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

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 1J31P-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.