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The addition of small molecules to (η-C5H5)2Rh2(CO)(CF3C2CF3)

Dickson, R.S., McLure, F.I. and Nesbit, R.J. (1988) The addition of small molecules to (η-C5H5)2Rh2(CO)(CF3C2CF3). Journal of Organometallic Chemistry, 349 (3). pp. 413-426.

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Reaction occurs immediately when solutions of (η-C5H5)2Rh2(μ-CO)(μ-η2-CF3C2CF3) (1) in hexane are treated with HCCR (R = H, CF3 or Ph), and the cyclobutenyl complexes (η-C5H5)2Rh2(μ-CO)[μ-η1,η3-C4(CF3)2HR] (2) separate in near quantitative yield. CO is lost fairly rapidly from solutions of 2 in polar organic solvents, and the metallacyclopentadiene complexes (η-C5H5)2Rh2[μ-η2,η4-C4(CF3)2HR] (3) are formed. The reactions between HCCR (R = Pr or CH2CO2Me) and 1 in hexane are also fast, but no precipitate is formed; infrared spectroscopy indicates that 2 (R = Pr or CH2CO2Me) is present in the reaction solution, but there is rapid conversion into 3 (ca. 80% yield after TLC work up). Slower reactions (2–5 min) occur between 1 and HCCR (R = CH2CH2CH2CCH or CMe=CH2) in hexane, and again all the products remain in solution. It is possible to separate 2 (R = CH2CH2CH2CCH or CMeCH2) (up to 65% yield obtained) from the corresponding 3 by immediate TLC, but 2 is converted fairly rapidly into 3 when left in solution. The reaction between 1 and HCCSiMe3 is significantly slower (ca. 15 min), and gives 3 (R = SiMe3) (64% yield) and (η-C5H5)2Rh2(CO)2CF3C2CF3 (21%) as major products. Another product, spectroscopically identified as (η-C5H5)2Rh2(μ-CO)[μ-C(O)C(CF3)C(CF3)](μ-HC2SiMe3) (7) can be isolated in significant amount only when TLC of the reaction solution is performed within 10 min of mixing the reactants. Spectroscopic analysis indicates complete regioselectivity in the formation of all metallacyclopentadiene complexes 3, with the H and R groups (from HCCR) located in the 3- and 2-positions respectively of the 1-metallacyclopentadiene ring.

Item Type: Journal Article
Publisher: Elsevier BV
Copyright: © 1988 Elsevier B.V.
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