Dirhodium(II) Compounds with Bridging Thienylphosphines: Studies on Reversible P,C/P,S Coordination |
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| Authors: | Julio Lloret Dr Francisco Estevan Dr Pascual Lahuerta Prof Pipsa Hirva Prof Julia Pérez‐Prieto Prof Mercedes Sanaú Dr |
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| Institution: | 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, Uniersit?t Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg (Germany);3. Department of Chemistry, University of Joensuu, P.O. Box 111, FIN‐80101 Joensuu (Finland), Fax: (+358)?132513390;4. Departamento de Química Orgánica/Instituto de Ciencia Molecular, Polígono La Coma s/n, 46980 Paterna, Valencia (Spain), Fax: (+34)?963543274 |
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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‐benzob]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‐C8H5 S )P(2‐C8H5S)2}2Cl2(O2CCH3)2] ( 3 b ) and Rh2{(2‐C4H3 S )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‐C4H3 S )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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| Keywords: | C?H activation coordination modes metalation rhodium thienylphosphines |
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