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We report the syntheses, electronic properties, and molecular structures of a series of polychalcogenido-bridged dinuclear uranium species. These complexes are supported by the sterically encumbering but highly flexible, single N-anchored tris(aryloxide) chelator (AdArO)3N3−. Reaction of an appropriate uranium precursor, either the U(III) starting...
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This manuscript reports the first examples of germylene stabilized cadmium complexes {[{(iBu)2ATIGe(i-Pr)}2(CdI2)] (3, monomeric), [{(i-Bu)2ATIGe(i-Pr)(CdCl2)}2] (6, dimeric), [{(iBu)2ATIGe(i-Pr)(CdI2)}2] (7, dimeric)} and novel germylene zinc complexes {[{(iBu)2ATIGe(i-Pr)}2(ZnCl2)] (2, monomeric), [{(i-Bu)2ATIGe(i-Pr)(ZnI2)}2] (5, dimeric)}
(ATI...
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... For example, Boncella et al. reported [{( t BuN) 2 U VI I( t Bu 2 bpy)} 2 (μ-η 2 :η 2 -Se 4 )] ( t Bu 2 bpy = 4,4'-ditert-butyl-2,2'-bipyridine), [11] (Figure 1c). [12] In all cases, bonds between uranium and the terminal selenium atoms are short, whereas longer dative interactions were proposed between uranium and the central selenium atoms in the Se 4 chain. Additionally, homoleptic [U IV (Se 2 PR 2 ) 4 ] (R = Ph, i Pr or t Bu; Figure 1d) complexes have been synthesized and crystallographically characterized, with one shorter and one longer UÀ Se distance to each diselenophosphinate ligand. ...
... The UÀ Se distances in 6 are 3.049(1) and 3.067(1) Å, which lie well within the sum of the covalent radii for selenium and uranium (3.16 Å). [18] In addition, it is notable that the difference between the shortest UÀ S bond in 5 and the longest UÀ Se bond in 6 is 0.10 Å, which is significantly smaller than the difference in the covalent radii of sulfur and selenium (0.15 Å). The UÀ Se distances in 6 are approximately 0.2 Å longer than the terminal selenolate distances in [U(SePh) 2 (μ-SePh) 2 (CH 3 CN) 2 ] 2 (2.849(1) Å) [22] and [(C 5 Me 5 ) 2 UMe(SePh)] (2.8432(7) Å). [23] However, they are significantly shorter than the UÀ Se distances in [{(4,6-t Bu 2 C 6 H 2 O) 2 Se} 2 U(THF) 2 ] (Figure 1b; 3.1642(6) and 3.2606(6) Å), [9] and the UÀ Se (2) (1) and 3.125(1) Å). [12] Additionally, they are only slightly elongated relative to the longer of the two UÀ Se distances (3.0076(4)-3.0477(7) Å) for each diselenophosphinate ligand in homoleptic uranium(IV) [U(k 2 -Se 2 PR 2 ) 4 ] (Se 2 PR 2 ; R = Ph, iPr or tBu) complexes (Figure 1d). ...
Rigid thioether‐ and selenoether‐containing pincer proligands H[AS2 ] (1) and H[ASe2 ] (2) were synthesized, and deprotonation provided the potassium salts [K(AS2 )(dme)] (3) and [K(ASe2 )(dme)2] (4). Reaction of two equivalents of 3 or 4 with [UI4(dioxane)2] afforded the uranium thioether complex [(AS2 )2UI2] (5) and the first example of a uranium‐selenoether complex, [(ASe2 )2UI2] (6). X‐ray structures revealed distorted square antiprismatic geometries in which the AE2 ligands are κ³‐coordinated. The nature of the U−ER2 bonding in 5 and 6, as well as methyl‐free analogues of 5 and 6 and a hypothetical ether analogue, was investigated computationally (including NBO, AIM, and ELF calculations) illustrating increasing covalency from O to S to Se.
... Recent work, however, suggests that U(VI) and U(IV) may have a softer nature than previously thought. For instance, Manos and Kanatzidis (2012) reported that layered metal sulfides can extract UO 2 2+ from seawater, supporting the hypothesis that U could form bonds with S with a higher level of covalence, possibly involving 5f orbitals (Andrez et al., 2016;Franke et al., 2014;Gardner et al., 2017). Speciation analysis of organic sulfur in NOM showed that di-and polysulfides are involved in forming intramolecular cross-links (Vairavamurthy et al., 1997;Prietzel et al., 2011). ...
Understanding the hydro-biogeochemical conditions that impact the mobility of uranium (U) in natural or artificial wetlands is essential for the management of contaminated environments. Field-based research indicates that high organic matter content and saturation of the soil from the water table create favorable conditions for U accumulation. Despite the installation of artificial wetlands for U remediation, the processes that can release U from wetland soils to underlying aquifers are poorly understood. Here we used a large soil core from a montane wetland in a 6 year lysimeter experiment to study the stability of U accumulated to levels of up to 6000 ppm. Amendments with electron acceptors showed that the wetland soil can reduce sulfate and Fe(III) in large amounts without significant release of U into the soil pore water. However, amendment with carbonate (5 mM, pH 7.5) resulted in a large discharge of U. After a six-month period of imposed drought, the re-flooding of the core led to the release of negligible amounts of U into the pore water. This long-term experiment demonstrates that U is strongly bound to organic matter and that its stability is only challenged by carbonate complexation.
... The U-Se bond lengths in 4 range from 2.9239(7)-2.9354(7)Å and the Se(1)-Se(2) bond length is 2.3682(9)Å; these compare well with 34 which also features a [m-h 2 :h 2 -Se 2 ] 2À ligand between the two U IV centres. Furthermore, the U-Se bond lengths in 4 are signicantly longer than those reported 35 which feature bridging [Se] 2À ligands between the two U centres, rendering the diselenide ligand in 4 best described as a bridging [Se 2 ] 2À ligand. ...
... Reactions involving A and S 8 or Se may proceed by one of two ways. First, similarly to the formation of complexes 1, 2, 5 and 6, complex A may be reacting with S 8 34 Alternatively, the bridging catecholate ligand could stabilise transient U III centres to enable a reductive activation pathway given that it may possess three different canonical forms; (A) a dianionic catecholate, (B) a monoanionic 1,2-semiquinone, and (C) a neutral 1,2-benzoquinone (Fig. 6). Given that strongly reducing metals are typically required for the activation of elemental chalcogens, 34 resonance structures (B) and (C) could be operative in order to provide access to U III centres, which would be sufficient for S 8 or Se activation (see Fig. 1B for an example of S 8 activation by a U III / U III complex). ...
... First, similarly to the formation of complexes 1, 2, 5 and 6, complex A may be reacting with S 8 34 Alternatively, the bridging catecholate ligand could stabilise transient U III centres to enable a reductive activation pathway given that it may possess three different canonical forms; (A) a dianionic catecholate, (B) a monoanionic 1,2-semiquinone, and (C) a neutral 1,2-benzoquinone (Fig. 6). Given that strongly reducing metals are typically required for the activation of elemental chalcogens, 34 resonance structures (B) and (C) could be operative in order to provide access to U III centres, which would be sufficient for S 8 or Se activation (see Fig. 1B for an example of S 8 activation by a U III / U III complex). It is possible that S 8 /Se activation may be proceeding via metal-based reactivity of a transient U III /U III or U III /U IV complex whereby short-lived monoanionic 1,2-semiquinone or neutral 1,2-benzoquinone resonance forms of the (m-O 2 C 6 H 4 ) ligand provides an extra 1 to 2 electrons to the metal centres. ...
The oxo- and catecholate-bridged UIV/UIV Pacman complex [{(py)UIVOUIV(µ-O2C6H4)(py)}(LA)] A (LA = a macrocyclic “Pacman” ligand; anthracenylene hinge between N4-donor pockets, ethyl substituents on meso-carbon atom of each N4-donor pocket) featuring...
... [28][29][30][31][32][33][34] These complexes have been supported by the sterically demanding ligand N(CH 2 CH 2 NSiPr i 3 ) 3 (Tren TIPS ), which also supported the synthesis of a terminal mono(oxo) complex. 35 Seeking to extend our range of chalcogenide complexes we extended our studies to heavier chalcogens, noting that from related group 15 and thorium derivatives, [28][29][30][31][32][33][34][36][37][38][39] and recent reports of diuranium-chalcogenide complexes, 14,[40][41][42][43][44] that complexes with bridging U-E-U cores were likely to result (E ¼ S, Se, Te). We reasoned that this would present a family of U-E-U complexes with which to systematically probe their electronic structure and magnetism. ...
... The two identical U-S bond distances in 2 of 2.6903(6)Å lie at the upper end of the range of bridging U IV -S bonds in reported examples [2.588(1)-2.713(2)Å], [40][41][42][43][44] alluding to the sterically encumbered nature of Tren TIPS , but are slightly shorter than the sum of the covalent single bond radii of uranium and sulfur (2.73Å), 46 supporting the presence of a U IV -S-U IV unit. ...
... A crop of orange crystals was isolated from the ltrate aer cooling to 5 C, which was identied as 2 by a crystallographic unit cell check and 1 H NMR spectroscopy. The very low yield of 2 from this reaction (7%) highlights the consistently poor crystalline yields of 2 due to the inherent sensitivity and lability of U-S and E-E bonds, 44,54,55 and also the thermodynamic favourability of U-S-U formation, given that 2 is the only product of note from this reaction. ...
We report the synthesis and characterisation of a family of diuranium(IV)-μ-chalcogenide complexes including a detailed examination of their electronic structures and magnetic behaviours. Treatment of [U(TrenTIPS)] [1, TrenTIPS = N(CH2CH2NSiPri3)3] with Ph3PS, selenium or tellurium affords the diuranium(IV)-sulfide, selenide, and telluride complexes [{U(TrenTIPS)}2(μ-E)] (E = S, 2; Se, 5; Te, 6). Complex 2 is also formed by treatment of [U(TrenTIPS){OP(NMe2)3}] (3) with Ph3PS, whereas treatment of 3 with elemental sulfur gives the diuranium(IV)-persulfido complex [{U(TrenTIPS)}2(μ-η2:η2-S2)] (4). Complexes 2-6 have been variously characterised by single crystal X-ray diffraction, NMR, IR, and optical spectroscopies, room temperature Evans and variable temperature SQUID magnetometry, elemental analyses, and complete active space self consistent field spin orbit calculations. The combined characterisation data present a self-consistent picture of the electronic structure and magnetism of 2, 5, and 6, leading to the conclusion that single-ion crystal field effects, and not diuranium magnetic coupling, are responsible for features in their variable-temperature magnetisation data. The presence of magnetic coupling is often implied and sometimes quantified by such data, and so this study highlights the importance of evaluating other factors, such as crystal field effects, that can produce similar magnetic observables, and to thus avoid misassignments of such phenomena.
... [46][47][48][49] Almost all instances of the activation of sulfur or sulfurcontaining small molecules by an actinide involve the assembly of two mononuclear U III centres around one or more atoms of elemental sulfur, or an S atom from CS 2 , providing two reducing electrons to form [U IV ] 2 products, occasionally with further incorporation of CS 2 . Products are oen formed as a mixture of the persuldo (E 2 ) 2À -bridged [U IV ] 2 complexes such as (m-h 2 :h 2 -S 2 )[UX 3 ] 2 (where [UX 3 ] ¼ [U(C 5 H 4 Me) 3 ], 47 [U(N 00 3 ) 3 ] (N 00 ¼ N(SiMe 3 ) 2 ), 27 [U{(SiMe 2 NPh) 3 tacn}], 50 and [U{( Ad ArO) 3 -tacn}], 51 ), and suldo (E) 2À -bridged [U IV ] 2 complexes such as (m-S)[U(N 00 3 ) 3 ] 2 , 27 and (m-S)[U((SiMe 2 NPh) 3 tacn)] 2 . 50 The rst terminal uranium persuldo complex was U[(SiMe 2 NPh) 3tacn](h 2 -S 2 ). ...
... 50 Incorporation of up to four S atoms has also been observed, e.g. in [K (18-crown-6)][(h n -S n )[U(N 00 3 ) 3 ] (n ¼ 1-3), 52 and (m-S 2 ) 2 [U{( Ad ArO) 3 tacn}] 2 . 51 One monosuldo complex adds CS 2 to form the [U IV ] 2 CS 3 adduct (m-k 2 :k 2 -CS 3 ) 2 -[U{( Ad ArO) 3 tacn}] 2 , which can also be formed directly from the U III precursor and CS 2 . Finally, the 'ate' U III siloxide complex [K(18-c-6)U{OSi(O t Bu) 3 } 4 ] has been shown to react with CS 2 to form a variety of potassium-bound reduction products including [K 2 (18-c-6) 2 U{OSi(O t Bu) 3 } 4 (m 3 -k 2 :k 2 :k 2 -CS 3 )]. ...
The first use of a dinuclear UIII/UIII complex in the activation of small molecules is reported. The octadentate Schiff-base pyrrole, anthracene-hinged 'Pacman' ligand LA combines two strongly reducing UIII centres and three borohydride ligands in [M(THF)4][{U(BH4)}2(μ-BH4)(LA)(THF)2] 1-M, (M = Li, Na, K). The two borohydride ligands bound to uranium outside the macrocyclic cleft are readily substituted by aryloxide ligands, resulting in a single, weakly-bound, encapsulated endo group 1 metal borohydride bridging the two UIII centres in [{U(OAr)}2(μ-MBH4)(LA)(THF)2] 2-M (OAr = OC6H2
t
Bu3-2,4,6, M = Na, K). X-ray crystallographic analysis shows that, for 2-K, in addition to the endo-BH4 ligand the potassium counter-cation is also incorporated into the cleft through η5-interactions with the pyrrolides instead of extraneous donor solvent. As such, 2-K has a significantly higher solubility in non-polar solvents and a wider U-U separation compared to the 'ate' complex 1. The cooperative reducing capability of the two UIII centres now enforced by the large and relatively flexible macrocycle is compared for the two complexes, recognising that the borohydrides can provide additional reducing capability, and that the aryloxide-capped 2-K is constrained to reactions within the cleft. The reaction between 1-Na and S8 affords an insoluble, presumably polymeric paramagnetic complex with bridging uranium sulfides, while that with CS2 results in oxidation of each UIII to the notably high UV oxidation state, forming the unusual trithiocarbonate (CS3)2- as a ligand in [{U(CS3)}2(μ-κ2:κ2-CS3)(LA)] (4). The reaction between 2-K and S8 results in quantitative substitution of the endo-KBH4 by a bridging persulfido (S2)2- group and oxidation of each UIII to UIV, yielding [{U(OAr)}2(μ-κ2:κ2-S2)(LA)] (5). The reaction of 2-K with CS2 affords a thermally unstable adduct which is tentatively assigned as containing a carbon disulfido (CS2)2- ligand bridging the two U centres (6a), but only the mono-bridged sulfido (S)2- complex [{U(OAr)}2(μ-S)(LA)] (6) is isolated. The persulfido complex (5) can also be synthesised from the mono-bridged sulfido complex (6) by the addition of another equivalent of sulfur.
... [166] The substituent in the paraposition to the hydroxyl substituent, on the other hand, is able to regulate the electronic properties of the ring, as well as the solubility of the phenolato complex. [166] These combined properties offer good steric control as well as electronic fine-tuning of the metal center and allowed for the selective and wellstudied activation of small molecules, such as like H 2 O, [167] , CO and CO 2 , [152,[168][169][170][171] SO 2 , [169] CS 2 , [170,172] alkynes, [173] chalcogenides, [174][175][176] azides, [168] and N 2 O [171] on uranium centers. In case of the carbene arms, substituents on the imidazole are oriented perpendicular to the metal-carbene plane (Figure 1.20, left), [67] whereas for the phenolate arms, the Finally, the scope of small molecule activations is expanded to the reduction of NO (Chapter 4). ...
Iron nitrido and nitrosyl/nitroxyl model complexes have been of great interest owing to their role as reactive intermediates and transfer reagents and their role in biochemical reactions involving nitrogen and NO. The stable iron(IV) nitrido complex [(TIMENMes)FeIV(N)]BPh4 (TIMENMes = tris-[2 (3-mesitylimidazol-2 ylidene)¬ethyl]¬amine), synthesized by Meyer and co-workers in 2008, proved to be uncreative towards electrophiles or nucleophiles and thus, the increase of its reactivity was tested by oxidizing it to the iron(V) complex [(TIMENMes)¬FeV(N)]2+. However, this reaction led to the insertion of the nitrido ligand into one of the iron-carbene bonds. To avoid this unwanted insertion reaction, other means to influence the reactivity of the nitrido ligand were investigated in this thesis. In order to reduce the electron density of the metal center in the trigonal iron(IV) nitrido complex without formally oxidizing it, better π acceptors on the ancillary ligand were introduced. For comparison with the TIMENMes system a ligand with similar steric demand was sought. Therefore, the imidazole ring of the TIMENMes ligand was substituted with its saturated counterpart imidazoline that exhibits increased π accepting properties. The protonated ligand precursor H3(sTIMENMes)(X)3 (tris¬(2 (3 mesityl¬imidazolinium)¬ethyl)¬amine, X = PF6 , ClO4 , BF4 , or BPh4 ) was synthesized via the reaction of tris(2-chloroethyl)amine with three equivalents of mesitylimidazoline and subsequent anion exchange. The free carbene tris¬(2 (3 mesityl¬imidazolin-2 ylidene)¬ethyl)¬amine (sTIMENMes) synthesized via deprotonation with various bases proved to be unstable in solution and prevented subsequent coordination. Other synthetic routes like thermolysis of the corresponding dimer, speeding up the reaction via one-pot syntheses or incorporating iron precursors comprising internal bases were not successful. Avoiding the presence of a Lewis acidic metal precursor finally led to the formation of the silver complex [µ3¬(sTIMENMes)(AgICl)3] from H3(sTIMENMes)(BPh4)3 and Ag2O. Transmetallation with an FeCl2 solution lead to formation of AgCl, but no other reproducible products could be isolated or identified. As an alternative influence on the reactivity the electron density at the iron center was increased in order to stabilize the iron(V) complex and thus, prevent the insertion of the nitrido ligand. This was achieved by exchanging two of the carbene bearing arms in the TIMENMes ligand with phenolate arms resulting in the mono-carbene bis-phenolate system (MIMPNMes,Ad,Me)2 . The protonated precursor H3(MIMPNMes,Ad,Me)BF4 was deprotonated to form the potassium salt of the employed ligand K2(MIMPNMes,Ad,Me) (potassium mono¬(2-(3 mesitylimidazol-2 ylidene)ethyl-bis¬(3 adamantyl-5 methyl-2 oxido¬phenyl)¬methyl)¬amine). This ligand was successfully coordinated to manganese(II), iron(II), and cobalt(II) resulting in the corresponding neutral complexes [(MIMPNMes,Ad,Me)MnII], [(MIMPNMes,Ad,Me)FeII], and [(MIMPNMes,Ad,Me)CoII]. Comparison of the 57Fe Mößbauer isomer shifts of the iron complex [(MIMPNMes,Ad,Me)FeII] with those of the tris-carbene and bis-carbene mono-phenolate complexes [(TIMENMes)FeII](OTf)2 and [(BIMPNMes,Ad,Me)¬FeII¬(MeCN)]¬Cl ((BIMPNMes,Ad,Me) = bis(2-(3 mesityl¬imidazol-2-ylidene)-ethyl-(3 adamantyl-5 methyl-2 oxidophenyl)¬methyl)¬amine) confirmed an increase in electron density at the iron(II) center with each additional phenolate substituting a carbene pendent arm. The (MIMPNMes,Ad,Me)2 system was further investigated for its ability to stabilize iron-nitrido entities formed via photolysis of the corresponding iron(II) and iron(III) azido complexes. However, the neutral iron(II) complex lacked the driving force to coordinate an azide ion, which precluded the formation of an iron(IV) nitrido complex with the (MIMPNMes,Ad,Me)2 system. In contrast, after oxidation by AgCl, the axially coordinated chlorido ligand of the iron(III) complex [(MIMPNMes,Ad,Me)FeIII(Cl)] can be exchanged by N3 yielding the iron(III) azido complex [(MIMPNMes,Ad,Me)FeIII(N3)]. Photolysis of [(MIMPNMes,Ad,Me)FeIII(N3)] at room temperature mainly resulted in the formation of [(MIMPNMes,Ad,Me)FeII] and N2 through photoreductive cleavage of N3·. The major side product of this reaction was identified as the iron(III) complex [(MIMPNMes,Ad,Me=N(H))FeIII] most likely formed through nitride-insertion of the intermediate iron(V) complex into the iron–carbene bond. Conducting the photolysis in frozen solution prevents the formation of the iron(II) complex, because the photoreduction is reversible under these conditions as the mobility of the azide radical is diminished in the frozen matrix. The photolysis of in frozen THF was monitored by EPR spectroscopy revealing a rhombic signal indicative of the presence of an S = 1/2 species. Due to the observed 60 to 70 MHz coupling to a nitrogen atom, the signal was assigned to the iron(V) nitrido complex [(MIMPNMes,Ad,Me)FeV(N)], that reacts to the aforementioned imine/imido complex upon increasing the temperature above 85 K. In order to further investigate the relation between the nitride ligand and its formally oxygenized form nitrosyl, NO was reductively activated on an iron complex. The reaction of [(TIMENMes)FeII](BF4)2 with NOBF4 yielded a yellow, diamagnetic complex that was identified by a combination of 1H NMR, IR, and applied-field 57Fe Mößbauer spectroscopy as well as DFT calculations as the {FeNO}6 complex [(TIMENMes)¬Fe(NO)¬(MeCN)]¬(BF4)3 with one acetonitrile coordinated in the equatorial position. Upon reduction with sodium amalgam, the equatorial ligand is cleaved off and the C3 symmetric {FeNO}7 complex [(TIMENMes)¬Fe(NO)]¬(BF4)2 is formed. With extended reaction time and addition of a Na/Hg excess, the {FeNO}8 complex [(TIMENMes)¬Fe(NO)]-BF4 could be obtained. Further reduction with Na/Hg in benzene provided the {FeNO}9 complex [(TIMENMes)Fe(NO)] and with a so-called “electride” solution the {FeNO}10 species [Cs(18 crown 6)2]-[(TIMENMes)Fe(NO)]. Thus, the TIMENMes ligand represents the first ligand system that is able to stabilize more than three oxidation states of Fe NO complexes. The complexes were extensively characterized with a combination of crystal structure determination, magnetic measurements, EPR-, IR-, electronic absorption, and applied-field 57Fe Mößbauer spectroscopy as well as DFT calculations. Due to its temperature sensitivity, the {FeNO}10 complex was characterized only by 57Fe Mößbauer and IR vibrational spectroscopy, as well as DFT calculations, precluding a more detailed comparison to the other reduced complexes. The reduced {FeNO}7 9 complexes exhibit a high-spin iron center that is anti-ferromagnetically coupled to a NO ligand. At the same time, [(TIMENMes)¬Fe(NO)]¬BF4 shows very distinct behavior compared to other reported {FeNO}8 complexes. Among all other reported {FeNO}8 complexes to date, only one exhibits a high-spin state. This complex is highly unstable and exhibits increasing iron-ancillary ligand bond lengths. Despite its high-spin state, the {FeNO}8 complex presented herein exhibits extraordinary stability and an increasing covalency of the iron-ligand bonds. The same is true for the {FeNO}9 complex with only one low-spin example reported, rendering the high-spin complex [(TIMENMes)Fe(NO)] unique in literature. The {FeNO}10 complex [Cs¬(18 crown 6)2]-[(TIMENMes)¬Fe-(NO)] shows a change in the spin state, with all ten electrons being located at the iron center. However, due to a very low iron character of the dxz and dyz orbitals, the actual electron distribution has to be described in the form of the two mesomeric forms Fe II NO+ with all ten electrons located at the iron center and FeII NO3 with six electrons located at the metal center and four electrons located in the NO π*-orbitals. Altogether, the complexes presented in this work are very well characterized and the electronic structures assigned to the complexes are supported by DFT calculations. Thus, this work provides valuable data for the research on reduced Fe-NO complexes, hopefully opening new avenues to future research on high-spin Fe-NO complexes.
... Instead, dimerization of the complexes via (poly-)chalcogenido as well as bis-hydrochalcogenido bridges was observed. 34,36,46 In order to prevent dimerization reactions, we made use of a well-established tacn anchored ligand, the sterically encumbered adamantyl derivative ( Ad,R ArO) 3 tacn) 3À (R ¼ tert-butyl, methyl). 29 Accordingly, the uranium(III) precursor [(( Ad,Me ArO) 3 tacn)U] (1) (( Ad,Me ArO) 3tacn 3À ¼ trianion of 1,4,7-tris(3-(1-adamantyl)-5-methyl-2hydroxybenzyl)-1,4,7-triazacyclononane) allowed for synthesis of the here reported monomeric uranium (hydro-) chalcogenido complexes. ...
... 50,61,62 Tetravalent uranium ions possess an f 2 valence electron conguration, which results in a non-magnetic ground state at very low temperatures; and consequently, strongly temperature-dependent magnetic moments, m eff , with values typically ranging from 0.3 m B at 2 K to 2.8 m B at room temperature. 36,46,50,51,53,61,63,64 In contrast, trivalent U III ions (f 3 ) possess a half integer spin with a doublet, EPR-active ground state (g t ¼ 1.912, g k ¼ 2.421 ( Fig. 4 top)) and should approach non-zero values at low temperatures. 53,65 Accordingly, only the effective magnetic moment at low temperatures, as well as the temperaturedependency of the complexes, can provide reasonable hints to the ions' formal oxidation state. ...
Herein, we report the synthesis and characterization of a series of terminal uranium(iv) hydrosulfido and sulfido complexes, supported by the hexadentate, tacn-based ligand framework (Ad,MeArO)3tacn³⁻ (= trianion of 1,4,7-tris(3-(1-adamantyl)-5-methyl-2-hydroxybenzyl)-1,4,7-triazacyclononane). The hydrosulfido complex [((Ad,MeArO)3tacn)U-SH] (2) is obtained from the reaction of H2S with the uranium(iii) starting material [((Ad,MeArO)3tacn)U] (1) in THF. Subsequent deprotonation with potassium bis(trimethylsilyl)amide yields the mononuclear uranium(iv) sulfido species in good yields. With the aid of dibenzo-18-crown-6 and 2.2.2-cryptand, it was possible to isolate a terminal sulfido species, capped by the potassium counter ion, and a "free" terminal sulfido species with a well separated cation/anion pair. Spectroscopic and computational analyses provided insights into the nature of the uranium-sulfur bond in these complexes.
... Table 1). 58,59,[61][62][63][64][65] Furthermore, the chalcogen-bound hydrogen could be located in the difference Fourier map and was subsequently treated using a riding model. The U-N distance of 2.616(2)Å and the U-O avg. ...
... bonds of 2.171Å are comparable to other complexes supported by the N-anchored ligand ( Ad ArO) 3 N 3À . 54,58,59 Additionally, the SH À ligand is not coordinated in the axial position directly trans to the nitrogen anchor, which is clearly shown in the N-U-S bond angle of 136.24 (4) . ...
... and can be compared to other complexes with U-Se single bond distances varying from 2.719(1) to 3.125(1)Å. [57][58][59][61][62][63]66,67 As in complex 1-SH, the N-U-Se angle is strongly bent with 133.44 (7) . In contrast to 1-SH, the seleniumbound hydrogen could not be located in the difference Fourier map, but was conrmed in 1 H and 2 H{ 1 H} NMR experiments. ...
We report the syntheses, electronic properties, and molecular structures of a series of mono- and dinuclear uranium(IV) hydrochalcogenide complexes supported by the sterically demanding but very flexible, single N-anchored tris(aryloxide) ligand (AdArO)3N)3–. The mononuclear complexes [((AdArO)3N)U(DME)(EH)] (E = S, Se, Te) can be obtained from the reaction of the uranium(III) starting material [((AdArO)3N)UIII(DME)] in DME via reduction of H2E and the elimination of 0.5 equivalents of H2. The dinuclear complexes [{((AdArO)3N)U}2(μ-EH)2] can be obtained by dissolving their mononuclear counterparts in non-coordinating solvents such as benzene. In order to facilitate the work with the highly toxic gases, we created concentrated THF solutions that can be handled using simple glovebox techniques and can be stored at –35 °C for several weeks.
... [1][2][3][4] Hence, there is a continuing interest in the coordination chemistry and reactivity of soft donor ligands that has come to the forefront of actinide chemistry. [5][6][7][8][9][10] In this context, a current area of interest in our group is homoleptic f-element complexes comprising soft donors for examination of metalligand bonding. However, in reported studies of soft extractants, their complexes lack for further reactivity because the coordination sphere is typically closed. ...
We report M(IV) M = Ti, Zr, Hf, Ce, and Th, complexes of a selenium bis(phenolate) ligand, 2,2′-selenobis(4,6-di-tert-butylphenol), (H2ArOSeO), 1. Reaction of Ti(NEt2)4 with two equivalents of 1 affords Ti(ArOSeO)2, 2. Salt metathesis of ZrCl4 and HfCl4 with two equivalents of Na2ArOSeO produces Zr(ArOSeO)2(THF), 3, and Hf(ArOSeO)2(THF), 4, respectively. Protonolysis of ThCl[N(SiMe3)2]3 with two equivalents of 1 yields Th(ArOSeO)2(THF)2, 5. Salt metathesis of Ce(OTf)3 and two equivalents of Na2ArOSeO produces [Na(THF)3][Ce(ArOSeO)2], which was oxidized in situ using 0.5 equivalents of I2 to yield the diamagnetic Ce(IV) product, Ce(ArOSeO)2(THF)2, 6. Addition of 2,2′-bipyridyl to 6 forms Ce(ArOSeO)2(bipy), 6a. Each diamagnetic complex was characterized using 1H, 13C, and 77Se NMR and IR spectroscopy and the structures of 2–6a were established with X-ray crystallography. Electrochemical measurements using cyclic voltammetry on complexes 2, 5, and 6 are also reported.
