Reaction of the Iridacyclopentadiene TpMe2Ir(C(R)-C(R)C(R)-C(R))(H2O) (R = CO2Me) with Alkynes

Abstract

The iridacyclopentadiene derivative TpMe2 Ir(C(R)_C(R)C(R)_ C(R))(H2O) (1) (TpMe2 = hydrotris(3,5-dimethylpyrazolyl)borate, R = CO2Me) reacts with an excess of MeCCMe with formation of the iridacycloheptatriene TpMe2Ir(C(Me)_C(Me)C(R)_C(R)C(R)_C(R))(H2O) (3) and the first metallabicyclo[3,2,0]heptatriene TpMe2 Ir(C(Me)_C(Me)C(R)_C(R)C(R)_C(R))(H2O) (4). Both species are involved in the equilibrium 3_4 + H2O, which has been studied as a function of temperature. By contrast, PhC CPh gives only a compound related to 4, namely, the species TpMe2 Ir(_C(Ph)C(Ph)_C(R) C(R)C(R)_ C(R))(H2O) (5), which does not react with water. Complex 1 incorporates two molecules of terminal alkynes such as HC CPh and HC CCH2CH2OH with formation of complex chelating alkenyl-allylic structures, and the same is true for Me3SiC CPh and Me3SiC CSiMe3, where the SiMe3 groups are replaced by hydrogen atoms under the reaction conditions. In all these cases the two alkynes are added consecutively into one of the Ir−C bonds of 1. Finally, the reaction of 1 with HC CCO2Me gives a fully substituted cyclopentadiene with two of the substituents being metalated by the iridium center and in this case the two Ir−C bonds of 1 are cleaved in the process. All the new compounds have been characterized by microanalysis, IR and NMR spectroscopies, and in some cases by X-ray diffraction analysis.