6-(2-Fluorophenyl)-triazolopyrimidines of the formula I in which the substituents are as defined below: R1 is C4-C8-alkyl, C4-C8-haloalkyl, substituted C3-C8-cycloalkyl, C3-C8-halocycloalkyl, C5-C8-alkenyl, C2-C8-haloalkenyl, C3-C6-cycloalkenyl, C3-C6-halocycloalkenyl, C2-C8-alkynyl, C2-C8-haloalkynyl or phenyl, naphthyl, or a five- or six-membered saturated, partially unsaturated or aromatic heterocycle which contains one to four heteroatoms from the group consisting of O, N and S, R2 is hydrogen, C1-C3-alkyl or one of the groups mentioned under R1, R1 and R2 together with the nitrogen atom to which they are attached may also form a five- or six-membered heterocyclyl or heteroaryl which is attached via N and contain one to three further heteroatoms from the group consisting of O, N and S as ring member, except for piperidin-1-yl optionally substituted by methyl groups; R1 and/or R2 may be substituted according to the description; L1 is chlorine or fluorine; L2 is hydrogen, is, if L1 is fluorine, also fluorine; X is alkyl; processes for preparing these compounds, compositions comprising them and their use for controlling phytopathogenic harmful fungi.