Supramolecular gold(I) thiobarbiturate chemistry: Combining aurophilicity and hydrogen bonding to make polymers, sheets, and networks

The cooperative forces of aurophilic and hydrogen bonding have been used in the self-assembly of phosphine or diphosphine complexes of gold(l) with the thiolate ligands derived from 2-thiobarbituric acid, SC4H4N2O2, by single or double deprotonation. The reaction of the corresponding gold(l) trifluoroacetate complex with SC4H4N2O2 gave the complexes [Au(SC4H3N2O2)(PPh3)], 1, [(AuSC4H3N2O2)(2)(mu-LL)], with LL = Ph2PCH2PPh2, 2a, Ph2P(CH2)(3)PPh2, 2b, or Ph2PCH=CHPPh2, 2c, or the cyclic complex [Au-2(mu-SC4H2N2O2)(mu-Ph2PCH2CH2PPh2)], 3. In the case with LL = Ph2P(CH2)(6)PPh2, the reaction led to loss of the diphosphine ligand to give [Au-6(SC4H3N2O2)(6)], 4, a hexagold(I) cluster complex in which each gold(l) center has trigonal AuS2N coordination. Structure determinations show that 1 has no aurophilic bonding, 2b, 3, and 4 have intramolecular aurophilic bonding, and 2c has intermolecular aurophilic bonding that contributes to the supramolecular structure. All the complexes undergo supramolecular association through strong (NHO)-O-... and/or (OHN)-N-... hydrogen bonding, and complex 3 also takes part in (CHO)-O-... hydrogen bonding. The supramolecular association leads to formation of interesting polymer, sheet, or network structures, and 4 has a highly porous and stable lattice structure.