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Lamellar and Three‐Dimensional Hybrid Compounds Formed by Cyclohexene‐ and Cyclohexanedicarboxylates of Pb, La, and Cd
Author(s) -
Rao K. Prabhakara,
Thirumurugan A.,
Rao C. N. R.
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200600966
Subject(s) - chemistry , metal , crystallography , lamellar structure , cyclohexene , hydrothermal circulation , hydrothermal synthesis , cyclohexane , stereochemistry , catalysis , geology , organic chemistry , seismology , biochemistry
To establish factors that determine the formation of three‐dimensional hybrid structures of metal dicarboxylates involving metal–oxygen–metal linkages, we have investigated metal dicarboxylates derived from 1,2‐cyclohexene as well as 1,2‐, 1,3‐, and 1,4‐cyclohexane dicarboxylic acids. Thus, we have synthesized a 1,2‐cyclohexenedicarboxylate of Cd, [Cd(1,2‐CHeDC)(H 2 O)] ( I ), a 1,2‐cyclohexanedicarboxylate of Pb, [Pb(1,2‐CHDC)] ( II ), and three 1,4‐cyclohexanedicarboxylates of La [La 2 (1,4‐CHDC) 3 (H 2 O) 4 ] ( III ), [La 3 (1,4‐HCHDC) 2 (1,4‐CHDC) 5 (H 2 O) 2 ]⋅H 2 O ( IV ) and [La 2 (1,4‐CHDC) 3 (H 2 O)]⋅2.5 H 2 O ( V ) under hydrothermal conditions and determined their structures. A mixed dicarboxylate involving both 1,3‐ and 1,4‐cyclohexenedicarboxylates of Pb, [Pb 3 O(1,3‐CHDC)(1,4‐CHDC)]⋅0.5 H 2 O ( VI ) and a 1,4 ‐ cyclohexanedicarboxylate of Pb, [Pb 6 O 2 (1,4‐CHDC) 3 (1,4‐HCHDC) 2 ], have also been synthesized and characterized. While the 1,2‐dicarboxylates have layered structures, the 1,4‐dicarboxylates and the mixed dicarboxylates possess three‐dimensional structures. Interestingly, both the 1,2 and 1,4‐dicarboxylates are true hybrid compounds composed of infinite M‐O‐M linkages. The equatorial–equatorial (e,e) conformation is adopted commonly in all these compounds, although less stable conformations are encountered occasionally. The formation of the layered and the three‐dimensional structures can be understood based on the relative disposition of the two carboxylic groups, the 1,4‐isomer favoring the three‐dimensional structure. Based on the results of the present study along with the available literature, we conclude that in order to obtain three‐dimensional hybrid structures with metal–oxygen–metal networks, it appears necessary to make use of the 1,4‐cyclohexanedicarboxylic acid.