202352-03-2Relevant academic research and scientific papers
3,5-dichlorotrifluorophenyl complexes, aryl derivatives with simple 19F NMR structural probes. The synthesis of general precursors for Pd- and Pt complexes
Espinet, Pablo,Martinez-Ilarduya, Jesus M.,Perez-Briso, Celeste,Casado, Arturo L.,Alonso, M. Aranzazu
, p. 9 - 20 (2007/10/03)
High yield methods for the synthesis of cis-[MR2(COD)] (M=Pd, Pt; R=3,5-C6Cl2F3), cis-[MR2(THF)2] (M=Pd; Pt), trans-[PdR2L2] (L=tht; SMe2), trans-[PtR2(SMe2)2], and [M2(μ-Cl)2R2L2] (M=Pd, L=NCPh, tht, SMe2; M=Pt, L=tht) are reported. These complexes are general precursors for the preparation of other complexes containing cis-MR2, trans-MR2 and MClR moieties in almost quantitative yields. Thus, by displacement of COD, THF, tht or SMe2 by other ligands, almost any isomer of any complex with one or two aryl rings can be prepared. The 19F NMR spectra of these complexes are simple compared to those of other polyfluorophenyl groups, and some examples of the spectral advantages of this partially fluorinated ligand are given.
A novel reversible aryl exchange involving two organometallics: Mechanism of the gold(I)-catalyzed isomerization of trans-[PdR2L2] complexes (R = Aryl, L = SC4H8)
Casado, Arturo L.,Espinet, Pablo
, p. 3677 - 3683 (2008/10/08)
[AuR1(tht)] (3a) (R1 = 3,5-C6Cl2F3, tht = tetrahydrothiophene) very efficiently catalyzes the isomerization of trans-[Pd(R1)2(tht)2] (1a) to cis-[Pd(R1)2(tht)2] in CDCl3. The 19F NMR kinetic study leads to the first-order rate law riso = kiso[1a] = (kspo + kcat[3a])[1a], where kspo = (1.50 ± 0.03) × 10-6 s-1 and kcat = a/(b + [tht]) with a = (1.32 ± 0.07) × 10-4 s-1 and b = (30 ± 0.2) × 10-5 mol L-1 (at 304.4 K). The reaction of 1a and [AuR2(tht)] (R2 = C6F5) yields cis-[PdR1R2(tht)2] and 3a, evidencing that the catalyzed isomerization takes place with aryl-group exchange between Pd(II) and Au(I). An associative mechanism passing through R-bridged intermediates [(tht)(R1)2Pd(μ-R2)Au(tht)] and a donor-acceptor activated . complex [(tht)(R1)2(R2)Pd→Au(tht)]? is proposed. The results suggest that the associative displacement of tht from 1a by the nucleophilic arylgold(I) complex to give [(tht)(R1)2Pd(μ-R2)Au(tht)] is the rate-determining step (k1). This is supported by the typical bimolecular activation parameters that were found: Δ1? = 56.4 ± 1.6 kJ mol-1 and ΔS1? = -46 ± 6 J K-1 mol-1.
An aryl exchange reaction with full retention of configuration of the complexes: Mechanism of the aryl exchange between [PdR2L2] complexes in chloroform (R = pentahalophenyl, L = thioether)
Casado, Arturo L.,Casares, Juan A.,Espinet, Pablo
, p. 5730 - 5736 (2008/10/08)
The complexes [Pd(3,5-C6Cl2F3)2L2] and [Pd(C6F5)2L2] (L = SC4H8 (tht), or SMe2) react in CCl3D to give a mixture also containing the heteroaryl products [Pd(3,5-C6Cl2F3)(C6F 5)L2], whereas for L = PPh3, AsPh3, 2-picoline, 4-picoline, or 1/2COD, this exchange is not observed. The 19F NMR kinetic study supports that the scrambling of the aryl groups takes place with retention of configuration at both Pd centers via a triply-bridged binuclear activated complex [L(C6Cl2F3)Pd(μ-C6Cl 2F3)(μ-C6F5)(μ-L)Pd(C 6F5)L]?. The aryl double bridge is supported by a bridging S-donor ligand facilitating an otherwise difficult exchange (not observed for other weak L ligands, such as picolines, lacking a second lone pair). This constitutes the first reported example of reversible migration of σ-C-bonded groups between bis-organo Pd(II) complexes proceeding without cis-trans isomerization. The isomerization process is also observed, occurring at a much slower rate.
