Characterization of DMSO Coordination to Palladium(II) in Solution and Insights into the Aerobic Oxidation Catalyst, Pd(DMSO)2(TFA)2
摘要:
Recent studies have shown that Pd(DMSO)(2)(TFA)(2) (TFA = trifluoroacetate) is an effective catalyst for a number of different aerobic oxidation reactions. Here, we provide insights into the coordination of DMSO to palladium(II) in both the solid state and in solution. A crystal structure of Pd(DMSO)(2)(TFA)(2) confirms that the solid-state structure of this species has one O-bound and one S-bound DMSO ligand, and a crystallographically characterized mono-DMSO complex, trans-Pd(DMSO)(OH2)(TFA)(2), exhibits an S-bound DMSO ligand. H-1 and F-19 NMR spectroscopic studies show that, in EtOAc and THF-d(8), Pd(DMSO)(2)(TFA)(2) consists of an equilibrium mixture of Pd(S-DMSO)(O-DMSO)(TFA)2 and Pd(S-DMSO)2(TFA)2. The O-bound DMSO is determined to be more labile than the S-bound DMSO ligand, and both DMSO ligands are more labile in THF relative to EtOAc as the solvent. DMSO coordination to Pd-II is substantially less favorable when the TFA ligands are replaced with acetate. An analogous carboxylate ligand effect is observed in the coordination of the bidentate sulfoxide ligand, 1,2-bis(phenylsulfinyl)ethane to Pd-II. DMSO coordination to Pd(TFA)2 is shown to be incomplete in AcOH-d(4) and toluene-d(8), resulting in Pd-II/DMSO adducts with <2:1 DMSO/Pd-II stoichiometry. Collectively, these results provide useful insights into the coordination properties of DMSO to Pd-II under catalytically relevant conditions.
DOI:
10.1021/ic301799p
作为产物:
描述:
palladium(II) trifluoroacetate 以
neat (no solvent) 为溶剂,
以25%的产率得到Pd3(TFA)6
参考文献:
名称:
用电子轰击质谱法研究气相中某些铂族金属的挥发性羧酸盐
摘要:
化合物Rh2 (RCOO)4[R=C(CH3)3 (I), CH(CH3)2 (II), CF3 (III)], Pd3(RCOO)6 [R=C(CH3)的质谱图3 (IV)、CH(CH3)2 (V)、CF3 (VI)]、Os2(RCOO)4Cl2 [R=C(CH3)3 (VII)] 和 Ru2(RCOO)4 [R=C(CH3) )3 (VIII)] 进行了调查。已经表明,气态化合物 I-III、VII 和 VIII 具有二聚体结构,而化合物 IV-VI 具有三聚体结构。化合物 I-VIII 的质谱显示了分子离子 [M]+ 的峰;分子离子的碎裂主要随着 RCOO 基团的消除而发生。已发现化合物 III 和 VI 具有消除 F2O 的重排,已发现化合物 IV 和 V 消除了 O=C--OH 的重排。氟原子迁移到化合物III中的金属而在化合物V中不存在氟原子已经在硬和软酸碱原理的框架中进行了解释。[M]+
Reactions catalyzed by palladium(II) acetate and trifluoroacetic acid (TFA) have a clear preactivation phase. However, the structure of real catalytic species remains unclear. We show that the key species are cyclic trinuclear complexes of composition [Pd3(OAc)6−x(OTFA)x] (x = 1–6) formed by a sequential ligand exchange from [Pd3(OAc)6]. Furthermore, we prove that the trinuclear palladium backbone