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Inorganics, Volume 6, Issue 1 (March 2018)

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Cover Story (view full-size image) The chiral trans-stereochemistry of the 1,2-diaminocyclohexane bridging diamine favors a different [...] Read more.
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Open AccessArticle Field-Induced Slow Relaxation in a Dinuclear Dysprosium(III) Complex Based on 3-Methoxycinnamic Acid
Received: 29 November 2017 / Revised: 2 February 2018 / Accepted: 23 February 2018 / Published: 20 March 2018
Cited by 1 | PDF Full-text (2105 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We report the synthesis, structure, and magnetic properties of a new dinuclear dysprosium(III) complex based on a 3-methoxycinnamate ligand. The centrosymmetric complex exhibits a field-induced SMM behavior. In contrast to the previously reported lanthanide-based systems with cinnamate derivatives that relax through a combination
[...] Read more.
We report the synthesis, structure, and magnetic properties of a new dinuclear dysprosium(III) complex based on a 3-methoxycinnamate ligand. The centrosymmetric complex exhibits a field-induced SMM behavior. In contrast to the previously reported lanthanide-based systems with cinnamate derivatives that relax through a combination of Raman and direct processes, an Orbach process is also involved in highlighting the role of the structural organization over the spin-lattice relaxations. Full article
(This article belongs to the Special Issue Single-Molecule Magnets)
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Open AccessReview Atomic Layer Deposition on Porous Materials: Problems with Conventional Approaches to Catalyst and Fuel Cell Electrode Preparation
Received: 12 February 2018 / Revised: 9 March 2018 / Accepted: 10 March 2018 / Published: 13 March 2018
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Abstract
Atomic layer deposition (ALD) offers exciting possibilities for controlling the structure and composition of surfaces on the atomic scale in heterogeneous catalysts and solid oxide fuel cell (SOFC) electrodes. However, while ALD procedures and equipment are well developed for applications involving flat surfaces,
[...] Read more.
Atomic layer deposition (ALD) offers exciting possibilities for controlling the structure and composition of surfaces on the atomic scale in heterogeneous catalysts and solid oxide fuel cell (SOFC) electrodes. However, while ALD procedures and equipment are well developed for applications involving flat surfaces, the conditions required for ALD in porous materials with a large surface area need to be very different. The materials (e.g., rare earths and other functional oxides) that are of interest for catalytic applications will also be different. For flat surfaces, rapid cycling, enabled by high carrier-gas flow rates, is necessary in order to rapidly grow thicker films. By contrast, ALD films in porous materials rarely need to be more than 1 nm thick. The elimination of diffusion gradients, efficient use of precursors, and ligand removal with less reactive precursors are the major factors that need to be controlled. In this review, criteria will be outlined for the successful use of ALD in porous materials. Examples of opportunities for using ALD to modify heterogeneous catalysts and SOFC electrodes will be given. Full article
(This article belongs to the Section Inorganic Solid-State Chemistry)
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Open AccessArticle Reaction of Non-Symmetric Schiff Base Metallo-Ligand Complexes Possessing an Oxime Function with Ln Ions
Received: 29 January 2018 / Revised: 19 February 2018 / Accepted: 23 February 2018 / Published: 9 March 2018
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Abstract
The preparation of non-symmetric Schiff base ligands possessing one oxime function that is associated to a second function such as pyrrole or phenol function is first described. These ligands, which possess inner N4 or N3O coordination sites, allow formation of cationic or neutral
[...] Read more.
The preparation of non-symmetric Schiff base ligands possessing one oxime function that is associated to a second function such as pyrrole or phenol function is first described. These ligands, which possess inner N4 or N3O coordination sites, allow formation of cationic or neutral non-symmetric CuII or NiII metallo-ligand complexes under their mono- or di-deprotonated forms. In presence of Lanthanide ions the neutral complexes do not coordinate to the LnIII ions, the oxygen atom of the oxime function being only hydrogen-bonded to a water molecule that is linked to the LnIII ion. This surprising behavior allows for the isolation of LnIII ions by non-interacting metal complexes. Reaction of cationic NiII complexes possessing a protonated oxime function with LnIII ions leads to the formation of original and dianionic (Gd(NO3)5)2− entities that are well separated from each other. This work highlights the preparation of well isolated mononuclear LnIII entities into a matrix of diamagnetic metal complexes. These new complexes complete our previous work dealing with the complexing ability of the oxime function toward Lanthanide ions. It could open the way to the synthesis of new entities with interesting properties, such as single-ion magnets for example. Full article
(This article belongs to the Special Issue Schiff-Base Metal Complexes)
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Open AccessEditorial Spin-Crossover Complexes
Received: 12 February 2018 / Revised: 26 February 2018 / Accepted: 27 February 2018 / Published: 1 March 2018
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Abstract
Spin-crossover (SCO) is a spin-state switching phenomenon between a high-spin (HS) and low-spin (LS) electronic configurations in a transition metal center. Full article
(This article belongs to the Special Issue Spin-Crossover Complexes) Printed Edition available
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Open AccessArticle Predicted Siliconoids by Bridging Si9 Clusters through sp3-Si Linkers
Received: 22 December 2017 / Revised: 4 February 2018 / Accepted: 17 February 2018 / Published: 26 February 2018
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Abstract
Charged and neutral silicon clusters comprising Si atoms that are exclusively connected to atoms of the same type serve as models for bulk silicon surfaces. The experimentally known nido-[Si9]4− Zintl cluster is investigated as a building block and allows
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Charged and neutral silicon clusters comprising Si atoms that are exclusively connected to atoms of the same type serve as models for bulk silicon surfaces. The experimentally known nido-[Si9]4− Zintl cluster is investigated as a building block and allows for a theoretical prediction of novel silicon-rich oligomers and polymers by interconnection of such building units to larger aggregates. The stability and electronic properties of the polymers { ( [ Si 9 ] ( SiCl 2 ) 2 ) 1 n } and { ( [ Si 9 ] ( SiH 2 ) 2 ) 1 n } , as well as of related oligomers are presented. Full article
(This article belongs to the Special Issue Coordination Chemistry of Silicon)
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Open AccessArticle Synthesis and Characterization of N-Heterocyclic Carbene-Coordinated Silicon Compounds Bearing a Fused-Ring Bulky Eind Group
Received: 23 December 2017 / Revised: 13 February 2018 / Accepted: 14 February 2018 / Published: 23 February 2018
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Abstract
The reactions of the fused-ring bulky Eind-substituted 1,2-dibromodisilene, (Eind)BrSi=SiBr(Eind) (1a) (Eind = 1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl (a)), with N-heterocyclic carbenes (NHCs) (Im-Me4 = 1,3,4,5-tetramethylimidazol-2-ylidene and Im-iPr2Me2 = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) are reported. While the reaction
[...] Read more.
The reactions of the fused-ring bulky Eind-substituted 1,2-dibromodisilene, (Eind)BrSi=SiBr(Eind) (1a) (Eind = 1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl (a)), with N-heterocyclic carbenes (NHCs) (Im-Me4 = 1,3,4,5-tetramethylimidazol-2-ylidene and Im-iPr2Me2 = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) are reported. While the reaction of 1a with the sterically more demanding Im-iPr2Me2 led to the formation of the mono-NHC adduct of arylbromosilylene, (Im-iPr2Me2)→SiBr(Eind) (2a′), a similar reaction using the less bulky Im-Me4 affords the bis-NHC adduct of formal arylsilyliumylidene cation, [(Im-Me4)2→Si(Eind)]+[Br] (3a). The NHC adducts 2a′ and 3a can also be prepared by the dehydrobromination of Eind-substituted dibromohydrosilane, (Eind)SiHBr2 (4a), with NHCs. The NHC-coordinated silicon compounds have been characterized by spectroscopic methods. The molecular structures of bis-NHC adduct, [(Im-iPr2Me2)2→Si(Eind)]+[Br] (3a′), and 4a have been determined by X-ray crystallography. Full article
(This article belongs to the Special Issue Coordination Chemistry of Silicon)
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Open AccessArticle Synthesis Target Structures for Alkaline Earth Oxide Clusters
Received: 21 November 2017 / Revised: 5 February 2018 / Accepted: 7 February 2018 / Published: 21 February 2018
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Abstract
Knowing the possible structures of individual clusters in nanostructured materials is an important first step in their design. With previous structure prediction data for BaO nanoclusters as a basis, data mining techniques were used to investigate candidate structures for magnesium oxide, calcium oxide
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Knowing the possible structures of individual clusters in nanostructured materials is an important first step in their design. With previous structure prediction data for BaO nanoclusters as a basis, data mining techniques were used to investigate candidate structures for magnesium oxide, calcium oxide and strontium oxide clusters. The lowest-energy structures and analysis of some of their structural properties are presented here. Clusters that are predicted to be ideal targets for synthesis, based on being both the only thermally accessible minimum for their size, and a size that is thermally accessible with respect to neighbouring sizes, include global minima for: sizes n = 9 , 15 , 16 , 18 and 24 for (MgO) n ; sizes n = 8 , 9 , 12 , 16 , 18 and 24 for (CaO) n ; the greatest number of sizes of (SrO) n clusters ( n = 8 , 9 , 10 , 12 , 13 , 15 , 16 , 18 and 24); and for (BaO) n sizes of n = 8 , 10 and 16. Full article
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Open AccessArticle Probing the Effect of Six-Membered N-Heterocyclic Carbene—6-Mes—on the Synthesis, Structure and Reactivity of Me2MOR(NHC) (M = Ga, In) Complexes
Received: 3 January 2018 / Revised: 31 January 2018 / Accepted: 12 February 2018 / Published: 16 February 2018
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Abstract
The investigation of the reactivity of six membered N-heterocyclic carbene 1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-1-ylidene (6-Mes) towards dialkylgallium and dialkylindium alkoxides/aryloxides has shown that both steric hindrances and donor properties of 6-Mes significantly influence the strength of M–C6-Mes bond, as well as the formation, structure
[...] Read more.
The investigation of the reactivity of six membered N-heterocyclic carbene 1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-1-ylidene (6-Mes) towards dialkylgallium and dialkylindium alkoxides/aryloxides has shown that both steric hindrances and donor properties of 6-Mes significantly influence the strength of M–C6-Mes bond, as well as the formation, structure and reactivity of Me2MOR(6-Mes) (M = Ga, In) complexes. While the reactions of simple dimethylgallium alkoxides with 6-Mes lead to the formation of stable monomeric Me2Ga(OCH2CH2OMe)(6-Mes) (1) and Me2GaOMe(6-Mes) complexes, the analogous Me2InOR(6-Mes) are unstable and disproportionate to methylindium alkoxides and Me3In(6-Mes) (2). The use of bulky alkoxide ligand—OCPh2Me or aryloxide ligand—OC6H4OMe allowed for the synthesis of stable Me2M(OCPh2Me)(6-Mes) (M = Ga (3) and In (4)) as well as Me2M(OC6H4OMe)(6-Mes) (M = Ga (5) and In (6)). The structures of 16 have been determined using both spectroscopic methods in solution and X-ray diffraction studies, which confirmed the effect of both steric hindrances and donor properties of 6-Mes on their structure and catalytic properties in the ring-opening polymerization (ROP) of rac-lactide. Full article
(This article belongs to the Special Issue N-Heterocyclic Carbene Metal Complexes: From Design to Applications)
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Open AccessArticle Cationic Protic Imidazolylidene NHC Complexes of Cp*IrCl+ and Cp*RhCl+ with a Pyridyl Tether Formed at Ambient Temperature
Received: 16 January 2018 / Revised: 6 February 2018 / Accepted: 7 February 2018 / Published: 14 February 2018
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Abstract
Protic NHC (PNHC) complexes with N1H, N2-alkyl/aryl imidazolylidene ligands are relatively rare, and routes for their synthesis differ from what is used to make non-protic analogs. Prior work from our group and others showed that in the presence of
[...] Read more.
Protic NHC (PNHC) complexes with N1H, N2-alkyl/aryl imidazolylidene ligands are relatively rare, and routes for their synthesis differ from what is used to make non-protic analogs. Prior work from our group and others showed that in the presence of a tethering ligand (phosphine or in one case, pyridine), CpM and Cp*M (M = Ir, Ru) PNHC complexes could be made by heating. Here, we find that the use of ionizing agents to activate [Cp*MIIICl(μ-Cl)]2 (M = Ir, Rh) allows for what we believe is unprecedented ambient temperature formation of PNHC complexes from neutral imidazoles; the product complexes are able to perform transfer hydrogenation. Full article
(This article belongs to the Special Issue N-Heterocyclic Carbene Metal Complexes: From Design to Applications)
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Open AccessReview Future Directions for Transuranic Single Molecule Magnets
Received: 18 January 2018 / Revised: 6 February 2018 / Accepted: 8 February 2018 / Published: 13 February 2018
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Abstract
Single Molecule Magnets (SMMs) based on transition metals and rare earths have been the object of considerable attention for the past 25 years. These systems exhibit slow relaxation of the magnetization, arising from a sizeable anisotropy barrier, and magnetic hysteresis of purely molecular
[...] Read more.
Single Molecule Magnets (SMMs) based on transition metals and rare earths have been the object of considerable attention for the past 25 years. These systems exhibit slow relaxation of the magnetization, arising from a sizeable anisotropy barrier, and magnetic hysteresis of purely molecular origin below a given blocking temperature. Despite initial predictions that SMMs based on 5f-block elements could outperform most others, the results obtained so far have not met expectations. Exploiting the versatile chemistry of actinides and their favorable intrinsic magnetic properties proved, indeed, to be more difficult than assumed. However, the large majority of studies reported so far have been dedicated to uranium molecules, thus leaving the largest part of the 5f-block practically unexplored. Here, we present a short review of the progress achieved up to now and discuss some options for a possible way forward. Full article
(This article belongs to the Special Issue Single-Molecule Magnets)
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Open AccessReview The Fe Protein: An Unsung Hero of Nitrogenase
Received: 7 December 2017 / Revised: 26 January 2018 / Accepted: 29 January 2018 / Published: 3 February 2018
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Abstract
Although the nitrogen-fixing enzyme nitrogenase critically requires both a reductase component (Fe protein) and a catalytic component, considerably more work has focused on the latter species. Properties of the catalytic component, which contains two highly complex metallocofactors and catalyzes the reduction of N
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Although the nitrogen-fixing enzyme nitrogenase critically requires both a reductase component (Fe protein) and a catalytic component, considerably more work has focused on the latter species. Properties of the catalytic component, which contains two highly complex metallocofactors and catalyzes the reduction of N2 into ammonia, understandably making it the “star” of nitrogenase. However, as its obligate redox partner, the Fe protein is a workhorse with multiple supporting roles in both cofactor maturation and catalysis. In particular, the nitrogenase Fe protein utilizes nucleotide binding and hydrolysis in concert with electron transfer to accomplish several tasks of critical importance. Aside from the ATP-coupled transfer of electrons to the catalytic component during substrate reduction, the Fe protein also functions in a maturase and insertase capacity to facilitate the biosynthesis of the two-catalytic component metallocofactors: fusion of the [Fe8S7] P-cluster and insertion of Mo and homocitrate to form the matured [(homocitrate)MoFe7S9C] M-cluster. These and key structural-functional relationships of the indispensable Fe protein and its complex with the catalytic component will be covered in this review. Full article
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Open AccessArticle Effect of Low Spin Excited States for Magnetic Anisotropy of Transition Metal Mononuclear Single Molecule Magnets
Received: 14 December 2017 / Revised: 17 January 2018 / Accepted: 25 January 2018 / Published: 27 January 2018
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Abstract
Rational, fine tuning of magnetic anisotropy is critical to obtain new coordination compounds with enhanced single molecule magnet properties. For mononuclear transition metal complexes, the largest contribution to zero-field splitting is usually related to the excited states of the same spin as the
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Rational, fine tuning of magnetic anisotropy is critical to obtain new coordination compounds with enhanced single molecule magnet properties. For mononuclear transition metal complexes, the largest contribution to zero-field splitting is usually related to the excited states of the same spin as the ground level. Thus, the contribution of lower multiplicity roots tends to be overlooked due to its lower magnitude. In this article, we explore the role of lower multiplicity excited states in zero-field splitting parameters in model structures of Fe(II) and Co(II). Model aquo complexes with coordination numbers ranging from 2 to 6 were constructed. The magnetic anisotropy was calculated by state of the art ab initio methodologies, including spin-orbit coupling effects. For non-degenerate ground states, contributions to the zero-field splitting parameter (D) from highest and lower multiplicity roots were of the same sign. In addition, their relative magnitude was in a relatively narrow range, irrespective of the coordination geometry. For degenerate ground states, the contribution from lower multiplicity roots was significantly smaller. Results are rationalized in terms of general expressions for D and are expected to be reasonably transferable to real molecular systems. Full article
(This article belongs to the Special Issue Single-Molecule Magnets)
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Open AccessArticle Sterically Bulky NHC Adducts of GaMe3 and InMe3 for H2 Activation and Lactide Polymerization
Received: 22 December 2017 / Revised: 20 January 2018 / Accepted: 23 January 2018 / Published: 25 January 2018
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Abstract
The sterically bulky Ga(III) and In(III) (IPr*)MMe3 adducts (1 and 2) and (SItBu)MMe3 adducts (3 and 4) (M = Ga, In; IPr* = 1,3-bis{2,6-bis(diphenylmethyl)-4-methylphenyl}-1,3-dihydro- imidazol-2-ylidene; SItBu = 1,3-bis(1,1-dimethylethyl)-imidazolidin-2-ylidene) were prepared and structurally characterized,
[...] Read more.
The sterically bulky Ga(III) and In(III) (IPr*)MMe3 adducts (1 and 2) and (SItBu)MMe3 adducts (3 and 4) (M = Ga, In; IPr* = 1,3-bis{2,6-bis(diphenylmethyl)-4-methylphenyl}-1,3-dihydro- imidazol-2-ylidene; SItBu = 1,3-bis(1,1-dimethylethyl)-imidazolidin-2-ylidene) were prepared and structurally characterized, allowing an estimation of the steric hindrance of such Lewis pairs (yields in 14: 92%, 90%, 73%, and 42%, respectively). While the IPr* adducts 1 and 2 are robust species, the more severely congested SItBu adducts 3 and 4 are more reactive and exhibit a limited stability in solution. Adduct (SItBu)GaMe3 (3) reacts quickly with H2 at room temperature to afford the corresponding aminal product, 1,3-di-tert-butylimidazolidine (5), along with free GaMe3. Such Frustrated Lewis Pair (FLP) reactivity constitutes the first instance of a H2 activation involving a simple trialkyl GaR3 species. Adduct 3 also mediates the ring-opening polymerization (ROP) of rac-lactide at room temperature to afford cyclic polylactide (PLA). Full article
(This article belongs to the Special Issue N-Heterocyclic Carbene Metal Complexes: From Design to Applications)
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Open AccessArticle A Robust Pyridyl-NHC-Ligated Rhenium Photocatalyst for CO2 Reduction in the Presence of Water and Oxygen
Received: 2 January 2018 / Revised: 19 January 2018 / Accepted: 22 January 2018 / Published: 25 January 2018
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Abstract
Re(pyNHC-PhCF3)(CO)3Br is a highly active photocatalyst for CO2 reduction. The PhCF3 derivative was previously empirically shown to be a robust catalyst. Here, the role of the PhCF3 group is probed computationally and the robust nature of
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Re(pyNHC-PhCF3)(CO)3Br is a highly active photocatalyst for CO2 reduction. The PhCF3 derivative was previously empirically shown to be a robust catalyst. Here, the role of the PhCF3 group is probed computationally and the robust nature of this catalyst is analyzed with regard to the presence of water and oxygen introduced in controlled amounts during the photocatalytic reduction of CO2 to CO with visible light. This complex was found to work well from 0–1% water concentration reproducibly; however, trace amounts of water were required for benchmark Re(bpy)(CO)3Cl to give reproducible reactivity. When ambient air is added to the reaction mixture, the NHC complex was found to retain substantial performance (~50% of optimized reactivity) at up to 40% ambient atmosphere and 60% CO2 while the Re(bpy)(CO)3Cl complex was found to give a dramatically reduced CO2 reduction reactivity upon introduction of ambient atmosphere. Through the use of time-correlated single photon counting studies and prior electrochemical results, we reasoned that this enhanced catalyst resilience is due to a mechanistic difference between the NHC- and bpy-based catalysts. These results highlight an important feature of this NHC-ligated catalyst: substantially enhanced stability toward common reaction contaminates. Full article
(This article belongs to the Special Issue N-Heterocyclic Carbene Metal Complexes: From Design to Applications)
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Open AccessArticle Synthesis and Functionalization of a 1,2-Bis(trimethylsilyl)-1,2-disilacyclohexene That Can Serve as a Unit of cis-1,2-Dialkyldisilene
Received: 5 January 2018 / Accepted: 17 January 2018 / Published: 24 January 2018
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Abstract
π-Electron compounds that include multiple bonds between silicon atoms have received much attention as novel functional silicon compounds. In the present paper, 1,2-bis(trimethylsilyl)-1,2-disilacyclohexene 1 was successfully synthesized as thermally stable yellow crystals. Disilene 1 was easily converted to the corresponding potassium disilenide 4
[...] Read more.
π-Electron compounds that include multiple bonds between silicon atoms have received much attention as novel functional silicon compounds. In the present paper, 1,2-bis(trimethylsilyl)-1,2-disilacyclohexene 1 was successfully synthesized as thermally stable yellow crystals. Disilene 1 was easily converted to the corresponding potassium disilenide 4, which furnished novel functionalized disilenes after the subsequent addition of an electrophile. Interestingly, two trimethylsilyl groups in 1 can be stepwise converted to anthryl groups. The novel disilenes derived from 1 were characterized by a combination of nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS), elemental analyses, and X-ray single crystal diffraction analysis. The present study demonstrates that disilene 1 can serve as a unit of cis-1,2-dialkyldisilene. Full article
(This article belongs to the Special Issue Coordination Chemistry of Silicon)
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Open AccessCommunication A Cryptand-Type Aluminum Tris(salophen) Complex: Synthesis, Characterization, and Cell Imaging Application
Received: 30 November 2017 / Revised: 18 January 2018 / Accepted: 19 January 2018 / Published: 24 January 2018
Cited by 1 | PDF Full-text (2285 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Metal salen/salophen complexes have been used as fluorescent probes for cell imaging with various metal centers. Herein we synthesized cryptand-type aluminum salophen complexes LAl3 and the corresponding mononuclear compound LAl. X-ray crystal diffraction verifies the cryptand-type structure of LAl3 with C
[...] Read more.
Metal salen/salophen complexes have been used as fluorescent probes for cell imaging with various metal centers. Herein we synthesized cryptand-type aluminum salophen complexes LAl3 and the corresponding mononuclear compound LAl. X-ray crystal diffraction verifies the cryptand-type structure of LAl3 with C3h symmetry. Both LAl3 and LAl show moderate green fluorescence with quantum yields of 0.17 and 0.05, respectively. The hydrophilic and cationic nature of these aluminum salophen complexes renders them enhanced cellular uptake. Both complexes are internalized into cells by energy-dependent pathways and they distribute in lysosomal organelles. Full article
(This article belongs to the Special Issue Schiff-Base Metal Complexes)
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Open AccessEditorial From Mechanisms in Homogeneous Metal Catalysis to Applications in Chemical Synthesis
Received: 30 December 2017 / Revised: 8 January 2018 / Accepted: 19 January 2018 / Published: 24 January 2018
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Abstract
Man-made homogeneous catalysis with the aid of transition metal compounds looks back on a long history of almost one hundred years. Still, more detailed insight into the underlying mechanisms is warranted. The knowledge of how transition metals with their specific/characteristic properties, such as
[...] Read more.
Man-made homogeneous catalysis with the aid of transition metal compounds looks back on a long history of almost one hundred years. Still, more detailed insight into the underlying mechanisms is warranted. The knowledge of how transition metals with their specific/characteristic properties, such as oxidations states, redox chemistry, spin states, kinetics, and coordination preference will contribute to these processes paving the way to optimize existing processes, and to finding new exciting organic, inorganic, and organometallic transformations and to broaden the substrate scope through catalyst design. This special issue collects very recent mechanistic insight from experimental, theoretical, and mixed experimental–theoretical approaches. Full article
Open AccessReview Exploring Mechanisms in Ni Terpyridine Catalyzed C–C Cross-Coupling Reactions—A Review
Received: 9 November 2017 / Revised: 30 December 2017 / Accepted: 18 January 2018 / Published: 23 January 2018
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Abstract
In recent years, nickel has entered the stage for catalyzed C–C cross-coupling reactions, replacing expensive palladium, and in some cases enabling the use of new substrate classes. Polypyridine ligands have played an important role in this development, and the prototypical tridentate 2,2′:6′,2′′-terpyridine (tpy)
[...] Read more.
In recent years, nickel has entered the stage for catalyzed C–C cross-coupling reactions, replacing expensive palladium, and in some cases enabling the use of new substrate classes. Polypyridine ligands have played an important role in this development, and the prototypical tridentate 2,2′:6′,2′′-terpyridine (tpy) stands as an excellent example of these ligands. This review summarizes research that has been devoted to exploring the mechanistic details in catalyzed C–C cross-coupling reactions using tpy-based nickel systems. Full article
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Open AccessArticle Bond Insertion at Distorted Si(001) Subsurface Atoms
Received: 22 December 2017 / Revised: 16 January 2018 / Accepted: 17 January 2018 / Published: 23 January 2018
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Abstract
Using density functional theory (DFT) methods, we analyze the adsorption of acetylene and ethylene on the Si(001) surface in an unusual bond insertion mode. The insertion takes place at a saturated tetravalent silicon atom and the insight gained can thus be transferred to
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Using density functional theory (DFT) methods, we analyze the adsorption of acetylene and ethylene on the Si(001) surface in an unusual bond insertion mode. The insertion takes place at a saturated tetravalent silicon atom and the insight gained can thus be transferred to other saturated silicon compounds in molecular and surface chemistry. Molecular orbital analysis reveals that the distorted and symmetry-reduced coordination of the silicon atoms involved due to surface reconstruction raises the electrophilicity and, additionally, makes certain σ bond orbitals more accessible. The affinity towards bond insertion is, therefore, caused by the structural constraints of the surface. Additionally, periodic energy decomposition analysis (pEDA) is used to explain why the bond insertion structure is much more stable for acetylene than for ethylene. The increased acceptor abilities of acetylene due to the presence of two π*-orbitals (instead of one π*-orbital and a set of σ*(C–H) orbitals for ethylene), as well as the lower number of hydrogen atoms, which leads to reduced Pauli repulsion with the surface, are identified as the main causes. While our findings imply that this structure might be an intermediate in the adsorption of acetylene on Si(001), the predicted product distributions are in contradiction to the experimental findings. This is critically discussed and suggestions to resolve this issue are given. Full article
(This article belongs to the Special Issue Coordination Chemistry of Silicon)
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Open AccessArticle Six-Coordinate Ln(III) Complexes with Various Coordination Geometries Showing Distinct Magnetic Properties
Received: 29 November 2017 / Revised: 14 January 2018 / Accepted: 15 January 2018 / Published: 18 January 2018
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Abstract
The syntheses, structural characterization, and magnetic properties of three lanthanide complexes with formulas [Ln(L1)3] (Ln = Dy (1Dy); Er (1Er)); and [Dy(L2)2] (2Dy) were reported. Complexes 1Dy and 1Er
[...] Read more.
The syntheses, structural characterization, and magnetic properties of three lanthanide complexes with formulas [Ln(L1)3] (Ln = Dy (1Dy); Er (1Er)); and [Dy(L2)2] (2Dy) were reported. Complexes 1Dy and 1Er are isostructural with the metal ion in distorted trigonal-prismatic coordination geometry, but exhibit distinct magnetic properties due to the different shapes of electron density for DyIII (oblate) and ErIII (prolate) ions. Complex 1Dy shows obvious SMM behavior under a zero direct current (dc) field with an effective energy barrier of 31.4 K, while complex 1Er only features SMM behavior under a 400 Oe external field with an effective energy barrier of 23.96 K. In stark contrast, complex 2Dy with the octahedral geometry only exhibits the frequency dependence of alternating current (ac) susceptibility signals without χ″ peaks under a zero dc field. Full article
(This article belongs to the Special Issue Single-Molecule Magnets)
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Open AccessArticle Hybrid Disila-Crown Ethers as Hosts for Ammonium Cations: The O–Si–Si–O Linkage as an Acceptor for Hydrogen Bonding
Received: 11 December 2017 / Revised: 9 January 2018 / Accepted: 11 January 2018 / Published: 16 January 2018
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Abstract
Host-guest chemistry was performed with disilane-bearing crown ethers and the ammonium cation. Equimolar reactions of 1,2-disila[18]crown-6 (1) or 1,2-disila-benzo[18]crown-6 (2) and NH4PF6 in dichloromethane yielded the respective compounds [NH4(1,2-disila[18]crown-6)]PF6 (3) and
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Host-guest chemistry was performed with disilane-bearing crown ethers and the ammonium cation. Equimolar reactions of 1,2-disila[18]crown-6 (1) or 1,2-disila-benzo[18]crown-6 (2) and NH4PF6 in dichloromethane yielded the respective compounds [NH4(1,2-disila[18]crown-6)]PF6 (3) and [NH4(1,2-disila-benzo[18]crown-6)]PF6 (4). According to X-ray crystallographic, NMR, and IR experiments, the uncommon hydrogen bonding motif O(Si)∙∙∙H could be observed and the use of cooperative effects of ethylene and disilane bridges as an effective way to incorporate guest molecules was illustrated. Full article
(This article belongs to the Special Issue Coordination Chemistry of Silicon)
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Open AccessArticle 96Zr Tracer Diffusion in AZrO3 (A = Ca, Sr, Ba)
Received: 30 November 2017 / Revised: 30 December 2017 / Accepted: 9 January 2018 / Published: 15 January 2018
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Abstract
Cation tracer diffusion in polycrystalline AZrO3 (A = Ca, Sr, Ba) perovskites was studied at 1300–1500 °C in air using the stable isotope 96Zr. Thin films of 96ZrO2 were deposited on polished ceramic pellets by drop casting of an
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Cation tracer diffusion in polycrystalline AZrO3 (A = Ca, Sr, Ba) perovskites was studied at 1300–1500 °C in air using the stable isotope 96Zr. Thin films of 96ZrO2 were deposited on polished ceramic pellets by drop casting of an aqueous precursor solution containing the tracer. The pellets were subjected to thermal annealing, and the isotope depth profiles were measured by secondary ion mass spectrometry. Two distinct regions with different slopes in the profiles enabled to assess separately the lattice and grain boundary diffusion coefficients using Fick’s second law and Whipple–Le Clair’s equation. The cation diffusion along grain boundaries was 4–5 orders of magnitude faster than the corresponding lattice diffusion. The magnitude of the diffusivity of Zr4+ was observed to increase with decreasing size of the A-cation in AZrO3, while the activation energy for the diffusion was comparable 435 ± 67, 505 ± 56, and 445 ± 45 and kJ·mol−1 for BaZrO3, SrZrO3, and CaZrO3, respectively. Several diffusion mechanisms for Zr4+ were considered, including paths via Zr- and A-site vacancies. The Zr4+ diffusion coefficients reported here were compared to previous data reported on B-site diffusion in perovskites, and Zr4+ diffusion in fluorite-type compounds. Full article
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Open AccessArticle Interface Enthalpy-Entropy Competition in Nanoscale Metal Hydrides
Received: 2 November 2017 / Revised: 5 January 2018 / Accepted: 8 January 2018 / Published: 12 January 2018
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Abstract
We analyzed the effect of the interfacial free energy on the thermodynamics of hydrogen sorption in nano-scaled materials. When the enthalpy and entropy terms are the same for all interfaces, as in an isotropic bi-phasic system, one obtains a compensation temperature, which does
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We analyzed the effect of the interfacial free energy on the thermodynamics of hydrogen sorption in nano-scaled materials. When the enthalpy and entropy terms are the same for all interfaces, as in an isotropic bi-phasic system, one obtains a compensation temperature, which does not depend on the system size nor on the relative phase abundance. The situation is different and more complex in a system with three or more phases, where the interfaces have different enthalpy and entropy. We also consider the possible effect of elastic strains on the stability of the hydride phase and on hysteresis. We compare a simple model with experimental data obtained on two different systems: (1) bi-phasic nanocomposites where ultrafine TiH2 crystallite are dispersed within a Mg nanoparticle and (2) Mg nanodots encapsulated by different phases. Full article
(This article belongs to the Special Issue Functional Materials Based on Metal Hydrides)
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Open AccessEditorial Acknowledgement to Reviewers of Inorganics in 2017
Received: 11 January 2018 / Revised: 11 January 2018 / Accepted: 11 January 2018 / Published: 11 January 2018
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Abstract
Peer review is an essential part in the publication process, ensuring that Inorganics maintains high quality standards for its published papers [...] Full article
Open AccessArticle Effect of Water Content on Properties of Homogeneous [bmim]Fe(III)Cl4–H2O Mixtures and Their Application in Oxidative Absorption of H2S
Received: 10 November 2017 / Revised: 22 December 2017 / Accepted: 3 January 2018 / Published: 8 January 2018
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Abstract
The potential of 1-butyl-3-methylimidazolium tetrachloroferrate ([bmim]Fe(III)Cl4) for replacing an iron(III) chelate catalytic solution in the catalytic oxidation of H2S is attributed to its no side reaction and no degradation of the chelating agent. The catalytic oxidation product of water
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The potential of 1-butyl-3-methylimidazolium tetrachloroferrate ([bmim]Fe(III)Cl4) for replacing an iron(III) chelate catalytic solution in the catalytic oxidation of H2S is attributed to its no side reaction and no degradation of the chelating agent. The catalytic oxidation product of water in non-aqueous [bmim]Fe(III)Cl4 possibly has an influence on the oxidative absorption of H2S. Water and hydrophobic [bmim]Fe(III)Cl4 mixtures at water volume percents from 40% to 70% formed separate phases after srirring, without affecting the oxidative absorption of hydrogen sulfide. Then, studies on the properties of homogeneous [bmim]Fe(III)Cl4–H2O mixtures at water volume percents in the range of 5.88–30% and above 80% reveal that these mixtures are both Brønsted and Lewis acids at vol % (H2O) ≤ 30%, and only Lewis acids at vol % (H2O) ≥ 80%. Raman spectra showed that [bmim]Fe(III)Cl4 was the dominating species at vol % (H2O) ≤ 30%, in contrast, [bmim]Fe(III)Cl4 decomposed into FeCl3·2H2O and [bmim]Cl at vol % (H2O) ≥ 80%. Further research on oxidative absorption of H2S by homogeneous [bmim]Fe(III)Cl4–H2O mixtures demonstrated that [bmim]Fe(III)Cl4 was reduced by H2S to [bmim]Fe(II)Cl4H and FeCl3·2H2O was reduced to FeCl2, at the same time, H2S was oxidized to S8. In addition, the decrease in acidity caused by increasing the water content increased the weight percent of absorbed H2S, and decreased volatile HCl emissions. However, it is difficult to prevent the suspended S8 generated at vol % (H2O) ≥ 80% from the formation of sulfur blockage. Therefore, oxidative absorption of H2S by [bmim]Fe(III)Cl4–H2O mixtures is feasible at vol % (H2O) < 80% without sulfur blockage. Full article
(This article belongs to the Special Issue Organometallic Ionic Liquid)
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Open AccessReview A Recycling Hydrogen Supply System of NaBH4 Based on a Facile Regeneration Process: A Review
Received: 24 October 2017 / Revised: 2 January 2018 / Accepted: 5 January 2018 / Published: 6 January 2018
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Abstract
NaBH4 hydrolysis can generate pure hydrogen on demand at room temperature, but suffers from the difficult regeneration for practical application. In this work, we overview the state-of-the-art progress on the regeneration of NaBH4 from anhydrous or hydrated NaBO2 that is
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NaBH4 hydrolysis can generate pure hydrogen on demand at room temperature, but suffers from the difficult regeneration for practical application. In this work, we overview the state-of-the-art progress on the regeneration of NaBH4 from anhydrous or hydrated NaBO2 that is a byproduct of NaBH4 hydrolysis. The anhydrous NaBO2 can be regenerated effectively by MgH2, whereas the production of MgH2 from Mg requires high temperature to overcome the sluggish hydrogenation kinetics. Compared to that of anhydrous NaBO2, using the direct hydrolysis byproduct of hydrated NaBO2 as the starting material for regeneration exhibits significant advantages, i.e., omission of the high-temperature drying process to produce anhydrous NaBO2 and the water included can react with chemicals like Mg or Mg2Si to provide hydrogen. It is worth emphasizing that NaBH4 could be regenerated by an energy efficient method and a large-scale regeneration system may become possible in the near future. Full article
(This article belongs to the Special Issue Functional Materials Based on Metal Hydrides)
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Open AccessArticle Photo-Modulation of Single-Molecule Magnetic Dynamics of a Dysprosium Dinuclear Complex via a Diarylethene Bridge
Received: 30 November 2017 / Revised: 11 December 2017 / Accepted: 28 December 2017 / Published: 2 January 2018
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Abstract
A photo-switchable single molecule-magnet (SMM) with two Dy ions bridged by a bis-bipyridine-dithienylethene ligand was synthesised. Isomerisation effects on the magnetic properties were investigated. Particular attention was paid to the slow relaxation of the magnetisation in order to determine precisely the role played
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A photo-switchable single molecule-magnet (SMM) with two Dy ions bridged by a bis-bipyridine-dithienylethene ligand was synthesised. Isomerisation effects on the magnetic properties were investigated. Particular attention was paid to the slow relaxation of the magnetisation in order to determine precisely the role played by the ligand. Photo-isomerization of the ligand induced a geometric rearrangement of the complex and an electronic reconfiguration. The changes were studied by solid and solution state magnetic measurements. Full article
(This article belongs to the Special Issue Single-Molecule Magnets)
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Open AccessArticle Supramolecular Aggregation of a New Substituted Bis(salicylaldiminato)zinc(II) Schiff-Base Complex Derived from trans-1,2-Diaminocyclohexane
Received: 1 December 2017 / Revised: 27 December 2017 / Accepted: 29 December 2017 / Published: 1 January 2018
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Abstract
In this contribution is reported the synthesis, characterization, and aggregation properties in solution of a novel Zn(II) complex, (R)-2, derived from the enantiopure chiral trans-1,2-diaminocyclohexane and a substituted salicylaldehyde. Detailed 1H NMR, DOSY NMR, optical absorption, and
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In this contribution is reported the synthesis, characterization, and aggregation properties in solution of a novel Zn(II) complex, (R)-2, derived from the enantiopure chiral trans-1,2-diaminocyclohexane and a substituted salicylaldehyde. Detailed 1H NMR, DOSY NMR, optical absorption, and circular dichroism spectroscopic studies and chemical evidence allowed to investigate the nature of aggregate species in solution. The high solubility of (R)-2 in solution of the non-coordinating chloroform solvent leads to formation of various aggregates, some of them consisting of large oligomers estimated to contain up to 27 monomeric units. The chiral trans-stereochemistry of the bridging diamine favors a different aggregation mode in these complexes, both in the oligomers and dimers, involving a tetrahedral coordination geometry around the metal center. Overall data suggest the formation of helical oligomers, (ZnL)n, in freshly prepared chloroform solutions which, by standing or heating, evolve towards a more thermodynamically stable, dinuclear double-helicate Zn2L2 dimer. Full article
(This article belongs to the Special Issue Schiff-Base Metal Complexes)
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Open AccessArticle Field-Induced Slow Magnetic Relaxation of Mono- and Dinuclear Dysprosium(III) Complexes Coordinated by a Chloranilate with Different Resonance Forms
Received: 14 November 2017 / Revised: 15 December 2017 / Accepted: 28 December 2017 / Published: 30 December 2017
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Abstract
We synthesized the dinuclear and mononuclear dysprosium(III) complexes [{Dy(Tp)2}2(Cl2An)]·2CH2Cl2 (1) and [Co(Cp)2][Dy(Tp)2(Cl2An)] (3), where Cl2An2− and Tp are the chloranilate
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We synthesized the dinuclear and mononuclear dysprosium(III) complexes [{Dy(Tp)2}2(Cl2An)]·2CH2Cl2 (1) and [Co(Cp)2][Dy(Tp)2(Cl2An)] (3), where Cl2An2− and Tp are the chloranilate and hydrotris(pyrazolyl)borate ligand, respectively. In addition, the magnitude of the magnetic coupling between the lanthanide centers through the Cl2An2− bridge has been probed through the synthesis of [{Gd(Tp)2}2(Cl2An)]·2CH2Cl2 (2), which is a gadolinium(III) analogue of 1. Complexes 13 were characterized by infrared (IR) spectroscopy, elemental analysis, single-crystal X-ray diffraction, and SQUID measurements. IR and single-crystal X-ray structural analyses confirm that the coordination environments of the lanthanide(III) centers in 1 and 3 are similar to each other; i.e., eight-coordinated metal centers, each occupied by an N6O2 donor set from two Tp ligands and one Cl2An2− ligand. The coordination geometries of the lanthanide(III) centers in 1 and 2 are distorted triangular dodecahedral, while that in the mononuclear complex 3 is square antiprismatic, where the Cl2An2− ligand takes the bi-separated delocalized form in 1 and 2, and the o-quinone form in 3. Alternating-current (AC) magnetic studies clearly reveal that both 1 and 3 exhibit field-induced slow relaxations of magnetization that occur via Raman and direct processes. Complexes 1 and 3 exhibit different spin relaxation behavior, which reflects the coordination geometry around each DyIII center and its nuclearity, as well as the molecular packing in the crystal lattice. Although the magnetic analysis of 2 revealed negligible magnetic coupling, Cl2An2− bridges with small biases may form in the dinuclear complexes, which play roles in the spin relaxation dynamics through dipolar interactions. Full article
(This article belongs to the Special Issue Single-Molecule Magnets)
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Open AccessCommunication Synthesis of a α-Chlorosilyl Functionalized Donor-Stabilized Chlorogermylene
Received: 8 December 2017 / Revised: 23 December 2017 / Accepted: 25 December 2017 / Published: 29 December 2017
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Abstract
Peripherally functionalized low-valent main group species allow for the introduction/interconversion of functional groups without increasing the formal oxidation state of the main group center. Herein, we report a straightforward method for the incorporation of a α-chlorosilyl moiety adjacent to the NHC-coordinated germanium(II) center.
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Peripherally functionalized low-valent main group species allow for the introduction/interconversion of functional groups without increasing the formal oxidation state of the main group center. Herein, we report a straightforward method for the incorporation of a α-chlorosilyl moiety adjacent to the NHC-coordinated germanium(II) center. Full article
(This article belongs to the Special Issue Coordination Chemistry of Silicon)
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