Abstract: Catalytic hydrogenation of o-nitrophenylazohydroxyaryls in an alkaline medium yields hydroxyarylbenzotriazoles; under mild conditions an N-oxide is formed. E.g., 6-tert-butyl-2-(5'-chloro-2'-nitrophenylazo)-p-cresol is hydrogenated to 5-chloro-2-(3'-tert-butyl-2'-hydroxy-5'-methylphenyl)benzotriazole, using platinum sulfide catalyst in the presence of sodium hydroxide: ##STR1## IN THIS CASE A in the starting chemical is 5-chloro, n is 1, Ar is a phenyl nucleus, m is 2, one B is 6-tertbutyl and the other B is 4-methyl; in the product x is zero. Chemicals useful for various purposes, including the stabilization of polymeric materials (e.g., polypropylene, polyvinyl chloride) against light, may be made by the process.

Abstract: The disclosure relates to a new class of compounds useful in stabilizing organic materials against the effects of heat and light, such materials especially including polymers such as polyolefins. The new compounds are hydrazine complexes of nickel thio-bis-phenolates, where the thio-bis-phenol is of the formula, ##STR1## where R is selected from the group consisting of hydrogen, normal alkyl or normal alkenyl, and R.sub.1 is selected from the group consisting of a normal, secondary, tertiary or cyclic alkyl group. The hydrazines used in making the complexes are of the formula ##STR2## where R.sub.2, R.sub.3 and R.sub.4 are independently chosen from the group hydrogen and primary, secondary and tertiary alkyl groups consisting of 1 to 8 carbon atoms and R.sub.3 and R.sub.4 may be joined together to form a heterocyclic structure.

Abstract: Catalytic hydrogenation of o-nitrophenylazohydroxyaryls in an alkaline medium yields hydroxyarylbenzotriazoles; under mild conditions an N-oxide is formed. E.g., 6-tert-butyl-2-(5'-chloro-2'-nitrohenylazo)-p-cresol is hydrogenated to 5-chloro-2-(3'-tert-butyl-2'-hydroxy-5'-methylphenyl)benzotriazole, using platinum sulfide catalyst in the presence of sodium hydroxide: ##SPC1##In this case A in the starting chemical is 5-chloro, n is 1, Ar is phenyl nucleus, m is 2, one B is 6-tert-butyl and the other B is 4-methyl; in the product x is zero. Chemicals useful for various purposes, including the stabilization of polymeric materials (e.g., polypropylene, polyvinyl chloride) against light, may be made by the process.