Monocyclopentadienyl(niobium) Compounds with Imido and Silsesquioxane Ligands: Synthetic, Structural and Reactivity Studies

García, Carlos J. Gómez; Gómez, Manuel; Gómez‐Sal, Pilar; Hernández, José Manuel

doi:10.1002/ejic.200900571

Cited by 12 publications

(5 citation statements)

References 145 publications

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“…In the case of the trimethyl tantalum derivative 6, a similar experiment leads to an unidentified mixture of products. In the remaining cases, the treatment of toluene solutions of [MR 3 (NtBu)] (M = Nb, R = CH 2 CMe 3 3, CH 2 CMe 2 Ph 4, CH 2 SiMe 3 5, CH 2 Ph; 12 M = Ta, R = CH 2 CMe 2 Ph 7, CH 2 SiMe 3 8, CH 2 CMe 3 7 ) with 2 equivalents of 2,6-Me 2 C 6 H 3 The IR spectra of all alkyl imido bisiminoacyl complexes 9-16 show the characteristic absorptions due to the n(M N-), 6b,6c,13,22 n{C(R) N} 6b,6c, 22 and n(M-C) 6b,6c,15,22 stretching vibrations at n 1360, 1575 and 443 cm -1 , respectively.…”

Section: Reactions With Isocyanidesmentioning

confidence: 99%

Trialkyl imido niobium and tantalum compounds: synthesis, structural study and migratory insertion reactions

et al. 2011

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Trialkyl imido niobium and tantalum complexes [MR(3)(NtBu)] (M = Nb, R = Me 2, CH(2)CMe(3)3, CH(2)CMe(2)Ph 4, CH(2)SiMe(3)5; M = Ta, R = Me 6, CH(2)CMe(2)Ph 7, CH(2)SiMe(3)8) have been prepared by treatment of solutions containing [MCl(3)(NtBu)py(2)] (M = Nb 1a, Ta 1b) with three equivalents of magnesium reagent. By an unexpected hydrolysis reaction of the tris-trimethylsilylmethyl imido tantalum compound 8a, a μ-oxo derivative [(Me(3)SiCH(2)O)(Me(3)SiCH(2))(3)Ta(μ-O)Ta(CH(2)SiMe(3))(2)(NtBu)] (8a) was formed and its structure was studied by X-ray diffraction methods. Reactions of trialkyl imido compounds with two equivalents of isocyanide 2,6-Me(2)C(6)H(3)NC result in the migration of two alkyl groups, leading to the formation of a series of alkyl imido bisiminoacyl derivatives [MR(NtBu){C(R)NAr}(2)] (Ar = 2,6-Me(2)C(6)H(3); M = Nb, R = Me 9, CH(2)CMe(3)10, CH(2)CMe(2)Ph 11, CH(2)SiMe(3)12, CH(2)Ph 13; M = Ta, R = CH(2)CMe(3)14, CH(2)CMe(2)Ph 15, CH(2)SiMe(3)16). All compounds were studied by IR and NMR ((1)H, (13)C and (15)N) spectroscopy.

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Section: Reactions With Isocyanidesmentioning

confidence: 99%

Trialkyl imido niobium and tantalum compounds: synthesis, structural study and migratory insertion reactions

et al. 2011

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“…45 The 29 Si{ 1 H} NMR spectrum (Figure 1a) clearly Nonetheless, the actual structure of lithium-T 7 cages is still controversial. Edelmann and co-workers observed by X-ray crystallography an unprecedented box-shaped dimeric complex of Li 6 O 6 with heptacyclohexyl-silsesquioxane trisilanolate as ligands, 17 while Garci ́a et al proposed a tetrameric complex in their study, 26 but the structure in this latter case was of very poor quality. Herein, the Li-T 7 coordination complex is also sensitive, and while the crystal is clear at the beginning of recrystallization, it gradually becomes opaque.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Lithium-Templated Formation of Polyhedral Oligomeric Silsesquioxanes (POSS)

et al. 2019

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A coordination complex, lithium hepta(i-butyl)silsesquioxane trisilanolate (1; Li-T7), a stable intermediate in silsesquioxane (SQ) syntheses, was successfully isolated in 65% yield and found to be highly soluble in nonpolar solvents such as hexane. The structure of Li-T7 was confirmed by NMR, IR spectroscopy, matrix-assisted laser desorption ionization time-of-flight mass spectrometry, electrospray ionization mass spectrometry, and computational simulation, providing detailed elucidation of the intermolecular self-association of the SQ cage with a box-shaped Li6O6 polyhedron through strong coordination bonds. After acid treatment, Li-T7 undergoes lithium–proton cationic exchange, yielding hepta(i-butyl)silsesquioxane trisilanol (2; H-T7) quantitatively. The high yield of H-T7 seems to be influenced by Li–O bonding in the Li-T7 complex that affects the selective formation of hepta(i-butyl)silsesquioxane trisilanolate and the bulky i-butyl groups which may prevent decomposition or SQ cage-rearrangement even at reflux under alkaline conditions. Single-crystal X-ray crystallography confirms the presence of the dumbbell-shaped SQ partial cages through strong intermolecular hydrogen bonds. Interestingly, lowering the polarity of the reaction solution by adding dichloromethane results in formation of the cubic octa(i-butyl)silsesquioxane (3; T8) cage in a good yield (47%), which is isolated by crystallization from the reaction solution.

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“…The use of lithium hydroxide for the CLMS design is in accordance with recent publications [ 30 , 87 ]. At the same time, classical approaches rely on more complicated reactions with either BuLi/LiN(SiMe 3 ) 2 (for metalation synthesis [ 88 , 89 , 90 , 91 ]) or LiCl (for transmetalation synthesis [ 92 ]).…”

Section: Resultsmentioning

confidence: 99%

A Novel Family of Cage-like (CuLi, CuNa, CuK)-phenylsilsesquioxane Complexes with 8-Hydroxyquinoline Ligands: Synthesis, Structure, and Catalytic Activity

et al. 2022

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The first examples of metallasilsesquioxane complexes, including ligands of the 8-hydroxyquinoline family 1–9, were synthesized, and their structures were established by single crystal X-ray diffraction using synchrotron radiation. Compounds 1–9 tend to form a type of sandwich-like cage of Cu4M2 nuclearity (M = Li, Na, K). Each complex includes two cisoid pentameric silsesquioxane ligands and two 8-hydroxyquinoline ligands. The latter coordinates the copper ions and corresponding alkaline metal ions (via the deprotonated oxygen site). A characteristic (size) of the alkaline metal ion and a variation of characteristics of nitrogen ligands (8-hydroxyquinoline vs. 5-chloro-8-hydroxyquinoline vs. 5,7-dibromo-8-hydroxyquinoline vs. 5,7-diiodo-8-hydroxyquinoline) are highly influential for the formation of the supramolecular structure of the complexes 3a, 5, and 7–9. The Cu6Na2-based compound 2 exhibits high catalytic activity towards the oxidation of (i) hydrocarbons by H2O2 activated with HNO3, and (ii) alcohols by tert-butyl hydroperoxide. Studies of kinetics and their selectivity has led us to conclude that it is the hydroxyl radicals that play a crucial role in this process.

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Monocyclopentadienyl(niobium) Compounds with Imido and Silsesquioxane Ligands: Synthetic, Structural and Reactivity Studies

Cited by 12 publications

References 145 publications

Trialkyl imido niobium and tantalum compounds: synthesis, structural study and migratory insertion reactions

Trialkyl imido niobium and tantalum compounds: synthesis, structural study and migratory insertion reactions

Lithium-Templated Formation of Polyhedral Oligomeric Silsesquioxanes (POSS)

A Novel Family of Cage-like (CuLi, CuNa, CuK)-phenylsilsesquioxane Complexes with 8-Hydroxyquinoline Ligands: Synthesis, Structure, and Catalytic Activity

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