(2,4,6-Tris(trifluoromethyl)phenyl)palladium(II) Complexes

Abstract

Complexes containing one or two Fmes ligands (Fmes = 2,4,6-tris(trifluoromethyl)phenyl = nonafluoromesityl) either trans or cis are obtained by treating palladium(II) chloro complexes with Li(Fmes): trans -[PdCl 2 L 2 ] (L = tetrahydrothiophene (tht), PPh 3 ) lead to trans -[Pd(Fmes)ClL 2 ] (L = tht, PPh 3 ) or trans -[Pd(Fmes) 2 L 2 ] (L = tht); [PdCl 2 (L-L)] (L-L = 1,5-cyclooctadiene, 2,2‘-bipyridine) give [Pd(Fmes)Cl(L-L)] (L-L = COD, bipy) or [Pd(Fmes) 2 (bipy)]. The structures of two complexes containing two Fmes ligands in trans and cis arrangement, trans -[Pd(Fmes) 2 (tht) 2 ] ( 2 ) and [Pd(Fmes) 2 (bipy)] ( 6 ), respectively, have been determined by X-ray diffraction. In spite of the severe steric congestion the complexes are four coordinated. Distortions due to the bulkiness of the ortho substituents and short Pd···F 3 C- ortho distances are observed. The high degree of steric crowding is also responsible for slow rotation around the Pd−P bonds in the complex trans -[Pd(Fmes)Cl(PPh 3 ) 2 ]. Δ G ⧧ associated with this motion is 12.8 kcal mol - 1, one of the highest values reported so far for rotation around M−PPh 3 bonds. Complexes 2 and 6 are redox inactive by cyclic voltammetry in the range −1.8 to +1.8 V.