of the adducts show a shift to shorter wavelength with addition of each S(2)Fe(2)(CO)(6) unit. Photoaddition of the phosphine complex Fe(2)S(2)(CO)(5)(PPh(3)) to C(60) gave C(60)[S(2)Fe(2)(CO)(5)(PPh(3))](n)(), where n = 1-3. (31)P{(1)H} NMR studies show that the double adduct consists of multiple isomers. Photoaddition of Fe(2)S(2)(CO)(6) to C(70) gave a series of adducts C(70)[S(2)Fe(2)(CO)(6)](n)() where n = 1-4. HPLC analyses show one, four, and three isomers for the adducts, respectively.

There is intense interest in the functionalization of the fullerenes, especially as these molecular allotropes of carbon become increasingly available. Metal complexes figure prominently in the array of reagents that attack the Cm, C70, and now c g 4 cages.' Fullerenes interact with metals most commonly via direct metal-cage bonding. Rarer are cases whereby the fullerene binds to ligands, the noteworthy examples are Hawkins' studies on the osmylation of Cm and c70.2 While not well developed, the ligand-based reactivity has the advantage of enhanced kinetic stability of the products and the potential for the decomplexation of modified fullerenes. The present work involves the reaction of c 6 0 with sulfido ligands; as such, it represents a continuation of our interest in carbon sulfide^.^ C -s g

The reaction of dihalohydrazones with Hünig's base gives 1-carbethoxy-3-phenyl-4-haloazodienes in-situ, which were found to combine with a variety of electron rich olefins to yield halo-substituted tetrahydropyridazines (Scheme 2 and Table 1 ). These haloazodiene cyclizations are best characterized as inverse electron demand, 4 + 2 hetero Diels-Alder reactions that maintain a high degree of regio- and stereochemical control (Schemes 5 and 6). The chloro-substituted tetrahydropyridazines that are formed give high yields of substituted pyridazines upon treatment with base (Table 1). The sequence of a chloroazodiene cyclization to a tetrahydropyridazine followed by an aromatization constitutes a new and general synthesis of substituted pyridazines. In contrast to the haloazodiene cyclizations, the novel cyclization reactions of the in-situ generated 1-carbethoxy-3-phenyl-4,4-dichloroazodiene were found to give N-aminopyrroles and pyridazines when combined with acyclic enamines (Table 3 ). However, reactions with cyclic enamines gave the N-aminopyrroles, pyridazines, a dihydropyridazine as products as well as the noncyclized enamine intermediates (Table 4 ). The noncyclized enamines could be converted to the N-aminopyrroles simply upon heating to higher temperatures, indicating a stepwise mechanism (Schemes 8 and 9). The examples described here are the first reported cyclization reactions for dichloroazodienes.

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