Structure and Thermal Properties of Volatile Iridium(I) Complexes with Cyclooctadiene-1,5 and β-Ketohydrazonate Ligands

Abstract

Within the search for novel promising volatile precursors for the atomic layer deposition new mixed-ligand complexes of iridium(I) with β-ketohydrazones are obtained: [Ir(cod)(dmht)] 1 and [Ir(cod)(dmha)] 2 (cod = cyclooctadiene-1,5, dmht = CF3C(O)CHC(NN(CH3)2)CH3, dmha = CH3C(O)CHC(NN(CH3)2)CH3). The compounds are characterized by the elemental analysis, IR and NMR spectroscopy, and their structures are determined by single crystal X-ray diffraction. In the complex molecules there is a distorted square coordination core IrNOC2′ (C′ is the center of the C=C bond in the cod ligand). The Ir-O, Ir-N bond lengths and Ir-C′ distances are in narrow ranges of 2.027(5)–2.039(3) A, 2.046(6)–2.074(3) A, and 1.982(5)–2.017(3) A respectively. The crystal packing of 1 is of the layered type. Weak pair interactions γC-H…F are observed between the layers. The molecules of 2 form columns packed in the square motif. Shortened intermolecular contacts are not revealed in this structure. The shortest Ir…Ir distances are 5.357 A and 6.420 A in 1 and 2 structures respectively. The synthesized complexes are capable of a quantitative transition to the vapor phase (100–120 °C, 0.05 Torr) and are characterized by relatively low melting points (105 °C and 121 °C for 1 and 2 respectively). The structure and thermal properties (thermogravimetry data) of β-ketohydrazonate complexes [Ir(cod)(L)] are compared with those of the related compounds containing β-diketonata and β-ketoiminate ligands.