Journal of Solid State Chemistry 151, 56 } 60 (2000) doi:10.1006/jssc.2000.8621, available online at http://www.idealibrary.com on Hydrothermal Synthesis and Structural Characterization of a Novel Hydroxo Stannate: Sr 2 Sn(OH) 8 Mingmei Wu,* Xiuling Li,* Guoping Shen,* Jing Li,- Ruren Xu,? and Davide M. ProserpioA * School of Chemistry and Chemical Engineering, Zhongshan University, Guangzhou, 510275, People+s Republic of China; -Department of Chemistry, Rutgers University, Camden, New Jersey 08102; ?Key Laboratory of Inorganic Hydrothermal Synthesis, Jilin University, Changchun, 130023, People+s Republic of China; and A Dipartimento di Chimica Strutturale e Stereochimica Inorganica, Universita % di Milano, Via G. Venezian 21, 20133 Milano, Italy Received October 5, 1999; in revised form December 22, 1999; accepted January 10, 2000 A new hydroxo stannate(IV), Sr 2 Sn(OH) 8 , has been syn- thesized by the hydrothermal method. Single-crystal X-ray dif- fraction shows that this compound crystallizes in the monoclinic space group P 2 1 /c with a  6.006(1) A  , b  11.058(2) A  , c  6.129(2) A  ,   112.98(2)3, V  374.8(2) A  3 , Z  2, R 0.022 (I > 2 (I )). The structure [Sr(OH) 6/3 (OH) 2/2 ] 2 [Sn(OH) 6/3 ] con- sists of Sn(OH) 6 octahedra and Sr(OH) 8 triangulated dodecahedra. These Sr(OH) 8 and Sn(OH) 6 polyhedra form a novel complex 3D packing arrangement that contains channels running along [001], 5lled with the in-pointing hydrogens of the hydroxo groups.  2000 Academic Press Key Words: structure; hydrothermal synthesis; extended framework; tin(IV). INTRODUCTION There has been much interest recently in the synthesis and characterization of new materials by soft chemistry ap- proaches that provide e!ective routes for synthesizing new functional materials with new architectures. The hydrother- mal method as such a soft route has been used to prepare a number of chemical stoichiometric complex oxides includ- ing MTiO  , MZrO  (M"Ca, Ba, Sr, or Pb) and their solid solutions (1). Results from both experimental and thermo- dynamic modeling demonstrate that hydrothermal syn- thesis of MO(M"Ca, Sr, Ba, or Pb) with TiO  and/or ZrO  under alkaline conditions usually leads to the forma- tion of ABO  -type complex oxides with perovskite struc- ture, such as SrTiO  , SrZrO  , and Ba(Ti, Zr)O  (1). As far as we know, however, no studies have been reported on direct hydrothermal synthesis of MSnO  complex oxides at tem- peratures below 2603C. We are interested in these com- pounds because of their applications in materials technology as a constituent in perovskite solid solutions with ABO  -type complex oxides such as BaTiO  (2). Kutty  To whom correspondence should be addressed. and Vivekanandan have attempted to prepare pure BaSnO  by a hydrothermal reaction starting from SnO  ) XH  O gel and Ba(OH)  at 150}2603C, which invariably led to the formation of hydroxide phases (2). This suggests that the chemical properties of tin compounds under alkaline hy- drothermal conditions are di!erent from those of titanium and zirconium, although they all adopt similar six-coord- ination in aqueous solutions, oxides, hydroxides, and hy- drates (3). Many hydrothermally synthesized 1-D, 2-D, and 3-D architectures are constructed by the SiO  , AlO  , and PO  tetrahedra (4) and/or based on four-, "ve- and/or six- coordinated metal species (5). Here we report on the synthesis and characterization of a novel hydroxo stannate (IV), Sr  Sn(OH)  , which we have discovered during the course of investigations on MO}SnO  systems with hydrothermal methods. EXPERIMENTAL All the reagents were commercially available, high-grade purity materials (Aldrich Chemicals, Shantou Guanghua Chemicals, Rugao Chemicals), used as supplied, without further puri"cation. IR spectra with samples in KBr pellets were collected on a Perkin}Elmer PC-16 spectrometer. X- ray powder di!raction spectra were collected on a Philips PW1830 horizontal-scan di!ractometer. Thermal analyses were performed in air on a Perkin}Elmer TGA 7 instrument with a heating rate of 53C/min. Hydrothermal Synthesis SrCl  ) 6H  O and SnCl  ) 5H  O were dissolved in distilled water and mixed thoroughly to form a homogeneous solu- tion. NaOH solution was then added into the mixture under magnetic stirring and the mixture gradually became milk- like. The "nal mixture in the ratio of 2.2 SrCl  : 1.0SnCl  : 20.0NaOH : 350H  O was transferred into a stain- less steel autoclave with a Te#on liner and heated to 2303C. 56 0022-4596/00 $35.00 Copyright  2000 by Academic Press All rights of reproduction in any form reserved.