This work describes the unexpected formation of an unusual phosphonium ylide when attempting the synthesis of bisphosphonium pyromellitic diimides. Spectroscopic and crystallographic characterization reveals that a combination of π–π and CH⋅⋅⋅O interactions leads to supramolecular homodimerization of the ylide both in solution and in the solid-state. Only strong acids are able to protonate the ylide, which is otherwise inert to Wittig and alkylation reactivity. Taken together, these observations indicate that this compound is one of the most highly stabilized phosphonium ylides discovered to date.
Bibliographical noteFunding Information:
This work was made possible by the Violet Olson Beltmann Fund and Collaborative Summer Research Funds from Macalester College. Acknowledgement is made to the Donors of the American Chemical Society Petroleum Research Fund for support of this research. Computational resources were provided by an NSF-MRI award #CHE-1039925 through the Midwest Undergraduate Computational Chemistry Consortium (MU3C). This work made use of the IMSERC at Northwestern University, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205), the State of Illinois, and the International Institute for Nanotechnology (IIN). X-ray analysis was performed on a Bruker-AXS D8 Venture diffractometer purchased through a grant from NSF/MRI (#1229400) and the University of Minnesota. We thank one of the peer reviewers for comments that helped to improve the manuscript.
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- supramolecular chemistry