Centro de Química Estrutural, Instituto Superior Técnico, TU Lisbon, 1049-001 Lisboa, Portugal.
Inorg Chem. 2010 Aug 16;49(16):7452-63. doi: 10.1021/ic1007704.
Vanadium diaminebis(phenolate) complexes of the general formulas [LVCl(THF)] (L = Me(2)NCH(2)CH(R)N(CH(2)-2-O-3,5-C(6)H(2)(t)Bu(2))(2), where R = H, Me) and [LV(O)X] [X = Cl; R = H (2), Me (3), O(i)Pr (4), (mu-O)V(O)L (5)] are described. All compounds display octahedral geometry and trans-O(Ph) coordination. For compounds 2, 3, and 5, only one isomer, presenting the V=O ligand trans to the tripodal nitrogen, was formed, while for 4, two isomers were observed by NMR in solution. The UV-vis and circular dichroism spectra of 2 and 3 display very intense charge-transfer transition bands from the phenolate donors to the vanadium, which are in agreement with the (51)V low-field shifts observed. All vanadium(V) complexes were tested as thioanisole sulfoxidation catalysts, revealing very high selectivity when H(2)O(2) was used as the oxidant. However, no enantioselectivity was observed even when enantiopure 3 was used as the catalyst precursor. (1)H and (51)V NMR studies were conducted for the reactions of 2 with aqueous solutions of H(2)O(2) in methanol-d(4) and in acetonitrile-d(3); 2 reacts with the solvents, leading to [LV(O)OMe], by replacement of Cl by MeO in methanol, and to a new vanadium aminebis(phenolate) complex, where the dimethylamine fragment of the original ligand L was replaced by CH(3)CN. In either case, (51)V NMR spectra suggest the formation of peroxovanadium species upon the addition of a H(2)O(2) solution. The subsequent addition of thioanisole to the methanol-d(4) solution leads to regeneration of the original complex.
钒二胺双（苯酚）配合物的通式为[LVCl(THF)]（L = Me(2)NCH(2)CH(R)N(CH(2)-2-O-3,5-C(6)H(2)(t)Bu(2))(2)，其中 R = H，Me）和[LV(O)X] [X = Cl；R = H（2），Me（3），O(i)Pr（4），（mu-O）V(O)L（5）]。所有化合物均具有八面体几何形状和反式-O(Ph)配位。对于化合物 2、3 和 5，仅形成一种异构体，其中 V=O 配体与三齿氮呈反式，而对于 4，通过 NMR 在溶液中观察到两种异构体。2 和 3 的 UV-vis 和圆二色光谱显示出非常强烈的从酚配体供体到钒的电荷转移跃迁带，这与观察到的(51)V 低场位移一致。所有的钒(V)配合物都被测试为硫代茴香醚氧化催化剂，当使用 H(2)O(2)作为氧化剂时，表现出很高的选择性。然而，即使使用手性纯 3 作为催化剂前体，也没有观察到对映选择性。进行了 2 与甲醇-d(4)和乙腈-d(3)中 H(2)O(2)水溶液的反应的(1)H 和(51)V NMR 研究；在甲醇中，2 通过 Cl 被 MeO 取代与溶剂反应，生成[LV(O)OMe]，并且生成一种新的钒胺双（苯酚）配合物，其中原始配体 L 的二甲胺片段被 CH(3)CN 取代。在任何情况下，(51)V NMR 光谱都表明在加入 H(2)O(2)溶液后形成过氧钒物种。随后将硫代茴香醚加入甲醇-d(4)溶液中，导致原始配合物的再生。
