Addition of small molecules to (η-C5H5)2Rh 2(μ-CO)(μ-CF3C2CF3). 7. Formation and properties of several isocyanide complexes (η-C5H5)2Rh 2(CO)(CNR)(μ-CF3C2CF3), crystal and molecular structure ...

John W. Bixler, Alan M. Bond, Ron S. Dickson, Gary D. Fallon, Rhonda J. Nesbit, Helen Pateras

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Abstract

Full title: Addition of small molecules to (η-C5H5)2Rh 2(μ-CO)(μ-CF3C2CF3). 7. Formation and properties of several isocyanide complexes (η-C5H5)2Rh 2(CO)(CNR)(μ-CF3C2CF3), crystal and molecular structure of the complex with R = 2,6-Me2C6H3, and structure and substituent influences on the electrochemistry of (η-C5H5)2Rh2(CO)L(μ-CF 3C2CF3) (L = CO, PPh3, or CN-t-Bu). The isocyanides CNR (R = Et, i-Pr, Cy, 2,6-Me2C6H3) add coordinatively to (η-C5H5)2Rh 2(μ-CO)(μ-CF3C2CF3) to give (η-C5H5)2Rh 2(CO)(CNR)(μ-CF3C2CF3). Spectroscopic results indicate that the CO and CNR ligands are both terminal. The complexes with R = Et, i-Pr, and Cy rearrange to isomeric species when left in solution, but those with R = 2,6-Me2C6H3 and t-Bu are stable to this rearrangement. The structure of the complex with R = 2,6-Me2C6H3 has been determined by X-ray crystallography. Crystal data: C24H19F6NORh2, Mr 657.9, orthorhombic, Pbca, a = 17.950 (8) Å, b = 17.161 (8) Å, c = 15.273 (7) Å, Z = 8, final R = 0.061 for 2306 "observed" reflections. The molecular structure reveals a trans arrangement of the CO and CNR ligands and an orientation of the alkyne parallel to the Rh-Rh bond. The electrochemical behavior of several complexes (η-C5H5)2Rh2(CO)L(μ-CF 3C2CF3) (L = CO, CN-t-Bu, PPh3) has been determined and contrasted with that already reported for (η-C5H5)2Rh 2(μ-CO)(μ-CF3C2CF3). Reduction and oxidation of (η-C5H5)2Rh2(CO) 2(μ-CF3C2CF3) are both more difficult to achieve than with (η-C5H5)2Rh 2(μ-CO)(μ-CF3C2CF3), and most of the redox intermediates formed are unstable. With (η-C5H5)2Rh2(CO) 2(μ-CF3C2CF3), the reduction and oxidation pathways are critically dependent on the orientation of the carbonyl groups. Oxidation of (η-C5H5)2Rh2(CO)L(μ-CF 3C2CF3) (L = CN-t-Bu, PPh3) leads to numerous pathways for rearrangement after electron transfer and to the formation of electrode- and solvent-dependent redox behavior. Chemical oxidation of the complexes (η-C5H5)2Rh 2(CO)(CNR)(μ-CF3C2CF3) with Me3NO gives the bridging acrylamide complexes (η-C5H5)2Rh2{μ-η 3-N(R)C(O)C(CF3)C(CF3)}. The same complexes are obtained upon treatment of (η-C5H5)2Rh2(CO) 2(μ-CF3C2CF3) with the isocyanates RNCO (R = Me, t-Bu, p-MeC6H4).

Original languageEnglish
Pages (from-to)2508-2517
Number of pages10
JournalOrganometallics
Volume6
Issue number12
Publication statusPublished - 1 Dec 1987

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