Platinum thiocyanates

Carbonyl Platinum Thiocyanate, Pt(CNS)2.CO.—A double salt of this substance with potassium thiocyanate,namely,Pt(CNS)2. CO. KCNS, is obtained 1 by adding a solution of potassium thiocyanate to one of carbonyl platinum dichloride in hydrochloric acid until the precipitate first formed is redissolved. On evaporation in the cold it crystallises in yellow needles, which decompose on wanning with water. 

Platinum thiocyanates are not known, except in combination with the thiocyanates of certain other metals. TMoeyanoplatinous acid, HaPt(CNS)4, and thiocyanoplatinic acid, H2Pt(CNS)e, are obtained in. solution by decomposition of the corresponding barium salts with the calculated quantities of dilute sulphuric acid. The acids decompose, however, on concentration beyond a certain point. 

Ultrasonic nebulizers have also been employed in continuous flow systems as interfaces between sample preparation steps in the analytical process and detection by virtue of their suitability for operating in a continuous mode. Thus, preconcentration devices have commonly been coupled to atomic spectrometers in order to increase the sensitivity of some analytical methods. An enhancement factor of 100 (10 due to USNn and 10 due to preconcentration) was obtained in the determination of platinum in water using a column packed with polyurethane foam loaded with thiocyanate to form a platinum-thiocyanate complex [51]. An enhancement factor of 216 (12 with USNn and 18 with preconcentration) was obtained in the determination of low cadmium concentrations in wine by sorption of metallic complexes with pyridylazo reagents on the inner walls of a PTFE knotted reactor [52]. One special example is the sequential determination of As(lll) and As(V) in water by coupling a preconcentration system to an ICP-AES instrument equipped with a USN. For this purpose, two columns packed with two different resins selective for each arsenic species were connected via a 16-port valve in order to concentrate them for their subsequent sequential elution to the spectrometer [53]. 

Stratifying water systems for selective extraction of thiocyanate complexes of platinum metals have been proposed. The extraction degree of mthenium(III) by ethyl and isopropyl alcohols, acetone, polyethylene glycol in optimum conditions amounts to 95-100%. By the help of electronic methods, IR-spectroscopy, equilibrium shift the extractive mechanism has been proposed and stmctures of extractable compounds, which contain single anddouble-chai-ged acidocomplexes [Rh(SCN)J-, [Ru(SCN)J, [Ru(SCN)J -have been determined. Constants of extraction for associates investigated have been calculated. 

The solution should be free from the following, which either interfere or lead to an unsatisfactory deposit silver, mercury, bismuth, selenium, tellurium, arsenic, antimony, tin, molybdenum, gold and the platinum metals, thiocyanate, chloride, oxidising agents such as oxides of nitrogen, or excessive amounts of iron(III), nitrate or nitric acid. Chloride ion is avoided because Cu( I) is stabilised as a chloro-complex and remains in solution to be re-oxidised at the anode unless hydrazinium chloride is added as depolariser. 

An ambidentate ligand has the choice of using two different types of donor atom. Two that have been extensively studied in their bonding to platinum and palladium are sulphoxides and thiocyanate. 

The thiocyanate K2[Pt(SCN)6].2H20 contains octahedrally coordinated platinum, confirming the readiness of platinum(IV) to bind to a soft donor atom like sulphur [182]. 

Tian ZQ, Ren B, Mao BW. 1997. Extending surface Raman spectroscopy to transition metal surfaces for practical applications. 1. Vibrational properties of thiocyanate and carbon monoxide adsorbed on electrochemically activated platinum surfaces. J Phys Chem B 101 1338-1346. 

Extraction with a tertiary amine, Alamine 336, followed by palladium stripping with thiourea (Tu), and platinum with thiocyanate ... 

Chelate complexes could only be prepared in the case of platinum(II) as the metal ion, while the group V atom alone acted as a donor toward palladium(II) and mercury(II). The coordinated olefin in the chelate complexes was found to be readily displaced by monodentate ligands such as tertiary arsines, -toluidine and the thiocyanate ion. It was suggested by these workers that chelation would take place more readily if the olefinic phosphine or arsine were subject to greater steric restrictions than was the pentenyl ligand. 

It may also be prepared by electrolysis of the alkali thiocyanates in aqueous or alcoholic solution, using a platinum gauze anode and a silver cathode. On evaporation under reduced pressure, thiocyanogen is obtained as a viscous oil, solidifying at —70° C.4... 

The coordination chemistry of the cyanate, thiocyanate and selenocyanate ligands has been recently reviewed.1874 Platinum(II) forms the complex ion Pt(SCN)2-, and the corresponding homoleptic platinum(IV) complex Pt(SCN)i can be prepared. Numerous mixed ligand complexes of platinum(II) are known containing the thiocyanate ligand and other ligands, although there are fewer platinum(IV) examples. 4... 

Much discussion on the coordination chemistry of the thiocyanate ligand centers on its function as an ambidentate ligand. For coordination to platinum both N-bonded and S-bonded thiocyanate ligands are found and the small energy difference between the two bonding modes leads to small effects such as steric and electronic factors, as well as solvent changes, causing conversion between S- and N-bonded thiocyanate. 

The heterobinuclear complex [PdPtCl2( -dppm)2] can also be prepared by treating the product from the reaction of dppm and [Pd(PPh3)4] with [PtCl2(NCBu,)2].76 The corresponding bromide, iodide and thiocyanate dipalladium and palladium-platinum complexes have been prepared by metathesis of the dichloride (9) with NaX.76... 

P NMR spectroscopy.53 Steric factors account for the different coordination modes, while the influence of electronic factors is evidenced by the difference in structure between analogous palladium(II) and platinum(II) compounds, for example, the thiocyanates are N- and S-bonded in [Pd(NCS)(SCN)(diars)], but only S-bonded in [Pt(SCN)2(diars)].54 These and other diphosphine or diarsine complexes of palladium(II) with thio- or seleno-cyanate ligands are further discussed in Section 51.8.2.6. 

Scheme 1 Linkage isomers of bis(thiocyanate)(2,2,-bipyridine)platinum(II)) their interconversion, and their emission maxima and excited states at 77 K. Based on data from [48]...

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