273750-25-7Relevant articles and documents
Mechanistic investigation of the reaction of iridium dihydride complexes with organic acid chlorides
Paisner, Sara N.,Burger, Peter,Bergman, Robert G.
, p. 2073 - 2083 (2008/10/08)
Treatment of Cp*(PMe3)IrH2 (1a) with aromatic and hindered aliphatic acid chlorides ClC-(O)R in benzene in the presence of an amine (N,N,N′,N′-tetramethyldiaminonaphthalene (7), (-)-sparteine (8), or triethylamine (9)), results in the formation of Ir(III) acyl hydride complexes, Cp*(PMe3)Ir(C(O)R)H (R = C6H5, 3a; p-CH3C6H4, 3b; p-CNC6H4, 3c; p-NO2C6H4, 3d; p-CF3C6H4, 3e; p-FC6H4, 3f; p-CH3OC6H4, 3g; CHMe2, 4; CHPh2, 5; CMe3, 6) with the accompanying precipitation of the corresponding ammonium chloride salt. Kinetic studies revealed the formation of 3-6 to be first order in 1a and acid chloride and zero order in amine. A Hammett correlation showed that the reaction rate is increased by electron-withdrawing groups on the aromatic ring of the aroyl chloride. Changing the substituent on the iridium-bound phosphine was found to have a significant steric effect along with an unexpected electronic effect. In contrast to the reaction seen with aroyl chlorides, the reaction of 1a with monosubstituted acetyl chlorides in the presence of Proton Sponge results in the formation of vinyl chloride complexes, Cp*(PMe3)Ir(CH=CHR)(Cl) (R = H, 15a; CH3, 15b; C6H5, 15c). On the basis of the kinetic results for the formation of 3-6, the formation of both acyl hydride and vinyl chloride complexes is proposed to occur via nucleophilic attack of the metal center at the carbonyl carbon as the first step.
