| Abstrakt: |
Two types of silver(I)-triphenylphosphine complexes with 2-mercaptonicotinic acid (H2mna) were prepared as [Ag(Hmna)(PPh3)n] (1, n= 2; 2, n= 3); their crystal structures determined by single-crystal X-ray diffraction. These complexes were obtained from reactions of the precursor, [Ag(Hmna)]n, with less excess (3 equiv) and large excess (20 equiv) amounts of PPh3, respectively. Complex 1was also obtained from a reaction among another precursor [AgCl(PPh3)3], H2mna and aqueous NaOH. The coordination geometry of 1was a trigonal pyramid with an AgSP2core; there was a weak interaction between the silver(I) center and the pyridine nitrogen atom, while that of 2was a distorted tetrahedron with an AgSP3core. In both 1and 2, the carboxyl group was protonated and its oxygen atoms did not participate in the coordination. In contrast to the formation of 1and 2, a related complex, [Ag(Hmba)(PPh3)3] 4(H2mba = 2–mercaptobenzoic acid), has been obtained from a reaction of [Ag(Hmba)]nwith a stoichiometric amount (3 equiv) of PPh3. On the other hand, the gold(I) complex, [Au(Hmna)(PPh3)] 3, with a 2-coordinate AuSP core, was prepared by a stoichiometric reaction among [AuCl(PPh3)], H2mna and aqueous NaOH. Complex 3in the solid state showed a supramolecular array based on a repetition of hydrogen-bonding interactions between the carboxyl group and the pyridine nitrogen atom, also being contrasted to the related complex, [Au(Hmba)(PPh3)] 5, with a hydrogen-bonding dimer structure in the solid state. In CHCl3, both 1and 2were present as several equilibrium species due to a successive dissociation of PPh3ligands, while 3was present as an almost monomer. The antimicrobial activities in aqueous media of 1—5, evaluated by minimum inhibitory concentration (MIC), were also tested. |
