Addition of Small Molecules To (i7-c₅h5)2rh2(m-co)(m-cf3c₂cf3): 7:¹Formation And Properties of Several Isocyanide Complexes (7i-c₅h₅)2rh₂(co){cnr)(p-cf₃c₂cf₃), Crystal And Molecular Structure of The Complex With R = 2,6-me₂c₆h₃, And Structure And Substituent Influences On The Electrochemistry of (77-c₅h₅)2rh2(co)l(m-cf₃c₂cf3) (l = Co, Pph₃, Or Cn-f-bu)

The isocyanides CNR (R = Et, i-Pr, Cy, 2,6-Me2C6H3) add coordinatively to (7?-C5H5)2Rh2bt-CO) (?- CF3C2CF3) to give (j7-C5H5)2Rh2(CO)(CNR)-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 f-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) Á, b = 17.161 (8) A, c = 15.273 (7) Á, 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 (7)-C5H5)2Rh2(CO)LU-CF3C2CF3) (L = CO, CN-i-Bu, PPh3) has been determined and contrasted with that already reported for (i7-C6Hs)2Rh2-CO) CF3C2CF3). Reduction and oxidation of (77-C5H5)2Rh2(CO)2-CF3C2CF3) are both more difficult to achieve than with (7;-C5H5)2Rh2- (?-CO) (?- 302 3), and most of the redox intermediates formed are unstable. With (jj-C5H6)2Rh2- (CO)2-CF3C2CF3), the reduction and oxidation pathways are critically dependent on the orientation of the carbonyl groups. Oxidation of (7j-C5H5)2Rh2(CO)L-CF3C2CF3) (L = CN-i-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 (r)-C5H5)2Rh2(CO)(CNR)-CF3C2CF3) with Me3NO gives the bridging acrylamide complexes (7)-C6H5)2Rh2-?)3-N(R)C(0)C(CF3)C(CF3)|. The same complexes are obtained upon treatment of (?7-C5H5)2Rh2(CO)2U-CF3C2CF3) with the isocyanates RNCO (R = Me, t-Bu, p-MeC6H4).