Titanium, zirconium and hafnium

Cotton, S. A.

doi:10.1039/b612679k

Annu. Rep. Prog. Chem., Sect. A: Inorg. Chem.

2007

DOI: 10.1039/b612679k

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Titanium, zirconium and hafnium

S. A. Cotton¹

Abstract: Highlights include some remarkable imide chemistry, notably from the Mountford laboratories, whilst applications involving TiO 2 continue to multiply.

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Cited by 3 publications

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“…Titanium complexes play a pivotal role in the polymerization of lactones. [25][26][27][28][29][30][31][32] Among the titanium alkoxides applied for the ROP of lactones, simple compounds like titanium tetramethoxide, titanium tetraisopropoxide, and titanium tetratertbutoxide so far played a subordinate role as catalysts due to their rather moderate activity. 16 However, the polymerization of ε-CL and dilactide catalyzed by Ti(OiPr) 4 was successfully accomplished.…”

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Synthesis of dihydroxy telechelic oligomers of β‐butyrolactone catalyzed by titanium(IV)‐alkoxides and their use as macrodiols in polyurethane chemistry

Altmann

Machat

Wolf

et al. 2021

Journal of Polymer Science

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We report on a solvent-free approach for the synthesis of low molecular weight, α,ω-dihydroxy telechelic poly(β-butyrolactone). In the presence of Ti(IV) alkoxides, mixtures of β-butyrolactone and diols, like di-or triethylene glycol, were reacted in ratios between 4:1 and 10:1. The oligomerization proceeds at elevated temperatures (80-100 C). Different alkoxide substituents (R = Me, iPr, tBu) of the Ti(IV)(OR) 4 catalyst were investigated. The resulting oligomers were characterized by nuclear magnetic resonance (NMR), infra-red (IR), gel-permeation chromatography (GPC), titration, and matrix-assisted laser desorption-time-of-flight mass spectrometry (MALDI-ToF-MS) analysis. Aside from low molecular weight products, special effort was devoted to achieve high O-acyl cleavage selectivity and to circumvent the formation of unsaturated end-groups in order to form exclusively dihydroxy-telechelic oligomers. Optimized results in terms of selectivity and reaction rates were achieved at 100 C using catalyst loadings of 0.2 mol% with respect to the monomer. The molecular weights determined by GPC were in good accordance with the ratio of monomer to diol used, confirming successful oligomer formation. Polyurethanes prepared from crude macrodiols without any additional catalyst feature molecular weights up to 50,000 g/mol. The reported work serves as concept to utilize β-lactones for tailored polyol synthesis; the resulting products are suitable for polyurethane chemistry.

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mentioning

confidence: 99%

Synthesis of dihydroxy telechelic oligomers of β‐butyrolactone catalyzed by titanium(IV)‐alkoxides and their use as macrodiols in polyurethane chemistry

Altmann

Machat

Wolf

et al. 2021

Journal of Polymer Science

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ChemInform Abstract: Titanium, Zirconium and Hafnium

Cotton¹

2008

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Probing the aromaticity of the [(HtAc)3(μ2-H)6], [(HtTh)3(μ2-H)6],+, and [(HtPa)3(μ2-H)6] clusters

Ramírez-Tagle

Alvarado-Soto

Arratia‐Pérez

et al. 2011

The Journal of Chemical Physics

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In this study we report about the aromaticity of the prototypical [(H(t)Ac)(3)(μ(2)-H)(6)], [(H(t)Th)(3)(μ(2)-H)(6)](+), and [(H(t)Pa)(3)(μ(2)-H)(6)] clusters via two magnetic criteria: nucleus-independent chemical shifts (NICS) and the magnetically induced current density. All-electron density functional theory calculations were carried out using the two-component zeroth-order regular approach and the four-component Dirac-Coulomb Hamiltonian, including scalar and spin-orbit relativistic effects. Four-component current density maps and the integration of induced ring-current susceptibilities clearly show that the clusters [(H(t)Ac)(3)(μ(2)-H)(6)] and [(H(t)Th)(3)(μ(2)-H)(6)](+) are non-aromatic whereas [(H(t)Pa)(3)(μ(2)-H)(6)] is anti-aromatic. However, for the thorium cluster we find a discrepancy between the current density plots and the classification through the NICS index. Our results also demonstrate the increasing influence of f orbitals, on bonding and magnetic properties, with increasing atomic number in these clusters. We think that the enhanced electron mobility in [(H(t)Pa)(3)(μ(2)-H)(6)] is due the significant 5f character of its valence shell. Also the participation of f orbitals in bonding is the reason why the protactinium cluster has the shortest bond lengths of the three clusters. This study provides another example showing that the magnetically induced current density approach can give more reliable results than the NICS index.

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Titanium, zirconium and hafnium

Abstract: Highlights include some remarkable imide chemistry, notably from the Mountford laboratories, whilst applications involving TiO 2 continue to multiply.

Cited by 3 publications

References 77 publications

Synthesis of dihydroxy telechelic oligomers of β‐butyrolactone catalyzed by titanium(IV)‐alkoxides and their use as macrodiols in polyurethane chemistry

Synthesis of dihydroxy telechelic oligomers of β‐butyrolactone catalyzed by titanium(IV)‐alkoxides and their use as macrodiols in polyurethane chemistry

ChemInform Abstract: Titanium, Zirconium and Hafnium

Probing the aromaticity of the [(HtAc)3(μ2-H)6], [(HtTh)3(μ2-H)6],+, and [(HtPa)3(μ2-H)6] clusters

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