The invention relates to compounds of the formula Ar(—CH2C6Br5)y, wherein Ar indicates a structure comprising one or more six-membered aromatic ring(s) and —CH2C6Br5 indicates a pentabromobenzyl group, characterized in that at least one carbon atom of said six-membered aromatic ring(s) is bonded to the benzylic carbon of said —CH2C6Br5 group, wherein y, which indicates the number of the —CH2C6Br5 groups in said compound, is not less than 1. Processes for preparing the compounds and their use as flame retardants are also disclosed.