Thermodynamic study of volatile iridium (I) complexes with 1,5-cyclooctadiene and acetylacetonato derivatives: Effect of (O,O) and (O,N) coordination sites

Abstract Three hetero-ligand volatile iridium (I) complexes with β-diketonate derivatives [Ir(cod)(L)] (cod = 1,5-cyclooctadiene, L = CH 3 C(O)CHC(X)CH 3 , X = O (acac) 1 , N–H ( i -acac) 2 , N–CH 3 (Me i -acac) 3 ) have been synthesized, purified and characterized in order to investigate the influence of (O,O) and (O,N) coordination sites in chelate ligand on the thermochemical properties of this type compounds. β-Ketoiminate complexes (L =  i -acac, Me i -acac) were prepared for the first time. Thermal behavior of iridium complexes in condensed phase has been studied by differential scanning calorimetry and thermodynamic parameters of melting processes (Δ melt. H m.p. , Δ melt. S ° m.p. ) have been determined for the first time. The temperature dependencies of saturated vapor pressures over the solid complexes have been measured by flow (transpiration) method (temperature intervals (363–423) K, (383–431) K and (383–420) K for compounds 1 , 2 and 3 , respectively). Using these data, the thermodynamic parameters of sublimation processes (Δ sub H T , Δ sub S ° T ) have been calculated. It has been found that although the ligand modification has a minor effect on the vaporization characteristics of this type complexes, the volatility unexpectedly decreases in the following sequence: L = acac >  i -acac > Me i -acac. However, the vapor pressure values in the above-mentioned temperature interval are sufficient to all complexes studied be used as effective volatile precursors to obtain iridium-containing coatings by chemical vapor-phase deposition methods.