Synthesis, Properties, and Catalytic Application of a Triptycene-Type Borate-Phosphine Ligand

A borate-containing caged triarylphosphine L-X (X = Na or NBu4), featuring a 9-phospha-10-boratriptycene framework, was synthesized and characterized by NMR spectroscopy and X-ray diffraction analysis. The NMR coupling constant of the corresponding phosphine selenide indicated a higher electron-donating property of the borate-phosphine L compared to that of the 9-phospha-10-silatriptycene derivative (Ph-TRIP). The coordination property of L-X to [PdCl­(η3-allyl)]2 was dependent on the countercation, giving a neutral Pd complex [PdCl­(η3-allyl)­(L-NBu4)] from L-NBu4 in CH2Cl2 or a zwitterionic Pd complex [Pd­(η3-allyl)­(MeCN)­(L)] from L-Na in MeCN/CH2Cl2. Utility of L-X as a ligand for metal catalysis was demonstrated in the Pd-catalyzed Suzuki–Miyaura cross-coupling of aryl chlorides.