Synthesis, Coordination Properties, and Catalytic Application of Triarylmethane-Monophosphines

A new class of triarylmethane-based phosphines (L1–L4) and their Pd­(II) and Rh­(I) complexes were synthesized and subsequently characterized by NMR spectroscopy and X-ray diffraction analysis. The reactions of these phosphines with [PdCl­(π-allyl)]2 gave the square-planar Pd­(II) complexes [PdCl­(π-allyl)­(L)] (L = L1–L4). The treatment of [PdCl­(π-allyl)­(L3)] and [PdCl­(π-allyl)­(L4)], which have CF3-substituted triarylmethane and 9-arylfluorene moieties, respectively, with LiOtBu afforded P,C­(sp3)-chelated palladacycle complexes. Reversibility between a C­(sp3)–M covalent bond and a C­(sp3)–H···M interaction was experimentally demonstrated using [RhCl­(nbd)]2 as a Rh­(I) source. The triarylmethane-monophosphines L1–L4 were applied to the Pd-catalyzed 1,4-addition of arylboronic acids to enones.