The sugars, methyl 4,6-di-O-methyl-α-D-mannopyranoside (H2m) and methyl 5-O-methyl-β-D-ribofuranoside (H2r) have been synthesized. These react smoothly with [VIVO(L)(H2O)] in methanol in air affording the dark coloured vanadates [VVO(Hm)(L)] and [VVO(Hr)(L)] in excellent yields (L2– = N-salicylideneglycinate). The crystal structure determination of [VVO(Hm)(L)] revealed five-membered chelation of VO3+ by the alcoholic and alkoxide oxygen atoms of the monoionised carbohydrate. The two atoms lie respectively trans to the oxo oxygen and aldimine nitrogen atoms. The five V–O bonds are unequal and span the range 1.57–2.37 Å. The asymmetric unit of the complex consists of two metrically similar molecules locked in carboxylate–alcohol O· · ·O hydrogen bonding generating a macrocyclic cavity. In solution each ester displays a single 51V resonance near δ –544. The 1H NMR parameters of the alkoxidic and alcoholic CH protons and of OMe protons are consistent with the O,O-chelation mode for both the vanadates.
我们合成了 4,6-二-O-甲基-α-D-
吡喃
甘露糖苷 (H2m) 和 5-O-甲基-β-D-
呋喃核糖苷 (H2r)。这些物质与
甲醇中的[VIVO(L)(
H2O)]在空气中顺利反应,生成深色的
钒酸盐[VVO(Hm)(L)]和[VVO(Hr)(L)],产量极高(
L2- = N-
水杨醛甘
氨酸)。对[VVO(Hm)(L)]晶体结构的测定显示,VO3+ 与单离子化
碳水化合物的醇氧原子和氧化烷氧原子之间存在五元螯合关系。这两个原子分别反式位于氧化氧原子和醛
亚胺氮原子上。复合物的不对称单元由两个度数相似的分子组成,它们通过羧基-醇基 O- - O 氢键结合形成一个大环空腔。在溶液中,每个酯都δ -544附近显示一个51V共振。烷氧基和
酒精 CH 质子以及 OMe 质子的 1H NMR 参数与这两种
钒酸盐的 O,O 螯合模式一致。