Hierarchical Structures in Tin(II) Oxalates

Abstract Six new Sn II oxalates exhibiting a hierarchy of structures have been prepared employing hydrothermal methods. The compounds I [C 10 N 2 H 10 ][Sn(C 2 O 4 ) 2 ], II [C 10 N 2 H 10 ][Sn 2 (C 2 O 4 ) 3 ], and III [C 8 N 4 H 26 ][Sn(C 2 O 4 ) 2 ] 2 · 2H 2 O possess zero‐dimensional molecular structures; IV [C 10 N 2 H 8 ] 2 [Sn(C 2 O 4 )] 2 and V [C 12 N 2 H 8 ][SnC 2 O 4 ] have one‐dimensional chain structures; and compound VI [C 5 N 2 H 14 ] 2 [Sn 4 (C 2 O 4 ) 6 ] · 7H 2 O has a two‐dimensional layer structure. The Sn II ions have 4‐ and 6‐coordination with square‐pyramidal or pentagonal‐bipyramidal geometry, in which the lone pair of electrons also occupies one of the vertices. Weak intermolecular forces such as hydrogen‐bond interactions, π ··· π interactions, and lone‐pair–π interactions have been observed and appear to lendstructural stability. Theoretical studies indicate that the π ··· π interaction energy between the bound 1,10‐phenanthroline molecules is of the order of 5–6 kcal mol –1 in V . Natural bond orbital (NBO) analysis on two model compounds, II and IV , indicates reasonable lone‐pair–π interactions. The close structural relationship between all the compounds indicates that a building‐up process from the zero‐dimensional monomer can be considered. The present structures provide opportunities for evaluating the structure‐directing role of the lone pair of electrons of Sn II .(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)