Redox-induced κ2–κ3 isomerisation in hydrotris(pyrazolyl)boratorhodium complexes: synthesis, structure and ESR spectroscopy of stabilised rhodium(II) species

Neil G. Connelly; David J. H. Emslie; William E. Geiger; Owen D. Hayward; Emma B. Linehan; A. Guy Orpen; Michael J. Quayle; Philip H. Rieger

doi:10.1039/B008131K

Redox-induced κ²–κ³ isomerisation in hydrotris(pyrazolyl)boratorhodium complexes: synthesis, structure and ESR spectroscopy of stabilised rhodium(II) species

Neil G. Connelly,*^a David J. H. Emslie,^a William E. Geiger,^b Owen D. Hayward,^a Emma B. Linehan,^a A. Guy Orpen,^a Michael J. Quayle^a and Philip H. Rieger^c

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* Corresponding authors

^a School of Chemistry, University of Bristol, Bristol, UK

^b Department of Chemistry, University of Vermont, Burlington, USA

^c Department of Chemistry, Brown University, Rhode Island, USA

Abstract

The complexes [Rh(CO)LTp′] {Tp′ = HBR₃, R = 3,5-dimethylpyrazolyl; L = PPh₃2, PCy₃3, L = P(NMe₂)₃4, P(C₆H₄Me-p)₃5 or P(C₆H₄Me-m)₃6}, prepared from [Rh(CO)₂Tp′] 1 and L, and [Rh(PPh₃)₂L′] [L′ = Tp′ 8, Tp 9 or B(pz)₄10 {Tp = HB(pz)₃, pz = pyrazolyl}] and [Rh(dppe)Tp′] 11, prepared from [{Rh(μ-Cl)(PPh₃)₂}₂] or [{Rh(μ-Cl)(dppe)}₂] and KL′, adopt four-co-ordinate κ² structures, confirmed in the cases of 2–4, 6 and 8 by X-ray structural studies. By contrast, complex [Rh(CO){P(OPh)₃}Tp′] 7 has a distorted five-co-ordinate square pyramidal structure with a long Rh ⋯ N contact [2.764(2) Å] in the apical site and an essentially planar Rh(CO)PN₂ basal plane. Each complex undergoes fluxional processes on the NMR timescale. One-electron oxidation of 1–11 gives the κ³ rhodium(II) cations 1⁺++–11⁺+; the crystal structures of salts of 2⁺ and 8⁺ confirm stabilisation of the unusual rhodium(II) oxidation state by axial co-ordination of the third pyrazolyl ring as a result of oxidatively induced κ²–κ³ isomerisation. These structures and ESR spectroscopy are consistent with a five-co-ordinate square pyramidal geometry with the unpaired electron in a σ* Rh–N_axial orbital.

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DOI: https://doi.org/10.1039/B008131K
Article type: Paper
Submitted: 09 Oct 2000
Accepted: 22 Dec 2000
First published: 14 Feb 2001

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J. Chem. Soc., Dalton Trans., 2001, 670-683

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Redox-induced κ²–κ³ isomerisation in hydrotris(pyrazolyl)boratorhodium complexes: synthesis, structure and ESR spectroscopy of stabilised rhodium(II) species

N. G. Connelly, D. J. H. Emslie, W. E. Geiger, O. D. Hayward, E. B. Linehan, A. G. Orpen, M. J. Quayle and P. H. Rieger, J. Chem. Soc., Dalton Trans., 2001, 670 DOI: 10.1039/B008131K

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Journal of the Chemical Society, Dalton Transactions

Redox-induced κ²–κ³ isomerisation in hydrotris(pyrazolyl)boratorhodium complexes: synthesis, structure and ESR spectroscopy of stabilised rhodium(II) species

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Redox-induced κ²–κ³ isomerisation in hydrotris(pyrazolyl)boratorhodium complexes: synthesis, structure and ESR spectroscopy of stabilised rhodium(II) species

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