Silver coordination complexes of 2-(diphenylphosphinomethyl)pyridine and their bipyridine derivatives

Reaction of 2-(diphenylphosphinomethyl)pyridine (PMP-21) with the silver(I) salts of tetrafluoroborate (BF4-), triflate (Otf−), and trifluoroacetate (tfa−) affords dinuclear complexes (2–4), where the ligand bridges the two silver centers, and the anions interact with the metal centers to varying degrees. Further reaction of AgBF4 and AgOtf with reaction solutions containing PMP-21 and either the bidentate 5,5′-dimethyl-2,2′-bipyridine or 4,4′-bipyridine ligands produce dimeric and bridged structural motifs. The ability of 5,5′-dimethyl-2,2′-bipyridine to chelate and the 4,4′-bipyridine to serve as a connector between metal centers, allows the construction of coordinative structures where the effect of ligand ratio and either interacting or non interacting anions influence the silver coordination environment, allowing it to take on several geometries including trigonal bipyramidal, 5, both T-shaped and tetrahedral in a single structure, 6 and 8, trigonal pyramidal, 7, and trigonal planar, 9. Structures 2, 3, and 4 display comparable Ag–Ag contacts ranging from 2.7979(10) to 3.0538(4) Å, with a corresponding weakening of the metallophilic interaction when a bipyridine ligand is coordinated. Low-temperature luminescence spectra were collected for all compounds and are compared.

Graphical abstractA series of bipyridine derivatives using different silver salts and the ambidentate ligand 2-(diphenylphosphinomethyl)pyridine were prepared by varying the ligand/metal ratio or by changes in solvent or counterion in charged systems.Figure optionsDownload full-size imageDownload as PowerPoint slide