75751-43-8Relevant articles and documents
Arene transition-metal chemistry. 5. Arene ligand exchange and reactivity in η6-arene iridium(I) complexes
Sievert,Muetterties
, p. 489 - 501 (2008/10/08)
The arene-exchange behavior of a number of arene complexes of the type [Ir(η6-arene)(η4-c-1,5-C8H 12)+](X-) was examined in acetone and chloroform solution. In acetone, the reaction [Ir(η6-arene)(η4-c-1,5-C8H 12)+](BF4-) + arene′ = [Ir(η6-arene′)(η4-c-1,5-C8H 12)+](BF4-) + arene proceeded via solvent displacement of coordinated arene to yield a spectroscopically observable intermediate, [Ir(η4-c-1,5-C8H12)(acetone) x]+, which subsequently reacted with arene′ to form the new arene′ complex. The rate of exchange was independent of arene′ concentration and the extent of methyl substitution on arene′ while it was dependent on the extent of methyl substitution of the initially coordinated arene. Competitive exchange reactions established that the rate of exchange was independent of the stereochemistry of methyl substitution if the incoming arene had three or fewer methyl substituents. However, for more highly substituted arenes, a steric effect was operative; the 1,2,3,4-C6H2(CH3)4 complex was the preferred kinetic product in competitive exchanges between 1,2,3,4-C6H2(CH3)4 and 1,2,3,5-C6H2(CH3)4, 1,2,4,5-C6H2(CH3)4, or C6(CH3)6. Arene exchange proceeded much more slowly in chloroform than in acetone and was anion dependent. Equilibrium constants for a number of arene-exchange reactions were measured. In accord with literature data for other transition-metal complexes, the stabilities of the iridium arene complexes were independent of the stereochemistry of methyl substitution and increased with increasing methyl substitution on the arene ring.
