The First Open-Framework Cadmium Phosphate, K_4[Cd_3(HPO_4)_4(H_2PO_4)_2],with a Layered Structure

摘要

A layered cadmium phosphate of the formula K_4[Cd_3(HPO_4)_4(H_2PO_4)_2], I, containing six-membered apertures, constituting the first example of an open-framework cadmium phosphate , has been synthesized under hydrothermal conditions, Crystal data: monoclinic P2_1(No.14),a=9.0698(3),b=6.7341(3),and c=18.2663(7)A, #beta#=93.092(1),V=1114.03A~3, Z=4.The structure consists of a network of CdO_3 octahedra and PO_3(OH) and PO_2(OH)_2 tetrahedra forming a spiro unit, which are connected through Cd_2O_2 two-membered rings forming one-dimenional chains .The chains are further connceted forming two-dimensional macroanionic layers with six-membered apertures possessing hanging phosphate units on either side of the layer. The layers are stabilized by strong hydrogen bond interactions between the terminal P-OH proups forming pseudo channels in which the charge-compensating extraframework K~+ ions are locatedl The presence of the spiro unit and the infinite one-dimensional Cd-O-Cd chains, along with the hanging phosphates are noteworthy structural features