Six-membered cyclopalladated N,N′,N″-triarylguanidines, [{κ2(C,N)Pd}2(μ-OAc)(μ-Pz)], [κ2(C,N)Pd(μ-Pz)]2 and a novel [AgNO3⊂{{κ2(C,N)Pd}2(μ-NO3)(μ-Pz)}]: Syntheses, reactivity studies, structural aspects, and solution behavior

Six-membered cyclopalladated N,N′,N″-triarylguanidines, [{κ2(C,N)Pd}2(μ-OAc)(μ-Pz)] (1–4), [κ2(C,N)Pd(μ-Pz)]2 (5–11), and [AgNO3⊂{{κ2(C,N)Pd}2(μ-NO3)(μ-Pz)}] (12) have been isolated in good yields and characterized by micro-analytical, IR, and NMR (1H, 19F, and 13C) spectroscopic techniques. Molecular structures of ten complexes were determined by SCXRD, which revealed cisoid in–out (1–4), transoid out–out (5, 6, 8 and 11), transoid in–in (7) and cisoid (12) conformations. VT 1H NMR spectra of 1 revealed the presence of cisoid in–in as the major species and an equilibrating mixture of cisoid in–out and cisoid out–out as the minor species in solution and this was verified by DFT calculations. In solution, 4 indicated the presence of a mixture of cisoid, and transoid conformers, [κ3(C,N,O)Pd(OAc)], and [κ2(C,N)Pd(κ2O,O′-OAc)] (VT 1H NMR), and a mixture of three conformers of each cisoid and transoid, and [κ3(C,N,O)Pd(Pz)] (VT 19F NMR). Palladacycles 5 and 10 revealed the presence of a mixture of four and five species, respectively in solution and these species are a mixture of cisoid and transoid conformers as revealed by VT 1H NMR. Factors that dictate the solid state conformations and number and nature of solution species of the new complexes are outlined.

Graphical abstractCyclopalladated N,N′,N″-tri(2-tolyl)guanidine, 6 encapsulates AgNO3 inside a cavity to afford complex 12 due to stabilization attained through Pd → Ag (d8 → d10) and Ag-η1arene (soft–soft) interactions.Figure optionsDownload full-size imageDownload as PowerPoint slide