RING-METHYL ACTIVATION IN PENTAMETHYLCYCLOPENTADIENYLIRIDIUM COMPLEXES - SYNTHESIS OF [(C5ME4CH2E)IRLN] (E = SIME3, PHCH2, CH2=CHCH2, PPH2, AND PT(PET3)2CL), AND SYNTHESIS AND X-RAY STRUCTURE OF [(1,3-C5ME3(CH2SIME3)2)IR(CO)ME(CL)]

The pentamethylcyclopentadienyliridium complex [C5Me5Ir(Me)CO(Ph)] (1) is metallated by sec-BuLi at a ring methyl. The lithio-complex intermediate, presumably Li[(C5Me4CH2)Ir(Me)CO(Ph)] (2) reacts with various halides (E-X) to give the appropriately substituted [(C5Me4CH2E)Ir(Me)CO(Ph)] (3) (E = SiMe3, a; PhCH2, b; CH2 = CHCH2, c; PPh2, d; and Pt(PEt3)2Cl, e). The Ir-Ph bond in 3a-c is cleaved by HCl to give [(C5Me4CH2E)Ir(Me)CO(Cl)] (4a-c), which are in turn converted into [(C5Me4CH2E)IrCO(Cl)2] (5a-c) with more HCl, and then into [{(C5Me4CH2E)Ir(Cl)2}2] (6a-b) on heating. The butenyl complex, [(C5Me4CH2CH2CH = CH2)IrCl2] (6c) is monomeric with an internally coordinated double bond. Two equivalents of 2 react with SiMe2Cl2 to give [Me2Si{CH2C5Me4Ir(Me)-CO(Ph)}2] (7). The di-iridium complex [(C5Me4CH2SiMe3)IrCl2(PPh2CH2C5Me4)Ir(Me)CO(Ph)] (8) is formed on reaction of 3d with 6a. The complex 3a could be remetallated by sec-BuLi and converted into the bistrimethylsilylmethylene complex [(C5Me3(CH2SiMe3)2)Ir(Me)CO(Ph)] (9). The 1,3-disposition of the Me3SiCH2 groups on the ring was shown by an X-ray structure determination of [(C5Me3(CH2E)2)-Ir(Me)CO(Cl)] (10). Complex [C5Me5IrMe4] (11) was also metallated by sec-BuLi and could be converted into [(C5Me4CH2E)Ir(Me)4] (12) (E = SiMe3, a; Et, f).