Synthesis of novel LaOAgS-type cation-deficient bismuth oxyhalides

Three new bismuth oxyhalides, PbxBi2−xCuxO2X2 (X = Cl, x ≈ 0.35–0.70; X = Br, x ≈ 0.35–0.65; X = I, x ≈ 0.35–0.55) have been predicted and synthesized from PbO, BiOX, and CuX. All three compounds adopt a very deficient LaOAgS (stuffed PbFCl) structure. Atomic parameters have been determined for Pb0.6Bi1.4Cu0.6O2Cl2 and Pb0.6Bi1.4Cu0.6O2Br2 (P4/nmm, Z = 1) as well as for a structurally and compositionally related Pb0.6Bi1.4Cs0.6O2Br2 (I4/mmm, Z = 2). Comparison of these structural data with bond distances and angles in related Pb0.6Bi1.4Q0.6O2X2 oxyhalides (Q = Rb, Cs, Tl; X = Cl, Br) reveals that replacement of CsCl-like [Q0.6X2] layers by anti-fluorite-like [Cu0.6X2] has a small effect on the Pb0.6Bi1.4–O and Pb0.6Bi1.4–X distances and a larger one on bond angles. We predict existence of isostructural compounds among multinary oxyhalides of bismuth and fluorohalides of lead. It is also likely that more complicated structures involving [CuxX2] layers can be realized.