The platina-β-diketone [Pt 2 {(COMe) 2 H} 2 (μ-Cl) 2 ] (1) easily reacts with chelating nitrogen ligands NN (2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen) derivatives) to form novel acyl(hydrido)platinum(IV) complexes [Pt(COMe) 2 Cl(H)(NN)] (NN=bpy 2a, 6-n-Bubpy 2b, 6-sec-Bubpy 2c, 6-Phbpy 2d, 4,4'-Me 2 bpy 2e, 4,4'-tert-Bu 2 bpy 2f, 4,4'-tert-Bu 2 -6-n-Bubpy 2g, phen 2h, 5-Mephen 2i, 4-Mephen 2j, 5-Phphen 2k) with good to excellent yields (55-95%). The identities of 2a-k were determined by microanalysis, NMR ( 1 H, 1 3 C) and IR spectroscopies. The crystal structure of [Pt(COMe) 2 Cl(H)(4,4'-tert-Bu 2 -6-n-Bubpy)] (2g) has been determined. The Pt H bond distance was found to be 1.79(2) 9. Complexes 2a-k show an astonishing thermal stability in the solid state (T d e c 140-180 o C) and decompose with cleavage of acetaldehyde to form acylplatinum(II) complexes [Pt(COMe)Cl(NN)] (3). For 2f it was shown that in boiling solvents (chloroform, methylene chloride, acetone, methanol, toluene, dimethyl sulfoxide, tetrahydrofuran) this decomposition reaction proceeds as well. In boiling chlorinated solvents [PtCl 2 (NN)] (4) is formed as a side product.