668488-14-0Relevant academic research and scientific papers
Synthesis, Structure, Theoretical Studies, and Ligand Exchange Reactions of Monomeric, T-Shaped Arylpalladium(II) Halide Complexes with an Additional, Weak Agostic Interaction
Stambuli, James P.,Incarvito, Christopher D.,Buehl, Michael,Hartwig, John F.
, p. 1184 - 1194 (2004)
A series of monomeric arylpalladium(II) complexes LPd(Ph)X (L = 1-AdP tBu2, PtBu3, or Ph 5FcPtBu2 (Q-phos); X = Br, I, OTf) containing a single phosphine ligand have been prepared. Oxidative addition of aryl bromide or aryl iodide to bis-ligated palladium(0) complexes of bulky, trialkylphosphines or to Pd(dba)2 (dba = dibenzylidene acetone) in the presence of 1 equiv of phosphine produced the corresponding arylpalladium(II) complexes in good yields. In contrast, oxidative addition of phenyl chloride to the bis-ligated palladium(0) complexes did not produce arylpalladium(II) complexes. The oxidative addition of phenyl triflate to PdL2 (L = 1-AdPtBu2, PtBu 3, or Q-phos) also did not form arylpalladium(II) complexes. The reaction of silver triflate with (1-AdPtBu2)Pd(Ph)Br furnished the corresponding arylpalladium(II) triflate in good yield. The oxidative addition of phenyl bromide and iodide to Pd(Q-phos)2 was faster than oxidative addition to Pd(1-AdPtBu2)2 or Pd(PtBu3)2. Several of the arylpalladium complexes were characterized by X-ray diffraction. All of the arylpalladium(II) complexes are T-shaped monomers. The phenyl ligand, which has the largest trans influence, is located trans to the open coordination site. The complexes appear to be stabilized by a weak agostic interaction of the metal with a ligand C-H bond positioned at the fourth-coordination site of the palladium center. The strength of the Pd...H bond, as assessed by tools of density functional theory, depended upon the donating properties of the ancillary ligands on palladium.
Effect of ligand steric properties and halide identity on the mechanism for oxidative addition of haloarenes to trialkylphosphine Pd(0) complexes
Barrios-Landeros, Fabiola,Carrow, Brad P.,Hartwig, John F.
, p. 8141 - 8154 (2009/12/02)
The oxidative addition of PhX (X ) I, Br, Cl) to the complexes Pd(P tBu3)2 (1), Pd(1-AdPtBu2)2 (2), Pd(CyPtBu2)2 (3), and Pd(PCy3) 2 (4) (1-Ad = 1-adamantyl, Cy = cyclohexyl) was studied todetermine the effect of steric properties on the coordination number of the species that undergoes oxidative addition and to determine whether the type of halide affects the identity of this species. The kinetic dat a imply that the number of phosphines coordinated to the complex that reacts in the irreversible step of the oxidative addition process for complexes 1-4 depends more on the halide than on the steric properties of the ligands. The rate-limiting step of the oxidative addition of PhI occurred with L2Pd(0) in all cases, as determined by the lack of dependence of kobs on [PtBu3], [1-AdPtBu2], or [CyPtBu2] and the inverse dependence of the rate constant on [PCy3] when the reaction was initiated with Pd(PCy3)3. The irreversible step of the oxidative addition of PhCl occurred with a monophosphine species in each case, as signaled by an inverse dependence of the rate constant on the concentration of ligand. The irreversible step of the oxidative addition of PhBr occurred with a bisphosphine species, as signaled by the zeroth-order or small dependence of the rate constant on the concentration of phosphine. Thus, the additions of the less reactive chloroarenes occurthrough lower-coordinate intermediates than additions of the more react ive haloarenes.
