Use in oleds of transition metal carbene complexes that contain no cyclometallation via non-carbenes

An organic light-emitting diode comprising at least one transition metal-carbene complex of the general formula (I)

• in which the symbols are each defined as follows:
• M′ is a metal atom selected from the group consisting of transition metals of group IIB, IIIB, IVB, VB, VIB, VIIB, VIII of the Periodic Table of the Elements (CAS version) and Cu, in any oxidation state possible for the particular metal atom;
• K is an uncharged mono- or bidentate ligand;
• L is a mono- or dianionic ligand which may be mono- or bidentate;
• m is from 0 to 5;
• o is from 0 to 5;
• n is from I to 6;
• p is the charge of the complex:
• 0, 1, 2, 3, 4;
• W− is a monoanionic counterion;
• where m, o, n and p are dependent upon the oxidation state and coordination number of the metal atom used and upon the charge of the ligands and the overall charge of the complex, and
• carbene is a carbene ligand of the general formula (IIa)
• in which the symbols are each defined as follows:
• Do is a donor atom selected from the group consisting of N, C, P, O, S and Si;
• r is 2 when Do is C or Si, is 1 when Do is N or P, and is 0 when Do is O or S;
• in which the curved line
• is a saturated or unsaturated bridge between the donor atom Do and the nitrogen atom, which has at least two atoms, where one or more atoms of the bridge may optionally be substituted by alkyl or aryl groups, where the groups may be substituted or unsubstituted, and/or groups with donor or acceptor action, and the bridge may optionally be fused to one or more rings;
• and
• R1, R2
• are each independently hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, aralkyl, alkenyl, alkynyl, where the groups may be substituted or unsubstituted, BR32, NR222, PR232, OR24, SR25 or SiR43;
• or
• R1 and/or R2 may each independently, together with one of the R1 and/or R2 radicals of one or two further carbene ligands, form a bridge, where the bridge may be defined as follows:
• alkylene, arylene, heteroarylene, alkynylene, alkenylene, where the groups may be substituted or unsubstituted, NR5, PR6, BR7, SR82−, CR9(O−), SO2, SiR10R11, CO, CO—O, O—CO and (CR12R13)x where one or more nonadjacent (CR12R13) groups may be replaced by arylene, heteroarylene, alkynylene, alkenylene, where the groups may be substituted or unsubstituted, NR5, PR6, BR7, BR82−, CR9(O−) O, S, SO, SO2, SiR10R11, CO, CO—O, O—CO;
• where
• x is from 2 to 10;
• R3, R4, R5, R6, R7, R8, R9, R10, R11, R22, R23, R24, R25 are each independently hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl, aralkyl, heteroaryl, alkenyl, alkynyl, alkoxy, where the groups may be substituted or unsubstituted;
• and
• R12, R13
• are each independently hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, aralkyl, alkynyl, alkenyl, where the groups may be substituted or unsubstituted, or groups with donor or acceptor action;
• wherein the transition metal complexes of formula I comprise bridged carbene ligands, in which case there is a bridge via the R1 and/or R2 radical to a further carbene ligand—likewise via the R1 and/or R2 radical of the further carbene ligand, wherein the bridge has the meaning mentioned in the definition of R1 and R2,
• wherein the carbene ligand(s) in the transition metal complexes of the formula I is bonded to the transition metal exclusively via carbene carbon atoms.