Structural relationships between o-, m- and p-tolyl substituted R3EI2 (E = As, P) and [(R3E)AuX] (E = As, P; X = Cl, Br, I)Electronic supplementary information (ESI) available: Characterisation data for all new adducts and complexes; Table of torsion angles and cone angles and packing diagrams for 1a-e and I-VII. CCDC reference numbers 7706521a, 7706531c, 7706541d, 7706551e and 7706562. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c0ce00024h

The compounds R 3 EI 2 (R = o -tolyl, E = As, 1a ; R = m -tolyl, E = P 1c ; R = p -tolyl, E = As, 1d , P, 1e ), which display the charge transfer spoke structure, and [( o -tolyl 3 As)AuCl] 2 have been synthesised and their solid state structures compared to the related complexes [(R 3 P)AuX] (R = o -tolyl, X = Cl, I , Ia ; Br, II ; I, III ; R = m -tolyl, X = Cl, IV ; R = p -tolyl, X = Cl, V , Va ; Br, VI ; I, VII ) on the basis of a similarity of their molecular shape and volume. All of the new compounds 1a , 1c- 1e and 2 have been fully spectroscopically characterised and by single crystal X-ray crystallography. The sterically demanding exo 3 o -tolyl ring conformation is observed for 1a , which is comparable to that reported for o -tolyl 3 PI 2 1b , with a long As-I bond 2.7351(14) Å and short I I distance 2.9528(11) Å. The exo 3 o -tolyl ring conformation is maintained on complexation to gold( i ) in 2 , but has no significant impact on the expected bond lengths, with As-Au 2.3443(15) Å and Au-Cl 2.284(4) Å. The exo 3 conformation appears to be stabilised in both cases by the formation of a six-fold edge-to-face (EF) 6 embrace. It is found that in some cases the structures of the dihalogen adducts and the gold( i ) complexes are isomorphous indicating that ligand packing requirements are most significant i.e. for 1c and IV . Where the structures digress this is due either to the greater ability of the dihalogen adduct to engage in hydrogen bonding 1a , b and I-III ; or subtle changes in the nature of the tolyl ring embraces 1d , e and V -VII . Subtle changes in the nature of the tolyl ring embraces also account for the different polymorphs I and Ia and V and Va . There is no credible evidence to suggest that the aurophilic contact, seen in only one polymorph Va , exerts any influence on the overall crystal packing. The structural comparisons presented here add further to the applicability of the recently recognised structural mimicking ability of the R 3 PX 2 systems and [R 3 PAuX] complexes, and that the aurophilic contact is a poor supramolecular synthon. o -, m -, or p -tolyl-ring embraces and hydrogen bonding are far more important in determining the crystal packing than Au Au contacts.