A metathesis reaction of [Cp*IrCl2]2 with butadienesulfinate lithium (SO2CHCRCHCHR)Li (R = H, 1Li; Me, 2Li) affords the dinuclear compounds [Cp*Ir(Cl)2{(5-η)-SO2CHCRCHCHR}(Li)(THF)]2 (R = H, 3; Me, 4), respectively. The single-crystal X-ray analysis of 3 and 4 reveals the presence of metallacyclic, five- and eight-membered rings, which easily break to afford compounds Cp*IrCl[(1,2,5-η)-SO2CHCRCHCHR] [R = H, (5), Me (6)], upon displacement of THF and LiCl. The 1H and 13C NMR data are consistent with the single-crystal X-ray diffraction structures of 3 and 4. Compounds 5 and 6 showed that the butadienesulfonyl ligands are coordinated through the sulfur atoms and the terminal double bonds, according to the X-ray study of compound 5 and NMR spectroscopy. Immediate formation of compound 5 can be achieved in 83% yield from [Cp*IrCl2]2 and 1K, showing that the alkaline metal is crucial in the isolation of the lithium derivatives 3 and 4.

General methodology for the synthesis of cationic ruthenium(II) η5-pentadienyl compounds stabilized by the (η6-C6Me6)Ru fragment has been developed. Pentadienyl compounds [(η6-C6Me6)Ru{η5-CH2C(R2)CHC(R4)CH(R5)}]BF4 (R2 = R4 = R5 = H, 2-BF4; R2, R4 = H, R5 = Me, 3; R2, R4 = Me, R5 = H, 4) can be prepared in good yields from reactions of the labile dication [(η6-C6Me6)Ru(acetone)3](BF4)2 (1) with 1-trimethylsilyl-2,4-pentadiene, 1-trimethylsilyl-2,4-hexadiene, and 2,4-dimethyl-1-trimethylstannyl-2,4-pentadiene, respectively. Compound 3 is isolated in 90% yield as a mixture of the syn and anti isomers. In contrast, the reaction of pentadienyllithium with [(η6-C6Me6)RuCl2]2 provides a nonselective reaction, which affords a mixture of isomeric η1-, η3-, and η5-coordinated pentadienyl complexes, [(η6-C6Me6)Ru(η5-CH2CHCHCHCH2)]Cl (2-Cl), [(η6-C6Me6)Ru(η3-CH2CHCHCHCH2)Cl] (5), and [(η6-C6Me6)Ru(η1-CH2CHCHCHCH2)Cl]2 (6); the reaction of 1,4-pentadiene and [(η6-C6Me6)RuCl2]2 in ethanolic carbonate similarly gives a mixture containing complex 5, [(η6-C6Me6)Ru{η3-C(Me)CHC(Me)}Cl] (7), and [(η6-C6Me6)Ru(η3-CH2CHCHCH2Me)Cl] (8). Using a similar strategy for the synthesis of the corresponding oxopentadienyl derivatives is much more complicated, even when using an enol silane as the nucleophilic precursor, reflecting a greater competition among alternative bonding modes for the oxopentadienyl derivatives compared to the corresponding pentadienyl analogues. The reaction of lithium oxopentadienide and [(η6-C6Me6)RuCl2]2 in THF affords [(η6-C6Me6)Ru(η3-exo-syn-CH2C(Me)CHC(Me)O)Cl] (11) in poor yield, although this complex readily affords [(η6-C6Me6)Ru(η5-CH2C(Me)CHC(Me)O)]BF4 (9) upon reaction with silver tetrafluoroborate. The analogous η6-benzene complex, [(η6-C6H6)Ru(η3-exo-syn-CH2C(Me)CHC(Me)O)Cl] (13), can be prepared, albeit in very low yield, in an analogous manner to that reported for complex 11, along with traces of an isomeric congener, 13-endo. The use of 1-trimethylsilyloxy-1,3-butadiene unexpectedly provided strongly contrasting results upon addition to dicationic complex 1, returning a mixture of η5- and η3-oxopentadienyl complexes [(η6-C6Me6)Ru(η5-CH2CHCHCHO)]BF4 (14) and [(η6-C6Me6)Ru(1−3,5-η-exo-syn-CH2CHCHCHO)]2(BF4)2 (15). Addition of water to the dimeric product 15 affords the monomeric aquo adduct [(η6-C6Me6)Ru(η3-exo-syn-CH2CHCHCHO)(H2O)]BF4 (16), but this complex is unstable toward isolation, reverting back to dimer 15 upon precipitation. A more stable adduct, [(η6-C6Me6)Ru(η3-exo-syn-CH2CHCHCHO)(MeCN)]BF4 (17), is isolated upon dissolution in acetonitrile, and addition of aqueous NaCl to 15 gives compound [(η6-C6Me6)Ru(η3-exo-syn-CH2CHCHCHO)Cl] (20). Compound 14 affords the decarbonylation product [(η6-C6Me6)Ru(η3-allyl)(CO)]BF4 (19) as a mixture of exo and endo allyl isomers. The solid-state structures for compounds 2-BF4, 4, 9, 11, 13, 15, and 19- exo, as determined by X-ray crystallography, are also reported.

Fullerene C60 reacts with a variety of nitrile oxides, providing access to an array of fullerene-fused heterocycles bearing covalently linked chelate moieties. The improved chelating property of the newly synthesized isoxazoline[60]fullerene adducts toward transition metals allows the syntheses of octahedral and square-planar organometallic compounds of rhenium, iridium, and platinum. This new approach has great potential as a general route to other novel derivatives containing catalytically active transition metals.

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