1,2‐Bis­(methylsulfanyl)‐1,2‐dicarba‐closo‐dodecaborane(12)

In the title compound, 1,2‐(SCH₃)₂‐1,2‐closo‐C₂B₁₀H₁₀ or C₄H₁₆B₁₀S₂, the methylsulfanyl groups are bonded to the C atoms of the 1,2‐dicarba‐closo‐dodecaborane cage. The C_cage—C_cage distance is 1.8033 (18) Å and the S—C_cage—C_cage—S torsion angle is 1.07 (13)°. The C_cage—C_cage distance is compared with those in other 1,2‐dicarba‐closo‐dodecaborane derivatives.     

7,8‐Di­phenyl‐9‐di­methyl­sulfido‐10,11‐μ‐hydro‐7,8‐dicarba‐nido‐undecaborane(9)

In the title compound, C₁₆H₂₅B₉S, there are two crystallographically independent mol­ecules, and the conformations of the phenyl and SMe₂ substituents indicate some intramolecular steric crowding. The bridging H atom is asymmetrically disposed. The title compound is a precursor to a crowded vertex‐labelled nido carborane ligand important in establishing the mechanism of isomerization of icosahedral heteroboranes.     

Two isostructural carboranes: 3‐phenyl‐1,2‐dicarba‐closo‐dodecaborane(12) and 1‐phenyl‐1,7‐dicarba‐closo‐dodecaborane(12)

Two phenyl‐substituted carboranes, 3‐phenyl‐1,2‐dicarba‐closo‐dodecaborane(12), C₈H₁₆B₁₀, (I), and 1‐phenyl‐1,7‐dicarba‐closo‐dodecaborane(12), C₈H₁₆B₁₀, (II), were found to be isostructural. Comparison of the bond angles at the ipso‐C atoms of the phenyl substituent for (I) and (II) [117.71 (3) and 118.45 (10)°, respectively] indicates that electron donation of the carborane cage for B‐ and C‐substituted carboranes is different.     

Solvent–metal interactions in bis[1,2‐dicarba‐closo‐dodecaboran(12)‐1‐yl]mercury(II) dichloromethane solvate and bis[1,12‐dicarba‐closo‐dodecaboran(12)‐1‐yl]mercury(II) tetrahydrofuran solvate

The title compounds, bis­[1,2‐dicarba‐closo‐dodecaboran(12)‐1‐yl]­mercury(II) di­chloro­methane solvate, [Hg(C₂B₁₀H₁₁)₂]·CH₂Cl₂, (I), and bis­[1,12‐dicarba‐closo‐dodecaboran(12)‐1‐yl]­mercury(II) tetra­hydro­furan solvate, [Hg(C₂B₁₀H₁₁)₂]·C₄H₈O, (II), were prepared in excellent yields using a robust synthetic procedure involving the reaction of HgCl₂ with the appropriate monoli­thiocarborane. X‐Ray analysis of the products revealed strong interactions between the Hg atoms in both complexes and the respective lattice solvent. The distances between the Hg^II centers and the Cl atoms of the dichloromethane solvent molecule in the ortho‐carborane derivative, (I), and the O atom of the tetra­hydro­furan molecule in the para‐carborane complex, (II), are shorter than the sums of the van der Waals radii for Hg and Cl (3.53 Å), and Hg and O (3.13 Å), respectively, indicating moderately strong interactions. There are two crystallographically independent mol­ecules in the asymmetric unit of both compounds, which, in each case, are related by differing relative positions of the cages.     

Synthesis of the First Example of the 12‐Vertex‐closo/12‐Vertex‐nido Biscarborane Cluster by a Metal‐Free B−H Activation at a Phosphorus(III) Center

An unusual 12‐vertex‐closo‐C₂B₁₀/12‐vertex‐nido‐C₂B₁₀ biscarborane cluster was synthesized through an unprecedented regioselective metal‐free B?H activation by a sterically hindered P^III center under mild conditions accompanied by cage‐opening rearrangement. A combination of the electron‐accepting properties of a carborane cage and steric enforcement of close interatomic contacts represent a new synthetic strategy for the activation of strong B?H bonds in carboranes.     

Visible‐Light‐Promoted Photocatalytic B−C Coupling via a Boron‐Centered Carboranyl Radical: Facile Synthesis of B(3)‐Arylated o‐Carboranes

A visible‐light‐mediated in situ generation of a boron‐centered carboranyl radical (o‐C₂B₁₀H₁₁ ^. ) has been described. With eosin Y as a photoredox catalyst, 3‐diazonium‐o‐carborane tetrafluoroborate [3‐N₂‐o‐C₂B₁₀H₁₁][BF₄] was converted into the corresponding boron‐centered carboranyl radical intermediate, which can undergo efficient electrophilic substitution reaction with a wide range of (hetero)arenes. This general and simple procedure provides a metal‐free alternative for the synthesis of 3‐(hetero)arylated‐o‐carboranes.     

Reaction of o‐Carboryne with Furans: Facile Synthesis of Carborane‐ Fused Oxanorbornenes and Their Derivatives

o‐Carboryne (1,2‐dehydro‐o‐carborane) is a very useful synthon for the synthesis of a variety of carborane‐functionalized molecules. Diels‐Alder reaction of o‐carboryne with furans gave a series of carborane‐fused oxanorbornenes in moderate to high yields using 1‐OTf‐1,2‐C₂B₁₀H₁₁ as carboryne precursor. The resultant cycloadducts can undergo hydrogenation, cyclic oxidation, bromination, [4 + 2]/[2 + 2] cycloaddition and nucleophilic ring opening reaction to afford a variety of highly functionalized carboranes that may find applications as useful basic units in medicine and materials science.     

A theoretical study on the stability difference of the borane and carborane C2Bn−2Hn (5 ≤ n ≤ 7) clusters

In order to study the electronic structure and structural stability of borane and carborane C₂B_n?2H_n (5 ≤ n ≤ 7) clusters, especially the stability difference between the borane and carborane C₂B₃H₅. The frontier orbital energy levels of the borane and carborane C₂B_n?2H_n (5 ≤ n ≤ 7) clusters are calculated at CCSD(T)/aug‐cc‐pVXZ//B3LYP/def2‐TZVPP level. The results are further analyzed by qualitative frontier orbital method based on the cap–ring interaction. The results reveal that: (1) the larger E_gap(HOMO‐LUMO energy gap) of carborane C₂B_n?2H_n (5 ≤ n ≤ 7) clusters than borane (5 ≤ n ≤ 7) clusters originates from the more effective cap–ring orbital overlap of carborane C₂B_n?2H_n (5 ≤ n ≤ 7) clusters than that of borane (5 ≤ n ≤ 7) clusters; (2) the smallest E_gap of the borane results from the highest energy level of the ring symmetry‐adapted linear combination orbital of cluster; and (3) the largest E_gap of the carborane C₂B₃H₅ is induced by the most effective cap–ring orbital interaction of C₂B₃H₅ cluster. © 2014 Wiley Periodicals, Inc.     

N‐Butylpyridinium undecachlorocarbadodecaborate and comparison with similar compounds

The title compound, C₉H₁₄N⁺·CHB₁₁Cl₁₁⁻, was obtained in the course of our continuing studies of the low‐melting salts of closo‐ and nido‐carborane cage anions with alkylpyridinium and dialkylimidazolium cations. The title compound is the first example of a pyridinium salt of a perchlorinated carborane anion. The structure consists of one N‐butylpyridinium cation counterbalanced by one perchlorinated carborane cage anion per asymmetric unit. By changing the counter‐ion, different packings are observed, and to try to understand this the new structure is compared with five similar compounds.     

20‐Hydroxy­imino‐5α‐pregna‐9(11),16‐dien‐3β‐yl acetate and 17‐oxo‐5α‐androst‐9(11)‐en‐3β‐yl acetate

In the title compounds, C₂₃H₃₃NO₃ and C₂₁H₃₀O₃, respectively, the ester linkage in ring A is equatorial. In these steroids, the six‐membered rings A and B have chair conformations, but ring C can be better described as a half‐chair. The five‐membered ring D adopts a 14α‐envelop conformation. The A/B, B/C and C/D ring junctions are trans.     

Hydrogen‐bonded chains of rings in 1‐(4‐chloroanilinomethyl)‐5‐(4‐chlorophenyl)‐1,3,5‐triazinane‐2‐thione and hydrogen‐bonded sheets in 1‐anilinomethyl‐5‐phenyl‐1,3,5‐triazinane‐2‐thione

In 1‐(4‐chloroanilinomethyl)‐5‐(4‐chlorophenyl)‐1,3,5‐triazinane‐2‐thione, C₁₆H₁₆Cl₂N₄S, there are two independent molecules in the asymmetric unit which form inversion dimers via two weak N—H...S hydrogen bonds. The dimers are then linked into C(9)C(14) chains by a C—H...S hydrogen bond and a C—H...Cl contact. In 1‐(anilinomethyl)‐5‐phenyl‐1,3,5‐triazinane‐2‐thione, C₁₆H₁₈N₄S, molecules are linked into complex sheets via a combination of N—H...S and C—H...π hydrogen bonds.     

Weak intermolecular interactions in isomorphous 5‐(2‐chloroethoxy)‐2,3‐dihydro‐1,4‐benzodioxine and 5‐(2‐bromoethoxy)‐2,3‐dihydro‐1,4‐benzodioxine: bonding or nonbonding interactions

The title compounds, C₁₀H₁₁ClO₃, (I), and C₁₀H₁₁BrO₃, (II), are isomorphous and effectively isostructural; all of the interatomic distances and angles are normal. The structures exhibit long intermolecular C—H...O and C—H...π contacts with attractive energies ranging from 1.17 to 2.30 kJ mol⁻¹. Weak C—H...O hydrogen bonds form C(3) and C(4) motifs, combining to form a two‐dimensional R₃⁴(12) net. No face‐to‐face stacking interactions are observed.     

Strychninium N‐phthaloyl‐β‐alaninate N‐phthaloyl‐β‐alanine and brucinium N‐phthaloyl‐β‐alaninate 5.67‐hydrate

Comparison of the structures of strychninium N‐phthaloyl‐β‐alaninate N‐phthaloyl‐β‐alanine, C₂₁H₂₃N₂O₂⁺·C₁₁H₈NO₄⁻·C₁₁H₉NO₄, and brucinium N‐phthaloyl‐β‐alaninate 5.67‐hydrate, C₂₃H₂₇N₂O₄⁺·C₁₁H₈NO₄⁻·5.67H₂O, reveals that, unlike strychninium cations, brucinium cations display a tendency to produce stacking inter­actions with cocrystallizing guests.     

4‐Ethynyl‐4‐hydroxycyclohexan‐1‐one and 4‐ethynyl‐4‐hydroxy‐2,3,5,6‐tetramethylcyclohexa‐2,5‐dien‐1‐one

The title compounds, C₈H₁₀O₂, (I), and C₁₂H₁₄O₂, (II), occurred as by‐products in the controlled synthesis of a series of bis­(gem‐alkynols), prepared as part of an extensive study of synthon formation in simple gem‐alkynol derivatives. The two 4‐(gem‐alkynol)‐1‐ones crystallize in space group P2₁/c, (I) with Z′ = 1 and (II) with Z′ = 2. Both structures are dominated by O—H?O=C hydrogen bonds, which form simple chains in the cyclo­hexane derivative, (I), and centrosymmetric dimers, of both symmetry‐independent mol­ecules, in the cyclo­hexa‐2,5‐diene, (II). These strong synthons are further stabilized by C[triple‐bond]C—H?O=C, C_methylene—H?O(H) and C_methyl—H?O(H) interactions. The direct intermolecular interactions between donors and acceptors in the gem‐alkynol group, which characterize the bis­(gem‐alkynol) analogues of (I) and (II), are not present in the ketone derivatives studied here.     

Triterpenoide. XIX. 3β‐Hydroxy‐11‐oxo‐18α‐olean‐12‐en‐28‐säure‐methyl­ester und 3,11‐Dioxo‐18α‐olean‐12‐en‐28‐säure‐methyl­ester

The X‐ray crystal structure analyses of 3β‐hydroxy‐11‐oxo‐18α‐olean‐12‐en‐28‐oic acid methyl ester ethanol solvate, C₃₁H₄₈O₄·C₂H₆O, (I), and 3,11‐dioxo‐18α‐olean‐12‐en‐28‐oic acid methyl ester, C₃₁H₄₆O₄, (II), are described. These two compounds differ only in the structure of ring A. In (I), ring A has a chair conformation, while in (II), it has a twisted boat conformation. In both compounds, ring C has a slightly distorted sofa conformation, rings B, D and E are in chair conformations, and rings D and E are trans‐fused. The asymmetric unit of (I) contains one mol­ecule of ethanol linked by hydrogen bonds with two different mol­ecules of (I).     

2,3‐Dihydro‐1,3‐benzothiazol‐2‐iminium monohydrogen sulfate and 2‐iminio‐2,3‐dihydro‐1,3‐benzothiazole‐6‐sulfonate: a combined structural and theoretical study

The 2‐aminobenzothiazole sulfonation intermediate 2,3‐dihydro‐1,3‐benzothiazol‐2‐iminium monohydrogen sulfate, C₇H₇N₂S⁺·HSO₄⁻, (I), and the final product 2‐iminio‐2,3‐dihydro‐1,3‐benzothiazole‐6‐sulfonate, C₇H₆N₂O₃S₂, (II), both have the endocyclic N atom protonated; compound (I) exists as an ion pair and (II) forms a zwitterion. Intermolecular N—H...O and O—H...O hydrogen bonds are seen in both structures, with bonding energy (calculated on the basis of density functional theory) ranging from 1.06 to 14.15 kcal mol⁻¹. Hydrogen bonding in (I) and (II) creates DDDD and C(8)C(9)C(9) first‐level graph sets, respectively. Face‐to‐face stacking interactions are observed in both (I) and (II), but they are extremely weak.     

13,13a‐Di­hydro‐13‐methoxy‐9‐methyl‐1‐benzo­pyrano­[4,3‐i]­dinaphtho­[2,1‐c;1′,2′‐f]‐2,8‐dioxa­bicyclo­[3.3.1]­nonane

The crystal structure of the title compound, C₃₂H₂₄O₄, contains three fused di­hydro­pyran rings (A, B and C); ring A is fused with a benzene ring while the other two rings, B and C, are fused with naphthalene rings. Ring A adopts a half‐chair conformation with an equatorial methoxy group, whereas ring B assumes a distorted half‐chair conformation, the A/B ring junction being trans. Ring C adopts a distorted half‐boat conformation and is nearly orthogonal to ring B. Ring C is inclined to the best plane of ring A at an angle of 112.1 (1)°.     

17α,21‐Di­hydroxy‐16β‐methylpregna‐1,4‐diene‐3,11,20‐trione (meprednisone)

The title compound, C₂₂H₂₈O₅, is a commercial therapeutic agent of the steroid class. Both independent mol­ecules in the asymmetric unit have six‐membered A rings that are planar, while the B and C rings adopt normal chair conformations. The five‐membered D ring is in a 13β,14α‐half‐chair con­formation, and the B/C and C/D ring junctions are in trans positions. Cohesion in the crystal is provided by O—H⃛O hydrogen bonds, which generate chains of mol­ecules that are organized in a plane that lies along the crystallographic b axis.     

Ethyl 2‐form­amido‐2‐(4‐iodo­benzyl)‐3‐(4‐iodo­phenyl)­propionate and ethyl 2‐(3‐bromo­benzyl)‐3‐(3‐bromo­phenyl)‐2‐form­amidopropionate

The title compounds, C₁₉H₁₉I₂NO₃ and C₁₉H₁₉Br₂NO₃, are derivatives of α‐amino­isobutyric acid with halogen substituents at the para and meta positions, respectively. The ethoxycarbonyl and formamide side chains attached to the C_α atom of the mol­ecule adopt extended and folded conformations, respectively. The crystal structures are stabilized by N—H⃛O, C—H⃛O, C—Br⃛O and C—I⃛O interactions.     

Synthesis and Supramolecular Studies of Chiral Boronated Platinum(II) Complexes: Insights into the Molecular Recognition of Carboranes by β‐Cyclodextrin

The synthesis and characterisation of a novel isomeric family of closo‐carborane‐containing Pt^II complexes ((R/S)‐( 1 – 4 )?2 NO₃) are reported. Related complexes ( 5 ?NO₃ and 6 ?NO₃) that contain the 7,8‐nido‐carborane cluster were obtained from the selective deboronation of the 1,2‐closo‐carborane analogues. The corresponding water‐soluble supramolecular 1:1 host–guest β‐cyclodextrin (β‐CD) adducts ((R/S)‐( 1 – 4 ) ? β‐CD?2 NO₃) were also prepared and fully characterised. HR‐ESI‐MS experiments confirmed the presence of the host–guest adducts, and 2D‐¹H{¹¹B} ROESY NMR studies showed that the boron clusters enter the β‐CD from the side of the wider annulus. Isothermal titration calorimetry (ITC) experiments revealed enthalpically driven 1:1 and higher‐order supramolecular interactions between β‐CD and (R/S)‐( 1 – 4 )?2 NO₃ in aqueous solution. A comparison of the predominate 1:1 binding mode established that the affinity of β‐CD for the guest molecule is mainly influenced by the pyridyl ring substitution pattern and chirality of the host, whilst the nature of the closo‐carborane isomer also plays some role, with the most favourable structural features for β‐CD binding being the presence of the 4‐pyridyl ring, 1,12‐closo‐carborane, and an S configuration. The results reported here represent the first comprehensive calorimetric study of the supramolecular interactions between closo‐carborane compounds and β‐CD, and it provides fascinating insights into the structural features influencing the thermodynamics of this phenomenon.