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Alteration in the Binding Property of a Laterally Nonsymmetric Aza Cryptand toward Cu II , Ag I , and Tl I Ions upon Derivatization with a Cyanomethyl Group
Author(s) -
Ray Debdas,
Bharadwaj Parimal K.
Publication year - 2006
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200501099
Subject(s) - chemistry , octahedron , cryptand , crystallography , metal , ion , yield (engineering) , stereochemistry , crystal structure , materials science , metallurgy , organic chemistry
Abstract The laterally nonsymmetric aza cryptand L o readily forms mononuclear inclusion complexes with metal ions like Cu II , Ni II , Ag I , Tl I , and so forth. However, when the secondary amines present in the three bridges are substituted by a cyanomethyl group to yield a new cryptand L , its metal‐binding properties are drastically altered. Thus, while L o binds Ag I at the tren end, showing AgN 4 coordination, in L , the bridgehead nitrogen atoms are pulled inside to form a two‐coordinate complex of Ag I and none of the O or N atoms present in the three bridges are involved in coordination. This is probably the first example where the two bridgehead atoms are pulled inside to the maximum to bind the metal ion. Likewise, the Tl I ion shows TlN 4 coordination with L o , while in L it is loosely bound at the tren end, showing TlN 3 coordination. Upon treatment with a Ag I salt, the Tl I can be replaced almost instantaneously. On the other hand, with copper( II ) tetrafluoroborate salt in moist DMF, two of the cyanide groups in L are converted to carboxylic acid groups and bind the metal ion from outside. The Cu II ion in this complex shows distorted octahedral coordination where the two O atoms from the two carboxylic acid groups and the two corresponding N atoms in the two bridges are bound equatorially. The two axial sites are occupied by the nearby bridgehead N atom and the O atom of a DMF molecule. All five complexes and the free ligands are characterized by spectroscopic and X‐ray crystallographic studies. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)