Gold(I) Complexes Bearing P^N-Ligands: An Unprecedented Twelve-membered Ring Structure Stabilized by Aurophilic Interactions

The P∩N-ligands Ph2Pqn, 1, Ph2 Piqn, 2, Ph2 Ppym, 3, and the As∩N-ligands Ph2Asqn, 4, Ph2Asiqn, 5, (Ph = phenyl, qn = 8-quinoline, iqn = 1-isoquinoline, pym = 2-pyrimidine) have been synthesized, the ligands 2 and 5 for the first time. Their ligand properties were probed by the synthesis of gold(I) complexes. Reaction with (tht)AuCl (tht = tetrahydrothiophene) yielded the chlorogold complexes Ph2RP–Au–Cl (R = qn, 6; iqn, 7; pym, 8) and Ph2RAs–Au–Cl (R = qn, 9; iqn, 10) in high yields. Further treatment of 7 and 8 with one equivalent of AgBF4 provided the complexes [(Ph2Piqn)Au]BF4, 11, [(Ph2Ppym)Au]BF4, 12, and [(Ph2Piqn)Au(tht)]BF4, 14. For comparison, the previously reported complex [(Ph2Ppy)Au]BF4 (py = pyridine), 13, was re-investigated. The compounds were characterized by elemental analyses, mass spectrometry and NMR spectroscopy. In addition, the solid-state structures of 2, 3, 6, 7, 9 – 14 have been determined by X-ray crystallography. The chloro-gold compounds crystallize in the common rod-like structure known from R3EAuCl (R = aryl, E = P, As) complexes without further aggregation via aurophilic interactions. In all cases the phosphine acts as a monodentate ligand. In the solid state compounds 11 – 13 feature an unprecedented cyclic trinuclear aggregation pattern, in which the Au(I) atoms are linearly coordinated by the bridging phosphine ligands forming a cyclic (P–Au–N)3 arrangement. The resulting twelvemembered ring is further stabilized by Au · · · Au interactions. Due to the presence of these Au · · · Au contacts, 11 – 13 are emissive in the solid state but not in solution.