Bis(ketopyrrolyl) complexes of Co(II) stabilised by trimethylphosphine ligands

S A Carabineiro, P T Gomes, L F Veiros, C Freire, L C J Pereira, R T Henriques, J E Warren, Sofia I Pascu

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Abstract

2-Formylpyrrole and 2-acetylpyrrole were deprotonated with NaH to give the corresponding Na salts 1a and 1b, respectively. The reactivity of these salts towards cobalt chloride compounds was studied. The resulting new bis(ketopyrrolyl) Co(II) 19-electron complexes [Co(kappa(2)N, O-2-NC(4)H(3)C(R)=O)(2)(PMe(3))(2)] (R = H 2a, and Me 2b) were characterised by single crystal X-ray diffraction, to show an octahedral geometry with the PMe(3) ligands in trans positions to each other, and two bidentate ketopyrrolyl ligands occupying the remaining coordination positions in a transoid conformation. Powder and solution magnetic susceptibility measurements together with EPR and UV/Vis/NIR spectra revealed a low-spin ground state (d(z)2, S = 1/2) for Co(II) in these compounds. Analysis of the EPR superhyperfine couplings suggested that the longer distances (z axis) of the hexacoordinate Co coordination sphere are occupied by the keto-O atoms of the bidentate ligand, leaving the pyrrolyl N and the phosphine P atoms within the equatorial plane. This is confirmed by means of DFT calculations, which also indicate that the most thermodynamically stable isomers are low-spin (S = 1/2) complexes with coordination geometries corresponding to the molecular structures obtained by X-ray crystallography.
Original languageEnglish
Pages (from-to)5460-5470
Number of pages11
JournalDalton Transactions
Volume2007
Issue number46
DOIs
Publication statusPublished - 2007

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phosphine
Ligands
Paramagnetic resonance
Salts
Atoms
Geometry
X ray crystallography
Magnetic susceptibility
Discrete Fourier transforms
Isomers
Powders
Ground state
Molecular structure
Conformations
Single crystals
X ray diffraction
Electrons
2-acetylpyrrole
cobaltous chloride

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Carabineiro, S. A., Gomes, P. T., Veiros, L. F., Freire, C., Pereira, L. C. J., Henriques, R. T., ... Pascu, S. I. (2007). Bis(ketopyrrolyl) complexes of Co(II) stabilised by trimethylphosphine ligands. Dalton Transactions, 2007(46), 5460-5470. https://doi.org/10.1039/b710162g

Bis(ketopyrrolyl) complexes of Co(II) stabilised by trimethylphosphine ligands. / Carabineiro, S A; Gomes, P T; Veiros, L F; Freire, C; Pereira, L C J; Henriques, R T; Warren, J E; Pascu, Sofia I.

In: Dalton Transactions, Vol. 2007, No. 46, 2007, p. 5460-5470.

Research output: Contribution to journalArticle

Carabineiro, SA, Gomes, PT, Veiros, LF, Freire, C, Pereira, LCJ, Henriques, RT, Warren, JE & Pascu, SI 2007, 'Bis(ketopyrrolyl) complexes of Co(II) stabilised by trimethylphosphine ligands', Dalton Transactions, vol. 2007, no. 46, pp. 5460-5470. https://doi.org/10.1039/b710162g
Carabineiro SA, Gomes PT, Veiros LF, Freire C, Pereira LCJ, Henriques RT et al. Bis(ketopyrrolyl) complexes of Co(II) stabilised by trimethylphosphine ligands. Dalton Transactions. 2007;2007(46):5460-5470. https://doi.org/10.1039/b710162g
Carabineiro, S A ; Gomes, P T ; Veiros, L F ; Freire, C ; Pereira, L C J ; Henriques, R T ; Warren, J E ; Pascu, Sofia I. / Bis(ketopyrrolyl) complexes of Co(II) stabilised by trimethylphosphine ligands. In: Dalton Transactions. 2007 ; Vol. 2007, No. 46. pp. 5460-5470.
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AB - 2-Formylpyrrole and 2-acetylpyrrole were deprotonated with NaH to give the corresponding Na salts 1a and 1b, respectively. The reactivity of these salts towards cobalt chloride compounds was studied. The resulting new bis(ketopyrrolyl) Co(II) 19-electron complexes [Co(kappa(2)N, O-2-NC(4)H(3)C(R)=O)(2)(PMe(3))(2)] (R = H 2a, and Me 2b) were characterised by single crystal X-ray diffraction, to show an octahedral geometry with the PMe(3) ligands in trans positions to each other, and two bidentate ketopyrrolyl ligands occupying the remaining coordination positions in a transoid conformation. Powder and solution magnetic susceptibility measurements together with EPR and UV/Vis/NIR spectra revealed a low-spin ground state (d(z)2, S = 1/2) for Co(II) in these compounds. Analysis of the EPR superhyperfine couplings suggested that the longer distances (z axis) of the hexacoordinate Co coordination sphere are occupied by the keto-O atoms of the bidentate ligand, leaving the pyrrolyl N and the phosphine P atoms within the equatorial plane. This is confirmed by means of DFT calculations, which also indicate that the most thermodynamically stable isomers are low-spin (S = 1/2) complexes with coordination geometries corresponding to the molecular structures obtained by X-ray crystallography.

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