Platinum salts

Addition to Olefins. OrganohydrosHanes can also be prepared by addition of halosHanes and organosilanes containing multiple Si—H bonds to olefins. These reactions are catalyzed by platinum, platinum salts, peroxides, ultraviolet light, or ionizing radiation. 

Pla.tinum, Platinum plating has found appHcation in the production of platinised titanium, niobium, or tantalum anodes which are used as insoluble anodes in many other plating solutions (see Metalanodes). Plating solutions were often based on platinum "P" salt, which is diamminedinitroplatiniim (IT). A dinitroplatinite sulfate—sulfuric acid bath has been used to plate direcdy onto titanium (129). This bath contains 5 g/L of the platinum salt, pH adjusted to 2.0 with sulfuric acid. The bath is operated at 40°C at 10—100 A/m. Other baths based on chloroplatinic acid have been used in both acid and alkaline formulations the acid bath uses 20 g/L of the platinum salt and 300 g/L hydrochloric acid at 65° C and 10—200 A/m. The alkaline bath uses 10 g/L of the platinum salt, 60 g/L of ammonium phosphate and ammonium hydroxide to give a pH of 2.5—9.0. The alkaline bath can be plated directly onto nickel-base alloys acid baths require a gold strike on most metals. 

Platinum salts Platinum refining workshops and some laboratories... 

Platinum metal and soluble platinum salts criteria document for an OEL... 

MS 22 The medical monitoring of workers exposed to platinum salts... 

Platin-plattierung,/. platinum plating, -reihe, /. platinum series, -rhodium, n. platinum-rh ium. -rohr, n.,-rohre,/. platinum tube, -rtickstand, m. platinum residue, -salmiak, m. ammonium chloroplatinate, -salz, n. platinum salt, -sand, m. sand for cleaning platinum, -saure, /. platinic acid, -schale. 

Platinum is used as a catalyst for nitric and sulphuric acid production, in petroleum refining and in catalytic mufflers to control air pollution. Platinum salts can cause respiratory complaints, asthma, and platinosis , an allergic response. Allergic dermatitis may also result from exposure to soluble platinum salts and once subjects have been sensitized it generally precludes continued occupational exposure at any level. The 8 hr TWA OEL for platinum metal is 5 mg/m but for soluble platinum salts it is only 0.002 mg/m. Handling precautions must include containment where possible, ventilation, personal protection, and the screening out of individuals who have become sensitized. 

Although a wide variety of metals were claimed as active catalysts for formaldehyde hydrophosphination, platinum salts were preferred. Similarly, Group 10 metal salts were used to catalyze acrylonitrile hydrophosphination. Russian workers showed that Ni(II) or Co(II) salts in the presence of ammonia or amines would also catalyze the addition of phosphine to formaldehyde [6]. More recently, academic and industrial interest in these reactions was sparked by a series of papers by Pringle, who investigated late metal phosphine complexes as hydrophosphination catalysts. These and related studies are arranged below by substrate. 

Besides Wacker oxidation, other transition-metal catalyzed oxidations have also been carried out in aqueous medium. For example, methyl groups can be selectively hydroxylated by platinum salts in water.88 In this way, p-toluenesulfonic acid was oxidized to benzy-lic alcohol, which was subsequently oxidized into the aldehyde (Eq. 3.19).89... 

Synthetic organic chemistry applications employing alkane C-H functionalizations are now well established. For example, alkanes can be oxidized to alkyl halides and alcohols by the Shilov system employing electrophilic platinum salts. Much of the Pt(ll)/Pt(rv) alkane activation chemistry discussed earlier has been based on Shilov chemistry. The mechanism has been investigated and is thought to involve the formation of a platinum(ll) alkyl complex, possibly via a (T-complex. The Pt(ll) complex is oxidized to Pt(iv) by electron transfer, and nucleophilic attack on the Pt(iv) intermediate yields the alkyl chloride or alcohol as well as regenerates the Pt(n) catalyst. This process is catalytic in Pt(ll), although a stoichiometric Pt(rv) oxidant is often required (Scheme 6).27,27l 2711... 

Respiratory hypersensitivity is an adverse reaction in the respiratory tract driven by immune mechanisms such as IgE antibody mediated allergic responses. Other less well understood mechanisms that have an immune component are also involved in respiratory hypersensitivity. OA is one outcome of respiratory hypersensitivity. Respiratory hypersensitivity and OA to proteins are primarily mediated by IgE antibody with subsequent inflammatory cell infiltrates. This same mechanism is responsible for OA to specific LMW chemicals such as the acid anhydrides and platinum salts. However, the role for IgE mediated responses in OA to other LMW chemicals such as the isocyanates and plicatic acid is poorly defined and other mechanisms may be responsible. 

Merget, R. et al., Exposure-effect relationship of platinum salt allergy in a catalyst production plant conclusions from a 5-year prospective cohort study, J. Allergy Clin Immunol., 105, 364, 2000. 

Newman Taylor, A.J. et al., Interaction of HLA phenotype and exposure intensity in sensitization to complex platinum salts, Am. J. Respir. Crit Care Med., 160, 435, 1999. 

Among the very few catalytic systems that allow not only C-H bond activation but also functionalization are those based on platinum(II) catalysts. Soon after the discovery that platinum salts in aqueous solution catalyze H/D exchange in hydrocarbons (9,10 a hydrocarbon functionalization cycle was developed on the basis of this system (11). This cycle is depicted in Scheme 2. 

The upper compartment is filled with 0.0025 M tetraamineplatinum chloride (Pt(NH3)4Cl2) aqueous solution for 30 min. to allow the cation form of platinum salt to difiuse into Nafion, whose roughened side is facing this solution. The volume of the solution was adjusted to give 0.1 mg/cm as the loading assuming all the salt in the solution is deposited. After the solution is removed, the compartment is washed with water lightly, then... 

Since platinxim exists in the solution as an anion form, it caimot enter into the membrane easily. In principle, neutral or cation forms of the reducing agents diffuse finm the lower compartment into the membrane and reduce platinum salt to platinum metal on the roughened surface of the membrane. 

Procedure The irradiated molybdenum is dissolved in cone, sulfuric acid and technetium is distilled with the acid. The distillate obtained is diluted to 4 M H2SO4, heated to boiling and treated with bromic water. A platinum salt (1 mg of Pt/200 ml solution) is added to the solution as collector, and technetiiun is coprecipitated with the platinum sulfide. The precipitate is dissolved in NH OH/ HjOj mixture and the solution evaporated to dryness. The residue is dissolved in cone. HjSO or HCIO4 and technetium separated from platimun by distillation. The solution is diluted and the sulfide precipitated. 

Smokers have been found to be at increased risk of sensitization by platinum salts. An historical perspective cohort study of 91 platinum refinery workers showed a four- to fivefold risk of developing a positive skin test to platinum salts in smokers. The risk of smokers developing symptoms was approximately twofold, and, among recent employees, the rate of development of a positive skin test result was faster in smokers versus nonsmokers. Smoking is thought to act by increasing the serum levels of IgE. In another report, 78 newly hired refinery workers were followed for 24 months platinum salt sensitivity developed in 41% of the new hires. Smoking was found to increase the risk of platinum salt sensitivity... 

Calverley AE, Rees D, Dowdeswell RJ, et al Platinum salt sensitivity in refinery workers incidence and effects of smoking and exposure. Occup Environ Med 52(10) 661-6, 1995... 

Parrot JL, Herbert R, Saindelle A, Ruff F Platinum and platinosis, allergy and histamine release due to some platinum salts. Arch Environ Health 19 685-691, 1969... 

Chloroplatinic acid is used in preparing most platinum salts and complexes. It also is used as an electroplating bath for plating and coating of platinum. Other applications are in catalysis. 

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