R6 and R7 independently of one another particularly preferably represent hydrogen, represent in each case optionally mono- to tri-fluorine- or -chlorine-substituted C1-C6-alkyl, C3-C6-cycloalkyl, C1-C6-alkoxy, C3-C6-alkenyl or C1-C6-alkoxy-C2-C6-alkyl, represent in each case optionally mono- to tri-fluorine-, -chlorine-, -bromine-, ???C1-C5-haloalkyl-, ???C1-C5-alkyl- or ???C1-C5-alkoxy-substitute