Metal-aryl bridge structures

Its crystal structure shows a beautiful Au6Ag wheel in which the six gold atoms form a hexagon with the silver atom in the center (Fig. 26). As observed in other aryl bridging complexes,27 83 110 143 145 the planar tris(isopropyl)phenyl groups are nearly perpendicular to the mean plane through the metallic atoms. The Au-C distances, with values between 2.111(7) and 2.200(7) A, are also similar to those in the previously mentioned mesityl complexes. 

An only partial execution of the aryl-aryl bridging approach at each second phenylene-phenylene linkage gives rise to PR PFs have been first synthesized by Yoshino [29,30] by the oxidative coupling of 9,9-dialkylfluorene monomers with FeCls- However, these initial products were characterized by an ill-defined chemical structure since the coupling did not proceed regioselectively at the 2- and 7-positions of the fluorene core. Later on, more effective transition metal-catalyzed aryl-aryl coupling methods have been also applied for the PF synthesis. 

A wide range of structural types is found among the organic derivatives of the elements of the first three groups. On the one hand the alkyls and aryls of the heavy alkali metals are essentially ionic in character. On the other, those of the least electropositive elements form covalently bonded monomers e.g. R3B, R M (M = Zn, Cd, Hg). Intermediate between these are the derivatives of Li, Be, Mg and A1 which are associated through alkyl or aryl bridges. 

Many Cu(I) compounds have polymeric structures with weak Cu—Cu bonds that are bridged by atoms or groups. These include Cu(I) carboxylates, alkyls and aryls, alkoxides and (CuXL) complexes (X = halide, L = ligand). In Cu(I) compounds Cu has a filled 3d shell, 3d , that does not participate in metal-metal bonding, so the extent of metal-metal bonding in these compounds is questionable. Calculations show that the metal-metal bonding is at best weak . These compounds arise from the same syntheses as would be used to prepare the monomer, and so they are not considered further here. 

Byers, P.K, Carr, N. and Stone, F.G.A. (1990) Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 106. Synthesis and reactions of the alkylidyne complexes [M ( CR)(CO)2 (C6F5)AuC(pz)3 j (M = W or Mo, R — alkyl or aryl, pz — pyrazol-l-yl) crystal structure of pjC PtAu(C6F5)( l3-CMe)(CO)2(PMe2Ph)2 (C6F5)AuC(pz)3 ]. Journal of the Chemical Society, Dalton Transactions, (12), 3701—3708. 

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