Synthesis and crystal structure of gold(I) complexes with triazole and triphenylphosphine ligands: monomeric complex [Au(1,2,3-L)(PPh3)] and dimeric complex [Au(1,2,4-L)(PPh3)]2 (HL = triazole) through an Au–Au bond in the solid state

Abstract

Two novel gold(I)–triphenylphosphine complexes with nitrogen-containing heterocycles, [Au(1,2,3-L)(PPh₃)] 1 and [Au(1,2,4-L)(PPh₃)]₂·xH₂O (x = 0.5–1.0) 2 (HL = triazole) were synthesized from stoichiometric reactions of a precursor complex [AuCl(PPh₃)] with HL in acetone in the presence of NaOH, and isolated as colorless needles and cubic crystals, respectively. The crystal structures of 1 and 2 were determined by single-crystal X-ray diffraction. Complexes 1 and 2 were also fully characterized by complete elemental analyses, TG/DTA and FT-IR in the solid state and by solution NMR (³¹P, ¹H and ¹³C) spectroscopies and solution molecular-weight measurements. Complex 1 consisted of a monomeric 2-coordinate AuNP core both in the solid state and in solution, while, in contrast, 2 comprised a dimeric (AuNP)₂ core through an Au–Au bond in the solid state, but a monomeric AuNP core in solution. Within the two gold(I) complexes composed of very closely related nitrogen-containing heterocycles and a common bulky PPh₃ ligand, it was found that aggregation through the Au· · ·Au interaction in 2 was overruled in 1. The molecular structures of 1 and 2 were also compared with those of the corresponding silver(I) analogs, [Ag(1,2,3-L)(PPh₃)₂]_n 3 and [Ag(1,2,4-L)(PPh₃)₂]_n 4, the molecular structures of which have been recently determined as helical polymers in the solid state.