The invention relates to compounds of the formula (I) wherein n is 0, 1 or 2; G is CH2 or CHR3; R1 is H, C,-C6-alkyl, C,-C6-alkyl substituted by C3-C6-cycloalkyl, C1-C6-hydroxyalkyl, fluorinated C,-C6-alkyl, C3-C6-cycloalkyl, fluorinated C3-C6-cycloalkyl, C3-C6 alkenyl, fluorinated C3-C6-alkenyl, formyl, acetyl or propionyl; R2, R3 and R4 are, independently of each other, H, methyl, fluoromethyl, difluoromethyl, or trifluoromethyl; A is phenylene, pyridylene, pyrimidylene, pyrazinylene, pyridazinylene or thiophenylene, which can be substituted by one or more substituents selected from halogen, methyl, methoxy and CF3; E is NR5 or CH2, wherein R5 is H or C1-C3-alkyl; Ar is a cyclic radical selected from the group consisting of phenyl, a 5- or 6-membered heteroaromatic radical comprising as ring members 1, 2 or 3 heteroatoms selected from N, O and S and a phenyl ring fused to a saturated or unsaturated 5- or 6-membered carbocyclic or heterocyclic ring, where the heterocyclic ring comprises as ring members 1, 2 or 3 heteroatoms selected from N, O and S and/or 1, 2 or 3 heteroatom-containing groups each independently selected from NR8, where R8 is H, C1-C4-alkyl, fluorinated C1-C4-alkyl, C1-C4alkylcarbonyl or fluorinated C1-C4-alkylcarbonyl, and where the cyclic radical Ar may carry 1, 2 or 3 substituents Ra, wherein the variable Ra has the meanings given in the claims and in the description; and physiologically tolerated acid addition salts thereof.; The invention also relates to the use of a compound of the formula I or a pharmaceutically acceptable salt thereof for preparing a pharmaceutical composition for the treatment of a medical disorder susceptible to treatment with a dopamine D3 receptor ligand.