(2,4,6-TRIS(TRIFLUOROMETHYL)PHENYL)PALLADIUM(II) COMPLEXES

Complexes containing one or two Fmes ligands (Fmes = 2,4,6-tris(triflu oromethyl)phenyl nonafluoromesityl) either trans or cis are obtained b y 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); [PdCl2( 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 com plexes 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 ster ic congestion the complexes are four coordinated. Distortions due to t he bulkiness of the ortho substituents and short Pd .. F3C-ortho dista nces are observed. The high degree of steric crowding is also responsi ble for slow rotation around the Pd-P bonds in the complex trans-[Pd(F mes)Cl(PPh(3))(2)]. Delta G(double dagger) associated with this motion is 12.8 kcal mol(-1), one of the highest values reported so far for r otation around M-PPh(3) bonds. Complexes 2 and 6 are redox inactive by cyclic voltammetry in the range -1.8 to +1.8 V.