Synthesis and structural studies of perfluoroalkyl-rhodium and iridium(iii) compounds containing tris(pyrazolyl)borateligands

Abstract

Oxidative addition of perfluorobenzyl iodide to TpRh(C₂H₄)₂ [Tp = tris(pyrazolyl)borate] affords TpRh(CF₂C₆F₅)(C₂H₄)I, from which the ethylene ligand can be displaced by CO to afford TpRh(CF₂C₆F₅)(CO)I. Similar reaction of perfluorobenzyl iodide with TpIr(CO)₂ or Tp*M(CO)₂ [Tp* = tris(3,5-dimethylpyrazolyl)borate; M = Rh, Ir] affords Tp*M(CF₂C₆F₅)(CO)I. Displacement of CO from the carbonyl complexes using PMe₃ is not clean and yields a mixture of compounds. However, displacement of ethylene from TpRh(CF₂C₆F₅)(C₂H₄)I using PMe₃ cleanly affords TpRh(CF₂C₆F₅)(PMe₃)I. Similar oxidative addition reactions of perfluoro-n-propyl iodide afford TpIr(C₃F₇)(CO)I, TpRh(C₃F₇)(CO)I, Tp*Rh(C₃F₇)(CO)I, Tp*Rh(C₃F₇)(PMe₃)I, and TpM(C₃F₇)(C₂H₄)I [M = Rh, Ir]. While displacement of ethylene from TpRh(C₃F₇)(C₂H₄)I by PMe₃, to give TpRh(C₃F₇)(PMe₃)I is facile, the corresponding reaction of the iridium analogue affords the salt [TpM(C₃F₇)(C₂H₄)(PMe₃)]⁺I⁻. Ethylene rotation barriers and Co stretching frequencies in these compounds are discussed. The molecular structures of TpIr(CF₂C₆F₅)(CO)I, TpRh(CF₂C₆F₅)(PMe₃)I, and TpRh(C₃F₇)(PMe₃)I have been determined, and are also discussed in detail.