Ferrocenyl phosphine mobility, positional isomerism and NMR fluxionality in triangular palladium sulfide aggregates. Crystal and molecular structures of [Pd3Cl2(η2-dppf)(μ-dppf)(μ 3-S)2] and [Pd3Cl(η2-dppf)2(PPh3)(μ 3-S)2]X [X = Cl or NO3, dppf = ...

Abstract

Title full: Ferrocenyl phosphine mobility, positional isomerism and NMR fluxionality in triangular palladium sulfide aggregates. Crystal and molecular structures of [Pd3Cl2(η2-dppf)(μ-dppf)(μ 3-S)2] and [Pd3Cl(η2-dppf)2(PPh3)(μ 3-S)2]X [X = Cl or NO3, dppf = Fe(η5-C5H4PPh2)2]. Three {Pd3S2} aggregates, [Pd3Cl2(η2-dppf)(μ-dppf)(μ 3-S)2] and [Pd3Cl(η2-dppf)2(PPh3)(μ 3-S)2]X [X = Cl or NO3, dppf = 1,1′-bis(diphenylphosphino)ferrocene] have been synthesized from metal addition to a {Pd2S2} molecular core in [Pd2(dppf)2(μ-S)2]. X-Ray single-crystal crystallographic analysis revealed a common sulfide-bicapped triangle with insignificant Pd ⋯ Pd interactions. The former is neutral with a bridging and a chelating dppf ligand as well as two terminal chlorides. The dynamic behaviour has been studied by variable temperature 31P and 2-D COSY NMR. A phosphine-chloride interchange and phosphine-phosphine exchanges enable the two dppf ligands to migrate around the Pd3 plane. The solid-state structure corresponds to the static structure in solution at 198 K. The mixed phosphine complex Sa (X = Cl) is ionic with two Pd-dppf chelating rings and a {Pd(PPh3)Cl} moiety. With a PPh3 group taking up one site, it is stereochemically rigid. The other two complexes were studied by electrospray mass spectrometry (ESMS) in solution. The {Pd3S2} core in the mixed phosphine (X = NO3) is relatively stable to fragmentation under ESMS conditions.