Organometallic Chemistry

Stabilization of Super Electrophilic Pd+2 Cations in Small-Pore SSZ-13 Zeolite

Abstract

We provide the first observation and characterization of super-electrophilic metal cations on a solid support. For Pd/SSZ-13 the results of our combined experimental (FTIR, XPS, HAADF-STEM) and density functional theory study reveal that Pd ions in zeolites, previously identified as Pd+3 and Pd+4, are in fact present as super electrophilic Pd+2 species (charge-transfer complex/ion pair with the negatively charged framework oxygens). In this contribution we re-assign the spectroscopic signatures of these species, discuss the unusual coordination environment of “naked” (ligand-free) super-electrophilic Pd+2 in SSZ-13, and their complexes with CO and NO. With CO, non-classical, highly positive [Pd(CO)2]2+ ions are formed with the zeolite framework acting as a weakly coordinating anion (ion pairs). Non-classical carbonyl complexes also form with Pt+2 and Ag+ in SSZ-13. The Pd+2(CO)2 complex is remarkably stable in zeolite cages even in the presence of water. Dicarbonyl and nitrosyl Pd+2 complexes, in turn, serve as precursors to the synthesis of previously inaccessible Pd+2-carbonyl-olefin [Pd(CO)(C2H4)] and -nitrosyl-olefin [Pd(NO)(C2H4)] complexes. Overall, we show that zeolite framework can stabilize super electrophilic metal (Pd) cations, and show the new chemistry of Pd/SSZ-13 system with implications for adsorption and catalysis.

Version notes

Version 2. In Version 2 we: a). expanded the introduction and discussion parts. b). added more data and information to the Supplementary information, further corroborating our findings c). all the conclusions remain the same as in Version 1.

Content

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