TECHNOLOGY FOCUS - ELECTRONICS - Preferred Layer: The light-emitting layer comprises at least one metal-carbene complex (A1) and a host material.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (Claimed): Preparation of metal-carbene complex (A1) involves contacting suitable compounds containing platinum and palladium (Pd or Pt) with compound of formula (V) and (VI).X=F, Cl, Br, I, phosphorus hexafluoride (PF6), or boron tetrafluoride (BF4).Preferred Compound: The complex (A1) is preferably a compound of formula (III) or (IV).R1a and R'1a=3-20C cycloalkyl, 6-30C aryl or 5-18C heteroaryl (all optionally substituted), or linear or branched 1-6C alkyl;R2a, R'2a, R3a and R'3a=R1a or a group with donor or acceptor action selected from halo radicals (preferably F or Cl, especially F), CF3, CN or Si(CH3)3;orR1a and R2a and/or R'1a and R'2a 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);R4a and R4'a=6-20C aryl or 5-18C heteroaryl (both optionally substituted) or 1-6C linear or branched alkyl. Preferred Definitions:    m=0;    L1= picolinato, salicylato, 8-hydroxyquinolato, or ligand of formula R5-C(=C(R4)(O-))-C(=O)-R'4;    R4 and R'4=linear or branched 1-6C alkyl (optionally bearing at least one functional group), 3-20C cycloalkyl, 6-20C aryl or 5-18C heteroaryl (all optionally substituted);    R5=6-20C aryl (optionally substituted), 1-6C linear or branched alkyl, or H.    SPECIFIC COMPOUNDS - 310 Compounds are disclosed as the complex (A1) e.g. compounds of formulae (IA)-(ID), and (IF).    EXAMPLE - A dried and argon flushed schlenk tube was charged with 1,4-bis(3-methylimidazolium)benzene iodide (0.40 g) and silver(I) oxide (0.20 g). After addition of dry 1,4-dioxane (20 ml), the reaction mixture was stirred under argon in the dark at room temperature for 48 hours. Dichloro(1,5-cyclooctadiene)platinum(II) (0.75 g) and 2-butanone (10 ml) were added and the mixture was heated to 115 degrees C and stirred for another 54 hours. Afterwards all volatiles were removed under reduced pressure and potassium tert-butanolate (0.72 g), acetylacetone (0.66 ml) and dry dimethyl formamide (DMF) (25 ml) were added under argon. After stirring for 28 hours at room temperature and 14 hours at 100 degrees C, all volatiles were again removed under reduced pressure leaving the crude product, which was washed with water and purified by flash chromatography with methylene chloride/acetone. The product containing fraction was finally recrystallized from methylene chloride/tetrahydrofuran solution and dried under vacuum yielding metal complex (IA) as light-yellow solid (0.03 g, 5%).