Crystal structure of the new compound Pb3+xSb3-xS7-xCl1+x(x similar to 0.45): The homologous series Pb(2+2N)(Sb,Pb)((2+2N))S(2+2N)(S,Cl)((4+2N))Cl-N and its polychalcogenide derivatives (N=1-3)

摘要

The new chloro-sulfosalt Pb3+xSb3-xS7-xC1+x. (x similar to 0.45) has been synthesized at 500 degrees C from a mixture of PbS, PbCl2 and Sb2S3. It , crystallizes in the orthorhombic system (space group Pbam), with a = 15.194(3) angstrom, b = 23.035(5) angstrom, c = 4.0591(8) angstrom, V = 1420.6 Z = 4. The crystal structure has been solved by X-ray single-crystal study, with a final R = 0.0497. Deviation from stoichiometric Pb3Sb3S7Cl (x coefficient) follows the substitution rule Sb3+ + S2- -> Pb2+ +Cl-. Sb and Ph sub-positions within mixed (Sb,Pb) sites are discussed; Pb excess precludes any superstructure along c. A unique'pure Cl position is bound only to Pb atoms with a distorted square coordination. The title compound is a rod-type structure derived from the SnS archetype, homeotypic with Pb6Sb6S14(S-3), where the (S3)(2-) trimer is replaced by two Cl-; this substitution is quite isovolumic. Other similar structures are: three polychalcogenides Sr(6)Sb(6)Sl(4)(S-3), Pb6Sb6Se14(Se-3) and EU6Sb6S14(S-3); KLa1.28Bi3.72S8 and its Ln isotypes; dadsonite, Pb23Sb25S60Cl. Pb3+xSb3-xS7-xCl1+x, is the N = 2 member of the homologous series Pb(2 + 2N)(Sb,Pb)((2 + 2N))S(2 + 2N)(S,Cl)((4 + 2N))Cl-N; the N = I member corresponds to the previously known -Pb4.3Sb3.7S8.7Cl2.3 Compound. Other polychalcogenide derivatives of this homologous series are K2Pr2-xSb4+xSe8(Se-4) and its Ln isotypes (N = 1), as well as SrBiSe3 (N = 3). Such a comparative modular analysis allowed to propose a structural model for the previous synthetic "Phase Y", similar to Pb10Sb10S23Cl4, corresponding to the combined N = (I + 2) homolog. (C) 2008 Elsevier Inc. All rights reserved.