Electron impact mass spectrometry of [C7H8N]+ and [C6H7]+ and [C6H7]+ fragment ions produced from o-toluidine and N-methylaniline

An energetic study of the production of [C₇H₈N]⁺ and [C₆H₇]⁺ fragment ions from o-toluidine and N-methylaniline is reported. The mechanisms for the formation of the ions are suggested. Metastable peaks associated with the formation and fragmentation of reactive [C₇H₈N]⁺ and [C₆H₇]⁺ ions were detected and kinetic energy released were determined. The results indicate that the [C₇H₈N]⁺ ion is formed at threshold from o-toluidine with an aminotropylium structure whereas for N-methylaniline the ion is formed with anN-phenylmethaniminium structure. [C₆H₇]⁺ ions are believed to be formed at threshold from the two precursors with a protonated benzene structure.     

A comparison of the unimolecular decomposition pathways of some C7 and C8 ions in the gas phase

[CnH_2n?3]⁺ and [C_nH_2n?4]⁺·(n = 7, 8) ions have been generated in the mass spectrometer from C_nH_2n?3 Br (n = 7, 8) precursors and from two steroids. The relative abundances of competing ‘metastable transitionss’ indicate (partial) isomerization to a common structure (or mixture of structures) prior to decomposition in most examples of all four types of ions. In contrast, [C₈H₁₀O]⁺· and [C₈H₁₂O]⁺· ions, generated from different sources as molecular ions and by fragmentation of steroids, do not decompose through common-intermediates.     

Chemical ionization mass spectra of selected C3H6O compounds

The chemical ionization mass spectra of five isomers of C₃H₆O (acetone, propionaldehyde, oxetane, propylene oxide and allyl alcohol) have been determined using a variety of reagent gases (H₂, D₂, N₂/H₂, CO₂/H₂ and CO/H₂). The [C₃H₇O]⁺ ions produced by protonation of these isomers undergo very similar reactions to those reported for analogous [C₃H₇O]⁺ metastable ions; however, decomposing ions generated by chemical ionization appear to have somewhat higher internal energies. The results of ²H labelling studies (D₂ reagent gas or labelled analogues of C₃H₆O) indicate that protonation occurs mainly on oxygen and are consistent with previous investigations of metastable oxonium ions. The protonated acetone ion is particularly stable, in agreement with the higher activation energies for fragmentation of this isomer than for other [C₃H₇O]⁺ structures. As the calculated heat of protonation of C₃H₆O is reduced by changing the reagent gas, so the extent to which fragmentation occurs decreases. This is discussed in the context of competition between fragmentation and collisional stabilization of the excited [C₃H₇O]⁺* ion. It is concluded that on average a large fraction (approaching 1) of the exothermicity of the protonation reaction resides in the [C₃H₇O]⁺* ions produced initially.     

Poly[nickel(II)‐di‐μ‐4,4′‐bipyridyl‐κ4N:N′‐μ‐dichromato‐κ2O:O′] and poly[copper(II)‐di‐μ‐4,4'‐bipyridyl‐κ4N:N′‐μ‐dichromato‐κ2O:O′]

The novel title hybrid isomorphous organic–inorganic mixed‐metal dichromates, [Ni(Cr₂O₇)(C₁₀H₈N₂)₂] and [Cu(Cr₂O₇)(C₁₀H₈N₂)₂], have been synthesized. A non‐centrosymmetric three‐dimensional (4,6)‐net is formed from a linear chain of vertex‐linked [Cr₂O]²⁻ and [MN₄O]²⁺ (M = Ni and Cu) units, which in turn are linked by the planar bidentate 4,4′‐­bipyridine ligand through the four remaining vertices of the [MN₄O]²⁺ octahedra. There are two such three‐dimensional nets that interpenetrate with inversion symmetry.     

Study of ion structures produced by the reaction of 2-propyl cations with water and methanol; covalently bound v. Hydrogen-bridged adducts

In contrast to an earlier report,¹ the collisonally induced dissociation of protonated 2-propanol and t-butyl alcohol yields spectra that are indistinguishable from those of the corresponding [C₃H₇/H₂O]⁺ and [C₄H₉/H₂O]⁺ ions generated by the (formal) gas phase addition reactions in a high pressure ion source of [s-C₃H₇]⁺ and [t-C₄H₉]⁺ ions with the n-donor H₂O. Similarly, [s-C₃H₇/CH₃OH]⁺ ions generated by both gas phase protonation of n- and s-propyl methyl ethers and addition reactions of [C₃H₇]⁺ to CH₃OH display mode-of-generation-independent collisionally induced dissociation characteristics. However, analysis of the unimolecular dissociation (loss of propene) of the [C₃H₇/CH₃OH]⁺ system, including a number of its deuterium, ¹³C- and ¹⁸O-labelled isotopomers, supports the idea that prior to unimolecular dissociation, covalently bound [C₃H₇- O(H)CH₃]⁺ ions intercovert with hydrogen-bridged adduct ions, analogous to the behaviour of the distonic ethene-, propene- and ketene-H₂O radical cations.     

Fragmentation of the enolate ion of 2,3-butanedione. Characterization of the acetyl anion by charge inversion mass spectrometry

The unimolecular and collision-induced fragmentation reactions of the enolate ion of 2,3-butanedione, [CH₃COCOCH₂]^?, have been studied, Unimolecular fragmentation on the metastable ion time-scale forms [HCCO]^?, [C₂H₃O]^?, [C₃H₅O]^? and [CH₃CO₂]^?. Charge inversion mass spectrometry shows that the [C₂H₃O]^? ion is the acetyl anion while the [C₃H₅O]^? product is the acetone enolate ion; formation of the latter product involves a large release of kinetic energy (T _1/2 = 0.99 eV). The fragmentation reactions occurring following collisional activation have been determined for 8 keV collisions and over the range 1.5–30 eV center-of-mass collision energy. Formation of [HCCO]^? and [CH₃CO]^? are of the most important reactions following collisional activation and it is concluded that the two reactions have similar critical reaction energies even though formation of [HCCO]^? is favored thermochemically.     

The structure of decomposing [C7H7O]+ ions: Benzyl versus tropylium ion structures

The unimolecular dissociation reactions for [C₇H₇O]⁺ ions generated by fragmentation of a series of precursor molecules have been investigated. The metastable kinetic energy values and branching ratios associated with decarbonylation and expulsion of a molecule of formaldehyde (CH₂O) from the [C₇H₇O]⁺ ions are interpreted as the hydroxybenzyl and hydroxytropylium [C₇H₇O]⁺ not interconverting to a common structure on the microsecond time-scale. In addition, similar measurements on protonated benzaldehyde, methylaryloxy and phenyl methylene ether [C₇H₇O]⁺ ions are interpreted as the dominant fraction of these decomposing ions having unique structures on the microsecond time-scale. These results are supported by experimental heats of formation calculated from ionization/appearance energy measurements. The experimental heats of formation are determined as: hydroxybenzyl ions, 735 kJ mol^?1; hydroxytropylium ions, 656 kJ mol^?1; phenyl methylene ether ions, 640 kJ mol^?1; methylaryloxy ions 803 kJ mol^?1. The combination of the results reported in this paper with previously reported experimental data for stable [C₇H₇O]⁺ ions (see Ref. 1, C. J. Cassady, B. S. Freiser and D. H. Russell, Org. Mass Spectrom.) is interpreted as evidence that the relative population of benzyl versus tropylium [C₇H₇O]⁺ ion structures from a given precursor molecule is determined by isomerization of the parent ion and not by structural equilibration of the [C₇H₇O]⁺ ion.     

Electron impact and ammonia chemical ionization mass spectra of n-azabicyclo[m.2.0]alkan-(n + 1)-ones (m = 3–6, n = 6–9)

Electron impact induced fragmentation of the title compounds obeys a route where the lactam moiety, OCNH, is cleaved first, with the accompanying formation of a cycloalkene ion. This can be verified by low-resolution, high-resolution, B/E and B²/E spectra as well as by collisional activation spectra of, for example, the ions m/z 82 and 67 from 7-azabicyclo[4.2.0]octan-8-one and from cyclohexene. The only, and fairly weak, fragment ions including O and N are [C₃H₃O]+, [C_kH_2k-2N]⁺ (k = 5–8) and [C₃H₆N]⁺. The ammonia chemical ionization spectra are also characteristic for all four lactams and show the same dominant ions in all cases, namely [M + 1]⁺, [M + 1 + NH₃]⁺˙ and [2 M + 1]⁺˙.     

Chiral anionic layers in tartramide spiroborate salts and variable solvation for [NR4][B(TarNH2)2] (R = Et,Pr or Bu)

The spiroborate anion, namely, 2,3,7,8‐tetracarboxamido‐1,4,6,9‐tetraoxa‐5λ⁴‐boraspiro[4.4]nonane, [B(TarNH₂)₂]^?, derived from the diol l ‐tartramide TarNH₂, [CH(O)(CONH₂)]₂, shows a novel self‐assembly into two‐dimensional (2D) layer structures in its salts with alkylammonium cations, [NR₄]⁺ (R = Et, Pr and Bu), and sparteinium, [HSpa]⁺, in which the cations and anions are segregated. The structures of four such salts are reported, namely, the tetrapropylazanium salt, C₁₂H₂₈N⁺·C₈H₁₂BN₄O₈^?, the tetraethylazanium salt hydrate, C₈H₂₀N⁺·C₈H₁₂BN₄O₈^?·6.375H₂O, the tetrabutylazanium salt as the ethanol monosolvate hemihydrate, C₁₆H₃₆N⁺·C₈H₁₂BN₄O₈^?·C₂H₅OH·0.5H₂O, and the sparteinium (7‐aza‐15‐azoniatetracyclo[7.7.1.0^2,7.0^10,15]heptadecane) salt as the ethanol monosolvate, C₁₅H₂₇N₂⁺·C₈H₁₂BN₄O₈^?·C₂H₅OH. The 2D anion layers have preserved intermolecular hydrogen bonding between the amide groups and a typical metric repeat of around 10 × 15 Å. The constraint of matching the interfacial area organizes the cations into quite different solvated arrangements, i.e. the [NEt₄] salt is highly hydrated with around 6.5H₂O per cation, the [NPr₄] salt apparently has a good metric match to the anion layer and is unsolvated, whilst the [NBu₄] salt is intermediate and has EtOH and H₂O in its cation layer, which is similar to the arrangement for the chiral [HSpa]⁺ cation. This family of salts shows highly organized chiral space and offers potential for the resolution of both chiral cations and neutral chiral solvent molecules.     

The crystal and molecular structures of three copper‐containing complexes and their activities in mimicking galactose oxidase

The structures of three copper‐containing complexes, namely (benzoato‐κ²O,O′)[(E)‐2‐({[2‐(diethylamino)ethyl]imino}methyl)phenolato‐κ³N,N′,O]copper(II) dihydrate, [Cu(C₇H₅O₂)(C₁₃H₁₉N₂O)]·2H₂O, 1 , [(E)‐2‐({[2‐(diethylamino)ethyl]imino}methyl)phenolato‐κ³N,N′,O](2‐phenylacetato‐κ²O,O′)copper(II), [Cu(C₈H₇O₂)(C₁₃H₁₉N₂O)], 2 , and bis[μ‐(E)‐2‐({[3‐(diethylamino)propyl]imino}methyl)phenolato]‐κ⁴N,N′,O:O;κ⁴O:N,N′,O‐(μ‐2‐methylbenzoato‐κ²O:O′)copper(II) perchlorate, [Cu₂(C₈H₇O₂)(C₁₂H₁₇N₂O)₂]ClO₄, 3 , have been reported and all have been tested for their activity in the oxidation of d ‐galactose. The results suggest that, unlike the enzyme galactose oxidase, due to the precipitation of Cu₂O, this reaction is not catalytic as would have been expected. The structures of 1 and 2 are monomeric, while 3 consists of a dimeric cation and a perchlorate anion [which is disordered over two orientations, with occupancies of 0.64 (4) and 0.36 (4)]. In all three structures, the central Cu atom is five‐coordinated in a distorted square‐pyramidal arrangment (τ parameter of 0.0932 for 1 , 0.0888 for 2 , and 0.142 and 0.248 for the two Cu centers in 3 ). In each species, the environment about the Cu atom is such that the vacant sixth position is open, with very little steric crowding.     

Diimido‐, Imido(oxo)‐, Dioxo‐ und Imido(alkyliden)‐Halbsandwich‐Verbindungen über selektive Hydrolyse und α—H‐Abstraktion an Organylkomplexen des sechswertigen Molybdäns und Wolframs

Diimido, Imido Oxo, Dioxo, and Imido Alkylidene Halfsandwich Compounds via Selective Hydrolysis and α—H Abstraction in Molybdenum(VI) and Tungsten(VI) Organyl Complexes Organometal imides [(η⁵‐C₅R₅)M(NR′)₂Ph] (M = Mo, W, R = H, Me, R′ = Mes, tBu) 4 — 8 can be prepared by reaction of halfsandwich complexes [(η⁵‐C₅R₅)M(NR′)₂Cl] with phenyl lithium in good yields. Starting from phenyl complexes 4 — 8 as well as from previously described methyl compounds [(η⁵‐C₅Me₅)M(NtBu)₂Me] (M = Mo, W), reactions with aqueous HCl lead to imido(oxo) methyl and phenyl complexes [(η⁵‐C₅Me₅)M(NtBu)(O)(R)] M = Mo, R = Me ( 9 ), Ph ( 10 ); M = W, R = Ph ( 11 ) and dioxo complexes [(η⁵‐C₅Me₅)M(O)₂(CH₃)] M = Mo ( 12 ), M = W ( 13 ). Hydrolysis of organometal imides with conservation of M‐C σ and π bonds is in fact an attractive synthetic alternative for the synthesis of organometal oxides with respect to known strategies based on the oxidative decarbonylation of low valent alkyl CO and NO complexes. In a similar manner, protolysis of [(η⁵‐C₅H₅)W(NtBu)₂(CH₃)] and [(η⁵‐C₅Me₅)Mo(NtBu)₂(CH₃)] by HCl gas leads to [(η⁵‐C₅H₅)W(NtBu)Cl₂(CH₃)] 14 und [(η⁵‐C₅Me₅)Mo(NtBu)Cl₂(CH₃)] 15 with conservation of the M‐C bonds. The inert character of the relatively non‐polar M‐C σ bonds with respect to protolysis offers a strategy for the synthesis of methyl chloro complexes not accessible by partial methylation of [(η⁵‐C₅R₅)M(NR′)Cl₃] with MeLi. As pure substances only trimethyl compounds [(η⁵‐C₅R₅)M(NtBu)(CH₃)₃] 16 ‐ 18 , M = Mo, W, R = H, Me, are isolated. Imido(benzylidene) complexes [(η⁵‐C₅Me₅)M(NtBu)(CHPh)(CH₂Ph)] M = Mo ( 19 ), W ( 20 ) are generated by alkylation of [(η⁵‐C₅Me₅)M(NtBu)Cl₃] with PhCH₂MgCl via α‐H abstraction. Based on nmr data a trend of decreasing donor capability of the ligands [NtBu]^2— > [O]^2— > [CHR]^2— ? 2 [CH₃]^— > 2 [Cl]^— emerges.     

Structure and mechanism of fragmentation of [C2H5O]+

The decomposition reactions of [C₂H₅O]⁺ ions produced by dissociative electron-impact ionization of 2-propanol have been studied, using ¹³C and deuterium labeling coupled with metastable intensity studies. In addition, the fragmentation reactions following protonation of appropriately labeled acetaldehydes and ethylene oxides with [H₃]⁺ or [D₃]⁺ have been investigated. In both studies particular attention has been paid to the reactions leading to [CHO]⁺, [C₂H₃]⁺ and [H₃O]⁺. In both the electron-impact-induced reactions and the chemical ionization systems the fragmentation of [C₂H₅O]⁺ to both [H₃O]⁺ and [C₂H₃]⁺ proceeds by a single mechanism. For each case the reaction involves a mechanism in which the hydrogen originally bonded to oxygen is retained in the oxygen containing fragment while the four hydrogens originally bonded to carbon become indistinguishable. The fragmentation of [C₂H₅O]⁺ to produce [CHO]⁺ proceeds by a number of mechanisms. The lowest energy route involves complete retention of the α carbon and hydrogen while a higher energy route proceeds by a mechanism in which the carbons and the attached hydrogens become indistinguishable. A third distinct mechanism, observed in the electron-impact spectra only, proceeds with retention of the hydroxylic hydrogen in the product ion. Detailed fragmentation mechanisms are proposed to explain the results. It is suggested that the [C₂H₅O]⁺ ions formed by protonation of acetaldehyde or ionization of 2-propanol are produced initially with the structure [CH₃CH?\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm O}\limits^ + $\end{document}H] (a), but isomerize to [CH₂?CH? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm O}\limits^ + $\end{document}H₂] (e) prior to decomposition to [C₂H₃]⁺ or [H₃O]⁺. The results indicate that the isomerization a → e does not proceed directly, possibly because it is symmetry forbidden, but by two consecutive [1,2] hydrogen shifts. A more general study of the electron-impact mass spectrum of 2-propanol has been made and the fragmentation reactions proceeding from the molecular ion have been identified.     

Novel hydrazone derivatives of 7‐hydroxy‐3′,3′‐dimethyl‐3′H‐spiro[chromene‐2,1′‐isobenzofuran]‐8‐carbaldehyde

The structures of new oxaindane spiropyrans derived from 7‐hydroxy‐3′,3′‐dimethyl‐3′H‐spiro[chromene‐2,1′‐isobenzofuran]‐8‐carbaldehyde (SP1), namely N‐benzyl‐2‐[(7‐hydroxy‐3′,3′‐dimethyl‐3′H‐spiro[chromene‐2,1′‐isobenzofuran]‐8‐yl)methylidene]hydrazinecarbothioamide, C₂₇H₂₅N₃O₃S, (I), at 120 (2) K, and N′‐[(7‐hydroxy‐3′,3′‐dimethyl‐3′H‐spiro[chromene‐2,1′‐isobenzofuran]‐8‐yl)methylidene]‐4‐methylbenzohydrazide acetone monosolvate, C₂₇H₂₄N₂O₄·C₃H₆O, (II), at 100 (2) K, are reported. The photochromically active C_spiro—O bond length in (I) is close to that in the parent compound (SP1), and in (II) it is shorter. In (I), centrosymmetric pairs of molecules are bound by two equivalent N—H...S hydrogen bonds, forming an eight‐membered ring with two donors and two acceptors.     

The Reactivity of Isomeric Nitrenium Lewis Acids with Phosphines,Carbenes, and Phosphide

Alkylation of spiro[fluorene-9,3’-indazole] at N(1) and N(2) with tBuCl affords the nitrenium cations [C₆H₄N₂(tBu)C(C₁₂H₈)][BF₄], 1 and 2 , respectively. Compound 1 converts to 2 over the temperature range 303–323 K with a free energy barrier of 28±5 kcal mol⁻¹. Reaction of 1 with PMe₃ afforded the N-bound phosphine adduct [C₆H₄N(tBu)N(PMe₃)C(C₁₂H₈)]BF₄] 3 . However, phosphines attack 2 at the para-carbon atom of the aryl group with concurrent cleavage of N(2)−C(1) bond and proton migration to C(1) affording [(R₃P)C₆H₃NN(tBu)CH(C₁₂H₈)][BF₄] (R=Me 4 , nBu 5 ). Analogous reactions of 1 and 2 with the carbene SIMes prompt attack at the para-carbon with concurrent loss of H^. affording the radical cation salts [(SIMes)C₆H₃N(tBu)NC(C₁₂H₈)^.][BF₄] 6 and [(SIMes)C₆H₃NN(tBu)C(C₁₂H₈)^.][BF₄] 7 , whereas reaction of 2 with BAC gives the Lewis acid-base adduct, [C₆H₄N(BAC)N(tBu)C(C₁₂H₈)][BF₄] 8 . Finally, reactions of 1 and 2 with KPPh₂ result in electron transfer affording (PPh₂)₂ and the persistent radicals C₆H₄N(tBu)NC(C₁₂H₈)^. and C₆H₄NN(tBu)C(C₁₂H₈)^.. The detailed reaction mechanisms are also explored by extensive DFT calculations.     

Phosphine (oxide)‐(thio) phenolate palladium complexes: Synthesis,characterization and (co)polymerization of norbornene

A series of palladium complexes ( 2a–2g ) ( 2a : [6‐^tBu‐2‐PPh₂‐C₆H₃O]PdMe(Py); 2b : [6‐C₆F₅–2‐PPh₂‐C₆H₃O]PdMe(Py); 2c : [6‐^tBu‐2‐PPh^tBu‐C₆H₃O]PdMe(Py); 2d : [2‐PPh^tBu‐C₆H₄O] PdMe(Py); 2e : [6‐SiMe₃–2‐PPh₂‐C₆H₃O]PdMe(Py); 2f : [2‐^tBu‐6‐(Ph₂P=O)‐C₆H₃O]PdMe(Py); 2g : [6‐SiMe₃–2‐(Ph₂P=O)‐C₆H₃S]PdMe(Py)) bearing phosphine (oxide)‐(thio) phenolate ligand have been efficiently synthesized and characterized. The solid‐state structures of complexes 2d , 2f and 2g have been further confirmed by single‐crystal X‐ray diffraction, which revealed a square‐planar geometry of palladium center. In the presence of B(C₆F₅)₃, these complexes can be used as catalysts to polymerize norbornene (NB) with relatively high yields, producing vinyl‐addition polymers. Interestingly, 2a /B(C₆F₅)₃ system catalyzed the polymerization of NB in living polymerization manner at high temperature (polydispersity index 1.07, M_n up to 1.5 × 10⁴). The co‐polymerization of NB and polar monomers was also studied using catalysts 2a and 2f . All the obtained co‐polymers could dissolve in common solvent.     

Two nickel(II) bis[(pyridin‐2‐yl)methyl]amine complexes with homophthalic and benzene‐1,2,4,5‐tetracarboxylic acids

Two new Ni^II complexes involving the ancillary ligand bis[(pyridin‐2‐yl)methyl]amine (bpma) and two different carboxylate ligands, i.e. homophthalate [hph; systematic name: 2‐(2‐carboxylatophenyl)acetate] and benzene‐1,2,4,5‐tetracarboxylate (btc), namely catena‐poly[[aqua{bis[(pyridin‐2‐yl)methyl]amine‐κ³N,N′,N′′}nickel(II)]‐μ‐2‐(2‐carboxylatophenyl)aceteto‐κ²O:O′], [Ni(C₉H₆O₄)(C₁₂H₁₃N₃)(H₂O)]_n, and (μ‐benzene‐1,2,4,5‐tetracarboxylato‐κ⁴O¹,O²:O⁴,O⁵)bis(aqua{bis[(pyridin‐2‐yl)methyl]amine‐κ³N,N′,N′′}nickel(II)) bis(triaqua{bis[(pyridin‐2‐yl)methyl]amine‐κ³N,N′,N′′}nickel(II)) benzene‐1,2,4,5‐tetracarboxylate hexahydrate, [Ni₂(C₁₀H₂O₈)(C₁₂H₁₃N₃)₂(H₂O)₂]·[Ni(C₁₂H₁₃N₃)(H₂O)₃]₂(C₁₀H₂O₈)·6H₂O, (II), are presented. Compound (I) is a one‐dimensional polymer with hph acting as a bridging ligand and with the chains linked by weak C—H...O interactions. The structure of compound (II) is much more complex, with two independent Ni^II centres having different environments, one of them as part of centrosymmetric [Ni(bpma)(H₂O)]₂(btc) dinuclear complexes and the other in mononuclear [Ni(bpma)(H₂O)₃]²⁺ cations which (in a 2:1 ratio) provide charge balance for btc⁴⁻ anions. A profuse hydrogen‐bonding scheme, where both coordinated and crystal water molecules play a crucial role, provides the supramolecular linkage of the different groups.     

Solvent‐mediated pseudo‐quadruple hydrogen‐bond motifs in three lamotrigine–carboxylic acid complexes

Lamotrigine, an antiepileptic drug, has been complexed with three aromatic carboxylic acids. All three compounds crystallize with the inclusion of N,N‐dimethylformamide (DMF) solvent, viz. lamotriginium [3,5‐diamino‐6‐(2,3‐dichlorophenyl)‐1,2,4‐triazin‐2‐ium] 4‐iodobenzoate N,N‐dimethylformamide monosolvate, C₉H₈Cl₂N₅⁺·C₇H₄IO₂⁻·C₃H₇NO, (I), lamotriginium 4‐methylbenzoate N,N‐dimethylformamide monosolvate, C₉H₇Cl₂N₅⁺·C₈H₈O₂⁻·C₃H₇NO, (II), and lamotriginium 3,5‐dinitro‐2‐hydroxybenzoate N,N‐dimethylformamide monosolvate, C₉H₈Cl₂N₅⁺·C₇H₃N₂O₇⁻·C₃H₇NO, (III). In all three structures, proton transfer takes place from the acid to the lamotrigine molecule. However, in (I) and (II), the acidic H atom is disordered over two sites and there is only partial transfer of the H atom from O to N. In (III), the corresponding H atom is ordered and complete proton transfer has occurred. Lamotrigine–lamotrigine, lamotrigine–acid and lamotrigine–solvent interactions are observed in all three structures and they thereby exhibit isostructurality. The DMF solvent extends the lamotrigine–lamotrigine dimers into a pseudo‐quadruple hydrogen‐bonding motif.     

Pseudosymmetry in a cyclopalladated compound

The enantiomerically pure title complex, [SP‐4‐4]‐(R)‐[2‐(1‐aminoethyl)phenyl‐κ²C¹,N]chlorido(quinoline‐κN)palladium(II) acetone hemisolvate, [Pd(C₈H₁₀N)Cl(C₉H₇N)]·0.5C₃H₆O, crystallizes with four molecules of the organopalladium complex and two molecules of acetone in the asymmetric unit. This corresponds to a discrete hydrogen‐bonded aggregate and to the content of the unit cell in the space group P1. Pronounced pseudo‐inversion symmetry relates pairs of these objects in the asymmetric unit.     

A concise and efficient synthesis of amino‐substituted (1H‐benzo[d]imidazol‐1‐yl)pyrimidine hybrids: synthetic sequence and the molecular and supramolecular structures of six examples

A concise and efficient synthesis of a series of amino‐substituted benzimidazole–pyrimidine hybrids has been developed, starting from the readily available N⁴‐(2‐aminophenyl)‐6‐methoxy‐5‐nitrosopyrimidine‐2,4‐diamine. In each of N⁵‐benzyl‐6‐methoxy‐4‐(2‐phenyl‐1H‐benzo[d]imidazol‐1‐yl)pyrimidine‐2,5‐diamine, C₂₅H₂₂N₆O, (I), 6‐methoxy‐N⁵‐(4‐methoxybenzyl)‐4‐[2‐(4‐methoxyphenyl)‐1H‐benzo[d]imidazol‐1‐yl]pyrimidine‐2,5‐diamine, C₂₇H₂₆N₆O₃, (III), 6‐methoxy‐N⁵‐(4‐nitrobenzyl)‐4‐[2‐(4‐nitrophenyl)‐1H‐benzo[d]imidazol‐1‐yl]pyrimidine‐2,5‐diamine, C₂₅H₂₀N₈O₅, (IV), the molecules are linked into three‐dimensional framework structures, using different combinations of N—H…N, N—H…O, C—H…O, C—H…N and C—H…π hydrogen bonds in each case. Oxidative cleavage of 6‐methoxy‐N⁵‐(4‐methylbenzyl)‐4‐[2‐(4‐methylphenyl)‐1H‐benzo[d]imidazol‐1‐yl]pyrimidine‐2,5‐diamine, (II), with diiodine gave 6‐methoxy‐4‐[2‐(4‐methylphenyl)‐1H‐benzo[d]imidazol‐1‐yl]pyrimidine‐2,5‐diamine, which crystallized as a monohydrate, C₁₉H₁₈N₆O·H₂O, (V), and reaction of (V) with trifluoroacetic acid gave two isomeric products, namely N‐{5‐amino‐6‐methoxy‐6‐[2‐(4‐methylphenyl)‐1H‐benzo[d]imidazol‐1‐yl]pyrimidin‐2‐yl}‐2,2,2‐trifluoroacetamide, which crystallized as an ethyl acetate monosolvate, C₂₁H₁₇F₃N₆O₂·C₄H₈O₂, (VI), and N‐{2‐amino‐6‐methoxy‐4‐[2‐(4‐methylphenyl)‐1H‐benzo[d]imidazol‐1‐yl]pyrimidin‐5‐yl}‐2,2,2‐trifluoroacetamide, which crystallized as a methanol monosolvate, C₂₁H₁₇F₃N₆O₂·CH₄O, (VIIa). For each of (V), (VI) and (VIIa), the supramolecular assembly is two‐dimensional, based on different combinations of O—H…N, N—H…O, N—H…N, C—H…O and C—H…π hydrogen bonds in each case. Comparisons are made with some related structures.     

Asymmetric ruthenium‐catalysed [2+2] cycloadditions between bicyclic alkenes and chiral aryl‐substituted acetylenic acyl camphorsultam alkynes

The regio‐ and absolute stereochemistry of (7S)‐N‐[4‐(3‐thienyl)tricyclo[4.2.1.0^2,5]non‐3‐en‐3‐ylcarbonyl]‐2,10‐camphorsultam tetrahydrofuran hemisolvate, C₂₄H₂₉NO₃S₂·0.5C₄H₈O, and (7S)‐N‐[4‐(4‐tolyl)tricyclo[4.2.1.0^2,5]non‐3‐en‐3‐ylcarbonyl]‐2,10‐camphorsultam, C₂₇H₃₃NO₃S, have been established. One contains a half‐occupancy tetrahydrofuran solvent molecule located on a twofold axis and the other contains two crystallographically unique molecules which are nearly identical. The extended structures of both complexes can be explained via weak C—H...O interactions, which link the molecules together into two‐dimensional sheets in the ab plane for the thienyl complex and ultimately into a three‐dimensional structure for the tolyl derivative. The stereochemistry of both structures confirms that [2+2] cycloadditions of bicyclic alkenes and alkynes catalysed by ruthenium are exclusively exo.