Argentophilic interaction

Ray, L., Shaikh, M.M. and Ghosh, P. (2008) Shorter Argentophilic Interaction than Aurophilic Interaction in a Pair of Dimeric (NHC)MC1 2 (M=Ag, Au) Complexes Supported over a N/O-Functionalized N-Heterocyclic Carbene (NHC) Ligand. Inorganic Chemistry, 47, 230-240. 

It is interesting to note that the C-C triple bond character for the acetylenediide inside the silver(l) cages is retained in most of the examples due to the close resemblance of their C=C bond lengths ( 1.09-1.28 A) with that observed in free acetylene (1.205 A).212 The Ag-C bond distances, on the other hand, span a fairly wide range ( 2.01-3.53 A) due to the presence of both a- and 7r-bonding interactions in these systems. The observation of short Ag-Ag contacts of 2.71-3.37A, compared to that in silver metal (2.89 A)213 and the sum of van der Waals radii for silver ( 3.4 A), 1 was suggestive of weak argentophilic interactions associated with these complexes. 

Figure 9.38 (a) A 6,3-sheet of [Ag2(9.14b)3] (BF4)2 and (b) the 2D— 2D parallel Borromean interpenetrating network that it forms with the means planes of the 2D sheets coincidental. The Ag atoms (spheres) lie above each other, held by argentophilic interactions, (c) Borromean rings in black on white marble at the Cappella Rucellai in the Church of San Pancrazio, now the Marino Marini Museum, in Florence. The rings form part of the coat of arms of the Borromeo family and are also said to be a symbol of the Florentine de Medici family (photograph courtesy of Prof. L. J. Barbour).37... 

Dobrzanska, L., Raubenheimer, H. G., Barbour, L. J., Borromean sheets assembled by self-supporting argentophilic interactions. Chem. Commun. 2005, 5050-5052. 

Pan, L., Woodlock, B., Wang, X., Lam, K.C., Rheingold, A. L., Novel silver -Organic Coordination Polymers conversion of extended structures in the solid state as driven by argentophilic interactions. Chem. Commun. 2001, 1762-1763. 

It is likely that the trinuclear arrangement of the silver(l) ions is forced by the geometry of the ligand making the observed argentophilic interactions [364-366] possible. 

A third structural motif for silver(l) pincer carbene complexes is the dimer observed by Nielsen et al. [490] (see Figure 3.169). This dimeric structure becomes possible because of the flexibility introduced into the pincer structure by the linker unit, which acts as a hinge. It makes it possible for the NHC donor ligands to align themselves parallel to each other and perpendicular to the C-Ag-C vector of the silver coordination sphere. The dimer is considered to possess no argentophilic interactions as the Ag-Ag distance is 31 pm longer than the sum of the van der Waal s radii (340 pm) [20]. 

Figure 4.37 (a) A (6,3)-sheet and (b) the 2D 2D parallel Borromean interpenetrating network that it forms (c) with the mean planes of the two-dimensional sheets coincidental. The Ag atoms (spheres) lie above each other, held by argentophilic interactions. 

Finally, a recent study by Jamali et al. [39] describes the preparation of a tetranuclear butterfly-shaped cluster in which each of two platinum(ll) centers binds to two silver(l) cations that are themselves connected by an argentophilic interaction. The cluster is stabilized by bidentate P,N ligands bridging a Pt-Ag bond each. Solution-phase NMR suggests an equilibrium between the butterfly geometry and a planar arrangement similar to that of [(NN)PtMe2l2Ag2(OTf)2 (see Sect. 3.1.1, Scheme 5). 

The argentophilic interaction in the product is lost, instead intermolecular Ag- - -C interactions connects the dimer complexes to form a 1D chain as shown in Figure 2. 

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