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

The iridacyclopentadiene derivative Tp(Me2)Ir(C(R)=C(R)C(R)=C(R))(H2O) (1) (Tp(Me2) = hydrotris(3,5-dimethylpyrazolyl)borate, R = CO2Me) reacts with an excess of MeC CMe with formation (R))(H,0) (3) and the first of the iridacycloheptatriene Tp(Me2)Ir(C(R)=C(R)C(R)=C(R))(H2O)metallabicyclof[3,2,0]heptatriene Tp(Me2)Ir(=C(Me)C(Me)=C(R)Y(R)C(R)=C(R))(H2O) (4). Both species are involved in the equilibrium 3 7 reversible arrow 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 Tp(Me2)Ir(C(R)=C(R)C(R)=C(R))(H2O) (5), Which does not react with water. Complex I 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 I 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 I are cleaved in the process. All the new compounds have been characterized by rnicroanalysis, IR and NMR spectroscopies, and in some cases by X-ray diffraction analysis.