Hypophosphite-reducing agents

Sodium hypophosphite reducing agent, eiectrodeiess nickel plating plastics... 

Triethylammonium formate is another reducing agent for q, /3-unsaturated carbonyl compounds. Pd on carbon is better catalyst than Pd-phosphine complex, and citral (49) is reduced to citronellal (50) smoothly[55]. However, the trisubstituted butenolide 60 is reduced to the saturated lactone with potassium formate using Pd(OAc)2. Triethylammonium formate is not effective. Enones are also reduced with potassium formate[56]. Sodium hypophosphite (61) is used for the reduction of double bonds catalyzed by Pd on charcoal[57]. 

Reductions. Hydrazine is a very strong reducing agent. In the presence of oxygen and peroxides, it yields primarily nitrogen and water with more or less ammonia and hydrazoic acid [7782-79-8]. Based on standard electrode potentials, hydrazine in alkaline solution is a stronger reductant than sulfite but weaker than hypophosphite in acid solution, it falls between and Ti ( 7). 

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). 

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

Further development was made by the General American Transportation Corporation, and their Kanigen process has been available since 1952. Other commercial processes based on the use of hypophosphite have since been developed. Work with reducing agents containing boron has given rise to the Nibodur process which has been available since 1965. 

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. 

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. 

As a last example on the fabrication of silver clusters, it is worth mentioning that they can also be prepared in microemulsions, where the small droplets of water act as nanoreactors. The surfactant used was AOT and the reducing agent was a very mild one, i.e. sodium hypophosphite. In this manner, fluorescent silver clusters with less than ten atoms are formed and showed planar shape when deposited onto gold substrates, as determined by scanning tunneling microscopy [67, 68]. 

Thus, one concludes that the mixed-potential theory is essentially verified for the case of electroless copper deposition. These conclusions were later confirmed by Donahue (15), Molenaar et al. (25), and El-Raghy and Abo-Salama (33). The mixed-potential theory has been verified for electroless copper deposition as well using hypophosphite as the reducing agent (72). 

A similar kinetic scheme can be applied to other reducing agents, such as borohy-dride (Red = BH4 ), hypophosphite (H2PO2 ), and hydrazine (NH2NH2) where the electroactive species RH are [BH2OH [HPO2 ]ads> and [N2H3]ads, respectively (21,38). 

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