Moreno Aitor, Pregosin Paul S, Veiros Luis F, Albinati Alberto, Rizzato Silvia
Laboratory of Inorganic Chemistry, ETHZ, Hönggerberg, 8093 Zürich, Switzerland.
Chemistry. 2009 Jul 13;15(28):6848-62. doi: 10.1002/chem.200900021.
Pulsed gradient spin-echo (PGSE) diffusion characteristics for a) the new [brucinium][X] salts 6 a-f [a: X = BF(4)(-); b: X = PF(6)(-); c: X = MeSO(3)(-), d: X = CF(3)SO(3)(-); e: X = BArF(-); f: X = PtCl(3)(C(2)H(4))(-)], b) 4-tert-butyl-N-benzyl analogue, 7 and c) the aryl carbocations (p-R-C(6)H(4))(2)CH 9 a (R = CH(3)O) and 9 b (R = (CH(3))(2)N), (p-CH(3)O-C(6)H(4))(x)CPh(3-x)(+) 10 a-c (x = 1-3, respectively) and (p-R-C(6)H(4))(3)C(+) 11 (R = (CH(3))(2)N) and 12 (R = H) all in several different solvents, are reported. The solvent dependence suggests strong ion pairing in CDCl(3), intermediate ion pairing in CD(2)Cl(2) and little ion pairing in [D(6)]acetone. (1)H, (19)F HOESY NMR spectra (HOESY: heteronuclear Overhauser effect spectroscopy) for 6 and 7 reveal a specific approach of the anion with respect to the brucinium cation plus subtle changes, which are related to the anion itself. Further, for carbocations 9-12, (all as BF(4)(-) salts) based on the NOE results, one finds marked changes in the relative positions of the BF(4)(-) anion. In these aryl cationic species the anion can be located either a) very close to the carbonium ion carbon b) in an intermediate position or c) proximate to the N or O atom of the p-substituent and remote from the formally positive C atom. This represents the first example of such a positional dependence of an anion on the structure of the carbocation. DFT calculations support the experimental HOESY results. The solid-state structures for 6 c and the novel Zeise's salt derivative, [brucinium][PtCl(3)(C(2)H(4))], 6 f, are reported. Analysis of (195)Pt NMR and other NMR measurements suggest that the eta(2)-C(2)H(4) bonding to the platinum centre in 6 f is very similar to that found in K[PtCl(3)(C(2)H(4))]. Field dependent T(1) measurements on [brucinium][PtCl(3)(C(2)H(4))] and K[PtCl(3)(C(2)H(4))], are reported and suggested to be useful in recognizing aggregation effects.
报道了以下物质在几种不同溶剂中的脉冲梯度自旋回波（PGSE）扩散特性：a）新型[马钱子碱][X]盐6 a - f [a：X = BF₄⁻；b：X = PF₆⁻；c：X = MeSO₃⁻；d：X = CF₃SO₃⁻；e：X = BArF⁻；f：X = PtCl₃(C₂H₄)⁻]，b）4 - 叔丁基 - N - 苄基类似物7，以及c）芳基碳正离子（p - R - C₆H₄）₂CH 9 a（R = CH₃O）和9 b（R = (CH₃)₂N）、（p - CH₃O - C₆H₄）ₓCPh₃₋ₓ⁺ 10 a - c（x分别为1 - 3）和（p - R - C₆H₄）₃C⁺ 11（R = (CH₃)₂N）以及12（R = H）。溶剂依赖性表明在CDCl₃中存在强离子对，在CD₂Cl₂中存在中等程度的离子对，而在[D₆]丙酮中离子对较少。6和7的¹H、¹⁹F HOESY NMR光谱（HOESY：异核Overhauser效应光谱）揭示了阴离子相对于马钱子碱阳离子的特定取向以及与阴离子本身相关的细微变化。此外，对于碳正离子9 - 12（均为BF₄⁻盐），基于NOE结果，发现BF₄⁻阴离子的相对位置有显著变化。在这些芳基阳离子物种中，阴离子可以位于：a）非常靠近碳正离子的碳原子；b）中间位置；或c）靠近对位取代基的N或O原子且远离形式上带正电的C原子。这是阴离子对碳正离子结构的这种位置依赖性的首个例子。DFT计算支持了实验性的HOESY结果。报道了6 c和新型蔡斯盐衍生物[马钱子碱][PtCl₃(C₂H₄)] 6 f的固态结构。¹⁹⁵Pt NMR分析和其他NMR测量表明，6 f中与铂中心的η² - C₂H₄键合与K[PtCl₃(C₂H₄)]中的非常相似。报道了对[马钱子碱][PtCl₃(C₂H₄)]和K[PtCl₃(C₂H₄)]的场依赖性T₁测量，并表明其有助于识别聚集效应。
