Isolation of Uranyl Dicyanamide Complexes from N-Donor Ionic Liquids

Abstract

An ionic liquid (IL) approach for soft-donor f-element chemistry has been demonstrated by the isolation of several new uranyl dicyanamide complexes through reactions of UO2(NO3)2·6H2O with dicyanamide ([N(CN)2](-))-containing ILs. The [N(CN)2](-) ions are able to rapidly substitute uranium's O-donor ligands, as evidenced by single-crystal X-ray diffraction studies on two anhydrous adducts of UO2(NO3)2 with [N(CN)2](-) ILs as well as by IR and NMR spectroscopic studies on solutions of UO2(NO3)2 in these ILs. By contrast, the slow reaction of UO2(OAc)2·2H2O with a nitrile-functionalized imidazolium dicyanamide IL in solvent and the reaction of UO2(NO3)2·6H2O with NaN(CN)2 at elevated temperature resulted in irreversible hydrolysis. The reaction of UO2SO4 with [N(CN)2](-) ions in an acidified aqueous solution resulted in the crystallization of a [UO2](2+) complex with biuret, a N(CN)2](-) hydrolysis product. [N(CN)2](-) ions in the form of ILs react rapidly with [UO2](2+) at room temperature, allowing ligand substitution with [N(CN)2](-) to out-compete the slower hydrolysis reaction, enabling the isolation of uranyl dicyanamide complexes and challenging assumptions regarding the affinity of uranium for O-donors.

Detection and identification of solids, surfaces, and solutions of uranium using vibrational spectroscopy

“…This results in a red-shift of the uranyl symmetric stretch from 880 [162,203] to 871 cm −1 [204]. Other ionic liquids, such as those containing dicyanamide [205], have the ability to complex with the uranyl cation as evidenced by crystallization studies. Additional experiments are necessary to determine the vibrational bands present in these solvents and the identity of other uranyl species that form in ionic liquids with O-and N-donor groups.…”

Salting‐Out Approach (SOAP) for the Synthesis of Nickel‐Based Coordination Polymer Nanorods from a Dicyanamide Ionic Liquid

“…It is known that dca‐based ILs can form CPs and have the additional benefit of introducing the properties of ILs into the structure of the CPs [21,22] . Ionic conductivity, for example, may occur by electronic transport of the cation of the IL through the pores of the CP if there is secondary coordination by the cation to balance the charge of the network structure [29,30] .…”

“…The dicyanamide anion (dca) is an effective ligand for d‐block and f‐block elements [14–22] . It has a multidentate structure and can act as a terminal or bridging ligand through eight types of binding modes (as shown in Figure 1) to generate a diverse range of structures.…”

“…The dicyanamide anion (dca) is an effective ligand for dblock and f-block elements. [14][15][16][17][18][19][20][21][22] It has a multidentate structure and can act as a terminal or bridging ligand through eight types of binding modes (as shown in Figure 1) to generate a diverse range of structures. The bent shape, rigid structure and short length of dca can produce CPs with relatively small voids.…”

“…[26][27][28] It is known that dca-based ILs can form CPs and have the additional benefit of introducing the properties of ILs into the structure of the CPs. [21,22] Ionic conductivity, for example, may occur by electronic transport of the cation of the IL through the pores of the CP if there is secondary coordination by the cation to balance the charge of the network structure. [29,30] This cationic charge balancing is a common occurrence in IL-containing CPs and is potentially useful for applications in solid state electrochemical devices and electrical double layer capacitors.…”