Gold-platinum derivatives

As far as we are aware, the number of luminescent extended systems with gold-platinum interactions is reduced to only one report. This is a puzzling situation since the situation of platinum in the periodic table suggests considerable relativistic effects for this atom and extended chains of squared-planar Pt(II) cation-anion complexes built by metal-metal interactions are not strange. In fact, salts such as [Pt(CNR)4][Pt(CN)4] ,67 which are luminescent and display vapochromic behavior, and the modified form of the Magnus salt [Pt(NH3)4][Pt(CN)4] ,68 which shows semiconducting properties, are examples of this type of supramolecular systems. Therefore, the stable combination of gold and platinum in cation/anion-acid/base systems should be anticipated. 

The report from Balch s laboratory describes the synthesis of the complex [Pt(NH3)4][Au(CN)2] 1.5(H20).69a Its structure displays two [Au(CN)2] ions above and bellow the plane of one [Pt(NH3)4]2+ cation, with Pt-Au interactions of 3.2804(4) and 3.2794(4) A. These units are arranged into extended chains through short gold-gold interactions of 3.1902(4) A. Additional cross-linking of these chains occur through Au Au contacts of similar lengths. 

The complex is nonluminescent at room temperature, but becomes luminescent in the solid state upon cooling at 77 K, showing an unstructured emission at 443 nm. This emission is independent of the excitation wavelength over the range 300 370 nm, and it is attributed to the gold centers or to the interaction between the gold and the platinum ions. In agreement with this, the isostructural product [Pt(NH3)4][Ag(CN)2] 1.4(H20) is not luminescent, 

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Platinum Derivatives.— These are prepared in a similar way to the gold compounds, using platinic chloride. The compounds are brown powders, soluble in water, alcohols, and sodium hydroxide. 

The photophysical properties of metal-alkyne materials are rich due to strong metal-ligand orbital overlap and unsaturated n system (16). Photoactive materials can be readily constructed from copper(l) (198-200), rhenium(l) (101, 186, 201-203) platinum(ll) alkynyls (13, 203-219), as well as various gold(l) derivatives (210, 220-226). 

Gold(III) and platinum(IV) complexes act as oxidants towards a number of substrates and can be reduced by sulfur-containing reductants. At the beginning of this century Herrmann established that alkyl sulfides reduce gold(III) chloride with formation of the gold(l) derivatives, [AuC1(SR2)]. Today, these well-documented reactions are carried out in aqueous or alcoholic solution, Eq. 9.29 ... 

Anhalojiidine, C Hi OgN, crystallises in small octahedra, m.p. 160-1°. The hydrochloride, B. HCl, forms prisms, but the platinum and gold salts are amorphous the picrate has m.p. 201-8°. The alkaloid contains two methoxyl groups, yields a monobenzoyl derivative, m.p. 189° and with methyl iodide forms A-methylanhalonidine hydriodide (pellotine hydi-iodide), yellow prisms, m.p. 125-130°. 

The compound 70 has also been reported showing the ambident character (both C- and N-coordination) of the cyano-stabilized ylide as ligand. The authors have also transposed their work concerning the keto-bis-ylide and palladium, with the synthesis of the C-bonded complex 71 or the new cycloplatinated or-thometallated compound 72. The latter by various treatments allows one to obtain other ylidic cationic complexes of platinum such as 73. A C,C,C-terdentate coordination of the keto bis-ylide, already observed with the palladium is also obtained from the reaction of 73 with gold derivatives. 

Methanol is a major bulk chemical, and its global annual production exceeds 37 million tons. It is mainly used for the production of formaldehyde and methyl 6butyl ether (MTBE). Especially, formaldehyde is dominantly used for producing resins. At present, methanol and its decomposed derivatives can be oxidized to CO2 and H2O by the proper selection of supported noble metal catalysts such as palladium, platinum, and gold. 

Eigure 3.9 shows temperatures for 50% conversion (T o) of CH3OH and its decomposed derivatives over Pt/y-Al203, Pd/y-Al203, and Au/a-Pe203 catalysts [52]. Eor MeOH oxidation, palladium is more active than platinum, while gold lies in between. These three catalysts are similarly active for the oxidation of HCHO and HCOOH. Catalytic oxidation at temperatures below 0°C can proceed over palladium and platinum for H2 oxidation, while it happens over gold for CO oxidation. 

IH of alkynylamines has been performed with a variety of catalytic systems based on palladium [274-281], cobalt, rhodium, iridium, ruthenium, platinum, copper, silver, zinc, cadmium, mercury [279-281], nickel [279-282], gold [279-281, 283], and molybdenum [284] derivatives. 

The coordination chemistry of tertiary phosphine-functionalized calix[4]arenes have been described.279 Treatment of a bis(diphenylphosphino) or bis(dimethylphosphino) derivative of calix[4]arene with [PtCl2(COD)] leads to the formation of the corresponding dichloroplatinum(II) complex. The related diplatinum(II) species has also been reported with the tetrafunctionalized calix[4]arene.280 The mononuclear derivative is susceptible to oligomerization if the two free phosphine ligands are not oxidized or complexed to another metal center such as gold(I).279 The platinum(II) coordination chemistry of a mono-281 and diphosphite282 derived calix[ ]arene (n = 4 and 6, respectively) has also been described. 

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