Ring-methyl activation in pentamethylcyclopentadienyliridium complexes. Part 2. Synthesis of C5Me4(functionalized alkyl) complexes and crystal structures of [(C5Me4CH2CPh2OH)-IrMe(CO)Ph] and [(C5Me4CH2CO2H)IrMe(CO)Cl]

Abstract

Reaction of [(C₅Me₅)IrMe(CO)Ph]1 with sec-butyllithium gives a lithio complex, presumably Li[(C₅Me₄CH₂)IrMe(CO)Ph]2, which reacts with PhCOR to give the appropriately substituted [{C₅Me₄CH₂CPh(OH)R}IrMe(CO)Ph]3a(R = Me) and 3b(R = Ph). Hydrogen chloride cleaved the Ir–Ph bonds in complexes 3a and 3b to give first [{C₅Me₄CH₂CPh(OH)R}IrMe(CO)Cl]4, which reacted further with HCl to give [{C₅Me₄CH₂CPh(Me)Cl}Ir(CO)Cl₂]5, from 4a, and [(C₅Me₄CHCPh₂)Ir(CO)Cl₂]6, from 4b. Complex 2 also reacted with PhCN and with CO₂ to give, after work-up, the substituted acetophenone and the substituted acetic acid complexes [(C₅Me₄CH₂COPh)IrMe(CO)Ph]7 and [(C₅Me₄CH₂CO₂H)IrMe(CO)Cl]8, respectively. Complex 8 was converted by further HCl into [(C₅Me₄CH₂CO₂H)Ir(CO)Cl₂]9, or esterified (ROH, base and dicyclohexylcarbodiimide) to give [(C₅Me₄CH₂CO₂R)IrMe(CO)Cl]10a(R = Me) or 10b(R = 1R,2S,5R-menthyl). Complex 9 was also esterified (EtOH, HCl) to give [(C₅Me₄CH₂CO₂Et)Ir(CO)Cl₂]11. Reaction of the complex [{C₅Me₄(CH₂SiMe₃)}IrMe(CO)Ph]12 with sec-butyllithium followed by CO₂ gave [{C₅Me₃(CH₂-CO₂H)(CH₂SiMe₃)}IrMe(CO)Cl]13. X-Ray structure determinations of complexes 3b and 8 were carried out: 3b shows no hydrogen bonding, but molecules of 8 are linked across a crystallographic inversion centre by pairs of strong hydrogen bonds between the carboxylic acid residues.