A bi- or polynuclear metal complex of a metal of groups Vb/VIb/VIIb (IUPAC groups 5-7), has a ligand of the structure (a), wherein R1 and R2, independently of each other, can be oxygen, sulfur, selenium, NH, or NR4, wherein R4 is selected from alkyls and aryls and can be bonded to R3; and R3 is selected from alkyls, long-chain alkyls, alkoxys, long-chain alkoxys, cycloalkyls, haloalkyls, aryls, arylenes, haloaryls, heteroaryls, heteroarylenes, heterocycloalkylenes, heterocycloalkyls, haloheteroaryls, alkenyls, haloalkenyls, alkynyls, haloalkynyls, ketoaryls, haloketoaryls, ketoheteroaryls, ketoalkyls, haloketoalkyls, ketoalkenyls, haloketoalkenyls, where one or more non-adjacent CH2 groups can be replaced, independently, with (1) —O—, —S—, —NH—, —NR∘—, —SiR∘R∘∘—, —CO—, —COO—, —OCO—, —OCO—O—, —SO2-, —S—CO—, —CO—S—, —CY1=CY2, or —C≡O— in such a way that O and/or S atoms are not bonded directly to each other, or (2) aryls or heteroaryls containing 1 to 30 C atoms, as a p-type doping agent for matrix materials of electronic components.