[Rh$_2$(phesp)$_2$]: a Bulkier [Rh$_2$(esp)$_2$] Analog to Tune the Site-Selectivity in Carbene C–H Insertion Reactions
Résumé
[Rh$_2$(phesp)$_2$], a new dirhodium(II) complex bearing a bulky bidentate bis-carboxylate ligand, has been prepared in two steps from commercially available compounds. Its X-ray structure revealed distinctive features with a strong distortion around the dirhodium(II) core, illustrated by important torsion angles of up to 9.0°. It has been evaluated as catalyst as a bulky version of the prominent [Rh$_2$(esp)$_2$] complex in carbene C–H insertion reactions. [Rh$_2$(phesp)$_2$] proved as active as [Rh$_2$(esp)$_2$], and showed an intermediate selectivity between [Rh$_2$(esp)$_2$] and bulky [Rh$_2$(tpa)$_4$] in both intra- and intermolecular reactions with donor-acceptor and acceptor-acceptor diazo compounds, comprising challenging C(sp$_3$)–H insertion into pentane.