RING-METHYL ACTIVATION IN PENTAMETHYLCYCLOPENTADIENYL COMPLEXES .3. SYNTHESIS AND REACTIONS OF (ETA-4-TETRAMETHYLFULVENE)(ETA-5-CYCLOPENTADIENYL)RHODIUM AND IRIDIUM

[Rh(eta5-C5Me5) (eta5-C5H5)]+ (1a) was deprotonated (by potassium tert-butoxide) to give the neutral tetramethylfulvene complex [Rh(eta4-C5Me4:CH2)(eta5-C5H5)] (2a), which was a good nucleophile toward Me3SiCl, CH2=CHCH2Br, PhCH2Br, Cl2, I2, CO2 (+MeI), and Ph2CO, giving [Rh(eta5-C5Me4CH2X)(eta5-C5H5)]+ (X = Me3Si-, CH2=CHCH2-, PhCH2-, Cl, I, MeO2C-, and Ph2C(OH)-, respectively). The complex 2a also yielded 1a both on protonation and on treatment with the ferrocenium ion in THF. Similar reactions were carried out on [lr(eta5-C5Me5)(eta5-C5H5)]+ (1b), deprotonated by lithium diisopropylamide in THF, yielding[Ir(eta5-C5Me4CH2X)(eta5-C5H5)]+ (X = Me3Si-, PhCH2-, or Ph2C(OH)-) with Me3SiCl, PhCH2Br, or Ph2CO; these reactions presumably proceeded via [Ir(eta4-C5Me4:CH2)(eta5-C5H5)] (2b). While both 2a and 2b reacted with MeI, 2a gave a mixture of complexes, [Rh(C5H5)(C5MenEt5-n)]+ (7a, n = 1-5), whereas the iridium complex 2b gave just [Ir(eta5-C5Me4Et)(eta5-C5H5)]+. Possible mechanisms for this process are reviewed.