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A simple four-step route to a chiral tetrahydrofluorenyl rhodium catalyst from naturally occurring (−)-α-pinene was developed. Our approach does not use multistep and time-consuming procedures such as chiral HPLC or diastereomeric resolution. The key to success lies in the face-selective coordination of rhodium to the sterically hindered tetrahydrofluorenyl ligand, giving only one diastereomeric complex. This catalyst proved to be highly efficient for asymmetric C–H annulation of aryl hydroxamates with alkenes (yield up to 95%, 91% ee) at low loading (up to 0.4 mol % based on Rh).

The reaction of cyclic nitronic esters (isoxazoline- and 5,6-dihydro-4H-1,2-oxazine-N-oxides) with hydrochloric acid affords geminal chloronitroso compounds bearing a distant hydroxyl group. The reaction is usually diastereoselective, and in some cases stereodivergent formation of isomers at different temperatures is observed. The discovered process represents the first example of an interrupted Nef reaction of nitronic esters. DFT calculations support the initial formation of N,N-bis(oxy)iminium cations (key intermediates in the Nef reaction), which are intercepted by the chloride anion followed by ring opening. The synthetic utility of the resulting functionalized chloronitroso compounds in the Diels–Alder reaction with cyclopentadiene was demonstrated.

Photoinduced charge transfer affects the efficiency and selectivity of photochemical reactions. Incorporation of donating groups into the isoquinolinium core allowed us to overcome the photochemical inactivity of the corresponding dithienyl-substituted terarylenes, presumably by redirecting the charge transfer within the molecule, and gave access to a new family of thermally reversible photoswitches.

Six-membered cyclic nitronates (5,6-dihydro-4H-1,2-oxazine-N-oxides) react with Kobayashi’s aryne precursors producing 3-(2-hydroxyaryl)-substituted 1,2-oxazines via deoxygenative C–H arylation. The process involves a hitherto unknown 1,3-dipolar cycloaddition of nitronate to the aryne to give an unusual tricyclic nitroso acetal, in which the N–O bond of the isoxazoline ring is selectively cleaved upon the action of a base (CsF) or an acid (TFA). The transient cycloadducts were isolated and characterized in some cases. The synthetic potential of the obtained 3-(2-hydroxyaryl)-substituted 1,2-oxazines was demonstrated by their stereoselective reduction to 1,4-amino alcohols and reductive 1,2-oxazine ring contraction to tetrahydrofuran derivatives.

We report the synthesis, structures, and magnetic investigations of two new octahedral dysprosium complexes, based on the original N-heterocyclic carbene (NHC) tridentate bis(phenoxide) ligand, of the respective formulas mer-[DyL(THF)2Cl] (1) and mer-[DyL(THF)3][BPh4] (2), where L = 1,3-bis(3,5-di-tert-butyl-2-oxidophenyl)-5,5-dimethyl-3,4,5,6-tetrahydropyrimidin-1-ium chloride and THF = tetrahydrofuran. The short Dy–O distances in the axial direction in association with the weak donor ability of the NHC moiety provide a suitable environment for slow relaxation of magnetization, overcoming the previous single-molecule magnets based on NHC ligands.

Reaction of six-membered cyclic nitronates with disubstituted ketenes affords hitherto unknown saturated oxazolo[3,2-b][1,2]oxazines possessing up to four contiguous stereogenic centers. The process involves a tandem of [3+2]-cycloaddition across the C═O bond of ketene, followed by a spontaneous [1,3]-rearrangement of transient vinylidene-substituted bicyclic nitrosoacetals. DFT calculations of the mechanism suggest that the [1,3]-O,C-shift proceeds through a recyclization of a biradical intermediate formed by an unusually mild homolytic cleavage of the N–O bond. The resulting products can be utilized as precursors of other fused 1,2-oxazines derivatives, in particular 1,2-oxazino-1,2,4-triazin-3-ones.

Here, we report the first (pseudo)clathrochelate of iron(II) to undergo a temperature-induced spin crossover (SCO) to an elusive high-spin state “trapped” in one of its solvatomorphs. An SCO-inducing ability of the resulting extended-tripodal (cage) ligand in an otherwise SCO-inactive type of iron(II) complexes arises from its molecular design that adapts to the metal ion in the two spin states by experiencing a massive trigonal twist distortion. Combined with the amenability of this ligand to further functionalization to produce a series of iron(II) (pseudo)clathrochelates with tunable SCO behaviors, it opens up a possibility for this unique class of trigonal-prismatic complexes to soon emerge as effective switchable components for molecular electronics and spintronics.

In the search for potential new metal-based antitumor agents, two series of nonclassical palladium(II) pincer complexes based on functionalized amides with S-modified cysteine and homocysteine residues have been prepared and fully characterized by 1D and 2D NMR (1H, 13C, COSY, HMQC or HSQC, 1H–13C, and 1H–15N HMBC) and IR spectroscopy and, in some cases, X-ray diffraction. Most of the resulting complexes exhibit a high level of cytotoxic activity against several human cancer cell lines, including colon (HCT116), breast (MCF7), and prostate (PC3) cancers. Some of the compounds under consideration are also efficient in both native and doxorubicin-resistant transformed breast cells HBL100, suggesting the prospects for the creation of therapeutic agents based on the related compounds that would be able to overcome drug resistance. An analysis of different aspects of their biological effects on living cells has revealed a remarkable ability of the S-modified derivatives to induce cell apoptosis and efficient cellular uptake of their fluorescein-conjugated counterpart, confirming the high anticancer potential of Pd(II) pincer complexes derived from functionalized amides with S-donor amino acid pendant arms.

Aerobic reactions of iron(III), nickel(II), and manganese(II) chlorides with formaldoxime cyclotrimer (tfoH3) and 1,4,7-triazacyclononane (tacn) produce indefinitely stable complexes of general formula [M(tacn)(tfo)]Cl. Although the formation of formaldoxime complexes has been known since the end of 19th century and applied in spectrophotometric determination of d-metals (formaldoxime method), the structure of these coordination compounds remained elusive until now. According to the X-ray analysis, [M(tacn)(tfo)]+cation has a distorted adamantane-like structure with the metal ion being coordinated by three oxygen atoms of deprotonated tfoH3ligand. The metal has a formal +4 oxidation state, which is atypical for organic complexes of iron and nickel. Electronic structure of [M(tacn)(tfo)]+cations was studied by XPS, NMR, cyclic (CV) and differential pulse (DPV) voltammetries, Mössbauer spectroscopy, and DFT calculations. Unusual stabilization of high-valent metal ion by tfo3–ligand was explained by the donation of electron density from the nitrogen atom to the antibonding orbital of the metal–oxygen bond via hyperconjugation as confirmed by the NBO analysis. All complexes [M(tacn)(tfo)]Cl exhibited high catalytic activity in the aerobic dehydrogenative dimerization of p-thiocresol under ambient conditions.

The reactions of picolinyl and 4-chloropicolinyl chlorides with methyl esters of S-methyl-l-cysteine, l- and d-methionine, and l-histidine afforded a series of functionalized carboxamides, which readily formed pincer-type complexes upon interaction with PdCl2(NCPh)2in solution under mild conditions. The direct cyclopalladation of the ligands derived was also accomplished in the solid phase, in particular, mechanochemically, although it was complicated by the partial deactivation of the starting amides. The resulting complexes with 5,5- and 5,6-membered fused metallocycles were fully characterized by IR and NMR spectroscopy, including variable-temperature and 2D-NMR studies. In the case of some cysteine- and methionine-based derivatives, the realization of κ3-N,N,S-coordination was supported by X-ray diffraction. The cytotoxic effects of these complexes were examined on HCT116, MCF7, and PC3 human cancer cell lines as well as HEK293 as a representative of normal cells. The comparative studies allowed us to determine that the presence of the sulfide ancillary donor group is crucial for cytotoxic activity of this type of Pd(II) complexes. The main structure–activity relationships and the most promising palladocycles were outlined. The additional studies by gel electrophoresis revealed that 4-chloropicolinyl derivatives, despite the nature of an amino acid, can bind with DNA and inhibit topoisomerase I activity.

Herein, we present the first example of Os-catalyzed efficient reductive amination under water–gas shift reaction conditions. The developed catalytic systems are formed in situin aqueous solutions, employ as small as 0.0625 mol% osmium and are capable of delivering reductive amination products for a broad range of aliphatic and aromatic carbonyl compounds and amines. The scope of the reaction, active catalytic systems, possible limitations of the method and DFT-supported mechanistic considerations are discussed in detail in the manuscript.

An asymmetric total synthesis of Merck’s hNK1antagonist and three of its stereoisomers was accomplished in 10 steps. The synthesis involves a stereoselective assembly of 1,2-oxazine N-oxide by the [4 + 2]-cycloaddition, site-selective C–H oxygenation using a novel tandem acylation/[3,3]-rearrangement process and the reductive 1,2-oxazine ring contraction into a pyrrolidine ring as key stages. Using this strategy, the fused pyrrolidine subunit was constructed with exceptionally high regio- and stereoselectivities. The approach described here can be used to access enantiopure 3,4-disubstituted prolinols, which are frequently found in pharmaceutically relevant molecules and organocatalysts.

Boron-cross-linked cobalt(II) pseudoclathrochelate was obtained by the template reaction of 2-acetylpyrazoloxime, phenylboronic acid, and a new DMF cobalt(II) solvato complex with a decachloro-closo-decaborate dianion. As confirmed by single-crystal X-ray diffraction, this complex crystallizes with two symmetry-independent cobalt(II) pseudoclathrochelate cations, one decachloro-closo-decaborate dianion, one benzene, one dichloromethane solvent molecule, and two molecules of DMF. The latter act as pseudocapping fragments to the monocapped tris-pyrazoloximate ligands by forming N–H···O hydrogen bonds with their pyrazole groups. The CoIIN6-coordination polyhedra adopt a nearly ideal TP geometry with distortion angles φ equal to 1.22(16) and 2.58(17)° for two symmetry-independent pseudoclathrochelate cations, both containing the encapsulated cobalt(II) ion in its high-spin state (Co–N 2.115(4)–2.198(3) Å). Magnetic properties of this complex were studied both by dc-magnetometry and by solution-state NMR spectroscopy to reveal a high magnetic anisotropy, thus suggesting a large magnetic susceptibility tensor anisotropy (25.8 × 10–32m3at 298 K) and a large negative zero-field splitting energy (−85 cm–1). The results of magnetometry studies in the ac magnetic field suggest a single molecule magnet behavior of this TP complex with an effective magnetization reversal barrier of approximately 130 cm–1. Its pseudocapping DMF molecules that form H-bonds with tris-pyrazoloximate fragments are easy to substitute by strong H-bond acceptors, such as chloride ions and di- and tetramethylureas, thus affecting the magnetic properties of a whole pseudomacrobicyclic paramagnetic system.

We report the synthesis and reactivity of the half-sandwich rhodium(III) complexes with the fully methylated cyclohexadienyl ligand C6Me7, which is analogous to the classical Cp*. The starting complex [(C6Me7)RhCl2]2(4) was obtained in high yield (92%) by the reaction of [(cyclooctene)2RhCl]2with the readily available 6-methylenehexamethylcyclohexadiene-1,4 (C6Me6═CH2) followed by addition of HCl. Reactions of complex 4with common two-electron ligands L gave the expected adducts (C6Me7)RhCl2L (L = pyridine, P(OEt)3, PPh3) in high yields (80–90%). At the same time, the interaction of 4with the stronger ligand tBuNC led to the replacement of the C6Me7ligand. The cationic complex [(C6Me7)Rh(dppe)Cl]PF6and the dicationic complex [(C6Me7)Rh(C6Me6)](BF4)2were obtained by abstraction of chlorides from 4with TlPF6or AgBF4in the presence of the corresponding ligands. The reaction of 4with 2-phenylpyridine in the presence of CsOAc proceeded via CH activation and gave the cyclometalated product (C6Me7)Rh(C6H4-Py)Cl in 85% yield. Accordingly, the catalytic reaction of 2-phenylpyridine with 3-hexyne in the presence of 4(5 mol %) gave the 9,10-diethyl-8a-azaphenanthrene cation in 61% yield. However, the catalytic efficientcy of 4was lower than that of the classical catalyst [Cp*RhCl2]2, possibly because the displacement of the cyclohexadienyl ligand interrupted the catalytic cycle. The DFT calculations suggested that the electron-donating ability of cyclic π ligands in the rhodium complexes (CnRn)RhCl2CO decreases in the order CnRn= C5Me5> C6Me7> C5H4OMe ≈ C5Me4CF3> C5Me3(COOMe)2≈ C5H4Me > C5H5> C5H4F ≈ C5H4COOMe > C5H4CF3.

In this article, comprehensive studies on the nucleophilic chlorination and bromination of readily available six-membered cyclic nitronates (1,2-oxazine-N-oxides) are reported. Under optimized conditions (POCl3or (COBr)2with Hünig’s base), 3-halo-substituted 1,2-oxazines, which are difficult to access by other routes, were obtained in good to high yields. The latter were shown to be convenient precursors to other 3-substituted 1,2-oxazine derivatives using Lewis/Brønsted acid-assisted substitution of the halide atom for C-, S-, and N-nucleophiles.

A correlation between the equilibrium ratio of tautomeric products generated by the asymmetric Michael reactions of cyclic carbon acids with β,γ-unsaturated α-keto esters and the chemical shift of the α-proton in starting nucleophilic substrates was revealed which makes equilibration predictable. New tetrahydropyran-fused benzo[a]phenazins were enantioselectively (up to 99% ee) synthesized from β,γ-unsaturated α-keto esters and benzo[a]phenazin-5-ol, a powerful anti-cancer agent sAJM589. Facile recyclability of catalyst Iain the catalytic reactions was demonstrated.

The η6-fluorene cyclopentadienyl complexes [(η5-C5R5)M(η6-fluorene)](SbF6)2(1: M = Co, R = Me; 2a: M = Rh, R = H; 2b: M = Ir, R = H) were synthesized by the iodide abstraction from [(η5-C5R5)MI2]nwith AgSbF6in the presence of fluorene. The procedure is also suitable for the synthesis of the indenyl derivatives [(η5-indenyl)M(η6-fluorene)](SbF6)2(3a: M = Rh; 3b: M = Ir) starting from [(η5-indenyl)MI2]n. The structures of [1](SbF6)2and [2b](SbF6)2were determined by X-ray diffraction. The rhodium complex [2a](SbF6)2readily undergoes the replacement of the fluorene ligand by mesitylene, being more reactive than the benzene derivative [CpRh(η6-C6H6)](SbF6)2. According to experimental data and DFT calculations, the fluorene elimination proceeds via a cascade of η6→ η5→ η1haptotropic rearrangements. The complex [2b](SbF6)2(at 1 mol % loading) effectively catalyzes the reductive amination reaction between aldehydes (or ketones) and primary aromatic (or secondary aliphatic) amines in the presence of carbon monoxide, giving the corresponding secondary and tertiary amines in the range of yields 59–91%. This protocol uses water as a solvent.

Single-crystal X-ray diffraction studies are among the best experimental methods for elucidating the structure of chemical compounds. Recently, their focus has been shifted towards extracting information on chemical bonding features and related valuable properties of these compounds from the analysis of charge density distribution obtained in high-resolution X-ray diffraction experiments; the latter are possible only for a limited number of well-ordered crystals of small molecules. In this review, the hybrid approaches are described that introduce quantum chemical methods into the refinement of X-ray diffraction data. Their use significantly extends the range of systems suitable for charge density studies (such as polypeptides, metal-organic frameworks, inclusion compounds and others) and the scope of problems that they solve, viz., from protein structure refinement to determination of thermodynamic or other wave function-derived properties of crystals. The potential of these hybrid approaches and prospects for their future applications are discussed.The bibliography includes 322 references.

Single-crystal X-ray diffraction studies are among the best experimental methods for elucidating the structure of chemical compounds. Recently, their focus has been shifted towards extracting information on chemical bonding features and related valuable properties of these compounds from the analysis of charge density distribution obtained in high-resolution X-ray diffraction experiments; the latter are possible only for a limited number of well-ordered crystals of small molecules. In this review, the hybrid approaches are described that introduce quantum chemical methods into the refinement of X-ray diffraction data. Their use significantly extends the range of systems suitable for charge density studies (such as polypeptides, metal-organic frameworks, inclusion compounds and others) and the scope of problems that they solve, viz., from protein structure refinement to determination of thermodynamic or other wave function-derived properties of crystals. The potential of these hybrid approaches and prospects for their future applications are discussed.The bibliography includes 322 references.

1-Dimethylthiocarbamoyloxy-3-diphenylphosphinobenzene was used as a key precursor for the synthesis of a whole series of organophosphorus(V) pincer ligands combining thiocarbamate donor group with P═X coordination arm, where X = S, Se, O, NR (R = Ph, 4-NO2C6H4, COOtBu, CH2Ph) or CHR′ (R′ = COOEt, CN). Direct cyclopalladation of the ligands obtained (used either as individual compounds or generated in situin the reaction mixture) afforded hybrid pincer complexes with five- and six-membered fused metallacycles. In the case of phosphine sulfide and phosphine selenide derivatives, the cyclopalladation can readily be accomplished in CH2Cl2at room temperature, leading to the target pincer complexes in high yields. Their phosphine imide and phosphonium ylide counterparts can also be obtained under mild reaction conditions, but the yields strongly depend on the ligand stability (35–93%). Even in the case of the phosphoryl-functionalized ligand, the desired pincer-type complex was synthesized in ca. 15% yield, although the main direction of metalation was C(sp3)–H bond activation of one of the methyl groups in OC(S)NMe2moiety. Realization of κ3-S,C,X-coordination (X = S, Se, O, N, or C) in the resulting pincer complexes was unambiguously confirmed based on the multinuclear NMR (1H, 13C, 31P, and 77Se) and IR spectroscopic data. Comparative single-crystal XRD analyses allowed for outlining the main structural features of the palladacycles obtained depending on the nature of ancillary P(V)-donor group. In addition, the possibility of solid-phase cyclopalladation was demonstrated by the examples of phosphine chalcogenide and stable phosphine imide ligands. In most cases, this approach afforded the desired complexes with the same or even higher efficiencies than the conventional solution-based method. Preliminary investigations on the cytotoxic activity of some of the complexes obtained against several human cancer cell lines revealed the high activity of phosphine imide-based palladacycles, rendering further studies in this field promising.

Zero-field splitting (ZFS) of three high-spin Co(I) (S= 1) clathrochelate complexes was determined by frequency-domain Fourier-transform THz-EPR (FD-FT THz-EPR). The following axial and rhombic ZFS values (Dand E, respectively) were determined: [N(n-Bu)4]CoI(GmCl2)3(BPh)2(1, D/hc= +16.43(1) cm–1, E/hc= 0.0(1) cm–1), [P(Me2N)4]CoI(GmCl2)3(BPh)2(2, D/hc= +16.67(4) cm–1, E/hc= 0.0(1) cm–1), and [P(C6H5)4]CoI(GmCl2)3(BPh)2(3, D/hc= +16.72(2) cm–1, E/hc= 0.24(3) cm–1). Complementary susceptibility χTmeasurements and quantum chemistry calculations on 1revealed hard-axis-type magnetic anisotropy and allowed for a correlation of ZFS and the electronic structure. Increased rhombicity of 3as compared to 1and 2was assigned to symmetry changes of the ligand structure induced by the change of the counterion. 1and 3exhibited temperature-dependent ZFS values. Possible reasons for this phenomenon, such as structural changes and weak chain-like intermolecular antiferromagnetic interactions, are discussed.

Acylation of nitronates affords α-acyloxyoxime derivatives via an umpolung functionalization of the α-position. This transformation involves generation of hithertounknown N-acyloxy,N-oxyenamines and their fast [3,3]-sigmatropic rearrangement driven by the cleavage of the weak N–O bond. The reaction has a broad scope, and it is regioselective in the case of nitronates possessing nonsymmetrically substituted α-positions. Application to the formal total synthesis of clausenamide and cis-clausenamide is presented.

Click-like condensation of boronic acids with specifically designed triols (boronate-triol coupling) produces stable diamantane adducts in aqueous medium, which can be controllably cleaved to initial components under acidic conditions or by using boric acid as a chemical trigger. This novel “click-declick” strategy allows for the creation of temporary covalent connections between two or more modular units, which was demonstrated by the synthesis of new fluorophore-labeled natural molecules (peptides, steroids), supramolecular assemblies, modified polymers, boronic acid scavengers, solid-supported organocatalysts, biodegradable COF-like materials, and dynamic combinatorial libraries.

An efficient protocol for synthesis of indenyl rhodium complexes with arene ligands has been developed. The hexafluoroantimonate salts [(η5-indenyl)Rh(arene)](SbF6)2(arene = benzene (2a), o-xylene (2b), mesitylene (2c), durene (2d), hexamethylbenzene (2e), and [2.2]paracyclophane (2g)) were obtained by iodide abstraction from [(η5-indenyl)RhI2]n(1) with AgSbF6in the presence of benzene and its derivatives. The procedure is also suitable for the synthesis of the dirhodium arene complex [(μ-η:η′-1,3-dimesitylpropane){Rh(η5-indenyl)}2](SbF6)4(3) starting from 1,3-dimesitylpropane. The structures of [2e](SbF6)2, [2g](SbF6)2, and [3](SbF6)4were determined by X-ray diffraction. The last species has a sterically unfavorable conformation, in which the bridgehead carbon atoms of the indenyl ligand are arranged close to the propane linker between two mesitylene moieties. Experimental and DFT calculation data revealed that the benzene ligand in 2ais more labile than that in the related cyclopentadienyl complexes [(C5R5)Rh(C6H6)]2+. Complex 2ceffectively catalyzes the reductive amination reaction between aldehydes and primary (or secondary) amines in the presence of carbon monoxide, giving the corresponding secondary and tertiary amines in very high yields (80–99%). This protocol is the most active in water.

The vibrational smearing of electron density was studied in the crystal of complex of Cr(CO)3with [2.2]paracyclophane. The combination of theoretical and experimental methods, including periodic calculations and screening of DFT calculated and multipole-decomposed electron densities, was utilized to reveal the vibrational smearing of electron density and its influence on the multipole-constructed electron density. The multipole model, commonly used to treat the high-resolution X-ray diffraction data, was shown to be rather inaccurate in description of electron density and its vibrational smearing in metal-π complex where the interchange between diatomic interactions can occur. Namely, some bond critical points can be hidden while analyzing multipole-decomposed electron density with proved effects of vibrational smearing even if the deconvolution problem is overcome by using the invariomapproach. On the contrary, the recently proposed “clouds of critical point variation” (CCPV) approach is demonstrated as the route to gather all reasonable bonding trends and to reconstruct static electron density pattern in metal-π complexes.

Spin transitions in spin-crossover compounds are now routinely studied in the solid state by magnetometry; however, only a few methods exist for studies in solution. The currently used Evans method, which relies on NMR spectroscopy to measure the magnetic susceptibility, requires the availability of a very pure sample of the paramagnetic compound and its exact concentration. To overcome these limitations, we propose an alternative NMR-based technique for evaluating spin-state populations by only using the chemical shifts of a spin-crossover compound; those can be routinely obtained for a solution that contains unknown impurities and paramagnetic admixtures or is contaminated otherwise.

High magnetic anisotropy is a key property of paramagnetic shift tags, which are mostly studied by NMR spectroscopy, and of single molecule magnets, for which magnetometry is usually used. We successfully employed both these methods in analyzing magnetic properties of a series of transition metal complexes, the so-called clathrochelates. A cobalt complex was found to be both a promising paramagnetic shift tag and a single molecule magnet because of it having large axial magnetic susceptibility tensor anisotropy at room temperature (22.5 × 10–32m3mol–1) and a high effective barrier to magnetization reversal (up to 70.5 cm–1). The origin of this large magnetic anisotropy is a negative value of zero-field splitting energy that reaches −86 cm–1according to magnetometry and NMR measurements.

A comparative electron density study (from X-ray diffraction and periodic quantum chemistry) of sodium and potassium nitrates is performed to test the performance of a transferrable aspherical atom model, which is based on the invarioms, to describe chemical bonding features of ions occurring in sites of different symmetry typical of inorganic salts and in different crystal environments. Relying on tabulated entries for the isolated ions (although tailor-made to account for different site symmetries), it takes the same time to employ as the spherical atom model routinely used in X-ray diffraction studies but provides an electron density distribution that faithfully reveals all the interionic interactionseven the weakest ones (such as between the nitrate anions or a K···N interaction found in the metastable form of KNO3) yet important for properties of inorganic materialsas if obtained from high-resolution X-ray diffraction data.

A novel rhodium-catalyzed tandem C–H annulation of commercially available benzaldehydes and aminobenzoic acids with 2 equiv of alkyne is reported for the construction of isocoumarin-conjugated isoquinolinium salts that demonstrate diverse outstanding photoactivity. Depending on the substituents in the isoquinolinium moiety, they display either highly efficient fluorescence (up to 99% of quantum yield) or strong fluorescence quenching, which is provided by the transfer of the HOMO from the isoquinolinium to the isocoumarin moiety. Importantly, the functional groups in the benzaldehyde coupling partner also strongly affect the reaction selectivity, shifting the pathway to the formation of the photoinactive isocoumarin-substituted indenone imines and indenyl amines. Selective formation of the latter can be achieved by using a reduced amount of the oxidizing additive.

The series of bimetallic complexes (tBuPXCYP)Pd(μ-OC)M(CO)2L (X, Y = CH2, O; M = W, Mo; L = Cp, Tp) catalyzes formic acid decomposition into H2/CO2in fairly mild conditions (25–50 °C, toluene) without any organic base additives. The catalytic activity of bimetallic complexes increases with CH2-substitution of the O-bridges in the (PXCYP)-frame as well as with the proton-donating ability of the Mo/W hydride. The best result was obtained with (tBuPCP)Pd(μ-OC)Mo(CO)2Cp (3), which gives complete conversion at 2 mol % loading in 30 min at 50 °C (TOF = 100 h–1). During the catalysis, LM(CO)3H and (tBuPXCYP)Pd(OCHO) form as visible intermediates, while the palladium hydride species are also involved in the catalytic cycle. The experimental data show that hydride abstraction/CO2release from palladium formates (tBuPXCYP)Pd(OCHO) is assisted by −OCHO···H–A hydrogen bonding with excess formic acid or acidic hydride LM(CO)3H. These findings highlight the pivotal role of the formate interaction with Brönsted or Lewis acids at the hydride abstraction/CO2release step and unify the mechanisms suggested for different catalytic systems.

Efficient protocols for the synthesis of triphenylcyclopentadienyl rhodium halides [(1,2,4-C5Ph3H2)RhX2]2(1a,b: X = Cl, I) starting from 1,2,4-triphenylcyclopentadiene or the cyclooctadiene derivative (1,2,4-C5Ph3H2)Rh(cod) (2) were developed. Iodide abstraction from 1bwith thallium or silver salts allowed us to prepare rhodocenium [(1,2,4-C5Ph3H2)RhCp]PF6(3PF6) and mesitylene complex [(1,2,4-C5Ph3H2)Rh(mesitylene)](SbF6)2(4(SbF6)2). Halides 1a,b(at 0.5 mol % loading) showed high catalytic activity in the construction of C–C, C–O, and C–N bonds via the C(sp2)–H activation approach. Their efficiency was demonstrated in the synthesis of more than 40 examples of polycyclic organic compounds (such as isocoumarins and naphthalenes, as well as isoquinolinium and dibenzo[a,f]quinolizinium salts). The protocols developed tolerate a wide range of functional groups. In particular, they were successfully used for the atom- and step-economical synthesis of hydroxy-substituted isocoumarins, including the natural product oospalactone 7fe. The 6- or 8-hydroxy-substituted isocoumarins showed moderate antiproliferative activity against several human cell lines in vitro.

A new synthetic pathway is devised to selectively produce previously elusive heteroleptic iron(II) complexes of terpyridine and N,N′-disubstituted bis(pyrazol-3-yl)pyridines that stabilize the opposite spin states of the metal ion. Such a combination of the ligands in a series of the heteroleptic complexes induces the spin-crossover (SCO) not experienced by the homoleptic complexes of these ligands or shifts it to lower/higher temperatures respective to the SCO-active homoleptic complex. The midpoint temperatures of the resulting SCO span from ca. 200 K to the ambient temperature and beyond the highest temperature accessible by NMR spectroscopy and SQUID magnetometry. The proposed “one-pot” approach is applicable to other N-donor ligands to selectively produce heteroleptic complexes─including those inaccessible by alternative synthetic pathways─with highly tunable SCO behaviors for practical applications in sensing, switching, and multifunctional devices.

Phenanthroline diamides (L) demonstrated a unique ability to extract uranium from nitric acid solutions into a polar organic solvent forming complexes of 1:2 stoichiometry as tight ion pairs {[UO2LNO3]+[UO2(NO3)3]−} by a novel extraction mechanism, which is a combination of two already well-known mechanisms: solvation and ion-pair anion exchange. A UV–vis study was used to confirm the formation of such complexes directly in the organic phase. Moreover, chemical synthesis and single crystal growth were performed to confirm unambiguously the structure of the complexes in the solid state.

The parent ethylene rhodium(I) complex [(C2H4)2RhCl]2reacts with internal alkynes to give binuclear metallacycles [(C4R4)Rh2Cl2(C2H4)]2(R = Me, Et, CH2OMe, Ph), which can act as catalytic intermediates in cyclotrimerization reactions. These metallacycles can be converted into catalytically inert metallocenes CpRh(η5-C4R4RhCp) by addition of CpTl. Further reactions of these metallocenes with [CpRhI2]xand AgBF4lead to the unique triple-decker complexes [CpRh(μ-C4R4RhCp)RhCp](BF4)2with metal atoms in the central ring. The structures of all three types of complexes have been established by X-ray diffraction.

Nowadays, design of the new chiral ligands for organometallic catalysts is often based on the step-by-step increase in their complexity to improve efficiency. Herein we describe that simple in situ addition of the fluoride source to the asymmetric organometallic catalyst can improve not only activity but also enantioselectivity. Bromide–nickel diimine complexes were found to catalyze asymmetric Michael addition in low yields and ee, but activation with fluoride leads to a significant improvement in catalyst performance. The developed approach was applied to prepare several enantioenriched GABA analogues.

Spintronics, a flourishing new field of microelectronics, uses the electron spin for reading and writing information in modern computers and other spintronic devices with a low power consumption and high reliability. In a quest to increase the productivity of such devices, the use of molecular materials as a spacer layer allowed them to perform equally well or even better than conventional all-inorganic heterostructures from metals, alloys, or inorganic semiconductors. In this review, we survey various classes of chemical compounds that have already been tested for this purpose─from organic compounds and coordination complexes to organic–inorganic hybrid materials─since the creation of the first molecule-based spintronic device in 2002. Although each class has its advantages, drawbacks, and applications in molecular spintronics, together they allowed nonchemists to gain insights into spin-related effects and to propose new concepts in the design and fabrication of highly efficient spintronic devices. Other molecular compounds that chemistry could offer in great numbers may soon emerge as suitable spacers or even electrodes in flexible magnetic field sensors, nonvolatile memories, and multifunctional spintronic devices.

AbstractEnergy and charge aspects of two types of ion association – between oppositely-charged and between like-charged species – were quantified using the topological analysis of the electron density function derived from the low-temperature X-ray diffraction experiment for a crystal of aminoacetonitrile picrate (sp. gr. Cmca, Z= 8, R= 0.0187), providing an experimental evidence of their “equal rights” in crystal packing formation.

The interaction of [Ru(η6‐C10H8)(Cp)]+(Cp=C5H5) with aromatic amino acids (L‐phenylalanine, L‐tyrosine, L‐tryptophane, D‐phenylglycine, and L‐threo‐3‐phenylserine) under visible‐light irradiation gives the corresponding [Ru(η6‐amino acid)(Cp)]+complexes in near‐quantitative yield. The reaction proceeds in air at room temperature in water and tolerates the presence of non‐aromatic amino acids (except those which are sulfur containing), monosaccharides, and nucleotides. The complex [Ru(η6‐C10H8)(Cp)]+was also used for selective labeling of Tyr and Phe residues of small peptides, namely, angiotensin I and II derivatives.

Theoretical and experimental data array confirming the possibility of occurrence of bonding interactions in a crystal between like-charged species, namely anions, that contribute significantly to the crystal packing formation is analyzed. The main types of anion-anion interactions, their strength and contribution to the stabilization of ionic crystals are systematically analyzed for a wide range of organic and inorganic salts. The potential of various theoretical and experimental methods of investigations aimed at detection of anion-anion interactions and estimation of their energy is discussed.

A thermally induced rearrangement of arylhydrazones 5 of furoxan-3-yl carbonyl compounds into 2-aryl-5-(hydroximino)(aryl)- methyl-2H-1,2,3-triazole 1-oxides 6 has been found for the first time; the crystal packing of compound 6a has been studied by X-ray diffraction analysis.

Herein we describe the synthesis and reactivity of rhodium catalysts with the very bulky cyclopentadienyl ligand C8H3tBu4(designated as tBu4Cp). The reaction of [Rh(cod)Cl]2with tert-butylacetylene in the presence of Et3N gives the complex (tBu4Cp)Rh(cod) (60–65% yield), in which the cyclopentadienyl ligand tBu4Cp is assembled from four alkyne molecules. The oxidation of (tBu4Cp)Rh(cod) with chlorine or bromine gives the corresponding halide complexes (tBu4Cp)RhX2(X = Cl (85%), Br (95%)), which have unusual 16-electron monomeric structures due to the steric shielding provided by tBu groups. A similar reaction with iodine gives the ionic dinuclear complex [(tBu4Cp)RhI3Rh(tBu4Cp)]I (99%) with halide bridges. The bromide complex (tBu4Cp)RhBr2reacts with phosphorus ligands such as P(OMe)3, P(OPh)3, PMe2Ph, and PMePh2to give the 18-electron adducts (tBu4Cp)RhBr2(PR3), but no reaction occurs with larger phosphines such as PPh3. The racemic chloride (tBu4Cp)RhCl2can be separated into enantiomers by preparative TLC of its diastereomeric adducts with (R)-phenylglycinol. The complex (tBu4Cp)RhBr2catalyzes C–H activation and annulation of O-pivaloyl-hydroxamate as well as insertion of phenyldiazoacetate into E–H bonds, although the reaction rates and the substrate scope are limited by the bulky tBu4Cp ligand.

Trial and error: Topological analysis of the experimental electron density distribution of trinitropyrazole has allowed the energetic consequences of an overlooked pseudosymmetry to be quantified for the first time. This has allowed measurement of how much a small error in the assignment of a space group may cost a crystal structure; in the case of trinitropyrazole this was 8.9 kcal mol−1.

Versuch und Irrtum: Die topologische Analyse der experimentellen Elektronendichteverteilung von Trinitropyrazol ermöglichte es erstmalig, die energetischen Folgen einer übersehenen Pseudosymmetrie zu quantifizieren. So ließ sich messen, wie sich ein scheinbar kleiner Fehler bei der Zuordnung einer Raumgruppe auf die Energie einer Kristallstruktur auswirken kann; im Fall des Trinitropyrazols waren dies 8.9 kcal mol−1.

The title reaction leads to the unexpected product (IV) formed via migration of the methoxy group.

Six compounds of type (III) are prepared by condensation reaction.

The reaction of 3H‐1,2‐dithiol‐3‐ones of type (I), (IV), and (VII) with isonitriles yields the corresponding 2‐iminothiophen‐3(2H)‐ones.