科研之友
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摘要
A combination of multinuclear ultra-wideline solid-state NMR, powder X-ray diffraction (pXRD), X-ray absorption fine structure experiments, and first principles calculations of platinum magnetic shielding tensors has been employed to reveal the previously unknown crystal structure of Magnus%26apos; pink salt (MPS), [Pt(NH3)(4)][PtCl4], study the isomeric Magnus%26apos; green salt (MGS), [Pt(NH3)(4)][PtCl4], and examine their synthetic precursors K2PtCl4 and Pt(NH3)(4)Cl-2 center dot H2O. A simple synthesis of MPS is detailed which produces relatively pure product in good yield. Broad Pt-195, N-14, and Cl-35 SSNMR powder patterns have been acquired using the WURST-CPMG and BRAIN-CP/WURST-CPMG pulse sequences. Experimentally measured and theoretically calculated platinum magnetic shielding tensors are shown to be very sensitive to the types and arrangements of coordinating ligands as well as intermolecular Pt-Pt metallophilic interactions. High-resolution Pt-195 NMR spectra of select regions of the broad Pt-195 powder patterns, in conjunction with an array of N-14 and Cl-35 spectra, reveal clear structural differences between all compounds. Rietveld refinements of synchrotron pXRD patterns, guided by first principles geometry optimization calculations, yield the space group, unit cell parameters, and atomic positions of MPS. The crystal structure has P-1 symmetry and resides in a pseudotetragonal unit cell with a distance of %26gt;5.5 angstrom between Pt sites in the square-planar Pt units. The long Pt-Pt distances and nonparallel orientation of Pt square planes prohibit metallophilic interactions within MPS. The combination of ultra-wideline NMR, pXRD, and computational Methods offers much promise for future investigation and characterization of Pt-containing systems.
- 出版日期2014-1-29
- 单位北京大学
