Cluster silver iodide

The crystal structure of the complex between silver iodide and piperidine has been determined.57 The colourless crystals were prepared by warming silver iodide with sufficient piperidine to allow the silver iodide to dissolve and then allowing the resulting solution to cool. The structure consisted of tetrahedral clusters of iodide ions with the silver atoms embedded into the faces of the tetrahedron. The (Agl)4 clusters were separated by the piperidine molecules which were bound to the silver via the N atom. The Ag—N bond lengths were 232.9 pm, while the Ag—I distances were 285.3, 293.6 and 294.2 pm. 

Ag3CuIg]4 clusters, in which copper(I) is three coordinated, whereas silver(I) is four coordinated or both three and four coordinated, respectively, from the metal iodides and tetraphenylphosphonium iodide in acetonitrile solution, may also be seen as lending support to the hypothesis that the primary process at the solution-crystal interface is cation-halide packing, the naked metal ion diffusing into the appropriate interstices. 

Calculations for unreconstructed AgBr (100) surfaces indicate that surface rumpling occurs as halide ions relax outwards and silver ions move in toward the bulk [35]. The results of fluorescence SEXAFS measurements are consistent with the presence of such surface rumpling [47]. The calculations also indicate that rumpling is enhanced by the presence of iodide at the surface and that surface iodide ions have a marked propensity to cluster. These predictions are consistent with the observation of enhanced iodide concentrations at surfaces in AgBr, yIy thin films and emulsion grains, as measured by secondary ion mass spectrometry and ion scattering spectrometry [48,49]. 

The 3 + 1 condensation of 7 with 2 gives the iodide salt 8. Anion exchange on 8 (X=I) with hfflU Fs gives 8 as the hexafluorophosphate salt. The combination of 8 (X=PF ) with four equivalents of AgaO gives the tetranuclear biscarbene dimer 9 (P). Compound 9 is a dimer con sed of a silver cluster that is stabilized by two cyclophanes. The structural bonding of 9 is similar to 6... 

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