Can the solid state structures of the dihalogen adducts R 3EX2 (E = P, As; R = alkyl, aryl; X = Br, I) with the molecular spoke geometry be considered good mimics of the gold(i) systems [(R3E)AuX] (E = As, P; R = alkyl, aryl; X = Cl, Br, I)?

The solid-state structures of compounds of the type R3EX 2 and [(R3E)AuX] (R = alkyl, aryl, E = As, P, X = Cl, Br, I) have been compared on the basis that they have similar molecular shape and volume with a view to determine whether this is a good approach to understand the formation of aurophilic interactions. To aid in the discussion the new compounds Ph2(C6H5-C6H4)P 1, Ph2(C6H5-C6H4)PI 21a, [Ph2(C6H5-C6H 4)PAuX] (X = Cl 2a, Br 2b, I 2c) and [(LAu)-C6H 4-2-OMe] (L = PPh33a, PCy33b; PPh 2-1-naphthyl 3c; PPh2-2-MeO-C6H43d) and [(LAu)-C6H3-2,5-(OMe)2] (L = PPh 34a, PCy34b; PPh2-1-naphthyl 4c; PPh 2-2-MeO-C6H44d, which have all been fully spectroscopically characterised and for 1a, 2a-c, 3a and 3c by X-ray crystallography, have been synthesised. It is found that in some cases the group 15 dihalogen adducts mimic the solid state structures of the gold halide complexes extremely well indicating the packing requirements of the ligand are dominant. In many other cases there are significant differences and these differences shed light on why it is difficult to predict with certainty the presence of an Au⋯Au contact. It also appears that complexes with an Au-I bond are most likely to form an Au⋯Au contact as the Au-I bond is the weakest hydrogen bond acceptor. © 2010 The Royal Society of Chemistry.