Abstract: The invention provides a compound of formulaA--E--SO.sub.2 --NH--SO.sub.2 --E--A (I),whereineach --E--, independently, signifies a bivalent aromatic radical,each --A, independently, signifies a heterocyclic group of formula ##STR1## and the group --R.sub.1 --R.sub.2 -- signifies a 2- or 3-membered bridging chain to form, together with the group ##STR2## to which it is bound, a 5- or 6-membered heterocycle, with the proviso that the carbon indicated by the asterisk * is capable of being coupled with a diazonium compound,or a mixture of compounds of formula (I), and the use thereof as (bis)coupling components for the production of azodyes and metal complexes, which are useful as dyes, especially for the dyeing of leather.

Abstract: The invention provides a process for the production of azodyes and their derivatives by diazotization and coupling reactions and optionally further modification reactions, wherein a compound of formula ##STR1## in which E signifies an aromatic bivalent radical,X.sub.1 signifies hydroxy or a primary amino group,Y.sub.1 signifies hydroxy or a primary amino group and in which the aminogroup linked to the --SO.sub.2 -bound phenyl radical may optionally be acylated,or a mixture of compounds of formula (I), is employed as a coupling component or/and--in the non-acylated form--as a diazo component,the invention in particular relates also to the novel dyes and their use and to the novel intermediates.

Abstract: Mixtures of iron complexes of metallizable disazo compounds, at least one compound being of the formula ##STR1## and at least one compound being of the formula ##STR2## wherein the substituents have the meaning given in the specification, are useful for dyeing substrates dyeable with anionic dyes, e.g., leather.