Gold(I) Complexes Containing Phosphanyl- and Arsanylborane Ligands

The structural and photophysical properties of a series of new Au-I compounds have been studied. The reactions of AuCl(tht) with the phosphanyl- and arsanylboranes RREBH2NMe3 (E=P, As; R=H, Ph; R=H, Ph, tBu) afford the complexes [AuCl(RREBH2NMe3)]. In the solid state, [AuCl(H2PBH2NMe3)](2) (2a) is a dimer showing unsupported intermolecular aurophilic interactions with short AuAu distances. In contrast, [AuCl(H2AsBH2NMe3)](n) (2b) aggregates to form 1D chains. Organic substituents on the pnictogen atoms lead to discrete molecules in [AuCl(RRPBH2NMe3)] (2c: R=H, R=tBu; 2d: R=R=Ph). To increase the aurophilicity, the ionic homoleptic complexes [Au(RREBH2NMe3)(2)][AlCl4] (3a-d) have been synthesized, for which 3a,b form chains in the solid state and exhibit luminescence. The emissions show a drastic redshift with temperature decrease, correlating with decreasing AuAu distances. DFT calculations provide insight into the bonding situation of the products.