Synthesis and structures of cyclic gold complexes containing diphosphine ligands and luminescent properties of the high nuclearity species

A mixture of cyclic gold(I) complexes [Au-2(mu-cis-dppen)(2)]X-2 (X = OTf1, PF6 3) and [Au(cis-dppen)(2)]X (X = OTf 2, PF6 4) is obtained from the reaction of [Au(tht)(2)]X (tht = tetrahydrothiophene) with one equivalent of cis-dppen [dppen = 1,2-bis(diphenylphosphino) ethylene]. The analogous reaction with trans-dppen or dppa [dppa = bis(diphenylphosphino) acetylene] affords the cyclic trinuclear [Au-3(mu-trans-dppen)(3)]X-3 (X = OTf 11, PF6 12) and tetranuclear [Au-4(mu-dppa)(4)]X-4 (X = OTf 13, PF6 14, ClO4 15) gold complexes, respectively. Recrystallization of 15 from CH2Cl2/MeOH yielded a crystal of the octanuclear gold cluster [Au8Cl2(mu-dppa)(4)](ClO4)(2) 16. Attempts to prepare dicationic binuclear gold(II) species from the reaction of a mixture of 3 and 4 with halogens gave a mixture of products, the components of which confirmed to be acyclic binuclear gold(I) [Au2X2(cis-dppen)] (X = I 5, Br 7) and cyclic mononuclear gold (III) [AuX2(cis-dppen)]PF6 (X = I 6, Br 8) complexes. Complexes 11-14 reveal weak emission in butyronitrile glass at 77 K, but they are non-emissive at room temperature. Ab initio modelling was performed to determine the charge state of the gold atoms involved. Extensive structural comparisons were made to experimental data to benchmark these calculations and rationalize the conformations.