Gold(i) and silver(i) complexes containing a tripodal tetraphosphine ligand: influence of the halogen and stoichiometry on the properties. The X-ray crystal structure of two gold(i) dimeric aggregates

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Complexes of the type [Au2(micro-PP3)2]X2 [X=Cl (), Br (), I ()], [Ag2(micro-PP3)2](NO3)2 (), Ag(PP3)Cl (), M3(micro-PP3)X3 [M=Au, X=Cl (), Br (), I (); M=Ag, X=NO3 ()] and Au4(micro-PP3)X4 [X=Cl (), Br (), I ()] have been prepared by interaction between gold(I) or silver(I) salts and the ligand tris[2-(diphenylphosphino)ethyl]phosphine (PP3) in the appropriate molar ratio. Microanalysis, mass spectrometry, IR and NMR spectroscopies and conductivity measurements were used for characterization. and are ionic dinuclear species containing four-coordinate gold(i) and four/three coordinate silver(i), respectively. Solutions of behave as mixtures of complexes in a 2:1 [Au2(micro-PP3)X2; X=Cl(), Br(), I()] and 4:1 () metal to ligand ratio. and react with free PP(3) in solution to generate the ionic compounds and , respectively. Complexes and , with four linear PAuX fragments per molecule, were shown by X-ray diffraction to consist of dimeric aggregates via close intermolecular gold(I)gold(I) contacts of 3.270 A () and 3.184 A (). The resultant octanuclear systems have an inversion center with two symmetry-related gold(I) atoms being totally out of the aurophilic area and represent a new form of aggregation compared to that found in other halo complexes of gold(I) containing polyphosphines. The luminescence properties of the ligand and complexes, in the solid state, have been studied. Most of the gold systems display intense luminescent emission at room and low temperature. The influence of the halogen on the aurophilic contacts of compounds with a 4:1 metal to ligand ratio results in different photophysical properties, while and are luminescent complex is nonemissive. The luminescence increases with increasing the phosphine/metal ratio affording for complexes , without aurophilic contacts, the stronger emissions. Silver complexes and are nonemissive at room temperature and show weaker emissions than gold(I) species at 77 K.