Abstract Complexes of the formula <IMAGE> WHEREIN V is hydroxy or amino, one of X1 and X2 is sulfo and the other is -NHR3, wherein R3 is heterocyclyl containing at least one substituent cleavable as an anion, preferably a halopyrimidyl or halotriazinyl group, Y is methyl, methoxy, ethoxy or methoxyethoxy, Z is hydrogen, methyl or methoxy, M IS 0 OR 1, AND N IS 2 OR 3, WITH THE PROVISO THAT THE -N=N- and -O-Cu-O- groups are bound to adjacent positions of the naphthalene ring, are useful for the dyeing or printing of natural or regenerated cellulosic fibres. The obtained dyeings and prints possess notable stability in alkaline medium and fastness to light and satisfactory fastness to wet treatments, chlorine and peroxide. The dyes possess notable build-up and fixation.