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Title
Octahedral complexes of a mixed N,N,O-donor ligand N-trans-(2'-hydroxycyclohexyl)-2-aminomethylpyridine
Author/Creator
Robertson, Mark J.;  Lawrance, Geoffrey A.;  Maeder, Marcel;  Turner, Peter
Institution
The University of Newcastle. Faculty of Science & Information Technology, School of Mathematical and Physical Sciences
Description
The unsymmetric mixed-donor Nam,Npy,O-ligand N-trans-(2'-hydroxycyclohexyl)-2-aminomethylpyridine (pyca, 1) was readily prepared by reaction of an epoxide (cyclohexene oxide) with (2-aminomethyl)pyridine. The ligand forms octahedral bis-tridentate complexes, exemplified with isolation of copper(II), nickel(II), zinc(II), and cobalt(III) compounds; in addition, a square-planar palladium(II) complex with the ligand behaving as bidentate was prepared. The bis-tridentate octahedral complexes may exist in six geometric isomeric forms, and molecular mechanics analysis was employed to predict the most stable isomer for copper(II), nickel(II), and cobalt(III) complexes. For the copper(II) and cobalt(III) complexes, the predictions match the X-ray crystal structures of the single isomer isolated in each case. Both the copper(II) complex [Cu . 1₂](ClO₄)₂ and the cobalt(III) complex [Co . 1 . (1–H)](ClO₄)₂ crystallized in the monoclinic space group P2₁/n (no. 14), with a 9.8400(13), b 15.434(2), c 10.0180(13) Å, and β 109.004(2)°, and a 14.162, b 18.583, c 21.596 Å, and β 100.04°, respectively. Both complexes adopt distorted octahedral structures. The copper(II) complex exists as the all-trans-fac isomer with Jahn–Teller elongation of the Cu–O bond [2.3795(19) Å] compared to Cu–Npy [2.040(2) Å] and Cu–Nam [2.024(2) Å] distances. The cobalt(III) complex appears as the cis,cis,trans(Npy) fac isomer, but deprotonation of one of the two alcohol groups leads to all six M–L distances differing: for each of two similar independent complex cations, Co–O [e.g. 1.9123(16), 1.9459(16) Å], Co–Nam [e.g. 1.949(2), 1.968(2) Å], and Co–Npy [e.g. 1.938(2), 1.940(2) Å] vary, with particularly the deprotonated alcohol bond significantly shorter than the protonated bond, despite a strong hydrogen bonding interaction with the protonated alcohol in the partner complex cation in the unit cell.
Relation
Australian Journal of Chemistry Vol. 57, Issue 5, p. 483-490
Publisher Link
http://dx.doi.org/10.1071/CH03208
Date
2004
Publisher
CSIRO Publishing
Keyword(s)
ligand;  N-trans-(2'-hydroxycyclohexyl)-2-aminomethylpyridine;  octahedral complexes
Resource Type
journal article
Identifier
http://hdl.handle.net/1959.13/33465
Identifier
ISSN:0004-9425
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Subject
"Australian Journal of Chemistry"
 
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