May 2023
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31 Reads
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1 Citation
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May 2023
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31 Reads
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1 Citation
September 2019
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250 Reads
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34 Citations
Although the chemistry of uranium-ligand multiple bonding is burgeoning, analogous complexes involving other actinides such as thorium remain rare and there are not yet any terminal thorium nitrides outside of cryogenic matrix isolation conditions. Here, we report evidence that reduction of a thorium-azide produces a transient Th≡N triple bond, but this activates C-H bonds to produce isolable parent imido derivatives or it can be trapped in an N-heterocycle amine. Computational studies on these thorium-nitrogen multiple bonds consistently evidences a σ > π energy ordering. This suggests pushing-from-below for thorium, where 6p-orbitals principally interact with filled f-orbitals raising the σ-bond energy. Previously this was dismissed for thorium, being the preserve of uranium-nitrides or the uranyl dication. Recognising that pushing-from-below perhaps occurs with thorium as well as uranium, and with imido ligands as well as nitrides, suggests this phenomenon may be more widespread than previously thought.
December 2017
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59 Reads
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62 Citations
We report the synthesis and characterisation of the compounds [An(TrenDMBS){Pn(SiMe3)2}] and [An(TrenTIPS){Pn(SiMe3)2}] [TrenDMBS = N(CH2CH2NSiMe2But)3, An = U, Pn = P, As, Sb, Bi; An = Th, Pn = P, As; TrenTIPS = N(CH2CH2NSiPri3)3, An = U, Pn = P, As, Sb; An = Th, Pn = P, As, Sb]. The U-Sb and Th-Sb moieties are unprecedented examples of any kind of An-Sb molecular bond, and the U-Bi bond is the first electron-precise one. The Th-Bi combination was too unstable to isolate, underscoring the fragility of these linkages. However, the U-Bi complex is the heaviest electron-precise pairing of two elements involving an actinide on a macroscopic scale under ambient conditions, and this is exceeded only by An-An pairings prepared under cryogenic matrix isolation conditions. Thermolysis and photolysis experiments suggest that the U-Pn bonds degrade by hemolytic bond cleavage, whereas the more redox robust thorium compounds engage in an acid-base/dehydrocoupling route.
December 2017
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65 Reads
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14 Citations
Angewandte Chemie
We report the synthesis and characterisation of the compounds [An(TrenDMBS){Pn(SiMe3)2}] and [An(TrenTIPS){Pn(SiMe3)2}] [TrenDMBS = N(CH2CH2NSiMe2But)3, An = U, Pn = P, As, Sb, Bi; An = Th, Pn = P, As; TrenTIPS = N(CH2CH2NSiPri3)3, An = U, Pn = P, As, Sb; An = Th, Pn = P, As, Sb]. The U-Sb and Th-Sb moieties are unprecedented examples of any kind of An-Sb molecular bond, and the U-Bi bond is the first electron-precise one. The Th-Bi combination was too unstable to isolate, underscoring the fragility of these linkages. However, the U-Bi complex is the heaviest electron-precise pairing of two elements involving an actinide on a macroscopic scale under ambient conditions, and this is exceeded only by An-An pairings prepared under cryogenic matrix isolation conditions. Thermolysis and photolysis experiments suggest that the U-Pn bonds degrade by hemolytic bond cleavage, whereas the more redox robust thorium compounds engage in an acid-base/dehydrocoupling route.
October 2017
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25 Reads
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3 Citations
Organometallics
The hybrid alkyl/cyclopentadienyl “constrained-geometry” proligands (Me3Si)2CH{SiMe2(C5H5)}, (Me3Si)2CH{SiMe2(C5Me4H)} and (Me3Si)2CH{SiMe2(C5H4-3-SiMe3)} were synthesized by the reaction of the bromosilane (Me3Si)2CH(SiMe2Br) with the corresponding lithium cyclopentadienides. Metalation of these proligands with an excess of MeK gives access to the corresponding dipotassium salts [(Me3Si)2C{SiMe2(C5H4)}]K2(OEt2)0.5, [(Me3Si)2C{SiMe2(C5Me4)}]K2(OEt2), and [[(Me3Si)2C{SiMe2(C5H3-3-SiMe3)}]K2(C6H6)]2·2C6H6 after recrystallization. Similarly, the reaction between the phosphine–borane-substituted chlorosilane (Me3Si)CH{PMe2(BH3)}(SiMe2Cl) and [C5Me4H]Li gives the proligand (Me3Si)CH{PMe2(BH3)}{SiMe2(C5Me4H)}, which reacts with 2 equiv of PhCH2K to give the dipotassium salt [(Me3Si)C{PMe2(BH3)}{SiMe2(C5Me4)}]K2(THF). X-ray crystallography revealed that the dipotassium salts of these hybrid ligands crystallize as zigzag polymers or three-dimensional networks. The suitability of the dipotassium salts as ligand transfer reagents for the synthesis of lanthanide complexes was probed through the synthesis of the lanthanum(III) complex [(Me3Si)2C{SiMe2(C5Me4)}]La(I)(THF)2, in which the dianionic ligand chelates the lanthanum center.
June 2017
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12 Reads
May 2017
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76 Reads
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35 Citations
The reaction of [Zr(TrenDMBS)(Cl)] [Zr1, TrenDMBS = N(CH2CH2NSiMe2But)3] with NaPH2 gave the terminal parent phosphanide complex [Zr(TrenDMBS)(PH2)] [Zr2, Zr-P = 2.685(2) Å]. Treatment of Zr2 with one equivalent of KCH2C6H5 and two equivalents of benzo-15-crown-5 ether (B15C5) afforded an unprecedented example outside of matrix isolation of a structurally authenticated transition metal terminal parent phosphinidene complex [Zr(TrenDMBS)(PH)][K(B15C5)2] [Zr3, Zr=P = 2.469(2) Å]. DFT calculations reveal a polarized-covalent Zr=P double bond, with a Mayer bond order of 1.48, and together with NMR and IR spectroscopic data also suggest an agostic-type Zr···HP interaction [∠ZrPH = 66.7°] which is unexpectedly similar to that found in cryogenic spectroscopically observed phosphinidene species. Surprisingly, computational data suggest that the Zr=P linkage reported here is as polarized, and thus as covalent, as essentially isostructural U=P and Th=P analogues.
May 2017
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48 Reads
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9 Citations
Angewandte Chemie
The reaction of [Zr(TrenDMBS)(Cl)] [Zr1, TrenDMBS = N(CH2CH2NSiMe2But)3] with NaPH2 gave the terminal parent phosphanide complex [Zr(TrenDMBS)(PH2)] [Zr2, Zr-P = 2.685(2) Å]. Treatment of Zr2 with one equivalent of KCH2C6H5 and two equivalents of benzo-15-crown-5 ether (B15C5) afforded an unprecedented example outside of matrix isolation of a structurally authenticated transition metal terminal parent phosphinidene complex [Zr(TrenDMBS)(PH)][K(B15C5)2] [Zr3, Zr=P = 2.469(2) Å]. DFT calculations reveal a polarized-covalent Zr=P double bond, with a Mayer bond order of 1.48, and together with NMR and IR spectroscopic data also suggest an agostic-type Zr···HP interaction [∠ZrPH = 66.7°] which is unexpectedly similar to that found in cryogenic spectroscopically observed phosphinidene species. Surprisingly, computational data suggest that the Zr=P linkage reported here is as polarized, and thus as covalent, as essentially isostructural U=P and Th=P analogues.
March 2017
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71 Reads
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54 Citations
Despite a major expansion of uranium–ligand multiple bond chemistry in recent years, analogous complexes involving other actinides (An) remain scarce. For thorium, under ambient conditions only a few multiple bonds to carbon, nitrogen, phosphorus and chalcogenides are reported, and none to arsenic are known; indeed only two complexes with thorium–arsenic single bonds have been structurally authenticated, reflecting the challenges of stabilizing polar linkages at the large thorium ion. Here, we report thorium parent–arsenide (ThAsH2), –arsinidiides (ThAs(H)K and ThAs(H)Th) and arsenido (ThAsTh) linkages stabilized by a bulky triamidoamine ligand. The ThAs(H)K and ThAsTh linkages exhibit polarized-covalent thorium–arsenic multiple bonding interactions, hitherto restricted to cryogenic matrix isolation experiments, and the AnAs(H)An and AnAsAn linkages reported here have no precedent in f-block chemistry. 7s, 6d and 5f orbital contributions to the Th–As bonds are suggested by quantum chemical calculations, and their compositions unexpectedly appear to be tensioned differently compared to phosphorus congeners.
March 2017
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14 Reads
Supplementary Figures, Supplementary Tables, Supplementary Methods and Supplementary References
... The original extended-Hückel theory study of PFB by Tatsumi and Hoffmann 10 , and subsequent related theoretical work 11-13,24 did not quantify PFB, and by extension ITI, in terms of energy across different types of compounds. Furthermore, the delocalized nature of the valence canonical MOs has made it difficult to assess the contributions of actinide 6p AOs in larger systems, such that PFB has been evaluated indirectly, for instance via calculations excluding or including 6p in frozen cores 13,16,18,24 . ...
September 2019
... [18] Apart from these observations, no systematic study on the stability of uranium phosphine complexes has been reported so far. While the nature of the bond of uranium with anionic Pbased ligands, such as phosphide, phosphinidiides and phosphinidenes has been studied in more detail in the last years, [28][29][30][31][32] bonding analyses of uranium-phosphine bonds have not been reported to the best of the authors knowledge. ...
December 2017
... U nexpected properties, structures, and reactivities emerge in heavy elements because their high nuclear charge accelerates surrounding electrons to relativistic speeds, altering orbital shapes and energies and the nature of chemical bonds 1 . This in turn, leads to abrupt changes in behavior between neighboring elements 2-8 and a breakdown of simple descriptions of electronic structure that can be used to explain emerging properties 1,[9][10][11][12][13][14][15][16][17] . Examples of these discontinuities include the large volume expansion between α-Pu and α-Am, and the corresponding localization of 5f electrons that leads to superconductivity in α-Am at low temperatures 18 , as well as the diminishment of redox activity that occurs at this same juncture in the actinide series 19 . ...
December 2017
Angewandte Chemie
... 163 The hybrid alkyl/cyclopentadienyl ''constrained-geometry'' proligand (149) was synthesized from in-situ generated [(Me 3 Si)CH(PMe 2 (BH 3 ))]Li and Me 2 SiCl 2 followed by the reaction with Cp * Li; (149) was isolated from the reaction mixture as one regioisomer. 164 New geminally bonded intramolecular donor-acceptor systems (150) and (151) ...
October 2017
Organometallics
... [6] However, due to the reactive triplet ground state, unsaturated valence shell, and relatively large size of heavier Pn ions, previous studies were mainly restricted to spectroscopic species, [7] or a small number of bridging PnH stabilised by transition metals. [8] Structurally authenticated molecules with terminal (i.e. the PnR group is bound to only one metal) PnH groups are sparse across the whole Periodic Table, with a handful of terminal parent phosphinidene (M=PH) compounds known for p-, [9] d-, [10] and f-blocks. [11] Terminal arsinidene (M=AsR) congeners have emerged for p- [12] and f-block [13] derivatives recently, but M=AsH remains unknown for the d-block; indeed, only five M=AsR d-block complexes have been crystallographically characterised in the past 28 years. ...
May 2017
Angewandte Chemie
... 119,120 Liddle also presented a follow-up paper on the analogous Zr complex (33), which reacts in a similar way to the uranium and thorium analogues (forming the respective phosphanide and phosphinidene compounds, 34 and 35, Scheme 23c). 121 We can draw links to possible onward organic Scheme 22. Schrock and Co-workers Have Undertaken a Systematic Study on the Coordination Chemistry of Molybdenum and Tungsten Amides, Phosphides, and Arsenides Scheme 23. (a, b) Liddle's Studies on the Phosphanide and Phosphinidene Chemistry of the Actinides; a (c) Studies on the Analogous Zr Complex a Na(12c4) 2 cations omitted for clarity, and 12-crown-4 (12c4) and benzo-15-crown-5 abbreviated for clarity (b15c5). ...
May 2017
... We previously reported parent phosphanide [61][62][63] , arsenide [63][64][65][66] , phosphinidene [61][62][63]67 , arsinidene [63][64][65] , phosphido 62,67 and arsenido [64][65][66] complexes of uranium and thorium supported by {N(CH 2 CH 2 NR) 3 } 3− triamidoamine ligands (Tren R ; R = SiPr i 3 , tri-isopropylsilyl, TIPS, or SiCy 3 , tri-cyclohexylsilyl, TCHS). Studying parent complexes is desirable because a H substituent is the simplest, most electronically innocent substituent to have, and from a main group perspective provides fundamental, metal-stabilized parent fragments for study. ...
March 2017
... We previously reported parent phosphanide 61-63 , arsenide 63-66 , phosphinidene [61][62][63]67 , arsinidene 63-65 , phosphido 62,67 and arsenido 64-66 complexes of uranium and thorium supported by {N(CH 2 CH 2 NR) 3 } 3− triamidoamine ligands (Tren R ; R = SiPr i 3 , tri-isopropylsilyl, TIPS, or SiCy 3 , tri-cyclohexylsilyl, TCHS). Studying parent complexes is desirable because a H substituent is the simplest, most electronically innocent substituent to have, and from a main group perspective provides fundamental, metal-stabilized parent fragments for study. ...
September 2016
... [1][2][3] This is due to a combination of: (i) three amide centres that are covalent σ-and dative π-donors; (ii) the presence of a tertiary amine that can modulate the strength of its dative σ-donation to a coordinated An-ion as required by the metal and also engage in inverse-trans-influence (ITI) binding; (iii) being a quadridentate ligand that maximises kinetic and thermodynamic stability of the resulting An-complexes; (iv) varied N-silyl substitution patterns that can systematically tune the steric and electronic properties of the Tren R scaffold, including producing a well-defined pocket at the coordinated An-metal with which to stabilise novel linkages or reactivity. It is therefore the case that Tren R -ligands have supported novel Anligand multiple bonds, [4][5][6][7][8][9][10][11][12][13][14][15] An-metal bonds, [16][17][18][19][20][21] novel main group moieties, [22][23][24][25][26][27][28][29][30][31] uranyl activation, [32,33] small molecule activation, [34][35][36][37][38][39][40][41][42][43] single-molecule magnetism and electronic communication, [44,45] novel photochemistry, [46] insight into fundamental f-block phenomena such as disproportionation, the ITI, pushing-from-below, [47][48][49][50][51] and NMR chemical shift anisotropy covalency studies. [52,53] The above advances have all been achieved utilising a relatively small range of silyl Tren R ligands, including trimethylsilyl (Tren TMS ), dimethyl-tert-butyl-silyl (Tren DMBS ), tri-iso-propylsilyl (Tren TIPS ), tricyclohexyl-silyl (Tren TCHS ), and triphenyl-silyl (Tren TPS ). ...
July 2016
Polyhedron