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Metal–organic materials such as [NH₂(CH₂–CH═CH₂)₂][Cr₇NiF₈(Pivalate)₁₆] can act as negative tone resists for electron beam lithography (EBL) with high-resolution patterning of sub-40 nanometer pitch while exhibiting ultrahigh dry etch selectivities >100:1 and giving line dose exposures >11,000 pC/cm. It is clear that the resist sensitivity is too low to be used to manufacture the latest nanoscale photomasks that are suitable for extreme ultraviolet lithography. Therefore, the focus of this work here is to improve the sensitivity of this resist while maintaining its resolution and dry etch selectivity. Using our latest Monte Carlo simulation called Excalibur, we predict that the sensitivity would increase by a factor of 1.4 when the nickel atom is substituted by a cadmium atom. EBL studies showed an excellent agreement with the simulation, and plasma etching studies demonstrated that this did not affect the dry etch performance of the resist which remains very good with a selectively of ca. 99:1 for the etching of silicon at these resolutions with a low sensitivity of 7995 pC/cm.

We report the synthesis and structural characterization of a series of heterometallic rings templated via alkylammonium or imidazolium cations. The template and preference of each metal’s coordination geometry can control the structure of heterometallic compounds, leading to octa-, nona-, deca-, dodeca-, and tetradeca-metallic rings. The compounds were characterized by single-crystal X-ray diffraction, elemental analysis, magnetometry, and EPR measurements. Magnetic measurements show that the exchange coupling between metal centres is antiferromagnetic. EPR spectroscopy shows that the spectra of {Cr7Zn} and {Cr9Zn} have S = 3/2 ground states, while the spectra of {Cr12Zn2} and {Cr8Zn} are consistent with S = 1 and 2 excited states. The EPR spectra of {(ImidH)-Cr6Zn2}, {(1-MeImH)-Cr8Zn2}, and {(1,2-diMeImH)-Cr8Zn2} include a combination of linkage isomers. The results on these related compounds allow us to examine the transferability of magnetic parameters between compounds.

We report two dichloride-bridged dinuclear dysprosium(III) complexes based on salen ligands, namely, [Dy(L1)(μ-Cl)(thf)]2 (1; H2L1 = N,Nʹ-bis(3,5-di-tert-butylsalicylidene)phenylenediamine) and [Dy2(L2)2(μ-Cl)2(thf)2]2 (2; H2L2 = N,Nʹ-bis(3,5-di-tert-butylsalicylidene)ethylenediamine). These two complexes have two short Dy−O(PhO) bonds that have angles of ~90° for 1 and ~143° for 2, leading to clear slow relaxation of the magnetization for 2 and not for 1. Compound 2 has a near-identical core to the recently reported compound [Dy2(L3)2(μ-Cl)2(thf)2] (3; H2L3 = N-(2-pyridylmethyl)-N,N-bis(2ʹ-hydroxy-3ʹ,5ʹ-di-tert-butylbenzyl)amine), the only substantial difference being the relative angle of the two O(PhO)−Dy−O(PhO) vectors, which are collinear in 2 owing to inversion symmetry and make an angle of ~68° in 3 owing to a molecular C2 axis. We show that this subtle structural difference leads to large differences in the dipolar ground states, giving rise to open magnetic hysteresis for 3 and not for 2.

Addition of 1,4,8,11-tetrazacyclotetradecane (cyclam) to a reaction that produces octametallic rings when simpler amines are used, produces {Cr

Understanding the fundamental reactivity of polymetallic complexes is challenging due to the complexity of their structures with many possible bond breaking and forming processes. Here, we apply ion mobility mass spectrometry coupled with density functional theory to investigate the disassembly mechanisms and energetics of a family of heterometallic rings and rotaxanes with the general formula [NH

Dipolar coupled multi-spin systems have the potential to be used as molecular qubits. Herein we report the synthesis of a molecular multi-qubit model system with three individually addressable, weakly interacting, spin

A negative tone heterometallic ring resist (HRR) based on a supramolecular assembly [NH₂(allyl)₂][Cr₇NiF₈(piv)₁₆] with previously demonstrated resolution down to sub 10-nm lines is evaluated in terms of its flexibility to be processed either “wet” (spin cast and solvent developed) or “dry” (deposition and development by vacuum sublimation). The implemented sublimation hardware fits easily in the wafer load-lock chamber of extreme ultraviolet and electron beam exposure systems dedicated to research and development activities and allows for HRR films to be uniformly deposited or developed in the same vacuum environment. The HRR shows a sublimation rate dependence on temperature that obeys a Clausius–Clapeyron relation, with thermal stability up to 275°C. Flood exposures of the HRR show identical sensitivity between wet- and dry-deposited films, whereas contrast degradation is observed when dry development is initiated by increasing the temperature prior to system pump down. A modified sublimation setup allows for the dry development of exposed HRR samples inside the electron beam tool without breaking vacuum. In this case, nominally patterned 25 nm L/S are identically resolved at 30 keV for wet- or dry-developed HRR.

A new class of electron bean negative tone resist materials has been developed based on heterometallic rings. The initial resist performance demonstrates a resolution of 15 nm half-pitch but at the expense of a low sensitivity. To improve sensitivity a 3D Monte Carlo simulation is used that utilizes a secondary and Auger electron generation model. The simulation suggests that the sensitivity can be dramatically improved while maintaining high resolution by incorporating appropriate chemical functionality around the metal–organic core. The new resists designs based on the simulation have the increased sensitivity expected and illustrate the value of the simulation approach.

Three distorted tetrahedral Dy(iii) aryloxide complexes, [Na(THF)6][Dy(OArAd2tBu)2Cl2] (1) (OArAd2tBu = OC6H2Adamantyl2-2,6-tBu-4) and [Na(THF)6][Dy(OMes*)3X] (X = Cl, 2; BH4, 3), (OMes* = OC6H2tBu3-2,4,6) exhibit easy axis magnetic anisotropy and slow magnetic relaxation at zero field, with relaxation rates 1 < 2 < 3., Magnetostructural correlations: The magnetic relaxation dynamics of three distorted tetrahedral dysprosium aryloxide complexes are shown to vary according to their local coordination environments.

A series of heterometallic [TiIV7MIII] rings are reported which contain a single paramagnetic metal centre, either FeIII or CrIII. The structures contain an octagon of metals bridged by oxides within the ring and pivalate ligands outside the ring. The structures encapsulate a single cation, either a secondary ammonium cation or a cesium. Multi-frequency EPR spectroscopy was used to measure the zero-field splitting parameters for the paramagnetic metal sites. The FeIII sites have rhombic anisotropy, with D around − 0.18 cm−1 and λ (= D/E) approximately 0.25. The CrIII have a more axial anisotropy, with D around − 0.5 cm−1 and λ around 0.05. Attempts to find a magneto-structural correlation are vitiated by the difficulty of refining the challenging crystal structures.

Four 3d-4f hetero-polymetallic complexes [Fe2Ln2((OCH2)3CR)2(O2CtBu)6(H2O)4] (where Ln = La (1 and 2) and Gd (3 and 4); and R = Me (1 and 3) and Et (2 and 4)) are synthesized and analyzed using elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, and SQUID magnetometry. Crystal structures are obtained for both methyl derivatives and show that the complexes are isostructural and adopt a defective dicubane topology. The four heavy metals are connected with two alkoxide bridges. These four precursors are used as single-source precursors to prepare rare-earth orthoferrite pervoskites of the form LnFeO3. Thermal decomposition in a ceramic boat in a tube furnace gives orthorhombic LnFeO3 powders using optimized temperatures and decomposition times: LaFeO3 formed at 650 °C over 30 min, whereas GdFeO3 formed at 750 °C over 18 h. These materials are structurally characterized using powder X-ray diffraction, Raman spectroscopy, scanning electron microscopy, energy-dispersive X-ray map spectroscopy, and SQUID magnetometry. EDX spectroscopy mapping reveals a homogeneous spatial distribution of elements for all four materials consistent with LnFeO3. Magnetic measurements on complexes 1-4 confirm the presence of weak antiferromagnetic coupling between the central Fe(III) ions of the clusters and negligible ferromagnetic interaction with peripheral Gd(III) ions in 3 and 4. Zero-field-cooled and field-cooled measurements of magnetization of LaFeO3 and GdFeO3 in the solid-state suggest that both materials are ferromagnetic, and both materials show open magnetic hysteresis loops at 5 and 300 K, with Msat higher than previously reported for these nanomaterials. We conclude that this is a new and facile low temperature route to these important magnetic materials that is potentially universal, limited only by what metals can be programmed into the precursor complexes.

The synthesis, structures, and properties of [4]- and [3]-rotaxane complexes are reported where [2]-rotaxanes, formed from heterometallic {Cr7Ni} rings, are bound to a fluoride-centered {CrNi2} triangle. The compounds have been characterized by single-crystal X-ray diffraction and have the formulas [CrNi2(F)(O2CtBu)6]{(BH)[Cr7NiF8(O2CtBu)16]}3 (3) and [CrNi2(F)(O2CtBu)6(THF)]{(BH)[Cr7NiF8(O2CtBu)16]}2 (4), where B = py-CH2CH2NHCH2C6H4SCH3. The [4]-rotaxane 3 is an isosceles triangle of three [2]-rotaxanes bound to the central triangle while the [3]-rotaxane 4 contains only two [2]-rotaxanes bound to the central triangle. Studies of the behavior of 3 and 4 in solution by small-angle X-ray scattering and atomistic molecular dynamic simulations show that the structure of 3 is similar to that found in the crystal but that 4 has a different conformation to the crystal. Continuous wave and pulsed electron paramagnetic resonance spectroscopy was used to study the structures present and demonstrate that in frozen solutions (at 5 K) 4 forms more extended molecules than 3 and with a wider range of conformations.

Paul O'Brien, known affectionately as ‘POB’, was one of the most imaginative and creative materials chemists of his generation. He brought a deep understanding and knowledge of classical coordination chemistry to bear on routes to thin films and nanoparticles of technologically important materials, particularly metal chalcogenides. His development of molecular precursor chemistry as a method to produce very high quality materials safely, inexpensively and on a large scale laid the foundations for the successful technological exploitation of quantum dots. Paul had a compendious knowledge of science, particularly inorganic chemistry, and was passionate about the exploitation of science and engineering to improve society, both in the UK and around the world, most notably in Africa. He was a wonderful raconteur, and a great counsellor to his many friends, and a source of endless jokes (many of them bad). His greatest passion was science, yet somehow he also found time for other interests, including reading, hill-walking and camping, theatre and football. Paul was diagnosed with glioblastoma multiforme on his sixty-fourth birthday in January 2018, and this led to his retirement in July 2018 and his appointment as Emeritus Professor at the University of Manchester. He approached his illness with his usual scientific curiosity and optimism. He passed away peacefully with his beloved wife Kym by his side.

A dichlorido-bridged dinuclear dysprosium(III) single-molecule magnet [Dy2 L2 (μ-Cl)2 (thf)2 ] has been made by using a diamine-bis(phenolate) ligand, H2 L. Magnetic studies show an energy barrier for magnetisation reversal (Ueff ) around 1000 K. An exchange-biasing effect is clearly seen in magnetic hysteresis with steps up to 3 K. Ab initio calculations exclude the possibility of a pure dipolar origin of this effect leading to the conclusion that super-exchange through the chloride bridging ligands is important.

Although the development of single-molecule magnets (SMMs) is rapid, there are only two families of high energy barrier (Ueff ) dysprosium(III) SMMs known so far: the cyclopentadienyl (Cp) family with a sandwich structure and the pentagonal-bipyramidal (PB) family with D5h symmetry. These high-barrier SMMs, which usually possess Ueff >500 cm-1 allow the separate study of the four magnetic relaxation paths, namely, direct, quantum tunnelling, Raman and Orbach processes, in detail. Whereas the first family is chemically more challenging to modify the Cp rings, it is shown herein that the latter family, with the common formulae [DyX1 X2 (Leq )5 ]+ , such as X1 /X2 =- OCMe3 , - OSiMe3 , - OPh, Cl- or Br- ; Leq =THF/pyridine/4-methylpyridine, can be readily fine-tuned with a range of axial and equatorial ligands by simple substitution reactions. This allows unambiguous confirmation that the Ueff mainly depends on the identity of X1 and X2 , rather than on Leq . More importantly, the fitted parameters are barrier dependent. If X1 is an O donor and X2 is a halide, 500

The dicarbollide ion, nido-C2 B9 H11 2- is isoelectronic with cyclopentadienyl. Herein, we make dysprosiacarboranes, namely [(C2 B9 H11 )2 Ln(THF)2 ][Na(THF)5 ] (Ln=Dy, 1Dy) and [(THF)3 (μ-H)3 Li]2 [{η5 -C6 H4 (CH2 )2 C2 B9 H9 }Dy{η2 :η5 -C6 H4 (CH2 )2 C2 B9 H9 }2 Li] 3Dy and show that dicarbollide ligands impose strong magnetic axiality on the central DyIII ion. The effective energy barrier (Ueff ) for the loss of magnetization can be varied by the substitution pattern on the dicarbollide. This finding is demonstrated by comparing complexes of nido-C2 B9 H11 2- and nido-[o-xylylene-C2 B9 H9 ]2- , which show a Ueff of 430(5) K and 804(7) K, respectively. The blocking temperature defined by the open hysteresis temperature of 3Dy reaches 6.8 K. Moreover, the linear complex [Dy(C2 B9 H11 )2 ]- is predicted to have comparable properties with the linear [Dy(CpMe3 )2 ]+ complex. As such, carboranyl ligands and their derivatives may provide a new type of organometallic ligand for high-performance single-molecule magnets.

Addition of 1,4,8,11-tetrazacyclotetradecane (cyclam) to a reaction that produces octametallic rings when simpler amines are used, produces {Cr11M2} "pretzels" (M = ZnII or CuII) where the cyclam coordinates to the MII ion which then sits at the centre of a twelve-metal macrocycle. Magnetic studies were fitted using the finite-temperature Lanczos method (FTLM), and the results demonstrate that exchange interactions are transferable from previous exchange-coupled CrIII rings.

Supramolecular chemistry has grown rapidly over the past three decades, yet synthetic supramolecular chemists still face several challenges when it comes to characterising their compounds. In this review, we present an introduction to structural characterisation techniques commonly used for non-crystalline supramolecular molecules, e.g. nuclear magnetic and electron paramagnetic resonance spectroscopy (NMR and EPR), mass spectrometry (MS), ion mobility mass spectrometry (IM-MS), small-angle neutron and X-ray scattering (SANS and SAXS) as well as cryogenic transmission electron microscopy (cryo-TEM). We provide an overview of their fundamental concepts based on case studies from different fields of supramolecular chemistry, e.g. interlocked structures, molecular self-assembly and host-guest chemistry, while focussing on particular strengths and weaknesses of the discussed methods. Additionally, three multi-technique case studies are examined in detail to illustrate the benefits of using complementary techniques simultaneously.

A family of heterometallic rings [Me

We discuss a cost-effective approach to understand magnetic relaxation in thenew generation of rare-earth single-molecule magnets. It combines ab initio calculations of thecrystal field parameters, of the magneto-elastic coupling with local modes, and of the phonondensity of states with fitting of only three microscopic parameters. Although much lessdemanding than a fully ab initio approach, the method gives important physical insights intothe origin of the observed relaxation. By applying it to high-anisotropy compounds with verydifferent relaxation, we demonstrate the power of the approach and pinpoint ingredients forimproving theperformance of single-molecule magnets.

We report the synthesis and characterization of two symmetric homo-dimetallic lanthanide complexes based on methyl-substituted 8-hydroxyquinoline (HMeQ). The aryloxo-bridged core gives rise to weak magnetic coupling between pairs of ErIII and YbIII ions, as revealed by magnetic and EPR spectroscopy studies. EPR measurements of magnetically dilute species, coupled with CASSCF-SO calculations, allows modelling of the EPR spectra of the exchange coupled species and the magnetic data simultaneously. This work adds to the database of exchange coupled {Ln}2 molecules which have been thoroughly characterised by EPR spectroscopy and modelled using an Seff = 1/2 approach to describe the interaction of ground Kramers states, and highlights the differences between centro-symmetric and asymmetric dimetallics.

A simplified uniaxial anisotropic Heisenberg model is proposed which describes the observed magnetic properties of a family of the Cr7M (M = Cd, Ni, Mn) molecular rings, and allows the determination of the coupling parameters which are all transferable among this family of molecular nanomagnets.

The implementation of a quantum computer requires both to protect information from environmental noise and to implement quantum operations efficiently. Achieving this by a fully fault-tolerant platform, in which quantum gates are implemented within quantum-error corrected units, poses stringent requirements on the coherence and control of such hardware. A more feasible architecture could consist of connected memories, that support error-correction by enhancing coherence, and processing units, that ensure fast manipulations. We present here a supramolecular {Cr7Ni}–Cu system which could form the elementary unit of this platform, where the electronic spin 1/2 of {Cr7Ni} provides the processor and the naturally isolated nuclear spin 3/2 of the Cu ion is used to encode a logical unit with embedded quantum error-correction. We demonstrate by realistic simulations that microwave pulses allow us to rapidly implement gates on the processor and to swap information between the processor and the quantum memory. By combining the storage into the Cu nuclear spin with quantum error correction, information can be protected for times much longer than the processor coherence., The implementation of a quantum computer requires protecting of information from noise and the ability to perform quantum gates. We present a molecular architecture providing both these ingredients, via an electronic spin 1/2 processor and a nuclear spin 3/2 memory.

Gold(i) bridged dimeric and trimeric structures of a ground state spin S = 1/2 heterometallic {Cr

A finite chain of thirty-one paramagnetic centers is reported, synthesised by reaction of hydrated chromium fluoride, copper carbonate and pivalic acid in the presence of 1,4,7,10-tetrazacyclododecane (cyclen). Magnetic studies show predominantly anti-ferromagnetic exchange leading to a high density of low-lying spin sites and large saturation fields.. © 2021 Wiley-VCH GmbH.

An approach is presented for nanoscale patterning of zinc oxide (ZnO) using electron beam (e-beam) lithography for future nanoelectronic devices and for hard lithographic masks. Zinc acetate (Zn4O(...

A finite chain of thirty‐one paramagnetic centers is reported, synthesized by reaction of hydrated chromium fluoride, copper carbonate and pivalic acid in the presence of 1,4,7,10‐tetrazacyclododecane (cyclen). Magnetic studies show predominantly anti‐ferromagnetic exchange leading to a high density of low‐lying spin states and large saturation field., The longest finite chain of metals is reported and the magnetic properties studied and modelled.

A new family of five‐coordinate lanthanide single‐molecule magnets (Ln SMMs) [Dy(Mes*O)2(THF)2X] (Mes*=2,4,6‐tri‐tert‐butylphenyl; X=Cl, 1; Br, 2; I, 3) is reported with energy barriers to magnetic reversal >1200 K. The five‐coordinate DyIII ions have distorted square pyramidal geometries, with halide anions on the apex, and two Mes*O ligands mutually trans‐ to each other, and the two THF molecules forming the second trans‐ pair. These geometrical features lead to a large magnetic anisotropy in these complexes along the trans‐Mes*O direction. QTM and Raman relaxation times are enhanced by varying the apex halide from Cl to Br to I, or by dilution in a diamagnetic yttrium analogue., Halide influence: A new family of five‐coordinate lanthanide‐based single‐molecule magnets, [Dy(Mes*O)2(THF)2X] (Mes*=2,4,6‐tri‐tert‐butylphenyl), (X=Cl, Br, I) is reported. While the influence of the different halides on the quantum tunnelling of magnetization and Raman processes is clearly established, the Orbach relaxation is independent of the halide substitution.

Here we report stable

We report magnetic hysteresis studies of three Dy(III) single-molecule magnets (SMMs). The three compounds are [Dy(tBuO)Cl(THF)5][BPh4] (1), [K(18-crown-6-ether)(THF)2][Dy(BIPM)2] (2, BIPM = C{PPh2NSiMe3}2), and [Dy(Cpttt)2][B(C6F5)4] (3), chosen as they have large energy barriers to magnetisation reversal of 665, 565, and 1223 cm-1, respectively. There are zero-field steps in the hysteresis loops of all three compounds, that remain in magnetically dilute samples and in samples that are isotopically enriched with 164Dy, which has no nuclear spin. These results demonstrate that neither dipolar fields nor nuclear hyperfine coupling are solely responsible for the quantum tunnelling of magnetisation at zero field. Analysing their vibrational modes, we find that the modes that most impact the first coordination sphere occur at the lowest energies for 1, at intermediate energies for 2 and at higher energies for 3, in correlation with the hysteresis coercive fields. Therefore, we suggest that the efficiency of quantum tunnelling of magnetisation is related to molecular flexibility.

Low coordinate metal complexes can exhibit superlative physicochemical properties, but this chemistry is challenging for the lanthanides (Ln) due to their tendency to maximize electrostatic contacts in predominantly ionic bonding regimes. Although a handful of Ln2+ complexes with only two monodentate ligands have been isolated, examples in the most common +3 oxidation state have remained elusive due to the greater electrostatic forces of Ln3+ ions. Here, we report bent Ln3+ complexes with two bis(silyl)amide ligands; in the solid state the Yb3+ analogue exhibits a crystal field similar to its three coordinate precursor rather than that expected for an axial system. This unanticipated finding is in opposition to the predicted electronic structure for two-coordinate systems, indicating that geometries can be more important than the Ln ion identity for dictating the magnetic ground states of low coordinate complexes; this is crucial transferable information for the construction of systems with enhanced magnetic properties.

The exposure of green crystals of the [CrF(O2CtBu)2]8Cr8 metallacrown to SO2 and H2S gases results in the binding of the gas molecules in the internal molecular cavity, despite the absence of any pores or channels in the structure. Single crystal X-ray diffraction studies show that the gas molecules bind weakly to the bridging fluoride ligands. The desorption process was followed by TGA, DSC and in situ variable temperature single crystal X-ray diffraction, obtaining the gas binding energies for the gas guest molecules. These results are supported by DFT calculations.

[2] and [3] hybrid rotaxanes are reported based on {Ti7M} rings (M is a trivalent metal such as FeIII or GaIII). NMR studies show that [2]rotaxanes can act as molecular shuttles, while EPR studies of [3]rotaxanes show weak interactions between the paramagnetic components of the supramolecular assemblies.

The detailed analysis of magnetic interactions in a giant molecule is difficult both because the synthesis of such compounds is challenging and the number of energy levels increases exponentially with the magnitude and number of spins. Here, we isolated a {Ni21Gd20} nanocage with a large number of energy levels (≈5 × 1030) and used quantum Monte Carlo (QMC) simulations to perform a detailed analysis of magnetic interactions. Based on magnetization measurements above 2 K, the QMC simulations predicted very weak ferromagnetic interactions that would give a record S = 91 spin ground state. Low-temperature measurements confirm the spin ground state but suggest a more complex picture due to the single ion anisotropy; this has also been modeled using the QMC approach. The high spin and large number of low-lying states lead to a large low-field magnetic entropy (14.1 J kg-1 K-1 for ΔH = 1 T at 1.1 K) for this material., This work was supported by the Natural Science Foundation of China (nos. 21473129, 21620102002, and 21773130), “National Young-1000-Plan” program, State Key Laboratory for Mechanical Behavior of Materials and the Cyrus Chung Ying Tang Foundation.

Monodisperse cobalt chromium ferrite (FeCoCrO4) nanoparticles have been synthesised using the trimetallic pivalate cluster [CrCoFeO(O2CtBu)6(HO2CtBu)3]. The precursor was thermolysed in oleylamine and oleic acid, with diphenyl ether as the solvent at 260 °C. The effect of time and the concentration of the precursor on the stoichiometry of the phase formed and/or the morphology of the nanoparticles was studied. The reaction time was investigated by withdrawing aliquots at different times. No products were formed after 5 minutes and aliquots withdrawn at reaction times of less than 1 hour contain traces of iron oxide (Fe2O3); only cubic cobalt chromium ferrite (FeCoCrO4) was obtained after one hour. Transmission Electron Microscopy (TEM) showed that more monodisperse spherical ferrite nanoparticles (4.0 ± 0.4 nm) were obtained at higher precursor concentrations. Magnetic measurements revealed that all the ferrite particles are superparamagnetic at room temperature but showed large hysteresis at low temperature. The nanoparticles were characterised by Powder X-Ray Diffraction (p-XRD) and Transmission Electron Microscopy (TEM). A Superconducting Quantum Interference Device (SQUID) was used to analyse the magnetic properties of the nanoparticles.

A family of heterometallic [Cat][TixMO(x+1)(O2CtBu)2x+2] rings is reported where Cat=a secondary or tertiary alkyl ammonium ion, x=7, 8 or 9, and M=FeIII, GaIII, CrIII, InIII and AlIII. The structures are regular polygons with eight, nine or ten vertices with each edge bridged by an oxide and two pivalates. The size of the ring formed is controlled by the alkylammonium cation present. In each case a homometallic by-product is found [Cat][TixO(x+1)(O2CtBu)2x−1].