Solution Behavior and Structural Diversity of Bis(dialkylphosphino)methane Complexes of Palladium
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- 作者：Craig B. Pamplin ; Steven J. Rettig ; Brian O. Patrick ; and Brian R. James
- 刊名：Inorganic Chemistry
- 出版年：2003
- 出版时间：June 30, 2003
- 年：2003
- 卷：42
- 期：13
- 页码：4117 - 4126
- 全文大小：170K
- 年卷期：v.42,no.13(June 30, 2003)
- ISSN：1520-510X
文摘
The preparation of dipalladium complexes containing sterically nondemanding diphosphine (P-P) ligands of thetype R2PCH2PR2 where R = Me (dmpm) or Et (depm) is reported. Variable-temperature 1H NMR spectra of thePdI2 complexes Pd2X2(dmpm)2 (X = Cl, Br, or I; the P-P ligands in the Pd2 complexes are always bridged, but forconvenience, the 
-symbol is omitted) show the complexes to be fluxional in solution, the barriers to a ring-flippingprocess being 
G
= 37.9, 39.0, and 43.2 ± 0.9 kJ mol-1 for the chloro, bromo, and iodo complexes, respectively.Treatment of Pd2X2(P-P)2 (X = Cl or Br) with X2 generates the stable, face-to-face PdII2 derivatives trans-Pd2X4(P-P)2, while oxidation of Pd2I2(P-P)2 complexes with I2 generates a new type of symmetrically di-iodo-bridged,five-coordinate complexes Pd2I2(-I)2(dmpm)2 and Pd2I2(-I)2(depm)2. The molecular crystal structures of fourdipalladium(II) complexes are described: trans-Pd2Cl4(dmpm)2·2CHCl3, trans-Pd2Br4(dmpm)2, trans-Pd2Cl4(depm)2,and Pd2I2(-I)2(dmpm)2. Solution NMR and UV-vis absorption spectra are consistent with the solid-state structuresdetermined by X-ray diffraction. The stability of the dimeric Pd(II) complexes is attributed primarily to ligand stericfactors.
-symbol is omitted) show the complexes to be fluxional in solution, the barriers to a ring-flippingprocess being G = 37.9, 39.0, and 43.2 ± 0.9 kJ mol-1 for the chloro, bromo, and iodo complexes, respectively.Treatment of Pd2X2(P-P)2 (X = Cl or Br) with X2 generates the stable, face-to-face PdII2 derivatives trans-Pd2X4(P-P)2, while oxidation of Pd2I2(P-P)2 complexes with I2 generates a new type of symmetrically di-iodo-bridged,five-coordinate complexes Pd2I2(-I)2(dmpm)2 and Pd2I2(-I)2(depm)2. The molecular crystal structures of fourdipalladium(II) complexes are described: trans-Pd2Cl4(dmpm)2·2CHCl3, trans-Pd2Br4(dmpm)2, trans-Pd2Cl4(depm)2,and Pd2I2(-I)2(dmpm)2. Solution NMR and UV-vis absorption spectra are consistent with the solid-state structuresdetermined by X-ray diffraction. The stability of the dimeric Pd(II) complexes is attributed primarily to ligand stericfactors.