NOVELTY - A dinuclear metal-carbene complex (A1) containing a central atom selected from platinum and palladium is new.    USE - As metal-carbene complex, which is used as charge transport material, charge blocker material, emitter, or matrix material in organic electronic device e.g. organic light-emitting diodes (OLEDs), organic photovoltaic cells (OPVs), organic field-effect transistors (OFETs) and light-emitting electrochemical cells (LEECs); in apparatus selected from stationary visual display units such as visual display units of computers, televisions, visual display units in printers, kitchen appliances and advertising panels, illuminations, information panels, and mobile visual display units such as visual display units in cellphones, laptops, digital cameras, MP3 players, vehicles and destination displays on buses and trains; illumination units; keyboards; items of clothing; furniture; and wallpaper; for electrophotographic photoreceptors, photoelectric converters, organic solar cells (organic photovoltaics), switching elements, organic light emitting field effect transistors (OLEFETs), image sensors, dye lasers (claimed).    ADVANTAGE - The metal complexes exhibit a spectrum of properties improved over known palladium (Pd) or platinum (Pt) complexes e.g. improved efficiencies, improved CIE color coordinates, decreased color dependency on the emitter doping concentration and/or improved lifetime/stability. The dinuclear metal-carbene complexes are generally notable for light emission in a wide range of the electromagnetic spectrum, thus suitable with particular preference as emitter material in organic light-emitting diodes (OLEDs).    DETAILED DESCRIPTION - A dinuclear metal-carbene complex (A1) having formula (I) or (II) containing a central atom selected from platinum and palladium, is new.    M=Pd or Pt;    m=0 or 1;    R1 and R'1=linear or branched 1-20C alkyl (optionally interrupted by at least one heteroatom, and optionally bearing at least one functional group), optionally substituted 3-20C cycloalkyl (optionally interrupted by at least one heteroatom, and optionally bearing at least one functional group), optionally substituted 6-30C aryl (optionally bearing at least one functional group), optionally substituted 5-18C heteroaryl (optionally interrupted by at least one heteroatom, and optionally bearing at least one functional group);    R2, R'2, R3 and R'3=R1 or a group with donor or acceptor action;or    R1 and R2 and/or R'1 and R'2 together with the atoms to which they are bonded=optionally substituted, saturated or unsaturated 5-18C aromatic ring (optionally interrupted by at least one further heteroatom), or optionally be fused to at least one further optionally substituted saturated or unsaturated 5-18C aromatic ring (optionally interrupted by at least one further heteroatom);    K1=neutral monodentate ligand;    L1=monoanionic mono- or bidentate ligand.    INDEPENDENT CLAIMS are included for the following:    (1) preparation of dinuclear metal-carbene complex (A1); and    (2) a light-emitting layer comprising at least one metal-carbene complex (A1).