NOVELTY - Organo-palladium(II) or -platinum(II) compounds with ortho-metallated 2-phenylpyridyl or 2-(2-furyl)-pyridyl groups (or analogous thiophene or selenothene derivatives), substituted in the non-pyridine ring with chlorine, bromine or iodine.    USE - In electrical or electronic components, e.g. as light-emitting materials in organic or polymeric light-emitting diodes, or in solar cells, lasers and photo-detectors etc..    ADVANTAGE - Halogen-functional organo-palladium and organo-platinum compounds which can be produced with high yield and selectivity and in a high state of purity by halogenation of planar quadratic (bis-ortho-metallated) metal complexes followed by reduction of the intermediate metal(IV) complexes, without expensive chromatographic purification procedures.    DETAILED DESCRIPTION - Compounds of formula (1) and (2) are new.    M = Pd or Pt;    X = Cl, Br or I;    Y = O, S or Se;    R = H, F, Cl, Br, I, nitro, CN, 1-20C alkyl or alkoxy (linear, branched or cyclic; optionally with one or more non-adjacent CH2 groups replaced by O, Si(R1)2, S, NR1 or CONR1 and optionally with one or more H replaced by F), 4-14C aryl or heteroaryl (optionally substituted with non-aromatic groups R), or several groups R on the same or different rings may form another mono- or poly-cyclic system;    R1 = H, or 1-20C aliphatic or aromatic hydrocarbyl;    a = 0-4;    b = 0-3;    n = 1 or 2.    INDEPENDENT CLAIMS are included for:    (1) compounds of formulae (1a), (2a), (3), (4), (5), (6), (7) and (8);    (2) a method for the production of these compounds from corresponding unhalogenated compounds, comprising reaction with a halogenating agent, followed by reduction conjugated or partly conjugated polymers (P1) containing one or more of the above compounds attached to the polymer by a bond at the position occupied by group X electrical components containing such polymers.    X = N, Cl, Br or I, with the proviso that at least one X in each molecule is Cl, Br or I;    Z' = F, Cl, Br, I, OR1, SR1 or N(R1)2;    L1 = a neutral monodentate ligand;    L2 = a mono-anionic monodentate ligand;    L3 = a neutral or mono- or di-anionic bidentate ligand;    m = 0, 1 or 2.