Formation of β-Metallanaphthalenes by the Coupling of a Benzo-Iridacyclopentadiene with Olefins

Abstract

We have synthesized a new type of metallaaromatic complexes, namely the hydride-β-iridanaphthalenes TpMe2tiebar above startr(H)[C(CH2R′)-C6H4-o-C(R)═tiebar above endC(R)] (benzo-3-H,CH2R′), by reaction of the benzo-iridacyclopentadiene TpMe2tiebar above startr[C6H4-o-C(R)═tiebar above endC(R)](OH2) (benzo-1-OH2) (TpMe2 = hydrotris(3,5-dimethylpyrazolyl)borate, R = CO2Me) with olefins of the type CH2═CHR′ (R′ = H, Me, C6H4-p-Me, OPh). These reactions are proposed to take place with the initial coordination of the olefin and isomerization to a carbene form and subsequent insertion into the Ir–C(phenylic) bond and a final α-H elimination. The reaction with ethoxyethylene does not afford the corresponding derivative but rather gives a mixture of three, isolable, compounds, which are proposed to derive from three different types of insertion of the olefin, one of them a typical 1,2-insertion and the other two as (different) carbenes. The related reactions of the iridacyclopentadiene TpMe2tiebar above startr[C(R)═C(R)-C(R)═tiebar above endC(R)](OH2) (1-OH2) are also discussed. For different combinations of precursor and olefin, we have observed differences in the regio- and stereochemistry of the insertions.