Isolation of a Cyclic Trinuclear Gold(I) Complex with Metalated Phosphorus Ylides: Synthesis and Structural Properties.

Abstract

The first chiral and luminescent cyclic trinuclear gold(I) complex, [{AuCH(PPh2Me)(Ph2P)}3]3+, has been isolated with metalated phosphorus ylides (PY). This complex was initially obtained through the reaction of either mononuclear [C6F5SAuCH(PPh2Me)(Ph2P)]OTf or dinuclear [C6F5S{AuCH(PPh2Me)(Ph2P)}2](OTf)2 thiolate-gold-phosphane complexes in the presence of NaH, followed by the abstraction of the thiopyridine moiety employing either AgOTf or [Cu(CH3CN)4]PF6. Our quest for a more efficient synthesis route led to the development of a streamlined one-pot synthesis method, employing Ag(acac) as both a halogen abstractor and a base, offering a quicker and more direct path to this intriguing trimer. Comprehensive computational studies have unveiled the luminescent characteristics of this complex, which can be attributed to phosphorescence. These emissions originate from ligand-to-metal (LMCT) and metal-centered (MC) charge transfer excited states. Furthermore, the structural analysis via X-ray crystallography corroborated the formation of a trimeric species, featuring three monomers with the [AuCH(PPh2Me)(Ph2P)] motif. Each monomer exhibits a single chiral center, leading to four possible absolute configurations (RRR, RRS, RSR, and SRR). NMR and X-ray spectroscopy have provided valuable insights, establishing that the former configuration (RRR) is disfavored due to steric hindrance, while the three remaining configurations can interconvert, arising from the structural arrangement of the metallacycle and inherent symmetry operations.