Editorial

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3 pages, 182 KiB

Open AccessEditorial

Carborane: Dedicated to the Work of Professor Alan Welch

by Georgina M. Rosair and Marina Yu. Stogniy

Crystals 2021, 11(11), 1365; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11111365 - 09 Nov 2021

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Abstract

In the 1950s, borohydrides arose as promising components of new rocket and aviation fuels [...] Full article

(This article belongs to the Special Issue Carborane: Dedicated to the Work of Professor Alan Welch)

Research

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9 pages, 3309 KiB

Open AccessCommunication

New Radical-Cation Salts Based on the TMTTF and TMTSF Donors with Iron and Chromium Bis(Dicarbollide) Complexes: Synthesis, Structure, Properties

by Denis M. Chudak, Olga N. Kazheva, Irina D. Kosenko, Gennady V. Shilov, Igor B. Sivaev, Georgy G. Abashev, Elena V. Shklyaeva, Lev I. Buravov, Dmitry N. Pevtsov, Tatiana N. Starodub, Vladimir I. Bregadze and Oleg A. Dyachenko

Crystals 2021, 11(9), 1118; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11091118 - 14 Sep 2021

Cited by 1 | Viewed by 1597

Abstract

New radical-cation salts based on tetramethyltetrathiafulvalene (TMTTF) and tetramethyltetraselenefulvalene (TMsTSF) with metallacarborane anions (TMTTF)[3,3′-Cr(1,2-C₂B₉H₁₁)₂], (TMTTF)[3,3′-Fe(1,2-C₂B₉H₁₁)₂], and (TMTSF)₂[3,3′-Cr(1,2-C₂B₉H₁₁)₂] [...] Read more.

New radical-cation salts based on tetramethyltetrathiafulvalene (TMTTF) and tetramethyltetraselenefulvalene (TMsTSF) with metallacarborane anions (TMTTF)[3,3′-Cr(1,2-C₂B₉H₁₁)₂], (TMTTF)[3,3′-Fe(1,2-C₂B₉H₁₁)₂], and (TMTSF)₂[3,3′-Cr(1,2-C₂B₉H₁₁)₂] were synthesized by electrocrystallization. Their crystal structures were determined by single crystal X-ray diffraction, and their electrophysical properties in a wide temperature range were studied. The first two salts are dielectrics, while the third one is a narrow-gap semiconductor: σ_RT = 5 × 10⁻³ Ohm⁻¹cm⁻¹; E_a ≈ 0.04 eV (aprox. 320 cm⁻¹). Full article

(This article belongs to the Special Issue Carborane: Dedicated to the Work of Professor Alan Welch)

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11 pages, 10684 KiB

Open AccessCommunication

1,12-Diiodo-Ortho-Carborane: A Classic Textbook Example of the Dihalogen Bond

by Kyrill Yu. Suponitsky, Alexei A. Anisimov, Sergey A. Anufriev, Igor B. Sivaev and Vladimir I. Bregadze

Crystals 2021, 11(4), 396; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11040396 - 08 Apr 2021

Cited by 12 | Viewed by 1916

Abstract

The crystal structure of 1,12-diiodo-ortho-carborane 1,12-I₂-1,2-C₂B₁₀H₁₀ was determined by single crystal X-ray diffraction. In contrary to earlier studied 1,12-dibromo analogue 1,12-Br₂-1,2- C₂B₁₀H₁₀, its crystal packing is [...] Read more.

The crystal structure of 1,12-diiodo-ortho-carborane 1,12-I₂-1,2-C₂B₁₀H₁₀ was determined by single crystal X-ray diffraction. In contrary to earlier studied 1,12-dibromo analogue 1,12-Br₂-1,2- C₂B₁₀H₁₀, its crystal packing is governed by the presence of the intermolecular I⋯I dihalogen bonds between the iodine atom attached to the carbon atom (acceptor) and the iodine atom attached to the antipodal boron atom (donor) of the carborane cage. The observed dihalogen bonds belong to the II type and are characterized by classical parameters: shortened I⋯I distance of 3.5687(9) Å, C–I⋯I angle of 172.61(11)° and B–I⋯I angle of 92.98(12)°. Full article

(This article belongs to the Special Issue Carborane: Dedicated to the Work of Professor Alan Welch)

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14 pages, 3804 KiB

Open AccessArticle

Carboranes as Lewis Acids: Tetrel Bonding in CB₁₁H₁₁ Carbonium Ylide

by Maxime Ferrer, Ibon Alkorta, José Elguero and Josep M. Oliva-Enrich

Crystals 2021, 11(4), 391; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11040391 - 07 Apr 2021

Cited by 6 | Viewed by 2440

Abstract

High-level quantum-chemical computations (G4MP2) are carried out in the study of complexes featuring tetrel bonding between the carbon atom in the carbenoid CB₁₁H₁₁—obtained by hydride removal in the C-H bond of the known closo-monocarbadodecaborate anion CB₁₁H [...] Read more.

High-level quantum-chemical computations (G4MP2) are carried out in the study of complexes featuring tetrel bonding between the carbon atom in the carbenoid CB₁₁H₁₁—obtained by hydride removal in the C-H bond of the known closo-monocarbadodecaborate anion CB₁₁H₁₂⁽⁻⁾ and acting as Lewis acid (LA)—and Lewis bases (LB) of different type; the electron donor groups in the tetrel bond feature carbon, nitrogen, oxygen, fluorine, silicon, phosphorus, sulfur, and chlorine atomic centres in neutral molecules as well as anions H⁽⁻⁾, OH⁽⁻⁾, and F⁽⁻⁾. The empty radial 2p_r vacant orbital on the carbon centre in CB₁₁H₁₁, which corresponds to the LUMO, acts as a Lewis acid or electron attractor, as shown by the molecular electrostatic potential (MEP) and electron localization function (ELF). The thermochemistry and topological analysis of the complexes {CB₁₁H₁₁:LB} are comprehensively analysed and classified according to shared or closed-shell interactions. ELF analysis shows that the tetrel C⋯X bond ranges from very polarised bonds, as in H₁₁B₁₁C:F⁽⁻⁾ to very weak interactions as in H₁₁B₁₁C⋯FH and H₁₁B₁₁C⋯O=C=O. Full article

(This article belongs to the Special Issue Carborane: Dedicated to the Work of Professor Alan Welch)

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11 pages, 1453 KiB

Open AccessArticle

Coordination Ability of 10-EtC(NHPr)=HN-7,8-C₂B₉H₁₁ in the Reactions with Nickel(II) Phosphine Complexes

by Marina Yu. Stogniy, Svetlana A. Erokhina, Kyrill Yu. Suponitsky, Igor B. Sivaev and Vladimir I. Bregadze

Crystals 2021, 11(3), 306; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11030306 - 19 Mar 2021

Cited by 9 | Viewed by 1992

Abstract

The complexation reactions of nido-carboranyl amidine 10-PrNHC(Et)=HN-7,8-C₂B₉H₁₁ with different nickel(II) phosphine complexes such as [(PR₂R’)₂NiCl₂] (R = R’ = Ph, Bu; R = Me, R’ = Ph) were investigated. As a [...] Read more.

The complexation reactions of nido-carboranyl amidine 10-PrNHC(Et)=HN-7,8-C₂B₉H₁₁ with different nickel(II) phosphine complexes such as [(PR₂R’)₂NiCl₂] (R = R’ = Ph, Bu; R = Me, R’ = Ph) were investigated. As a result, a series of novel half-sandwich nickel(II) π,σ-complexes [3-R’R₂P-3-(8-PrN=C(Et)NH)-closo-3,1,2-NiC₂B₉H₁₀] with the coordination of the carborane and amidine components was prepared. The acidification of obtained complexes with HCl led to the breaking of the Ni-N bond with formation of nickel(II) π-complexes [3-Cl-3-R’R₂P-8-PrNH=C(Et)NH-closo-3,1,2-NiC₂B₉H₁₀]. The crystal molecular structure of [3-Ph₃P-3-(8-PrN=C(Et)NH)-closo-3,1,2-NiC₂B₉H₁₀] was determined by single crystal X-ray diffraction. Full article

(This article belongs to the Special Issue Carborane: Dedicated to the Work of Professor Alan Welch)

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16 pages, 5574 KiB

Open AccessArticle

Tuning the Liquid Crystallinity of Cholesteryl-o-Carborane Dyads: Synthesis, Structure, Photoluminescence, and Mesomorphic Properties

by Albert Ferrer-Ugalde, Arántzazu González-Campo, José Giner Planas, Clara Viñas, Francesc Teixidor, Isabel M. Sáez and Rosario Núñez

Crystals 2021, 11(2), 133; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11020133 - 28 Jan 2021

Cited by 4 | Viewed by 2264

Abstract

A set of mesomorphic materials in which the o-carborane cluster is covalently bonded to a cholesteryl benzoate moiety (mesogen group) through a suitably designed linker is described. The olefin cross-metathesis between appropriately functionalized styrenyl-o-carborane derivatives and a terminal alkenyl cholesteryl [...] Read more.

A set of mesomorphic materials in which the o-carborane cluster is covalently bonded to a cholesteryl benzoate moiety (mesogen group) through a suitably designed linker is described. The olefin cross-metathesis between appropriately functionalized styrenyl-o-carborane derivatives and a terminal alkenyl cholesteryl benzoate mesogen (all type I terminal olefins) leads to the desired trans-regioisomer, which is the best-suited configuration to obtain mesomorphic properties in the final materials. The introduction of different substituents (R = H (M2), Me (M3), or Ph (M4)) to one of the carbon atoms of the o-carborane cluster (C_cluster) enables the tailoring of liquid crystalline properties. Compounds M2 and M3 show the chiral nematic (N*) phase, whereas M4 do not show liquid crystal behavior. Weaker intermolecular interactions in the solid M3 with respect to those in M2 may allow the liquid crystallinity in M3 to be expressed as enantiotropic behavior, whereas breaking the stronger intermolecular interaction in the solid state of M2 leads directly to the isotropic state, resulting in monotropic behavior. Remarkably, M3 also displays the blue phase, which was observed neither in the chiral nematic precursor nor in the styrenyl-cholesterol model (M5) without an o-carborane cluster, which suggests that the presence of the cluster plays a role in stabilizing this highly twisted chiral phase. In the carborane-containing mesogens (M2 and M3), the o-carborane cluster can be incorporated without destroying the helical organization of the mesophase. Full article

(This article belongs to the Special Issue Carborane: Dedicated to the Work of Professor Alan Welch)

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12 pages, 3061 KiB

Open AccessArticle

Exploration of Bis(nickelation) of 1,1′-Bis(o-carborane)

by Dipendu Mandal and Georgina M. Rosair

Crystals 2021, 11(1), 16; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11010016 - 27 Dec 2020

Cited by 6 | Viewed by 1805

Abstract

The metalation of [Tl]₂[1-(1′-3′,1′,2′-closo-TlC₂B₉H₁₀)-3,1,2-closo-TlC₂B₉H₁₀], with the smaller {Ni(dmpe)} fragment sourced from [Ni(dmpe)Cl₂], is explored. The bis(metalated) products are obtained as a diastereoisomeric mixture. [...] Read more.

The metalation of [Tl]₂[1-(1′-3′,1′,2′-closo-TlC₂B₉H₁₀)-3,1,2-closo-TlC₂B₉H₁₀], with the smaller {Ni(dmpe)} fragment sourced from [Ni(dmpe)Cl₂], is explored. The bis(metalated) products are obtained as a diastereoisomeric mixture. These isomers were separated, fully characterised spectroscopically and crystallographically and identified as rac-[1-(1′-3′-(dmpe)-3′,1′,2′-closo-NiC₂B₉H₁₀)-3-(dmpe)-3,1,2-closo-NiC₂B₉H₁₀] (1) and meso-[1-(1′-3′-(dmpe)-3′,1′,2′-closo-NiC₂B₉H₁₀)-3-(dmpe)-3,1,2-closo-NiC₂B₉H₁₀] (2). Previously, these 3,1,2-NiC₂B₉-3′,1′,2′-NiC₂B₉ architectures (where both cages are not isomerised), were inaccessible, and thus new structures can be achieved during bis(nickelation) with {Ni(dmpe)}. Further, the metalation of the tetra-thallium salt with the bulky {Ni(dppe)} fragment sourced from [Ni(dppe)Cl₂] was also studied. These bis(nickelated) products were also fully characterised and are afforded as the stereospecific species rac-[1-(1′-3′-(dppe)-3′,1′,2′-closo-NiC₂B₉H₁₀)-3-(dppe)-3,1,2-closo-NiC₂B₉H₁₀] (3) and [1-(2′-4′-(dppe)-4′,1′,2′-closo-NiC₂B₉H₁₀)-3-(dppe)-3,1,2-closo-NiC₂B₉H₁₀] (4α). In the latter metalation, compound 3 shows intramolecular dihydrogen bonding, contributing to the stereospecificity, whereas isomerisation from 3,1,2 to 4,1,2- in the 4α is related to steric relief. Full article

(This article belongs to the Special Issue Carborane: Dedicated to the Work of Professor Alan Welch)

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14 pages, 3459 KiB

Open AccessArticle

“Free of Base” Sulfa-Michael Addition for Novel o-Carboranyl-DL-Cysteine Synthesis

by Julia Laskova, Irina Kosenko, Ivan Ananyev, Marina Stogniy, Igor Sivaev and Vladimir Bregadze

Crystals 2020, 10(12), 1133; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst10121133 - 11 Dec 2020

Cited by 2 | Viewed by 1913

Abstract

The sulfa-Michael addition reaction was applied for the two-step synthesis of o-carboranyl cysteine 1-HOOCCH(NH₂)CH₂S-1,2-C₂B₁₀H₁₁ from the trimethylammonium salt of 1-mercapto-o-carborane and methyl 2-acetamidoacrylate. To avoid the decapitation of o-carborane into its [...] Read more.

The sulfa-Michael addition reaction was applied for the two-step synthesis of o-carboranyl cysteine 1-HOOCCH(NH₂)CH₂S-1,2-C₂B₁₀H₁₁ from the trimethylammonium salt of 1-mercapto-o-carborane and methyl 2-acetamidoacrylate. To avoid the decapitation of o-carborane into its nido-form, the “free of base” method under mild conditions in a system of two immiscible solvents toluene-H₂O was developed. The replacement of H₂O by ²H₂O resulted in carboranyl-cysteine containing a deuterium label at the α-position of the amino acid 1-HOOCCD(NH₂)CH₂S-1,2-C₂B₁₀H₁₁. The structure of the protected o-carboranyl cysteine was determined by single-crystal X-ray diffraction. The obtained compounds can be considered as potential agents for the Boron Neutron Capture Therapy of cancer. Full article

(This article belongs to the Special Issue Carborane: Dedicated to the Work of Professor Alan Welch)

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12 pages, 5516 KiB

Open AccessArticle

Reactions of Experimentally Known Closo-C₂B₈H₁₀ with Bases. A Computational Study

by Josef Holub, Jindřich Fanfrlík, Michael L. McKee and Drahomír Hnyk

Crystals 2020, 10(10), 896; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst10100896 - 03 Oct 2020

Cited by 5 | Viewed by 2069

Abstract

On the basis of the direct transformations of closo-1,2-C₂B₈H₁₀ with OH⁽⁻⁾ and NH₃ to arachno-1,6,9-OC₂B₈H₁₃⁽⁻⁾ and arachno-1,6,9-NC₂B₈H₁₃, respectively, which were experimentally [...] Read more.

On the basis of the direct transformations of closo-1,2-C₂B₈H₁₀ with OH⁽⁻⁾ and NH₃ to arachno-1,6,9-OC₂B₈H₁₃⁽⁻⁾ and arachno-1,6,9-NC₂B₈H₁₃, respectively, which were experimentally observed, the DFT computational protocol was used to examine the corresponding reaction pathways. This work is thus a computational attempt to describe the formations of 11-vertex arachno clusters that are formally derived from the hypothetical closo-B₁₃H₁₃⁽²⁻⁾. Moreover, such a protocol successfully described the formation of arachno-4,5-C₂B₆H₁₁⁽⁻⁾ as the very final product of the first reaction. Analogous experimental transformations of closo-1,6-C₂B₈H₁₀ and closo-1,10-C₂B₈H₁₀, although attempted, were not successful. However, their transformations were explored through computations. Full article

(This article belongs to the Special Issue Carborane: Dedicated to the Work of Professor Alan Welch)

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