Redox Non-innocence of Thioether Crowns: Elucidation of the Electronic Structure of the Mononuclear Pd(III) Complexes [Pd([9]aneS3)2]3+ and [Pd([18]aneS6)]<

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• 作者：Emma Stephen ; Alexander J. Blake ; Emma Carter ; David Collison ; E. Stephen Davies ; Ruth Edge ; William Lewis ; Damien M. Murphy ; Claire Wilson ; Robert O. Gould ; Alan J. Holder ; Jonathan McMaster ; Martin Schr枚der
• 刊名：Inorganic Chemistry
• 出版年：2012
• 出版时间：February 6, 2012
• 年：2012
• 卷：51
• 期：3
• 页码：1450-1461
• 全文大小：636K
• 年卷期：v.51,no.3(February 6, 2012)
• ISSN：1520-510X

文摘

The Pd(II) complexes [Pd([9]aneS₃)₂](PF₆)₂路2MeCN (1) ([9]aneS₃ = 1,4,7-trithiacyclononane) and [Pd([18]aneS₆)](PF₆)₂ (2) ([18]aneS₆ = 1,4,7,10,13,16-hexathiacyclooctadecane) can be oxidized electrochemically or chemically oxidized with 70% HClO₄ to [Pd([9]aneS₃)₂]³⁺ and [Pd([18]aneS₆)]³⁺, respectively. These centers have been characterized by single crystal X-ray diffraction, and by UV/vis and multifrequency electron paramagnetic resonance (EPR) spectroscopies. The single crystal X-ray structures of [Pd^III([9]aneS₃)₂](ClO₄)₆路(H₃O)₃路(H₂O)₄ (3) at 150 K and [Pd([18]aneS₆)](ClO₄)₆路(H₅O₂)₃ (4) at 90 K reveal distorted octahedral geometries with Pd鈥揝 distances of 2.3695(8), 2.3692(8), 2.5356(9) and 2.3490(6), 2.3454(5), 2.5474(6) 脜, respectively, consistent with Jahn鈥揟eller distortion at a low-spin d⁷ Pd(III) center. The Pd(II) compound [Pd([9]aneS₃)₂](PF₆)₂ shows a one-electron oxidation process in MeCN (0.2 M NBu₄PF₆, 293 K) at E_1/2 = +0.57 V vs. Fc⁺/Fc assigned to a formal Pd(III)/Pd(II) couple. Multifrequency (Q-, X-, S-, and L-band) EPR spectroscopic analysis of [Pd([9]aneS₃)₂]³⁺ and [Pd([18]aneS₆)]³⁺ gives g_iso = 2.024, |A_iso(Pd)| = 18.9 脳 10^鈥? cm^鈥?; g_xx = 2.046, g_yy = 2.041, g_zz = 2.004;聽|A_xx(Pd)| = 24 脳 10^鈥? cm^鈥?, |A_yy(Pd)| = 22 脳 10^鈥? cm^鈥?, |A_zz(Pd)| = 14 脳 10^鈥? cm^鈥?, |a_xx(H)| = 4 脳 10^鈥? cm^鈥?, |a_yy(H)| = 5 脳 10^鈥? cm^鈥?, |a_zz(H)| = 5.5 脳 10^鈥? cm^鈥? for [Pd([9]aneS₃)₂]³⁺, and g_iso = 2.015, |A_iso(Pd)| = 18.8脳 10^鈥? cm^鈥?; g_xx = 2.048 g_yy = 2.036, g_zz = 1.998; |a_xx(H)| = 5, |a_yy(H)| = 5, |a_zz(H)| = 6 脳 10^鈥? cm^鈥?; |A_xx(Pd)| = 23脳 10^鈥? cm^鈥?, |A_yy(Pd)| = 22 脳 10^鈥? cm^鈥?, |A_zz(Pd)| = 4 脳 10^鈥? cm^鈥? for [Pd([18]aneS₆)]³⁺. Both [Pd([9]aneS₃)₂]³⁺ and [Pd([18]aneS₆)]³⁺ exhibit five-line superhyperfine splitting in the g_zz region in their frozen solution EPR spectra. Double resonance spectroscopic measurements, supported by density functional theory (DFT) calculations, permit assignment of this superhyperfine to through-bond coupling involving four ¹H centers of the macrocyclic ring. Analysis of the spin Hamiltonian parameters for the singly occupied molecular orbital (SOMO) in these complexes gives about 20.4% and 25% Pd character in [Pd([9]aneS₃)₂]³⁺ and [Pd([18]aneS₆)]³⁺, respectively, consistent with the compositions calculated from scalar relativistic DFT calculations.