ASYMMETRICAL 1:2 CHROMIUM COMPLEX AZO DYESTUFFS

1,139,149. Mixed chromium metal complexes. J. R. GEIGY A.G. 21 Nov., 1966 [22 Nov., 1965], No. 52014/66. Heading C4P. The invention comprises mixed dye chromium metal complexes of the general formula wherein X is hydrogen or a nitro group; D is an unsulphonated or sulphonated nitrophenylene radical containing the -O- group ortho to the azo link, A is an aliphatic sulphonyl or mononuclear arylsulphonyl radical and M + is a cation, and mixtures of these dyestuffs. Preferably -NHA is in a #-position, e.g. the 7-position. They are prepared by reacting one of the unmetallized monazo dyestuffs with a chroming agent optionally in presence of an organic solvent and an acid binding agent, and the 1: 1 complex formed with the other azo dyestuff. Mixtures of the metal complexes may be obtained by using mixtures of the nitrophenylene containing azo dyestuffs or by simple mixing of the products. The dyes are used to dye chrome tanned suede and grain leather.