Oxygen-17 NMR studies indicated that the hexametalates [MW5O19]n– or their derivatives [(MeO)MW5O18](n–1)–(M = Ti, Zr, V, Nb, Ta, Mo or W) can be obtained by hydrolysis of the appropriate mixture of metal alkoxides in the presence of M′O42–(M′= W or Mo) with remarkable selectivity in some cases, giving a very efficient method of preparing 17O-enriched polyoxometalates. The crystal structure of [NBun4]3[(MeO)TiW5O18]·0.5MeCN shows the terminal Ti–OMe bond in the anion to have Ti–O 1.760(10)Å and Ti–O–C 150.1(12)° and also reveals W–O bridging bond length alternations due to the substitution of Ti(OMe)3+ for WO4+ in the [W6O19]2– structure. Hydrolysis of [NBun4]2[(MeO)NbW5O18] gives [NBun4]4[(NbW5O18)2O] and the crystal structure revealed two eclipsed NbW5O18 oxide fragments joined by a strictly linear Nb–O–Nb linkage with Nb–O 2.264(8)Å.
                                    氧-17 NMR 研究表明,在 M′O42-(M′= W 或 Mo)存在下,通过
水解适当的
金属烷氧基化物混合物,可以获得六
金属盐 [MW5O19]n- 或其衍
生物 [(MeO)MW5O18](n-1)-(M = Ti、Zr、V、Nb、Ta、Mo 或 W),在某些情况下具有显著的选择性,这为制备富含 17O 的多氧
金属盐提供了一种非常有效的方法。[NBun4]3[(MeO)TiW5O18]-0.5MeCN的晶体结构显示,阴离子中的末端Ti-OMe键的Ti-O为1.760(10)埃,Ti-O-C为150.1(12)°,还显示了由于[W6O19]2-结构中Ti(OMe)3+取代WO4+而引起的W-O桥键长度交替。
水解[NBun4]2[(MeO)NbW5O18]可得到[NBun4]4[(NbW5O18)2O],其晶体结构显示了由严格线性 Nb-O-Nb 连接(Nb-O 2.264(8)埃)连接的两个黯淡的 NbW5O18 氧化物片段。