Comproportionation reaction and hindered rotation of coordinated pyridine rings in an acetate-bridged tetraplatinum(II) cluster with pyridine-based ligands in the cluster plane

Tadashi Yamaguchi, Akira Shibata, Tasuku Ito

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Abstract

A series of pyridine-substituted derivatives of octaacetatotetraplatinum(II), [Pt4(CH3COO)8-n(L)2n]n+ (L = 4-dimethylaminopyridine (dmap), pyridine (py), 4-cyanopyridine (cpy); n = 1 - 4) were prepared, and the tetra- and octasubstituted forms (n = 2 and 4) were isolated. 1H NMR spectra showed that this type of cluster undergoes a comproportionation reaction. Reactions between clusters in which n = 0 and 2, n = 0 and 4, and n = 2 and 4 afforded Pt4 clusters with n = 1, 2, and 3, respectively, as a main product in acetonitrile. The dmap-substituted clusters, trans-[Pt4(CH3COO)6(dmap)4](ClO 4)2 · 3CH3NO2 (3a(ClO4)2·3CH3NO2) and [Pt4(CH3COO)4(dmap)8](ClO 4)4·4H2O (5a(ClO4)4·4H2O), have been structurally characterized. Both 3a and 5a have a square-planar cluster core comprised of four PtII ions, and all eight out-of-plane coordination sites are occupied by acetate ligands in a bridging mode. In 5a, all of the in-plane sites are occupied by dmap ligands. In 3a, four dmap ligands occupy the coordination sites at the two mutually opposite edges of the square planar cluster skeleton, giving a trans tetrasubstituted form of [Pt4(CH3COO)8] (1). In octasubstituted 5a, adjacent dmap ligands are so closely arranged that the Pt-N distances (2.20(3), 2.30(3) Å) are longer than those in tetrasubstituted 3a (2.13(1), 2.15(1) Å) and related Pt4 clusters. Furthermore, rotation of the dmap ligand about the Pt-N bond in 5a was restricted, and the rate constant of the rotation was 4.5s-1 at 20°C from dynamic NMR study. Cluster [Pt4(CH3COO)5-(dmap)6]3+ (4a) also exhibited similar hindered rotation with the rate constants of 2.0s-1, 12s-1 and ≈ 104s-1 at 20°C depending on the coordination sites of the dmap ligands in 4a.

Original languageEnglish
Pages (from-to)5409-5418
Number of pages10
JournalChemistry - A European Journal
Volume7
Issue number24
Publication statusPublished - 2001 Dec 17
Externally publishedYes

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Pyridine
Acetates
Ligands
Rate constants
Nuclear magnetic resonance
Acetonitrile
pyridine
4-dimethylaminopyridine
Derivatives
Ions

Keywords

  • Cluster compounds
  • Comproportionation
  • Metal-metal interactions
  • Platinum
  • Restricted rotation

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

@article{97146fbfb87f4fc9b65231f692500df1,
title = "Comproportionation reaction and hindered rotation of coordinated pyridine rings in an acetate-bridged tetraplatinum(II) cluster with pyridine-based ligands in the cluster plane",
abstract = "A series of pyridine-substituted derivatives of octaacetatotetraplatinum(II), [Pt4(CH3COO)8-n(L)2n]n+ (L = 4-dimethylaminopyridine (dmap), pyridine (py), 4-cyanopyridine (cpy); n = 1 - 4) were prepared, and the tetra- and octasubstituted forms (n = 2 and 4) were isolated. 1H NMR spectra showed that this type of cluster undergoes a comproportionation reaction. Reactions between clusters in which n = 0 and 2, n = 0 and 4, and n = 2 and 4 afforded Pt4 clusters with n = 1, 2, and 3, respectively, as a main product in acetonitrile. The dmap-substituted clusters, trans-[Pt4(CH3COO)6(dmap)4](ClO 4)2 · 3CH3NO2 (3a(ClO4)2·3CH3NO2) and [Pt4(CH3COO)4(dmap)8](ClO 4)4·4H2O (5a(ClO4)4·4H2O), have been structurally characterized. Both 3a and 5a have a square-planar cluster core comprised of four PtII ions, and all eight out-of-plane coordination sites are occupied by acetate ligands in a bridging mode. In 5a, all of the in-plane sites are occupied by dmap ligands. In 3a, four dmap ligands occupy the coordination sites at the two mutually opposite edges of the square planar cluster skeleton, giving a trans tetrasubstituted form of [Pt4(CH3COO)8] (1). In octasubstituted 5a, adjacent dmap ligands are so closely arranged that the Pt-N distances (2.20(3), 2.30(3) {\AA}) are longer than those in tetrasubstituted 3a (2.13(1), 2.15(1) {\AA}) and related Pt4 clusters. Furthermore, rotation of the dmap ligand about the Pt-N bond in 5a was restricted, and the rate constant of the rotation was 4.5s-1 at 20°C from dynamic NMR study. Cluster [Pt4(CH3COO)5-(dmap)6]3+ (4a) also exhibited similar hindered rotation with the rate constants of 2.0s-1, 12s-1 and ≈ 104s-1 at 20°C depending on the coordination sites of the dmap ligands in 4a.",
keywords = "Cluster compounds, Comproportionation, Metal-metal interactions, Platinum, Restricted rotation",
author = "Tadashi Yamaguchi and Akira Shibata and Tasuku Ito",
year = "2001",
month = "12",
day = "17",
language = "English",
volume = "7",
pages = "5409--5418",
journal = "Chemistry - A European Journal",
issn = "0947-6539",
publisher = "Wiley-VCH Verlag",
number = "24",

}

TY - JOUR

T1 - Comproportionation reaction and hindered rotation of coordinated pyridine rings in an acetate-bridged tetraplatinum(II) cluster with pyridine-based ligands in the cluster plane

AU - Yamaguchi, Tadashi

AU - Shibata, Akira

AU - Ito, Tasuku

PY - 2001/12/17

Y1 - 2001/12/17

N2 - A series of pyridine-substituted derivatives of octaacetatotetraplatinum(II), [Pt4(CH3COO)8-n(L)2n]n+ (L = 4-dimethylaminopyridine (dmap), pyridine (py), 4-cyanopyridine (cpy); n = 1 - 4) were prepared, and the tetra- and octasubstituted forms (n = 2 and 4) were isolated. 1H NMR spectra showed that this type of cluster undergoes a comproportionation reaction. Reactions between clusters in which n = 0 and 2, n = 0 and 4, and n = 2 and 4 afforded Pt4 clusters with n = 1, 2, and 3, respectively, as a main product in acetonitrile. The dmap-substituted clusters, trans-[Pt4(CH3COO)6(dmap)4](ClO 4)2 · 3CH3NO2 (3a(ClO4)2·3CH3NO2) and [Pt4(CH3COO)4(dmap)8](ClO 4)4·4H2O (5a(ClO4)4·4H2O), have been structurally characterized. Both 3a and 5a have a square-planar cluster core comprised of four PtII ions, and all eight out-of-plane coordination sites are occupied by acetate ligands in a bridging mode. In 5a, all of the in-plane sites are occupied by dmap ligands. In 3a, four dmap ligands occupy the coordination sites at the two mutually opposite edges of the square planar cluster skeleton, giving a trans tetrasubstituted form of [Pt4(CH3COO)8] (1). In octasubstituted 5a, adjacent dmap ligands are so closely arranged that the Pt-N distances (2.20(3), 2.30(3) Å) are longer than those in tetrasubstituted 3a (2.13(1), 2.15(1) Å) and related Pt4 clusters. Furthermore, rotation of the dmap ligand about the Pt-N bond in 5a was restricted, and the rate constant of the rotation was 4.5s-1 at 20°C from dynamic NMR study. Cluster [Pt4(CH3COO)5-(dmap)6]3+ (4a) also exhibited similar hindered rotation with the rate constants of 2.0s-1, 12s-1 and ≈ 104s-1 at 20°C depending on the coordination sites of the dmap ligands in 4a.

AB - A series of pyridine-substituted derivatives of octaacetatotetraplatinum(II), [Pt4(CH3COO)8-n(L)2n]n+ (L = 4-dimethylaminopyridine (dmap), pyridine (py), 4-cyanopyridine (cpy); n = 1 - 4) were prepared, and the tetra- and octasubstituted forms (n = 2 and 4) were isolated. 1H NMR spectra showed that this type of cluster undergoes a comproportionation reaction. Reactions between clusters in which n = 0 and 2, n = 0 and 4, and n = 2 and 4 afforded Pt4 clusters with n = 1, 2, and 3, respectively, as a main product in acetonitrile. The dmap-substituted clusters, trans-[Pt4(CH3COO)6(dmap)4](ClO 4)2 · 3CH3NO2 (3a(ClO4)2·3CH3NO2) and [Pt4(CH3COO)4(dmap)8](ClO 4)4·4H2O (5a(ClO4)4·4H2O), have been structurally characterized. Both 3a and 5a have a square-planar cluster core comprised of four PtII ions, and all eight out-of-plane coordination sites are occupied by acetate ligands in a bridging mode. In 5a, all of the in-plane sites are occupied by dmap ligands. In 3a, four dmap ligands occupy the coordination sites at the two mutually opposite edges of the square planar cluster skeleton, giving a trans tetrasubstituted form of [Pt4(CH3COO)8] (1). In octasubstituted 5a, adjacent dmap ligands are so closely arranged that the Pt-N distances (2.20(3), 2.30(3) Å) are longer than those in tetrasubstituted 3a (2.13(1), 2.15(1) Å) and related Pt4 clusters. Furthermore, rotation of the dmap ligand about the Pt-N bond in 5a was restricted, and the rate constant of the rotation was 4.5s-1 at 20°C from dynamic NMR study. Cluster [Pt4(CH3COO)5-(dmap)6]3+ (4a) also exhibited similar hindered rotation with the rate constants of 2.0s-1, 12s-1 and ≈ 104s-1 at 20°C depending on the coordination sites of the dmap ligands in 4a.

KW - Cluster compounds

KW - Comproportionation

KW - Metal-metal interactions

KW - Platinum

KW - Restricted rotation

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JO - Chemistry - A European Journal

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