TERMINALLY BIFURCATED TETRAAURIO-ALPHA,OMEGA-BIS(SULFONIUM) SALTS AS BUILDING-BLOCKS FOR AURIOPHILICITY-DETERMINED COORDINATION POLYMERS

Treatment of alpha,omega-dithiols HS(CH2)(n)SH, n = 4 or 5, with tris[ (triphenylphosphine)aurio]oxonium tetrafluoroborate affords the corres ponding rio]-alpha,omega-alkanediylbis(tetrafluoroborates) of the type (3)P)Au]S-2(CH2)(n)S[AU(PPh(3))](2)}(2+)2BF(4)(-). The crystal struct ure of the species with n = 5 has been determined by single crystal X- ray diffraction studies. In the lattice the unfolded dications are lin ked into chains through short double Au-Au contacts between the termin al bifurcated diauriosulfonium centers. The analogous reactions with ( racemic) 1,2-dithioglycerol and 1,2,3-trithioglycerol also give tri- a nd tetranuclear complexes with a varying distribution of the metal ato ms over the chalcogen(ium) centers. As again demonstrated in a single crystal X-ray diffraction study, the dications {HOCH2HCS[(Ph(3)P)Au]2C H2S[Au(PPh(3))](2)}(2+) of the dithioglycerol compound form only dimer s through auriophilicity-determined pairing of the bifurcated ends, wh ile the open ends are shielded by the dangling hydroxyl group. The tri nuclear complex of 1,2-dithioglycerol is fluxional in solution; the cr ystal structure has not been determined but is expected to be similar to that derived for the analogous dithioglycol complex. The tetranucle ar, trithioglycerol-based dications of ]SCH2CHS[Au(PPh(3))]CH2S[Au(PPh (3))](2)}(BF4-)-B-+ are isolated in the lattice and feature an unsymme trical complexation, which is an extension of the structure of the tri nuclear dithioglycol analogue {(CH2S)(2)[Au(PPh(3))](3)}(+) with its s trong intramolecular Au-Au contacts. A similar structure is proposed f or the monocation {CH2(CH2S)(2)-[Au(PPh(3))](3)}(+) obtained from prop ane-1,3-dithiol. The structures of these cations are also fluxional in solution, however, as shown by variable-temperature NMR studies.