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

We
have synthesized a new type of metallaaromatic complexes, namely
the hydride-β-iridanaphthalenes TpMe2Ir­(H)­[C­(CH2R′)-C6H4-o-C­(R)C­(R)] (benzo-3-H,CH2R′), by reaction of the benzo-iridacyclopentadiene
TpMe2Ir­[C6H4-o-C­(R)C­(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 TpMe2Ir­[C­(R)C­(R)-C­(R)C­(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.