Gold(I) Complexes Containing Phosphanyl- and Arsanylborane Ligands.

The structural and photophysical properties of a series of new AuI compounds have been studied. The reactions of AuCl(tht) with the phosphanyl- and arsanylboranes RR' EBH2 NMe3 (E=P, As; R=H, Ph; R'=H, Ph, tBu) afford the complexes [AuCl(RR' EBH2 NMe3 )]. In the solid state, [AuCl(H2 PBH2 NMe3 )]2 (2 a) is a dimer showing unsupported intermolecular aurophilic interactions with short Au⋅⋅⋅Au distances. In contrast, [AuCl(H2 AsBH2 NMe3 )]n (2 b) aggregates to form 1D chains. Organic substituents on the pnictogen atoms lead to discrete molecules in [AuCl(RR' PBH2 NMe3 )] (2 c: R=H, R'=tBu; 2 d: R=R'=Ph). To increase the aurophilicity, the ionic homoleptic complexes [Au(RR' EBH2 NMe3 )2 ][AlCl4 ] (3 a-d) have been synthesized, for which 3 a,b form chains in the solid state and exhibit luminescence. The emissions show a drastic redshift with temperature decrease, correlating with decreasing Au⋅⋅⋅Au distances. DFT calculations provide insight into the bonding situation of the products.