Dihydrogen Addition in a Dinuclear Rare-Earth Metal Hydride Complex Supported by a Metalated TREN Ligand

Half-Sandwich Cerium and Lanthanum Dialkyl Complexes: Synthesis, Structure, and Reactivity Studies

Cerium and lanthanum dialkyl complexes [η5-1,2,4-(Me3C)3C5H2]Ln(CH2C6H4-o-NMe2)2 (Ln = Ce 1 and La 2), supported by a tri-tert-butylcyclopentadienyl ligand, have been successfully synthesized. Studies demonstrate that these complexes possess diverse reactivity toward various small molecules. For example, the reaction of complexes 1 and 2 with diphenyl dichalcogenides PhEEPh (E = S, Se) results in the formation of lanthanide thiolates [(η5-1,2,4-(Me3C)3C5H2)Ln(SPh)(μ-SPh)]2 (Ln = Ce 3 and La 4) and selenolates [(η5-1,2,4-(Me3C)3C5H2)Ln(SePh)(μ-SePh)]2 (Ln = Ce 5 and La 6), concomitantly releasing PhE(CH2C6H4-o-NMe2). Furthermore, complexes 1 and 2, upon reaction with dibenzyl disulfide, yield tetranuclear rare-earth metallomacrocyclic compounds {[(η5-1,2,4-(Me3C)3C5H2)Ln(μ-SCH2C6H5)]2(μ-η3:η3-SCHC6H5)}2 (Ln = Ce 7 and La 8). This reaction may involve a process of σ-bond metathesis and C-H activation. While the reaction of 1 and 2 with dibenzyl diselenide in the presence of LiCH2C6H4-o-NMe2 leads to the formation of lanthanide-lithium selenido clusters [(η5-1,2,4-(Me3C)3C5H2)La(μ-SeCH2C6H5)]3(μ3-Se)[μ3-SeLi(THF)3] (Ln = Ce 9 and La 10). Meanwhile, lanthanide selenido clusters [(η5-1,2,4-(Me3C)3C5H2)La(μ-SeCH2C6H4-o-NMe2)]4(μ3-Se)2 (Ln = Ce 11 and La 12) can be obtained by treating 1 and 2 with elemental selenium in a 1:2 molar ratio. Additionally, the treatment of 1 and 2 with benzoxazole generates ring-opening/C-C coupling/C-N coupling products {(η5-1,2,4-(Me3C)3C5H2)La[μ-OC6H4-o-N═CHN(CH(CH2C6H4-o-NMe2)2C6H4-o-O]}2 (Ln = Ce 13 and La 14). All new compounds were characterized by various spectroscopic methods, and their solid-state structures were confirmed by single-crystal X-ray diffraction analyses.

f-Block hydride complexes - synthesis, structure and reactivity

Complexes formed between the heaviest and lightest elements in the periodic table yield the f-block hydrides, a unique class of compounds with wide-ranging utility and interest, from catalysis to light-responsive materials and nuclear waste storage. Recent developments in syntheses and analytics, such as exploiting low-oxidation state metal ions and improvements in X-ray diffraction tools, have transformed our ability to understand, access and manipulate these important species. This perspective brings together insights from binary metal hydrides, with molecular solution phase studies on heteroleptic complexes and gas phase investigations. It aims to provide an overview of how the f-element influences hydride formation, structure and reactivity including the sometimes-surprising power of co-ligands to tune their behaviour towards a variety of applications.

Synthesis, Characterization, and Reactivity Studies of New Cyclam-Based Y(III) Complexes

[(Bn2Cyclam)Y(N(SiMe3)2)] was prepared by reaction of H2Bn2Cyclam with Y[N(SiMe3)2]3. The protonation of the macrocycle ligand in [(Bn2Cyclam)Y(N(SiMe3)2)] is observed upon reaction with [HNMe3][BPh4] leading to the formation of [(HBn2Cyclam)Y(N(SiMe3)2)][BPh4]. DFT analysis of [(Bn2Cyclam)Y(N(SiMe3)2)] showed that the HOMO is located on the anionic nitrogen atoms of the cyclam ring indicating that protonation follows orbital control. Addition of H2Bn2Cyclam and H2(3,5-tBu2Bn)2Cyclam to a 1:3 mixture of YCl3 and LiCH2SiMe3 in THF resulted in the formation of [((C6H4CH2)BnCyclam)Y(THF)(µ-Cl)Li(THF)2] and [Y{(η3-3,5-tBu2Bn)2Cyclam}Li(THF)], respectively. The reaction of H23,5-tBu2Bn2Cyclam with Y(CH2SiMe3)3(THF)2 was studied and monitored by a temperature variation NMR experiment revealing the formation of [(3,5-tBu2Bn2Cyclam)Y(CH2SiMe3)]. Preliminary catalytic assays have shown that [Y{(η3-3,5-tBu2Bn)2Cyclam}Li(THF)] is a very efficient catalyst for the intramolecular hydroamination of 2,2-diphenyl-pent-4-enylamine.

Scandium and lanthanum hydride complexes stabilized by super-bulky penta-arylcyclopentadienyl ligands

Hydrogenolysis of the half-sandwich penta-arylcycopentadienyl-supported rare-earth metal dibenzyl complexes [(Cp^Ar5)Ln(p-CH₂-C₆H₄-Me)₂(THF)] (Cp^Ar5 = C₅Ar₅, Ar = 3,5-ⁱPr₂-C₆H₃; Ln = Sc, La) afforded a bimetallic scandium complex [(Cp^Ar5)Sc(H)(μ-OC₄H₉)]₂ (2) with two terminal hydrido ligands, and a double-sandwich bimetallic lanthanum hydride complex [(Cp^Ar5)La(μ-H)]₂ (4) bearing the reduced Cp^Ar5 ligand. DFT calculations were conducted to elucidate the reaction profiles.

Molecular Zinc Hydride Cations [ZnH]+ : Synthesis, Structure, and CO2 Hydrosilylation Catalysis

Protonolysis of [ZnH2 ]n with the conjugated Brønsted acid of the bidentate diamine TMEDA (N,N,N',N'-tetramethylethane-1,2-diamine) and TEEDA (N,N,N',N'-tetraethylethane-1,2-diamine) gave the zinc hydride cation [(L2 )ZnH]+ , isolable either as the mononuclear THF adduct [(L2 )ZnH(thf)]+ [BArF 4 ]- (L2 =TMEDA; BArF 4 - =[B(3,5-(CF3 )2 -C6 H3 )4 ]- ) or as the dimer [{(L2 )Zn)}2 (μ-H)2 ]2+ [BArF 4 ]- 2 (L2 =TEEDA). In contrast to [ZnH2 ]n , the cationic zinc hydrides are thermally stable and soluble in THF. [(L2 )ZnH]+ was also shown to form di- and trinuclear adducts of the elusive neutral [(L2 )ZnH2 ]. All hydride-containing cations readily inserted CO2 to give the corresponding formate complexes. [(TMEDA)ZnH]+ [BArF 4 ]- catalyzed the hydrosilylation of CO2 with tertiary hydrosilanes to give stepwise formoxy silane, methyl formate, and methoxy silane. The unexpected formation of methyl formate was shown to result from the zinc-catalyzed transesterification of methoxy silane with formoxy silane, which was eventually converted into methoxy silane as well.

Regioselective Hydrosilylation of Olefins Catalyzed by a Molecular Calcium Hydride Cation

Chemo- and regioselectivity are often difficult to control during olefin hydrosilylation catalyzed by d- and f-block metal complexes. The cationic hydride of calcium [CaH]+ stabilized by an NNNN macrocycle was found to catalyze the regioselective hydrosilylation of aliphatic olefins to give anti-Markovnikov products, while aryl-substituted olefins were hydrosilyated with Markovnikov regioselectivity. Ethylene was efficiently hydrosilylated by primary and secondary hydrosilanes to give di- and monoethylated silanes. Aliphatic hydrosilanes were preferred over other commonly employed hydrosilanes: Arylsilanes such as PhSiH3 underwent scrambling reactions promoted by the nucleophilic hydride, while alkoxy- and siloxy-substituted hydrosilanes gave isolable alkoxy and siloxy calcium derivatives.

Novel strategies for synthesizing energetic materials based on BTO with improved performances

The layer-by-layer assembly of molecules is ubiquitous in nature. Highly ordered structures formed in this manner often exhibit fascinating material properties. A layer hydrogen bonding pairing approach allows the development of tunable energetic materials with targeted properties. A series of unusual energetic compounds based on 1H,1'H-5,5'-bistetrazole-1,1'-diolate (1), such as the salts of 3-amino-1,2,4-triazolium (2), aminoguanidinium (3), and hydrazinium (4), and the cocrystals of 4-amino-1H-pyrazole (5), 2-methylimidazole (6), and imidazole (7), were synthesized using this strategy. The structures of the obtained products 2-7 were fully characterized by elemental analysis, IR spectroscopy, ¹H NMR and ¹³C NMR spectroscopy, and single-crystal X-ray analysis. Their thermal decomposition behavior was studied by differential scanning calorimetry and thermogravimetry. Their mechanical sensitivities and detonation performances were also analyzed in detail. Results show that products 2-7 exhibit higher density, better detonation performances, and more excellent sensitivities than those of the same species of cation salts previously reported.

Theoretical screening of bistriazole-derived energetic salts with high energetic properties and low sensitivity

We designed four series of energetic anions by replacing nitro group (NO₂) with trinitromethyl group (C(NO₂)₃) or by inserting N-bridging groups (-NH-, -NH-NH-, -N[double bond, length as m-dash]N-, -N[double bond, length as m-dash]N(O)-) into the bistriazole frameworks. The properties of 40 energetic salts, based on the bistriazole-derived anions and hydroxylammonium cation, were studied by density functional theory (DFT) and volume-based thermodynamics calculations (VBT). It is found that the newly designed energetic salts have good detonation properties due to their larger nitrogen content and better oxygen balance. And one of their corresponding hydroxylammonium salts exhibits better detonation performance (D = 10.06 km s^-1 and P = 48.58 GPa) than CL-20 (D = 9.54 km s^-1 and P = 43.36 GPa). Moreover, 10 energetic salts not only exhibit excellent energetic properties superior to CL-20, but also have lower sensitivity than CL-20 (h ₅₀ = 13.81 cm). In addition, we rationally selected salt B6 from the 10 salts to predict its crystal structure under pressures. By converting energetic molecules with excellent detonation properties into energetic ions, some highly bistriazole-derived energetic salts with both excellent performance and low sensitivity could be developed strategically.

Scandium alkyl and hydride complexes supported by a pentadentate diborate ligand: reactions with CO2 and N2O

Alkyl and hydrido scandium complexes of the dianionic pentadentate ligand B2Pz4Py are reported.

Rare-earth metal hydrides supported by silicon-bridged boratabenzene fluorenyl ligands: synthesis, structure and reactivity

The first boratabenzene derivatives of rare-earth metal hydrides were synthesized, and their reactivity was studied.

Small molecule activation by mixed methyl/methylidene rare earth metal complexes

Diverse reactivity patterns of mixed tetramethyl/methylidene rare-earth complexes bearing bulky benzamidinate coligands with PhCN, alkynes, and CS₂ have been established and fully characterized.

Dinuclear zinc hydride supported by an anionic bis(N-heterocyclic carbene) ligand

Methylene-linked bis(N,N′-di-tert-butylimidazol-2-ylidene) 1 reacted with diethylzinc to give dinuclear zinc ethyl compound 2, which contains a formally anionic bis(carbene) ligand as a result of deprotonation of the methylene bridge. The reaction of 2 with PhSiH3 gave the phenylsilyl compound 3. The zinc hydride 4 was obtained by the reaction of 2 with LiAlH4 or Ph3SiOH followed by treatment with PhSiH3. X-ray diffraction studies show that compounds 2, 3, and 4 all have a similar dimeric structure with D2h symmetry. The reaction of hydride 4 with carbon dioxide and N,N′-diisopropylcarbodiimide gave formato (5) and formamidinato (7) derivatives as a result of the insertion of the heterocumulene into both Zn-H bonds. Reaction with Ph2CO gave the diphenylmethoxy compound 6. Hydride 4 shows catalytic activity in the hydrosilylation of 1,1-diphenylethylene and methanolysis of silanes.

Neutral binuclear rare-earth metal complexes with four μ2-bridging hydrides

The first neutral dimeric rare-earth metal hydride complexes containing quadruply bridged hydrido ligands were prepared, in which the intramolecular activation triggered by a THF molecule has been observed.