The study of Metal Ligand Cooperativity (MLC) and the reactivity of transition metals with non-innocent ligands is a flourishing field in organometallic chemistry. While phosphines are ubiquitous in organometallic and coordination chemistry, the field of “non-innocent” phosphorus chemistry is relatively undeveloped. We report the synthesis of a sterically hindered trisphosphine-pincer iridium complex, (PPHP)Ir, containing a secondary phosphine that is capable of acting as a proton donor to yield a terminal phosphide. A stereoselective loss of H2 from the trihydride complex, (PPHP)IrH3, yields a rare example of a four-coordinate iridium monohydride, (PPHP)IrH; this complex undergoes intramolecular proton transfer from phosphorus to iridium to yield (PPP)IrH2. This terminal phosphido analogue of well-studied PCP and PNP pincer ligands was then used for alkane transfer dehydrogenation. This is the first example of catalysis by a terminal phosphido iridium complex. The steric bulk provided by the tert-butyl groups strongly decreases iridium-olefin bond strengths, even with the small olefins ethylene or propylene, and thereby allows very high activity with the use of these olefins as hydrogen acceptors.

Alkane dehydrogenation by a terminal phosphido iridium complex activated by novel phosphorus metal-ligand cooperativity

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.