Effect of Base on the Solution Behavior of Oxo(D-PENICILLAMINATO)(L-penicillaminato)rhenate(V)

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• 作者：Lory Hansen ; Xiaolong Xu ; Kwok To Yue ; Andrew Taylor ; Jr. ; and Luigi G. Marzilli
• 刊名：Inorganic Chemistry
• 出版年：1996
• 出版时间：May 8, 1996
• 年：1996
• 卷：35
• 期：10
• 页码：2785 - 2791
• 全文大小：410K
• 年卷期：v.35,no.10(May 8, 1996)
• ISSN：1520-510X

文摘

The effect of base on the solution behavior ofoxo(D-penicillaminato)(L-penicillaminato)rhenate(V)(1) wasinvestigated by ¹H NMR, resonance Raman, and UV-visiblespectroscopy. The ¹H NMR spectrum of 1consistedof two sets of sharp pen signals in DMSO-d₆ andD₂O below pH 8 (penicillamine = penH₄, thesubscript on Hindicating the number of dissociable protons present). The datawere consistent withReO(D-penH₃)(L-penH₂)and its enantiomerReO(L-penH₃)(D-penH₂),with penH₃ coordinated by N, S, and carboxyl O. Theseenantiomershave a cis-N₂,cis-S₂coordination of the pen ligands, both CO₂ groupsanti to the oxo ligand and one CO₂coordinatedtrans to the oxo ligand (form I). InD₂O, between pH 8.6 and 10.1, the signals broadened,collapsed, and re-emerged as one set of signals, but no accompanying changes were observedin either the resonance Raman or theUV-visible spectra. The NMR spectral changes were attributed tobase-catalyzed interconversion between twoenantiomers; both CO₂ groups are deprotonated inD₂O, and they alternate between ligated and deligatedstates.Near pH 11, a new form (II) in slow exchange with formI was detected by NMR spectroscopy. TheRe=ORaman band of I (963 cm^-1) wasreplaced by a new midfrequency band (930cm^-1). The UV-visiblebands(346 and 492 nm) decreased in intensity. With increasing pH andnear pH 12, the ¹H NMR signals of IIshifted.The midfrequency Re=O band was replaced by a low-frequency band(845 cm^-1), and both the UV andvisiblebands continued to decline as new shorter wavelength bands emerged.These spectral changes were consistentwith deprotonation of II to give II'. The¹H NMR spectra of 1 andReO(D-penH₃)(D-penH₂)were nearly identicalat pH 12. At this pH, the latter complex is atrans-dioxo species with a Re=O band at 846cm^-1; the similarNMR spectrum and Re=O band of 1 suggest thatII' is a trans-dioxo species also. Thisconclusion was supportedby studies in methanol which showed that[ReO(OCH₃)(D-penH₂)(L-penH₂)]^2-did not deprotonate.