Rigid NON- and NSN-ligand complexes of tetravalent and trivalent uranium: comparison of U–OAr2 and U–SAr2 bonding
作者:Balamurugan Vidjayacoumar、Sougandi Ilango、Matthew J. Ray、Terry Chu、Kristopher B. Kolpin、Nicholas R. Andreychuk、Carlos A. Cruz、David J. H. Emslie、Hilary A. Jenkins、James F. Britten
DOI:10.1039/c2dt30247k
日期:——
A rigid NSN-donor proligand, 4,5-bis(2,6-diisopropylanilino)-2,7-di-tert-butyl-9,9-dimethylthioxanthene (H2[TXA2], 1) was prepared by palladium-catalyzed coupling of 2,6-diisopropylaniline with 4,5-dibromo-2,7-di-tert-butyl-9,9-dimethylthioxanthene. Deprotonation of 1 using nBuLi provided Li2(DME)2[TXA2] (2), and subsequent reaction with UCl4 afforded [Li(DME)3][(TXA2)UCl3] (4). The analogous NON-donor ligated complex [(XA2)UCl3K(DME)3] [3; XA2 = 4,5-bis(2,6-diisopropylanilino)-2,7-di-tert-butyl-9,9-dimethylxanthene] was prepared by the reaction of K2(DME)x[XA2] with UCl4. A cyclic voltammogram (CV) of 3 in THF/[NBu4][B(C6F5)4] at 200 mV sâ1 showed an irreversible reduction to uranium(III) at Epc = â2.46 V versus FeCp20/+1, followed by a product wave at E1/2 = â1.83 V. Complex 4 also underwent irreversible reduction to uranium(III) [Epc = â2.56 V], resulting in an irreversible product peak at Epa = â1.83 V. One-electron reduction of complexes 3 and 4 using K(naphthalenide) under an argon atmosphere in DME yielded 6-coordinate [(XA2)UCl(DME)] (5) and the thermally unstable 7-coordinate [(TXA2)U(DME)Cl2Li(DME)2] (6), respectively. The UâS distances in 4 and 6 are uncommonly short, the CâSâU angles are unusually acute, and the thioxanthene backbone of the TXA2 ligand is significantly bent. By contrast, the xanthene backbone in XA2 complexes 3 and 5 is planar. However, κ3-coordination and an approximately meridional arrangement of the ancillary ligand donor atoms is maintained in all complexes. DFT and Atoms in Molecules (AIM) calculations were carried out on 3, 4, 5, 6, [(XA2)UCl3]â (3B), [(TXA2)UCl2(DME)]â (6B) and [(TXA2)UCl(DME)] (6C) to probe the extent of covalency in UâSAr2 bonding relative to UâOAr2 bonding.
通过钯催化 2,6-二异丙基苯胺与 4,5-二溴-2,7-二叔丁基-9,9-二甲基二氧杂蒽的偶联,制备了一种刚性 NSN 供体原配体 4,5-双(2,6-二异丙基苯胺)-2,7-二叔丁基-9,9-二甲基二氧杂蒽(H2[TXA2],1)。用 nBuLi 对 1 进行去质子化反应,得到 Li2(DME)2[TXA2] (2),随后与 UCl4 反应,得到 [Li(DME)3][(TXA2)UCl3] (4)。K2(DME)x[XA2]与 UCl4 反应制备了类似的非供体配位复合物[(XA2)UCl3K(DME)3][3;XA2 = 4,5-双(2,6-二异丙基苯胺基)-2,7-二叔丁基-9,9-二甲基呫吨]。络合物 3 在 THF/[NBu4][B(C6F5)4] 中于 200 mV sâ1 的循环伏安图(CV)显示,在 Epc = â2.46 V 处对 FeCp20/+1 进行不可逆还原成铀(III),随后在 E1/2 = â1.83 V 处出现一个产物波。在二甲醚中的氩气环境下,用 K(萘)对络合物 3 和 4 进行单电子还原,分别得到了 6 配位的 [(XA2)UCl(DME)] (5) 和热不稳定的 7 配位的 [(TXA2)U(DME)Cl2Li(DME)2] (6)。4 和 6 中的 UâS 间距非常短,CâSâU 角异常锐利,TXA2 配体的硫杂蒽骨架明显弯曲。相比之下,XA2 复合物 3 和 5 中的氧杂蒽主链是平面的。不过,所有复合物都保持了δ3 配位和辅助配体供体原子的近似经向排列。对 3、4、5、6、[(XA2)UCl3]â (3B)、[(TXA2)UCl2(DME)]â (6B) 和 [(TXA2)UCl(DME)](6C)进行了 DFT 和原子分子(AIM)计算,以探究 UâSAr2 键相对于 UâOAr2 键的共价程度。