 To whom correspondence should be addressed. E-mail: liikh@cc.ncu. edu.tw. Journal of Solid State Chemistry 157, 233 } 239 (2001) doi:10.1006/jssc.2000.9081, available online at http://www.idealibrary.com on Synthesis and Characterization of New Iron Phosphatooxalates: [(S )-C 5 H 14 N 2 ] [Fe 4 (C 2 O 4 ) 3 (HPO 4 ) 2 (H 2 O) 2 ] and [(S )-C 5 H 14 N 2 ] [Fe 4 (C 2 O 4 ) 3 (HPO 4 ) 2 ] Wen-Jung Chang,* Hsiu-Mei Lin,- and Kwang-Hwa Lii*- * Department of Chemistry, National Central University, Chungli, Taiwan, Republic of China; and - Institute of Chemistry, Academia Sinica, Taipei, Taiwan, Republic of China Received September 26, 2000; in revised form December 4, 2000; accepted December 8, 2000 Two new organically templated iron(II) phosphatooxalates, [(S)-C 5 H 14 N 2 ] [Fe 4 (C 2 O 4 ) 3 (HPO 4 ) 2 (H 2 O) 2 ] (1) and [(S)-C 5 H 14 N 2 ] [Fe 4 (C 2 O 4 ) 3 (HPO 4 ) 2 ] (2), have been synthesized under hy- drothermal conditions and characterized by single-crystal X-ray di4raction and Mo K ssbauer spectroscopy. Crystal data are as follows: compound 1, triclinic, P1 (No. 1), a  7.6999(4) A  , b  7.9542(4) A  , c  9.8262(5) A  ,   74.8444(7)3,   81.7716(8)3,   85.4075(8)3, V  574.34(8) A  3 , Z  1, and R 1  0.0255; compound 2, monoclinic, P 2 1 (No. 4), a  7.5943(8) A  , b  7.8172(8) A  , c  18.318(2) A  ,   99.111(2)3, V  1073.8(3) A  3 , Z  2, and R 1  0.0281. The structure of 1 consists of dimers of edge-sharing FeO 6 octahedra that are linked by phosphate and oxalate groups to generate a three-dimensional framework with intersecting tunnels parallel to the [100] and [010] directions. Diprotonated (S )-2-methylpiperazinium cations are located at the intersections of these tunnels. Compound 1 crystallizes as a minor product when a racemic mixture of 2-methylpiperazine is used in the synthesis, and can be prepared as a major product with a small amount of 2 if optically pure (S )-2-methylpiperzine is used. The structure of 2 is similar to that of 1 except that the coordination around the iron centers in the dimer are square pyramidal and octahedral. The two compounds are the 5rst 3-dimensional phosphatooxalates containing a chiral amine.  2001 Academic Press INTRODUCTION Recently, many research activities have focused on the synthesis of new open-framework metal phosphates, owing to their diverse structural chemistry and potential applica- tions (1). In the context of building open frameworks, it is also possible to use organic molecules in the skeleton (2}7). As compared with inorganic phosphates, the organic mol- ecules have larger sizes of polyhedral centers and a wide variety of means of connection. An interesting variant of the metal phosphates is obtained by incorporating the oxalate unit in the materials. A large number of phosphatooxalates of Fe (8}13), V (14), Al (15, 16), Ga (17}19), In (20), and Mn (21) have been reported during past few years. In this new class of organically modi"ed inorganic materials, there have been relatively more reports on the Fe}PO} Ox system. All of these iron compounds adopt three-dimensional frame- work structures. Most of them consist of anionic frame- works templated with organic amines in protonated forms, while a few contain neutral frameworks without amine templates. In our continuing research on this system, we have discovered two novel iron phosphatooxalates tem- plated with a chiral amine, [(S)-C  H  N  ][Fe  (C  O  )  (HPO  )  (H  O)  ] (1) and [(S)-C  H  N  ][Fe  (C  O  )  (HPO  )  ](2). Most interestingly, only the chiral species acts as a template in 1, although a racemic mix of 2-methyl- piperazine is used in the synthesis. Compound 2 crystallizes as a minor product when the chiral amine (S)-2-methyl- piperazine is used as a template. To our knowledge, no three-dimensional metal phosphate-oxalate framework templated with a chiral amine has been reported before this work. EXPERIMENTAL SECTION Synthesis. The compounds were synthesized hydrother- mally in a 23-mL Te#on-lined autoclave under autogenous pressure. Reaction of a racemic mixture of 2-methyl- piperazine (5 mmol), iron metal powder (3 mmol), H  PO  (7 mmol), oxalic acid (4 mmol), and H  O (10 mL) at 1653C for 3 days followed by slow cooling at 103C/h to room temperature produced a small amount of red crystals of [(S)-C  H  N  ][Fe  (C  O  )  (HPO  )  (H  O)  ] (1) and or- ange crystals of [C  H  N  ][Fe  (C  O  )  (HPO  )  ](3) as the major products. The "lling rate of the bomb was about 50%. The initial and "nal pH values were 4.6 and 5.9, 233 0022-4596/01 $35.00 Copyright  2001 by Academic Press All rights of reproduction in any form reserved.