Can Solventless Reactions Sometimes Succeed When Solvent-Mediated Reactions Fail? A Second Case Study for Cu(I) and Ag(I) Complexes of Divergently Bridging Diimines without or with Fluorinated Azolates

ABSTRACT

This paper provides the fifth manifestation of a new tradition by which the editors of Comments on Inorganic Chemistry wish to lead by example, whereby we start publishing original research content that, nonetheless, preserves the Journal’s identity as a niche for critical discussion of contemporary literature in inorganic chemistry (For the previous manifestations, see: Comments Inorg. Chem. 2018, 38, 1–35; 2019, 39, 1–26; 2019, 39, 188–215; 2020, 40, 1–24.) Herein, synthetic details, solid-state structures, and photophysical properties of a group of silver(I) and copper(I) complexes are described. Two silver-based coordination polymers have been obtained: {[3,5-(CF₃)₂Pz]₂(bpp)Ag₂}_∞ (1) and {[3,5-(CF₃)₂Pz][5-(C₆F₅)Ttz](bpp)Ag}_∞ (2) – constructed from bent 1,3-bis(4-pyridyl)propane (bpp), 3,5-bis(trifluoromethyl)pyrazole ([3,5-(CF₃)₂Pz]H) and 5-pentafluorophenyl-tetrazole ([5-(C₆F₅)Ttz]H) in order to inspect the influence of mixed ligands on the resulting silver-based coordination complexes. The structure of 1 shows a distorted trigonal planar geometry with both the bpp and [3,5-(CF₃)₂Pz] ligands binding to the silver atom. The silver in 2 shows an uncommon interaction with the three different ligands. Also, two different geometries including distorted tetrahedral and distorted trigonal were presented for two different silver atoms. An interesting result was obtained for the Cu(I) coordination polymer {[Cu(bpp)₂][BF₄]}_∞ (3) which was successfully synthesized in a solventless reaction but not a solvent-mediated reaction, hence manifesting a “green” chemistry route. The structure of 3 shows an ideal tetrahedral geometry similar to that for the silver analogue, {[Ag(bpp)₂][BF₄]}_∞ (3a), published previously, whereas herein we obtained the same product with the same crystal structure via a more facile conventional synthetic route. All four complexes show bpp ligand-centered green emissions at ambient and cryogenic temperatures. Finally, a commentary is added to contrast the solventless vs solvent-mediated reactions in both this investigation and a precedent thereof by the same corresponding author’s group (Inorg. Chem. 2018, 57, 9962–9976), whereby reactions proceeded successfully only via the solventless route through mechanical grinding herein and spontaneous sublimation by vapor diffusion from the solid-state of one reactant to another yet nonvolatile reactant in the literature precedent, respectively.

Graphical Abstract

KEYWORDS:

• Solventless synthesis
• green chemistry
• mechanical grinding
• coordination polymers
• coordination oligomers

Acknowledgments

This work was made possible by the Robert A. Welch Foundation (Grant B-1542 to M.A.O. and departmental grant M-0200 to M.A.R.-O. at Texas Woman’s University) and the National Science Foundation (CHE-1413641 to M.A.O.). We also acknowledge the NSF MRI Program (CHE-1726652) and the University of North Texas for supporting the acquisition of the Rigaku XtaLAB Synergy-S X-ray diffractometer.

Supplementary Material

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Additional information

Funding

This work was supported by the Division of Chemistry of the National Science Foundation [CHE-1413641] and by the Welch Foundation [B-1542, M-0200].