Self-assembly of heteroleptic dinuclear silver(i) complexes bridged by bis(diphenylphosphino)ethyne

Abstract

We present a study of the self-assembling behaviour in solution of Ag[PF₆] with one equivalent of an N^N ligand (N^N = 6,6′-dimethyl-2,2′-bipyridine (6,6′-Me₂bpy) or 2,2′:6′,2′′-terpyridine (tpy)), together with either 0.5 or one equivalent of the bridging ligand bis(diphenylphosphino)ethyne (dppa). Each product contains a dinuclear cation, with one or two dppa ligands bridging the two Ag⁺ centres; 6,6′-Me₂bpy and tpy, respectively, act as chelating ligands. The compounds have been analysed in solution using NMR spectroscopic methods (¹H, ¹H{³¹P}, COSY, NOESY, ¹³C, HMQC and HMBC), including room and low temperature measurements. ³¹P{¹H} NMR spectra recorded at different temperatures allow a deeper insight into the dynamic equilibrium processes. In addition, solution ³¹P–¹⁰⁹Ag HSQC spectroscopic measurements were performed and show, inter alia, the ratio of the splitting in the F1 dimension and the ¹J_{³¹P–¹⁰⁹Ag} coupling constant in the fully coupled HSQC. Single crystal X-ray diffraction yielded two pseudo-polymorphic structures for the doubly-bridged [Ag₂(dppa)₂(tpy)₂][PF₆]₂ and one for the singly-bridged [Ag₂(dppa)(6,6′-Me₂bpy)₂][PF₆]₂.