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 Tp Me2 r(H)[C(CH 2 R′)-C 6 H 4 - o -C(R)═ C(R)] ( benzo - 3 -H,CH 2 R′), by reaction of the benzo-iridacyclopentadiene Tp Me2 r[C 6 H 4 - o -C(R)═ C(R)](OH 2 ) ( benzo - 1 -OH 2 ) (Tp Me2 = hydrotris(3,5-dimethylpyrazolyl)borate, R = CO 2 Me) with olefins of the type CH 2 ═CHR′ (R′ = H, Me, C 6 H 4 - 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 Tp Me2 r[C(R)═C(R)-C(R)═ C(R)](OH 2 ) ( 1 -OH 2 ) are also discussed. For different combinations of precursor and olefin, we have observed differences in the regio- and stereochemistry of the insertions.