Gold bimetallic complexes

The chemistry of metal-gold-containing ylide bimetallic complexes based on methylenethiophosphinate ligand was developed by Fackler and coworkers [34—39]. The chemical similarities of Au(I) and Hg(II) ions were used to synthesize a series of complexes, as shown in Scheme 4.2. 

Bimetallic gold-silver complexes may be prepared from gold bis(ylide) species such as [Au(CH2PPh3)2]ClC>4 and AgC104 (leading to neutral clusters, equation 54) or... 

The paper discloses one example of enantioselective variant. The catalytically active species is a cationic bimetallic complex generated from the (/ )-xylyl-SDP-gold pre-catalyst C5 after addition of a silver salt. The expected polycyclic product could be isolated in good yield, with 82% enantiomeric excess. 

In this case also, bimetallic complexes of atropisomeric diphosphines proved to be optimal pre-catalysts. (/ )-Xylyl-BINAP and (/ )-DTBM-4Segphos (L4-b) gold(I) complexes have been applied to the synthesis of 8 and 7-membered rings, respectively, with enantiomeric excesses in the range 85-92%. Selected results are given in Fig. 10.51. 

Other one-pot preparations of bimetallic nanoparticles include NOct4(BHEt3) reduction of platinum and ruthenium chlorides to provide Pto.sRuo.s nanoparticles by Bonnemann et al. [65-67] sonochemical reduction of gold and palladium ions to provide AuPd nanoparticles by Mizukoshi et al. [68,69] and NaBH4 reduction of dend-rimer—PtCl4 and -PtCl " complexes to provide dend-rimer-stabilized PdPt nanoparticles by Crooks et al. [70]. 

Siloxane compounds, in vitreous silica manufacture, 22 414 Siloxane materials, 20 240 Siloxane oligomers, in silicone polymerization, 22 555-556 Siloxanols, silylation and, 22 703 Silsesquioxane hybrids, 13 549 Silsesquioxanes, 15 188, 22 589-590 SilvaGas process, 3 696, 697 Silver (Ag), 22 636-667. See also Silver compounds. See Ag entries Argentothiosulfate complexes Batch desilverizing Lead-silver alloys Palladium-silver alloy membranes analytical methods for, 22 650-651 applications of, 22 636-637, 657-662 as bactericide, 22 656, 657, 660 barium alloys with, 3 344 in bimetallic monetary system, 22 647-648 in cast dental gold alloys, 8 307t coke formation on, 5 266 colloidal precipitation color, 7 343t colloidal suspensions, 7 275 color, 7 334, 335... 

Bimetallic catalysts can be prepared by a direct redox method when a cationic complex of a metal of higher electrochemical potential is reduced by another metal of lower electrochemical potential that has been deposited and reduced first187 (see Table 4.10) PdAu/SiO 88 and PdAu/C189 have been made in this way, gold being deposited after the palladium. Small amounts of the metals were found in filtrates, and XRD and temperature-programmed decomposition of palladium hydride indicated a substantial... 

Bimetallic molecular cluster compounds containing gold will adsorb intact on supports, and the ligands may then be removed by heating, but only a few such compounds are available. Simple carbonyl complexes do not exist,... 

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