Synthesis of Rhodium Complexes with Novel Perfluoroalkyl Substituted Cyclopentadienyl Ligands

Abstract

Mixtures of isomers of (perfluoroalkyl)tetramethylcyclopenta-1,3-dienes (CH 3 ) 4 C 5 H(CF 2 ) n CF 3 ( n = 3, 5, 7, 9) were synthesized as precursors of new cyclopentadienyl ligands for organotransition metal catalysis in fluorous biphase media and characterized by combination of GC-MS and 13 C NMR spectroscopy. Rhodium(III) chloro complexes [Rh{(CH 3 ) 4 C 5 (CF 2 ) n CF 3 }Cl 2 ] 2 and rhodium(I) carbonyl complexes [Rh{(CH 3 ) 4 C 5 (CF 2 ) n CF 3 }(CO) 2 ] were prepared from the cyclopentadienes and molecular structure of [Rh{(CH 3 ) 4 C 5 (CF 2 ) 5 CF 3 }Cl 2 ] 2 was determined by X-ray diffraction. The ligands are electronically close to the unsubstituted cyclopentadienyl as shown by values of carbonyl stretching frequencies in the carbonyl complexes. Neither carbonyl frequencies nor NMR chemical shifts of the complexes are substantially affected by the length of the perfluoroalkyl chain.