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Solution fluxionality of some pyridine-2,6-dialdehydes, -diketones and -diesters when acting as bidentate ligands in rhenium(I) and platinum(IV) complexes. Crystal structure of ReBr(CO)(3)L (L = methylethyldipicolinate)

Solution fluxionality of some pyridine-2,6-dialdehydes, -diketones and -diesters when acting as bidentate ligands in rhenium(I) and platinum(IV) complexes. Crystal structure of ReBr(CO)(3)L (L = methylethyldipicolinate)
Solution fluxionality of some pyridine-2,6-dialdehydes, -diketones and -diesters when acting as bidentate ligands in rhenium(I) and platinum(IV) complexes. Crystal structure of ReBr(CO)(3)L (L = methylethyldipicolinate)
2,6-Disubstituted pyridines, where the substituents are aldehyde, ketone or ester functions, form bidentate chelate complexes with the transition metal moieties fac-(ReX)-X-I(CO)(3) (X = halogen). 2-Substituted pyridines, where the substituents are aldehyde or ester functions, form similar types of complexes with the isoelectronic transition metal moieties fac-(ReX)-X-I(CO), and (PtXMe3)-X-IV. The fac-(ReX)-X-I(CO)(3) complexes of the 2,6-disubstituted pyridine ligands were shown by H-1 NMR spectra to undergo metallotropic shifts whereby the Re coordination switches between adjacent ON pairs of the ONO ligand donor set. Rates and activation energies of these fluxional shifts were measured by dynamic NMR bandshape analysis. Magnitudes of DeltaG(double dagger) (298.15 K) were in the range 59-64 kJ mol(-1) for the diketone and diester ligands. The dialdehyde ligand, 2,6-pyridinedicarboxaldehyde, formed an appreciably less-stable Re-I complex that was highly fluxional and showed a tendency to dissociation at ambient solution temperatures. The unsymmetrical diester ligand, methylethyldipicolinate, formed two distinct Re-I complex species in solution, in the approximate abundance ratio of 2:1, the more abundant structure involving coordination to the carbonyl of the ethyl ester function. This particular complex forms exclusively in the solid state and an X-ray crystal structure of [ReBr(CO)(3)L] (L = methylethyldipicolinate) is reported.
rhenium, platinum, pyridine diketones and diesters, fluxionality, dynamic nmrtricarbonyl halide-complexes, nuclear-magnetic-resonance, nmrinvestigations, derivatives, shifts, acid
0277-5387
1973-1982
Creber, M. L.
71d2ca9d-7d07-4571-a634-7afcb7c1ac0c
Orrell, K. G.
e291cfb7-374a-4a7f-8e30-d9513f5203c4
Osborne, A. G.
9430fd91-c186-4b98-a713-74d9b6fbba4b
Sik, V.
ce381a83-89b1-4d4c-82b0-57a0c143dd36
Hursthouse, M. B.
57a2ddf9-b1b3-4f38-bfe9-ef2f526388da
Light, M. E.
cf57314e-6856-491b-a8d2-2dffc452e161
Creber, M. L.
71d2ca9d-7d07-4571-a634-7afcb7c1ac0c
Orrell, K. G.
e291cfb7-374a-4a7f-8e30-d9513f5203c4
Osborne, A. G.
9430fd91-c186-4b98-a713-74d9b6fbba4b
Sik, V.
ce381a83-89b1-4d4c-82b0-57a0c143dd36
Hursthouse, M. B.
57a2ddf9-b1b3-4f38-bfe9-ef2f526388da
Light, M. E.
cf57314e-6856-491b-a8d2-2dffc452e161

Creber, M. L., Orrell, K. G., Osborne, A. G., Sik, V., Hursthouse, M. B. and Light, M. E. (2001) Solution fluxionality of some pyridine-2,6-dialdehydes, -diketones and -diesters when acting as bidentate ligands in rhenium(I) and platinum(IV) complexes. Crystal structure of ReBr(CO)(3)L (L = methylethyldipicolinate). Polyhedron, 20 (15-16), 1973-1982. (doi:10.1016/S0277-5387(01)00798-7).

Record type: Article

Abstract

2,6-Disubstituted pyridines, where the substituents are aldehyde, ketone or ester functions, form bidentate chelate complexes with the transition metal moieties fac-(ReX)-X-I(CO)(3) (X = halogen). 2-Substituted pyridines, where the substituents are aldehyde or ester functions, form similar types of complexes with the isoelectronic transition metal moieties fac-(ReX)-X-I(CO), and (PtXMe3)-X-IV. The fac-(ReX)-X-I(CO)(3) complexes of the 2,6-disubstituted pyridine ligands were shown by H-1 NMR spectra to undergo metallotropic shifts whereby the Re coordination switches between adjacent ON pairs of the ONO ligand donor set. Rates and activation energies of these fluxional shifts were measured by dynamic NMR bandshape analysis. Magnitudes of DeltaG(double dagger) (298.15 K) were in the range 59-64 kJ mol(-1) for the diketone and diester ligands. The dialdehyde ligand, 2,6-pyridinedicarboxaldehyde, formed an appreciably less-stable Re-I complex that was highly fluxional and showed a tendency to dissociation at ambient solution temperatures. The unsymmetrical diester ligand, methylethyldipicolinate, formed two distinct Re-I complex species in solution, in the approximate abundance ratio of 2:1, the more abundant structure involving coordination to the carbonyl of the ethyl ester function. This particular complex forms exclusively in the solid state and an X-ray crystal structure of [ReBr(CO)(3)L] (L = methylethyldipicolinate) is reported.

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Published date: 30 June 2001
Keywords: rhenium, platinum, pyridine diketones and diesters, fluxionality, dynamic nmrtricarbonyl halide-complexes, nuclear-magnetic-resonance, nmrinvestigations, derivatives, shifts, acid

Identifiers

Local EPrints ID: 19462
URI: http://eprints.soton.ac.uk/id/eprint/19462
ISSN: 0277-5387
PURE UUID: c20d6a56-9df0-469a-bcba-6f5be5a11898
ORCID for M. E. Light: ORCID iD orcid.org/0000-0002-0585-0843

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Date deposited: 13 Feb 2006
Last modified: 16 Mar 2024 03:04

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Contributors

Author: M. L. Creber
Author: K. G. Orrell
Author: A. G. Osborne
Author: V. Sik
Author: M. E. Light ORCID iD

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