Properties and X-ray structural study of volatile dimethylgold(III) β-iminoketonates

Three complexes of dimethylgold(III) of a general formula of (CH₃)₂Au(R¹-CNH-CH-CO-R²) involving β-imino-derivatives of acetylacetone (k-acac), trifluoroacetylacetone (k-tfa), and pivaloyltrifluoroacetone (k-pta) are studied for the first time with single crystal X-ray diffraction. Synthesis and properties of these compounds are presented along with thermal properties determined by the DTA technique. The structures of the compounds in question are based on monomeric complexes. Gold atoms have a slightly distorted square-planar coordination involving oxygen and nitrogen atoms of the β-iminoketonate ligand and two methyl groups. Geometrical characteristics of the coordination cores are the following: bond lengths of Au-C_Me fall within 2.008–2.050 Å; average Au-O and Au-N distances are 2.094 Å and 2.068 Å respectively. In the structure of (CH₃)₂Au(k-acac) gold complexes are joined by hydrogen bonds to give infinite chains with the shortest Au...Au separation of 5.396 Å. In the crystals of the fluorinated compounds coplanar molecules make infinite stacks. The shortest intra-stack Au...Au separation of 3.416 Å is observed for the complex of (CH₃)₂Au(k-pta) that possesses the largest thermal stability among the investigated compounds.