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Dirhodium(II) Compounds with Bridging Thienylphosphines: Studies on Reversible P,C/P,S Coordination

Authors

  • Julio Lloret Dr.,

    1. Departamento de Química Inorgánica, Facultad de Química, Universidad de Valencia, Dr. Moliner 50, 46100 Burjassot, Valencia (Spain), Fax: (+34) 963543929
    2. Anorganisch-Chemisches Institut, Uniersität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg (Germany)
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  • Francisco Estevan Dr.,

    1. Departamento de Química Inorgánica, Facultad de Química, Universidad de Valencia, Dr. Moliner 50, 46100 Burjassot, Valencia (Spain), Fax: (+34) 963543929
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  • Pascual Lahuerta Prof.,

    1. Departamento de Química Inorgánica, Facultad de Química, Universidad de Valencia, Dr. Moliner 50, 46100 Burjassot, Valencia (Spain), Fax: (+34) 963543929
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  • Pipsa Hirva Prof.,

    1. Department of Chemistry, University of Joensuu, P.O. Box 111, FIN-80101 Joensuu (Finland), Fax: (+358) 132513390
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  • Julia Pérez-Prieto Prof.,

    1. Departamento de Química Orgánica/Instituto de Ciencia Molecular, Polígono La Coma s/n, 46980 Paterna, Valencia (Spain), Fax: (+34) 963543274
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  • Mercedes Sanaú Dr.

    1. Departamento de Química Inorgánica, Facultad de Química, Universidad de Valencia, Dr. Moliner 50, 46100 Burjassot, Valencia (Spain), Fax: (+34) 963543929
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Abstract

Monocyclometalated compound [Rh2{(C8H4S)P(C8H5S)2}(CH3CO2H)2(O2CCH3)3] (1 a) and bis-cyclometalated compound [Rh2{(C8H4S)P(C8H5S)2}2(CH3CO2H)2(O2CCH3)2] (2 a) have been isolated from the reaction of dirhodium tetraacetate and tris(2-benzo[b]thienyl)phosphine (2 BTP) using low acidic solutions. By contrast, in pure acetic acid the reaction of Rh2(O2CCH3)4 with 2 BTP and tris(2-thienyl)phosphine (2 TP), followed by replacement of the axial acetate ligands by chlorides, led to [Rh2{(2-C8H5S)P(2-C8H5S)2}2Cl2(O2CCH3)2] (3 b) and [Rh2{(2-C4H3S)P(C4H3S)2}2Cl2(O2CCH3)2] (5 b), respectively. These new dirhodium(II) compounds possess equatorial bridging ligands in a phosphorous–sulfur (P,S) coordination mode. The reversible switching between the P,C and P,S bonding mode of the phosphine has been studied in the monocyclometalated [Rh2{(C4H2S)P(C4H3S)2}(CH3CO2H)2(O2CCH3)3] (6 a), which was selectively transformed into compound [Rh2{(2-C4H3S)P(C4H3S)2}(CF3SO3)(CH3CO2H)(O2CCH3)3] (7 c) in triflic acid media. Remarkably, compound 7 c reverts to the starting compound 6 a upon treatment with sodium acetate. Theoretical DFT calculations for both the P,C/P,S rearrangement and the base-promoted reversion have been performed to explain the experimental findings. Data suggest the P,C/P,S rearrangement occurs by means of a “concerted protonation–demetalation mechanism” followed by η2 coordination of the thienyl ring and subsequent isomerization to the S-η1-coordination mode. In the reversion reaction, the base coordinated at the axial position would promote a concerted metalation–deprotonation mechanism.

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