Flux Synthesis of LiAuS and NaAuS: “Chicken-Wire-Like” Layer Formation by Interweaving of (AuS)nn- Threads. Comparison with α-HgS and AAuS (A = K, Rb)

From the reaction of Au with alkali metal polysulfide liquids, LiAuS and NaAuS were discovered. Orange crystals of LiAuS crystallize in the monoclinic space group C2/c, (no. 15), with a = 8.994(2) Å, b = 8.956(2) Å, c = 7.201(3) Å, beta = 128.68(1) degrees, and Z = 8. Light-yellow planks of NaAuS crystallize in the orthorhombic space group Ccca, (no. 68), with a = 14.658(5) Å, b = 21.043(7) Å, c = 7.118(4) Å, and Z = 32. Both compounds contain infinite one-dimensional (AuS)(n)()(n)()(-) chains, featuring alternating sulfide anions and linear coordinated Au centers. In LiAuS, the chains are zigzag and fully extended and they pack in two mutually perpendicular sets. In NaAuS, the same chains coil in an unusual fashion so that they become interwoven to form layers reminiscent of "chicken-wire". This novel coiling mode allows Au-Au contacts to form, which help to stabilize the structure. The structural relationships between LiAuS, NaAuS, Na(7)Au(5)S(6), AAuQ (A = K, Rb, Cs; Q = S, Se), and alpha-HgS are explored.