Elucidation of hemilabile-coordination-induced tunable regioselectivity in single-site Rh-catalyzed heterogeneous hydroformylation.

ABSTRACT

Revealing key factors that modulate the regioselectivity in heterogeneous hydroformylation requires identifying and monitoring the dynamic evolution of the truly active center under real reaction conditions. However, unambiguous in situ characterizations are still lacking. Herein, we elaborately construct a series of Rh-POPs catalysts for propylene hydroformylation which exhibited tunable regioselectivity. Multi-technique approaches reveal the unique microenvironment of the diverse HRh(CO)(PPh3-frame)2 sites with distinct P-Rh-P bite angles ranging from 90° to 120° and 158° to 168°, respectively. In situ time-resolved XAFS, FT-IR, and quasi-in situ Solid-state NMR experiments combined with DFT calculations explain the dynamic evolution of the electronic and coordinate state of the distinct active sites induced by hemilabile PPh3-frame ligands and further disclose the regulatory mechanism of regioselectivity. These state-of-the-art techniques and multiscale analysis advance the understanding of how hemilabile coordination influences regioselectivity and will provide a new thought to modulate the regioselectivity in future industrial processes.