Hypophosphites, reactions

In electroless deposition, the substrate, prepared in the same manner as in electroplating (qv), is immersed in a solution containing the desired film components (see Electroless plating). The solutions generally used contain soluble nickel salts, hypophosphite, and organic compounds, and plating occurs by a spontaneous reduction of the metal ions by the hypophosphite at the substrate surface, which is presumed to catalyze the oxidation—reduction reaction. 

However, hydrogen is formed in two side reactions, ie, by the decomposition of some sodium hypophosphite (eq. 2) and by the direct reaction of phosphoms with sodium hydroxide (eq. 3). 

The reaction proceeds quantitatively and the hydroiodic acid can be removed by repeated distillation at 5.3 kPa (40 mm Hg), leaving pure H2PO2 as the product. Phosphinic acid may also be prepared by the treatment of barium hypophosphite [14871-79-5] with a stoichiometric quantity of sulfuric acid to precipitate barium sulfate. 

Commercially, phosphinic acid and its salts are manufactured by treatment of white phosphoms with a boiling slurry of lime. The desired product, calcium phosphinite [7789-79-9], remains ia solution andiasoluble calcium phosphite [21056-98-4] is precipitated. Hydrogen and phosphine are also formed, the latter containing sufficient diphosphine to make it spontaneously flammable. The details of this compHcated reaction, however, are imperfectly understood. Under some conditions, equal amounts of phosphoms appear as phosphine and phosphite, and the volume of the hydrogen Hberated is nearly proportional to the hypophosphite that forms. 

Hand in hand with this research on finding a suitable carboxyUc acid chemical for cross-linker has been the search for an economical catalyst system. The catalyst found to be most effective for the esterification reaction was sodium hypophosphite (NaH2P02). This material was also costiy and out of range for the textile industry. Because weak bases function as catalyst, a range of bases has been explored, including the sodium salts of acids such as malic acid. 

Deposition reactions for some reducing agents are given in Table 1 hydrogen is a principal by-product of each reduction. Elemental phosphoms or boron is codeposited with the reduced metal from hypophosphite, borohydride, or organoborane baths (15). Other minor reactions can also occur (18). All of these reductions can be viewed as dehydrogenation reactions (16,19). 

Pd-C, R0H,.HC02NH4J hydrazine or sodium hypophosphite, 42-91% yield. 2-Benzylaminopyridine and benzyladenine were stable to these reaction conditions. Lower yields occurred because of the water solubility of the product, thus hampering isolation. 

The most extensively used reducing agent for the electroless deposition of nickel is hypophosphite", and the reaction is as follows ... 

Two preparations of diesters of phosphonous acid have been reported, - One of these, which claims to be the first preparation of these derivatives, involves the reaction of ammonium hypophosphite with triaikylsilylamines to give bis(trialkylsilyl) esters (127) in excellent yield. These compounds are extremely reactive, e.g. they are spontaneously inflammable in air. Dialkyl phosphonites (128) have also been prepared by the reduction of... 

Sodium hydrogen telluride, (NaTeH), prepared in situ from the reaction of tellurium powder with an aqueous ethanol solution of sodium borohydride, is an effective reducing reagent for many functionalities, such as azide, sulfoxide, disulfide, activated C=C bonds, nitroxide, and so forth. Water is a convenient solvent for these transformations.28 A variety of functional groups including aldehydes, ketones, olefins, nitroxides, and azides are also reduced by sodium hypophosphite buffer solution.29... 

Mital et al. [40] studied the electroless deposition of Ni from DMAB and hypophosphite electrolytes, employing a variety of electrochemical techniques. They concluded that an electrochemical mechanism predominated in the case of the DMAB reductant, whereas reduction by hypophosphite was chemically controlled. The conclusion was based on mixed-potential theory the electrochemical oxidation rate of hypophosphite was found, in the absence of Ni2 + ions, to be significantly less than its oxidation rate at an equivalent potential during the electroless process. These authors do not take into account the possible implication of Ni2+ (or Co2+) ions to the mechanism of electrochemical reactions of hypophosphite. 

The interesting complex chemistry of rhodium has been rather neglected this is probably because most of the synthetic methods for obtaining complexes have been tedious. In general, substitutions of chlorine atoms bonded to rhodium by other ligands are slow, and products have usually been mixtures. The situation is now changing, since novel catalytic approaches to rhodium complexes have been developed.1 The catalysis in the present synthesis involves the rapid further reaction of the hydrido complex formed from l,2,6-trichIorotri(pyridine)rho-dium(III) in the presence of hypophosphite ion. 

The procedure given here has been developed from the reaction with hypophosphite. Other reducing agents such as ethanol, hydrazine, or even molecular hydrogen6 are very effective catalysts and may be used instead of hypophosphite. 

The incorporation of a third element, e.g. Cu, in electroless Ni-P coatings has been shown to improve thermal stability and other properties of these coatings [99]. Chassaing et al. [100] carried out an electrochemical study of electroless deposition of Ni-Cu-P alloys (55-65 wt% Ni, 25-35 wt% Cu, 7-10 wt% P). As mentioned earlier, pure Cu surfaces do not catalyze the oxidation of hypophosphite. They observed interactions between the anodic and cathodic processes both reactions exhibited faster kinetics in the full electroless solutions than their respective half cell environments (mixed potential theory model is apparently inapplicable). The mechanism responsible for this enhancement has not been established, however. It is possible that an adsorbed species related to hypophosphite mediates electron transfer between the surface and Ni2+ and Cu2+, rather in the manner that halide ions facilitate electron transfer in other systems, e.g., as has been recently demonstrated in the case of In electrodeposition from solutions containing Cl [101]. 

Electroless Ni-Ge-P was studied as a model system for ternary alloy deposition [112], A chloride-free solution with GeC>2 as a source of Ge, hypophosphite as reducing agent, aspartic acid as a selective complexant for Ni2+ ions, which was operated at 80 °C in the pH range of 5-5.8, was developed for depositing Ni-Ge-P films with a tunable Ge content from 0 to 25+ at%. The use of a complexant such as citric acid, which complexed Ge(IY) ions as well as Ni2+ ions, resulted in a much lower Ge content in the electroless deposit, and a more complicated solution to study for the reasons discussed above. The aspartate-containing electroless solution, with its non-complexing pH buffer (succinic acid), approximated a modular system, and, with the exception of the aspartic acid - Ni2+ complexation reaction, exhibited a minimum level of interactions in solution. 

The addition of hypophosphites to alkenes under Et3B initiation is also reported [27]. Piettre described recently the addition of diethylthiophosphite to alkenes leading to the formation of thiophosphonates (Scheme 9, Eq. 9a) [28]. Interestingly, this reaction can be used for cyclization of dienes and ring opening of strained alkenes such as a-pinene (Eq. 9b). Parson prepared an... 

The usual flood of reports concerning the addition of phosphites to imines has appeared. These include the reaction of hypophosphites to give a-aminoalkyl-phosphinic acid salts possessing antibacterial activity22 and the synthesis of AM, 4,2-A5-oxazaphospholines (30) from phosphites and carboxamides.23 The addition of... 

A synthesis of A-substituted a-aminobenzylphosphinic acids starts from ammonium hypophosphite this is allowed to react with primary amines together with aldehydes or ketones in the presence of HC1.60 The nature of the products and general success of the Atherton-Todd reaction for the preparation of dialkyl- and diaryl-phosphinic amides from secondary phosphine oxides depends on the order in which reactants are mixed and on the choice of polyhalogen reactant.61... 

The H-P bond in hypophosphites appears much more reactive than that in the phosphinate products the reactions of alkynes do not form symmetrically dialkenyl-substituted phosphinate R2P(0)(0R ) (R=alkenyl group). 

The kinetics of reaction of Fe " aq, of FeOH +aq, and of Fe2(OH)2 " "aq with variously proto-nated forms of phosphate, phosphite, hypophosphite, sulfate, and selenite have been investigated, mainly at 283 K. The formation mechanism from the dimer is somewhat complicated, e.g., by formation of mononuclear complexes, probably via /i-hydroxo-/r-oxoanion di-iron intermediates, after the initial 4 complexation step. ... 

Sulfenyl cldorides, sulfinic acids and sulfinyl chlorides were reduced in good yields by lithium aluminum hydride to disulfides [680], The same products were obtained from sodium or lithium salts of sulfinic acids on treatment with sodium hypophosphite or ethyl hypophosphite [507]. Sulfoxy-sulfones are intermediates in the latter reaction [507]. 

In fact, this is the first stage of the reaction. In the presence of protons released by the reaction, oxidation to phosphorous acid occurs. If the reaction mixture is kept only weakly acid throughout the whole reaction, only hypophosphite is actually formed in the solution. 

By treating sodium hypophosphite, NaH2P02 with an ion-exchange resin. The sodium salt may be produced by boding white phosphorus with a solution of sodium hydroxide, a reaction similar to (1) above. 

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