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Polyanionic Imido-P(V) Ligands: From Transition Metal Complexes to Coordination Driven Self-Assemblies
The Chemical Record ( IF 7.0 ) Pub Date : 2021-12-27 , DOI: 10.1002/tcr.202100281
Meghamala Sarkar 1 , Prabhakaran Rajasekar 1 , Cavya Jose 1 , Ramamoorthy Boomishankar 1, 2
Affiliation  

The chemistry of the imido-anions of the main group elements has been studied for more than three decades. The imido (NR) group is isoelectronic to the oxo (=O) group and can coordinate with metal ions through its lone pairs of electrons. The polyimido-P(V) anions are well explored as they resemble the phosphorus oxo moieties such as H3PO4, H2PO4, HPO42− and PO43− species. These imido anions are typically generated using strong main group organometallic reagents such as nBuLi, Et2Zn, Me3Al and nBu2Mg, etc. As a result, their coordination chemistry has been restricted to reactions in anhydrous aprotic solvents for a few main group metal ions. This account presents our findings on using certain soft transition metal such Ag(I) and Pd (II) for isolating these imido-P(V) anions as their corresponding self-assembled clusters and cages. Using the various salts of Ag(I) ions in reaction with 2-pyridyl (2Py) functionalized phosphonium salts and phosphoric triamides, we obtained the mono- and dianionic form of these imido ligands {[P(N2Py)2(NH2Py)2], [P(N2Py)2(NH2Py)], [PO(N2Py)(NH2Py)2]2−} and derived interesting examples of tri, penta, hepta and octanuclear Ag(I) clusters. Interestingly, by using the salts of Pd (II) ions, the elusive imido-phosphate trianions of the type [(RN)3PO]3− (R=tBu, cHex, iPr) were generated in a facile one pot reaction as their corresponding tri- and hexanuclear clusters of the type {Pd3[(NR)3PO](OAc)3}n (n=1 or 2). These trianions acts as a cis-coordinated hexadentate ligand for a trinuclear Pd (II) cluster and serve as the polyhedral building units for constructing hitherto unknown family of neutral cages in tetrahedral {Pd3[(NiPr)3PO]4(L)6} and cubic {Pd3[(NiPr)3PO]8(L)12} structures in the presence of suitable linker ligands (L2−). These cages show interesting host-guest chemistry and post-assembly reactions. Remarkably, by employing chiral tris(imido)phosphate trianions, enantiopure chiral cages of the type [(Pd3X*)4(L)6], ([X*]3−=RRR- or SSS-[PO(N(*CH(CH3)Ph)3]3−), were synthesized and used for the chiral-recognition and enantio-separation of small racemic guest molecules. Some of these chiral cages were also shown to exhibit polyradical framework structures. In future, these and other similar types of cages are envisioned as potential molecular vessels for performing the reactions in their confined environment. The enantiomeric cages can be probed for asymmetric catalysis and the separation of a range of small chiral molecules.

中文翻译:

聚阴离子酰亚胺-P(V) 配体:从过渡金属配合物到配位驱动的自组装

主族元素的亚氨基阴离子的化学已经研究了三十多年。亚氨基 (NR) -基团与氧代 (=O) 基团是等电子的,并且可以通过其孤对电子与金属离子配位。聚酰亚胺-P(V) 阴离子被很好地探索,因为它们类似于磷氧部分,例如 H 3 PO 4、H 2 PO 4 -、HPO 4 2-和 PO 4 3-物种。这些亚氨基阴离子通常使用强主族有机金属试剂如n BuLi、Et 2 Zn、Me 3 Al 和n Bu 2生成Mg 等。因此,它们的配位化学仅限于在无水非质子溶剂中对少数主族金属离子的反应。该帐户介绍了我们使用某些软过渡金属如 Ag(I) 和 Pd(II) 来分离这些亚氨基-P(V) 阴离子作为它们相应的自组装簇和笼的发现。使用 Ag(I) 离子的各种盐与 2-吡啶基 ( 2 Py) 官能化的鏻盐和磷酸三酰胺反应,我们获得了这些亚氨基配体的单离子和双离子形式 {[P(N 2 Py) 2 (NH 2 Py) 2 ] - , [P(N 2 Py) 2 (NH 2 Py)] - , [PO(N2 Py)(NH 2 Py) 2 ] 2− } 并衍生出有趣的三、五、七和八核 Ag(I) 簇的例子。有趣的是,通过使用 Pd (II) 离子的盐,[(RN) 3 PO] 3- (R= t Bu, c Hex, i Pr)类型的难以捉摸的亚氨基磷酸三阴离子在一个简单的一锅中产生反应作为它们相应的 {Pd 3 [(NR) 3 PO](OAc) 3 } n (n=1 或 2)类型的三核和六核簇。这些 trianions 充当顺式-配位的六齿配体,用于三核 Pd (II) 簇,并用作构建四面体 {Pd 3 [(N i Pr) 3 PO] 4 (L) 6 } 和立方 {中迄今为止未知的中性笼族的多面体构建单元Pd 3 [(N i Pr) 3 PO] 8 (L) 12 } 在合适的接头配体 (L 2- ) 存在下的结构。这些笼子展示了有趣的主客体化学和组装后反应。值得注意的是,通过使用手性三(亚氨基)磷酸三阴离子,[(Pd 3 X*) 4 (L) 6类型的对映纯手性笼], ([X*] 3− =RRR- or SSS-[PO(N(*CH(CH 3 )Ph) 3 ] 3− ), 被合成并用于小外消旋体的手性识别和对映分离客体分子。这些手性笼中的一些也显示出多自由基框架结构。在未来,这些和其他类似类型的笼被设想为潜在的分子容器,用于在其受限环境中进行反应。对映体笼可以被探测为不对称催化和分离一系列小手性分子。
更新日期:2021-12-27
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