Solid-state 31 P and 109 Ag CP/MAS NMR as a powerful tool for studying of silver(I) complexes with N-thiophosphorylated thiourea and thioamide ligands

A family of three- and four-coordinated silver(I) complexes of formulas [Ag(PPh₃ )₂ L], [Ag(PPh₃ )L], and [AgL]_n with N-thiophosphorylated thiourea and thioamide ligands of general formula RC(S)NHP(S)(OPri)₂ [R = Ph, PhNH, iPrNH, tBuNH, NH₂ ] have been studied by solid-state ¹⁰⁹ Ag and ³¹ P CPMAS NMR spectroscopy. ¹⁰⁹ Ag NMR spectra have provided valuable structural information about Ag coordination, which is in good accordance with the available crystal structure data. The data presented in this work represent a significant addition to the available ¹⁰⁹ Ag chemical shifts and chemical shifts anisotropies. The silver chemical shift ranges for different P,S-environments and coordination state were discussed in detail. The ¹ J(³¹ P-^107/109 Ag) and ² J(³¹ P-³¹ P) values were determined and analyzed.

Ligand-induced substrate steering and reshaping of [Ag2(H)](+) scaffold for selective CO2 extrusion from formic acid

Metalloenzymes preorganize the reaction environment to steer substrate(s) along the required reaction coordinate. Here, we show that phosphine ligands selectively facilitate protonation of binuclear silver hydride cations, [LAg₂(H)]⁺ by optimizing the geometry of the active site. This is a key step in the selective, catalysed extrusion of carbon dioxide from formic acid, HO₂CH, with important applications (for example, hydrogen storage). Gas-phase ion-molecule reactions, collision-induced dissociation (CID), infrared and ultraviolet action spectroscopy and computational chemistry link structure to reactivity and mechanism. [Ag₂(H)]⁺ and [Ph₃PAg₂(H)]⁺ react with formic acid yielding Lewis adducts, while [(Ph₃P)₂Ag₂(H)]⁺ is unreactive. Using bis(diphenylphosphino)methane (dppm) reshapes the geometry of the binuclear Ag₂(H)⁺ scaffold, triggering reactivity towards formic acid, to produce [dppmAg₂(O₂CH)]⁺ and H₂. Decarboxylation of [dppmAg₂(O₂CH)]⁺ via CID regenerates [dppmAg₂(H)]⁺. These gas-phase insights inspired variable temperature NMR studies that show CO₂ and H₂ production at 70 °C from solutions containing dppm, AgBF₄, NaO₂CH and HO₂CH.

Designing catalysts and understanding the influence of ligands for particular transformations remains a highly challenging task. Here, the authors show that bisphosphine ligands can alter the geometry of the active site in silver catalysts, driving protonation and ultimately extrusion of carbon dioxide from formic acid.

An unusual co-crystal [(μ2-dcpm)Ag2(μ2-O2CH)(η2-NO3)]2·[(μ2-dcpm)2Ag4(μ2-NO3)4] and its connection to the selective decarboxylation of formic acid in the gas phase

Binuclear silver cluster with μ₂-formate and μ₂-dcpm catalyses the decomposition of HCO₂H. This structural motif is present in the crystal.

A Cyclic Hexamer of Silver Trifluoroacetate Supported by Four Triphenylphosphine Sulfide Template Molecules

Crystallization of silver trifluoroacetate from chloroform solutions containing triphenylphosphine sulfide affords a trigonal and a monoclinic form of a 6:4 complex {[CF3C(O)OAg]6(Ph3PS)4} of C2 symmetry with different amounts of chloroform in the crystals. With the Ph3PS components as template molecules, the CF3C(O)OAg units are assembled to form a 6-membered metallacycle codetermined by metallophilic bonding and enclosed by a 24-membered ring [AgOCO]6. A complex of the type [LAgOC(O)CF3]2, with L representing the isocyanide ligand pTolSO2CH2NC, has been shown to have a conventional bicyclic structure with three-coordinate silver atoms engaged in transannular metallophilic interactions.