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A series of novel non-symmetric neutral N,N′,O-chelating ligands derived from the α-iminopyridine 2-(C(R1)[double bond, length as m-dash]N(C6H3-2,6-iPr2))-6-(R2R3P[double bond, length as m-dash]O)C5H3N (L1: R1 = H, R2 = R3 = Ph; L2: R1 = Me, R2 = R3 = Ph; L3: R1 = H; R2 = Ph, R3 = EtO; L4: R1 = Me, R2 = Ph, R3 = EtO; L5: R1 = H, R2 = R3 = iPrO; L6: R1 = Me, R2 = R3 = iPrO) were synthesized. Ligands L1–6 were reacted with SnCl2 and Sn(OTf)2 with the aim of studying the influence of different R2R3P[double bond, length as m-dash]O functional groups on the Lewis base mediated ionization of SnCl2 and Sn(OTf)2. While all ligands L1–6 provided the corresponding ionic tin(II) complexes [L1–6 → SnCl]+[SnCl3]− (1–6), only ligands L1, L4 and L6 were able to stabilize tin(II) dications [L1,4,6 → Sn(H2O)][OTf]2 (7–9). The auto-ionized compounds [L3–6 → SnCl]+[SnCl3]− possessing ethylphenyl phosphinate and diisopropylphosphite substituents undergo elimination of EtCl and iPrCl, respectively, yielding compounds 10–13. Thesecan either be interpreted as neutral tin(II)phosphinate chloride (10, 11) and tin(II)phosphonate chloride (12, 13), respectively, containing Sn–O and Sn–Cl bonds, and a P[double bond, length as m-dash]O → SnCl2 interaction, or as zwitterionic compounds, where the positive charge of the central tin atom is compensated by an [OSnCl2]− anion. Finally, DFT studies were performed to better understand the steric and electronic properties of the ligands L1–6 as well as the nature of the bonds in the resulting products, with a particular focus on complexes 10–13.

The synthesis and structure of lithium, magnesium, and zinc complexes

We report the difunctional modification of an anionic cobalta bis(dicarbollide)(1-) cluster with a B(8,8')-oxygen bridging unit that provides structural rigidity and an organic alkylazide substituent(s) on the carbon atoms of the metallacarborane cage. These ions present a good binding motif for incorporation into organic molecules using Huisgen-Sharpless (2+3) cycloaddition reactions. In addition, the compounds are chiral, as verified by separation of enantiomers using HPLC on chiral stationary phases (CSPs) and provide a high electrochemical peak in the window located outside of typical signals of biomolecules.

Peri-substituted naphthalene 1-PPh2-8-SnL-C10H6 (1) [L = 2,6-(Me2NCH2)2C6H3] was used as a ligand for the complexation of transition metals (TMs). The presence of two donor atoms provided rigid κ2P,Sn-coordinated complexes of TM. Correspondingly, reactions of 1 with binuclear Mn2(CO)10 and Co2(CO)8 yielded ionic complexes [(κ2-1)Mn(CO)4]+ [Mn(CO)5]− (2) and [(κ2-1)Co(CO)3]+ [Co(CO)4]− (3), first examples of Sn-coordinated Mn(CO)4+ and Co(CO)3+ cations. The reactivity of 1 toward TM–Cl complexes is quite different. During these reactions, transmetallation with subsequent elimination of L(Cl)Sn was observed. However, L(Cl)Sn remained in the coordination sphere of the TM, yielding P-coordinated heterobimetallic TM complexes 1-PPh2-8-[Rh(COD){Sn(Cl)L}]C10H6 (7), 1-PPh2-8-[Ir(COD){Sn(Cl)L}]C10H6 (8), and 1-PPh2-8-[Pd(Cl){Sn(Cl)L}]-C10H6 (9) with additional Sn→TM intermolecular coordination. These transmetallations may be kinetically driven, as suggested by density functional theory calculations and isolation of the κ2P,Sn-coordinated complex of PtCl2, [(κ2-1)PtCl2] (10). Thus, the reactivity of 1 clearly deviates from the P,Sn-based ligands studied so far.

The electrophilic substitution of icosahedral closo-1-SB11H11 with methyl iodide has resulted in two B-functionalized thiaboranes, 7,12-I2-2,3,4,5,6,8,9,10,11-(CH3)9-1-closo-SB11 and 7,8,12-I3-2,3,4,5,6,9,10,11-(CH3)8-closo-1-SB11, with the former being significantly predominant. These two icosahedral thiaboranes are the first cases of polysubstituted polyhedral boron clusters with another vertex that differs from B and C. Such polyfunctionalizations have increased the earlier observed thiaborane icosahedral barrier, not exhibiting any reactivity toward bases, unlike the parent thiaborane. The search for methylation pathways has revealed that the complete B11-methylation is impossible, like in the case of decaborane(14), where this seems to be a result of the positively charged upper parts of these two molecules.

Stannylenes of L2Sn type bearing either C,N-chelating (1, L = LCN = 2-(N,N-dimethylaminomethyl)phenyl) or bulky amido (2, L = LN = N(SiMe3)2) ligands react with cyanogen bromide (Br–CN) via an oxidative-addition reaction to give monomeric six-coordinate (LCN)2Sn(Br)CN (1a) and four-coordinate (LN)2Sn(Br)CN (2a) stannanes in moderate yields. In solution, both 1a and 2a undergo instantaneous bromido-cyanido ligand redistribution reactions, leading to mixtures containing 1a, (LCN)2SnBr2 (1b) and (LCN)2Sn(CN)2 (1c) or 2a, (LN)2SnBr2 (2b) and (LN)2Sn(CN)2 (2c), respectively. The prepared species were characterised by multinuclear NMR spectroscopy in solution (1a–c and 2a–c) and in the solid state (1a–c). The crystal structures of 1a/b/c, 2a/b/c and sole 2b were determined by XRD analyses. DFT calculations and QTAIM analysis were also carried out to corroborate the experimental results.

Reported herein are mutual rearrangements in the whole series of seven bicapped-square antiprismatic closo-C2B8H10 by means of high-quality computations that disprove the earlier postulated dsd (diamond-square-diamond) scheme for these isomerizations. The experimentally existing closo-1,2-C2B8H10 was able to be converted to 1,6-, and 1,10-isomers by pyrolysis, and the dsd (diamond-square-diamond) mechanism was offered as an explanation of these processes. However, these computations disprove the postulated dsd scheme for these isomerizations that take place in the ten-vertex closo series. Experimentally observed thermal rearrangements, both in the parent and substituted closo-1,2-C2B8H10, closo-1-CB9H10−, and closo-B10H102−, indirectly support these refined computations. All these processes are based on the new concept of the so-called Z-mechanism, being consistent with a transition state of a boat shape with an open hexagonal belt that results from the initial breakage of three bonds. Such bond breakings and the consequent bond formations bring to mind the shape of the letter Z. In effect, the pattern of multicenter bonding shifts from reactant through a transition state to product. The molecular rearrangements that are available experimentally favour either the axial or equatorial isomers, and this ratio depends on temperature and the type of cluster and its substitution.

Herein, we describe the synthesis of two families of compounds accessible from [3 + 2] cycloaddition reactions of known B8-substituted isonitrilium and new C1-alkylnitrile and C(1,1')-dialkylnitrile derivatives of the [(1,2-C2B9H11)2-3,3'-Co(III)]- ion with an azide ion that produce a tetrazole ring substitution at the cobaltacarborane cage. In addition, we outline the important differences in reactivity observed for the two types [B-isonitrilium/C-(alkyl)nitrile] of cobaltacarborane derivatives. The first family of compounds described corresponds to C5-atom-boronated tetrazole rings, with the five-membered moiety in the second type being doubly substituted at the N1 and C5 positions. This substitution opens cobaltacarborane chemistry to a new type of functional group at the cage of potential utility as structural blocks for use in medicinal chemistry or materials science. Our study includes single-crystal X-ray structures of the starting nitriles and both families of tetrazole derivatives, and the structural features that arise from the substitutions are discussed.

Carbonic anhydrase IX (CA IX), a tumor-associated metalloenzyme, represents a validated target for cancer therapy and diagnostics. Herein, we report the inhibition properties of isomeric families of sulfonamidopropyl-dicarba-closo-dodecaboranes group(s) prepared using a new direct five-step synthesis from the corresponding parent cages. The protocol offers a reliable solution for synthesis of singly and doubly substituted dicarba-closo-dodecaboranes with a different geometric position of carbon atoms. The closo-compounds from the ortho- and meta-series were then degraded to corresponding 11-vertex dicarba-nido-undecaborate(1-) anions. All compounds show in vitro enzymatic activity against CA IX in the low nanomolar or subnanomolar range. This is accompanied by clear isomer dependence of the inhibition constant (Ki ) and selectivity towards CA IX. Decreasing trends in Ki and selectivity index (SI ) values are observed with increasing separation of the cage carbon atoms. Interactions of compounds with the active sites of CA IX were explored with X-ray crystallography, and eight high-resolution crystal structures uncovered the structural basis of inhibition potency and selectivity.

Amidotin(ii) benzamidinates were prepared via addition of Sn[N(SiMe3)2]2 to mono-, di- and trinitriles. A reversible addition of [PhC(NSiMe3)2]SnN(SiMe3)2 with an excess of benzonitrile to its homoleptic [PhC(NSiMe3)2]2Sn was studied by NMR and DFT.

The paper reports specific syntheses of methylated decaborane(14), nido-B10H14 (1), derivatives. The reaction of 1 with an excess of neat MeI and AlCl3 yields 1,2,3,4-Me4-nido-B10H10 (2) essentially quantitatively when performed at room temperature. Heating the same mixture to 120 °C provides 1-I-2,3,4,5,7,8,10-Me7-nido-B10H6 (3a). The formation of analogous 1-CF3SO2O-2,3,4,5,7,8,10-Me7-nido-B10H6 (3b) is achieved by heating 1 or 2 with an excess of MeSO3CF3 in the presence of a catalytic amount of HOSO2CF3 to 120 °C. Compounds 2 and 3 can be deprotonated to yield the corresponding anions [1,2,3,4-Me4-nido-B10H9]- (2-), [1-I-2,3,4,5,7,8,10-Me7-nido-B10H5]- (3a-), and [1-CF3SO2O-2,3,4,5,7,8,10-Me7-nido-B10H5]- (3b-). The structure of all the compounds isolated has been unambiguously confirmed by multinuclear (11B and 1H) NMR measurements, and the structures of 2-, 3a, 3a-, and 3b have been established by X-ray diffraction analyses. The very high volatility of 2 has made it impossible to apply X-ray diffraction in this case; therefore, its structure has been derived computationally using the ab initio/GIAO/NMR tool. DFT-based computational protocols have also outlined the reason why it is impossible to obtain an octamethyl derivative of 1 experimentally.

Comparative studies of the synthesis of lithium guanidinates via nucleophilic addition of lithium amides to carbodiimides were performed. Four combinations of small or sterically crowded carbodiimide and sterically crowded lithium amide or lithium amide containing an adjacent amino donor group give ten different types of complexes. In particular, 2,6-[(CH3)2CH]2C6H3NHLi (DipNHLi, 1) reacts with (CH3)2CHN═C═NCH(CH3)2 upon the formation of the dissymmetric dimeric complex 2 with four-coordinate Li atoms. In contrast, 1 with DipN═C═NDip gives the mononuclear lithium guanidinate 3 with two-coordinate lithium by κ1-guanidinate, solvent molecule, and additional interaction with a π-electron cloud of one of the Dip groups. Analogous reactions of 2-[(CH3)2NCH2]C6H4NHLi (7) yield complexes 8 and 9, where the adjacent amino donors are always coordinated. Further deprotonation of 2, 3, 8, and 9 leads to dilithium guanidinates(2-)-4, 5, 10, and 11, among which only 5, containing three Dip groups, is monomeric with contacts to two π-electron systems of Dip groups. The rest of the complexes are tetranuclear with different structural patterns. In the central parts of molecules, toward which the nitrogen atoms of the guanidinates are oriented, lithium atoms are usually pseudotetrahedral, but trigonal in peripheral parts. Adjacent solvent molecules, chelating amino groups, and π-electron systems of Dip groups are coordinated in order to complete coordination polyhedra. Complexes 4 and 5 deoligomerize in solution upon the formation of fluxional monomeric dilithium species. Conversely, 11 is a dimer in solution due to the strong donation of an amino group. The silylated lithium amide {2-[(CH3)2NCH2]C6H4}[(Si(CH3)3]NLi (12) reacts with both carbodiimides to give dinuclear 13 obtained from diisopropylcarbodiimide and monomeric 14 from the second carbodiimide. Complexes 13 and 14 structurally resemble 8 and 9, with the highest degree of the localization of π-electron density within the N3C guanidinate system, η3-contact to the Dip ring, and a lack of the solvent molecule in 14.

Prostaglandins (PGs) are natural organic molecules that effect a wide range of biological processes, which is why they are often used in clinical and veterinary practice.1–3 The most well-known syn...

Utilization of the N,C,N-chelating ligand L (L={2,6-(Me2 NCH2 )2 C6 H3 }- ) in the chemistry of 13 group elements provided either N→In coordinated monomeric chalcogenides LIn(μ-E4 ) (E=S, Se) with unprecedented InE4 inorganic ring or monomeric chalcogenolates LM(EPh)2 (M=Ga, In). Complex LGa(SePh)2 was selected as the most suitable single source precursor (SSP) for the deposition of amorphous semiconducting GaSe thin films using spin coating method.

Alpha-Iminopyridine ligands L-1(2-(CH=N(C6H2-2,4,6-Ph-3))C5H4N), L-2 (2-(CH=N(C6H2-2,4,6-tBu(3)))C5H4N) and L-3 (1,2-(C5H4N-2-CH=N)(2)CH2CH2) differing by the steric demand of the substituent on the imine CH=N group and by the number of donating nitrogen atoms were utilized to initiate a Lewis base mediated ionization of SnCl2 in an effort to prepare ionic tin(II) species [L1-3 -> SnCl][SnCl3]. The reaction of L-1 and L-2 with SnCl2 led to the formation of neutral adducts [L-1 -> SnCl2] (2) and [L-2 -> SnCl2] (3). The preparation of the desired ionic compounds was achieved by subsequent reactions of 2 and 3 with an equivalent of SnCl2 or GaCl3. In contrast, ligand L-3 containing four donor nitrogen atoms showed the ability to ionize SnCl2 and also Sn(OTf)(2), yielding [L-3 -> SnCl][SnCl3] (7) and [L-3 -> Sn(H2O)][OTf](2) (8). The study thus revealed that the reaction is dependent on the type of the ligand. The prepared complexes 4-8 together with the previously reported [{2-((CH3)C=N(C6H3-2,6-iPr(2)))-6-CH3O-C5H3N}SnCl][SnCl3] (1) were tested as catalysts for the ROP of L-lactide, which could operate via an activated monomer mechanism. Finally, a DFT computational study was performed to evaluate the steric and electronic properties of the ionic tin(II) species 1 and 4-8 together with their ability to interact with the L-lactide monomer. Alfa-iminopyridinové ligandy L-1(2-(CH=N(C6H2-2,4,6-Ph-3))C5H4N), L-2 (2-(CH=N(C6H2-2,4,6- tBu(3)))C5H4N) a L-3 (1,2-(C5H4N-2-CH=N)(2)CH2CH2) lišící se stericitou substituentu na iminové skupině CH=N a počtem donorových atomů dusíku byly použity k autoionizaci SnCl2 zprostředkované Lewisovou bází ve snaze připravit cínaté iontové komplexy [L1-3 -> SnCl][SnCl3]. Reakce L-1 a L-2 se SnCl2 vedla ke vzniku neutrálních aduktů [L-1 -> SnCl2] (2) a [L-2 -> SnCl2] (3). Příprava požadovaných iontových sloučenin byla dosažena následnými reakcemi s ekvivalentem SnCl2 nebo GaCl3. Naproti tomu ligand L-3 obsahující čtyři donorové atomy dusíku vykazoval schopnost ionizovat SnCl2 a také Sn(OTf)(2), čímž vznikl [L-3 -> SnCl][SnCl3] (7) a [L-3 -> Sn(H20)][OTf](2) (8). Studie tak odhalila, že reakce je závislá na typu ligandu. Připravené komplexy 4-8 spolu s dříve uvedeným [{2-((CH3)C=N(C6H3-2,6-iPr(2)))-6-CH3O-C5H3N}SnCl][SnCl3] (1) byly testovány jako katalyzátory pro ROP L-laktidu prostřednictvím mechanismu aktivovaného monomeru. Nakonec byla provedena výpočetní DFT studie, aby se vyhodnotily sterické a elektronické vlastnosti cínatých iontových komplexů 1 a 4-8 spolu s jejich schopností interagovat s monomerem L-laktidu.

α-Iminopyridine ligands L

The electrophilic substitution of icosahedral

Stannylenes of L2Sn type bearing either C,N-chelating (1, L = LCN = 2-(N,N-dimethylaminomethyl)phenyl) or bulky amido (2, L = LN = N(SiMe3)2) ligands react with cyanogen bromide (Br-C[triple bond, length as m-dash]N) via an oxidative-addition reaction to give monomeric six-coordinate (LCN)2Sn(Br)CN (1a) and four-coordinate (LN)2Sn(Br)CN (2a) stannanes in moderate yields. In solution, both 1a and 2a undergo instantaneous bromido-cyanido ligand redistribution reactions, leading to mixtures containing 1a, (LCN)2SnBr2 (1b) and (LCN)2Sn(CN)2 (1c) or 2a, (LN)2SnBr2 (2b) and (LN)2Sn(CN)2 (2c), respectively. The prepared species were characterised by multinuclear NMR spectroscopy in solution (1a-c and 2a-c) and in the solid state (1a-c). The crystal structures of 1a/b/c, 2a/b/c and sole 2b were determined by XRD analyses. DFT calculations and QTAIM analysis were also carried out to corroborate the experimental results.

Methyl-camouflaged dicarbaboranes closo-1,2- and 1,10-H2C2B8Me8 have been prepared in high yields either from nido-5,6-H2C2B8H10 or closo-1,2-H2C2B8H8 via electrophilic methylation reactions and cl...

Direct synthesis of magnesium amidinates of the general formula [RNC(R1)NR]MgR2 has been performed from appropriate carbodimide and Grignard reagents (R = iPr, Cy, pTol; R1 = Me, nBu; R2 = nBu, Cl, I). Magnesium bisamidinates of the composition [RNC(R1)NR]2Mg(solvent)2 are accessible from [RNC(R1)NR]MgR2 and via the Schlenk-like equilibrium in coordinating solvents. The only isolated amidinatomagnesium halide, preserved in the dinuclear form of {[pTolNC(Me)N-pTol]Mg(THF)}2-μ-(THF)-μ-(Cl)2, has been obtained from the reaction of pTol-N[double bond, length as m-dash]C[double bond, length as m-dash]N-pTol with MeMgCl(THF)n in hexane. The reaction of pTol-N[double bond, length as m-dash]C[double bond, length as m-dash]N-pTol with two equivalents of MeMgI gives an unprecedented dinuclear cyclic adduct {μ-[pTolNC(Me)N-pTol][MgI(OEt2)]2-μ-Me}. The structures of these complexes have been investigated by NMR spectroscopy, sc-XRD and theoretical methods. Selected complexes have been tested as initiators of ring-opening polymerization reactions with various substrates, the copolymerization of oxiranes and CO2 as well as the esterification of lactides.

Here we report the synthesis of aminoborane HN(BCy2) (C6H3-2,6-Me2) (1) (Cy = cyclohexyl), that was successfully deprotonated and its lithium salt {LiN(BCy2) (C6H3-2,6-Me2)}2 (2) has been characterised. The borylamide ligand -N(BCy2) (C6H3-2,6-Me2) was used for the preparation of N→Sn coordinated stannylene [2,6-(Me2NCH2)2C6H3]Sn [N(BCy2) (C6H3-2,6-Me2)] (3) and two coordinate tetrylenes {E [N(BCy2) (C6H3-2,6-Me2)]2} (E = Sn (4), Pb (5)). Experimental and theoretical studies suggested σ character of E-N bonds without additional N(p)→E(p) donation as the result of the preference of N(p)→B(p) donation in 4 and 5. DFT studies on 4 and 5 also reveal theirs HOMO to exhibit E lone pair character and theirs LUMO to include p-orbital character located on metal atoms E.

Reported herein are mutual rearrangements in the whole series of seven bicapped-square antiprismatic

The reaction of an alpha-ketimininopyridine ligand 2-((Me)C = N(C6H3-2,6-iPr(2)))-6-(OMe)C5H3N (L-1) with metal-alkyls, such as MeLi, Et2Zn, Me3Al and Me2AlCl, was studied. The reaction of L-1 with MeLi led exclusively to the formation of [2-((H2C)C-N(C6H3-2,6-iPr(2)))-6-(OMe)C5H3N]Li center dot(THF)(2) (1 center dot(THF)(2)) with a deprotonated ketimine methyl group as a product of methane elimination. The treatment of L-1 with Et2Zn provided, at the first stage, only complex [2-((Me)C = N(C6H3-2,6-iPr(2)))-6-(OMe)C5H3N]ZnEt2 (2). The nonstability of 2 led to ethane elimination along with the deprotonation of a ketimine methyl group, which further yielded [2-((H2C)C-N(C6H3-2,6-iPr(2)))-6-(OMe)C5H3N]ZnEt (3). In contrast, Me3Al reacted with L-1 in a carboalumination fashion and [2-((Me)(2)C-N(C6H3-2,6-iPr(2)))-6-(OMe)C5H3N]AlMe2 (4) was isolated. In the case of Me2AlCl, an ionic species {[2-((Me)C = N(C6H3-2,6-iPr(2)))-6-(OMe)C5H3N]AlMe2}(+) {Me2AlCl2}(-) (5) was formed as a result of a spontaneous dissociation of Me2AlCl initiated by the ligand L-1. Since compounds 2-5 contain a metal-alkyl fragment, they were used as pre-catalysts in ROP of epsilon-caprolactone, as well as compound 1 center dot(THF)(2). Alfa-ketimininopyridinový ligand 2-((Me)C=N(C6H3-2,6-iPr2))-6-(OMe)C5H3N (L1) byl studován v reakcích s alkyl-kovy, jako jsou MeLi, Et2Zn, Me3Al a Me2AlCl. Reakce ligandu L1 s MeLi vedla výhradně ke vzniku [2-((H2C)CN(C6H3-2,6-iPr2))-6-(OMe)C5H3N]Li·(THF)2 (1·(THF)2) s deprotonovanou methylovou skupinou ketiminu jako produktu eliminace metanu. Reakce ligandu L1 s Et2Zn poskytla v prvním stupni pouze komplex [2-((Me)C=N(C6H3-2,6-iPr2))-6-(OMe)C5H3N]ZnEt2 (2). Nestabilita sloučeniny 2 vedla k eliminaci etanu společně s deprotonací methylové skupiny ketiminu za poskytnutí [2-((H2C)CN(C6H3-2,6-iPr2))-6-(OMe)C5H3N]ZnEt (3). Naproti tomu, Me3Al reagoval s ligandem L1 karbaluminačním způsobem a byl izolován amid hlinitý [2-((Me)2C-N(C6H3-2,6-iPr2))-6-(OMe)C5H3N]AlMe2 (4). V případě reakce s Me2AlCl vznikl iontový komplex {[2-((Me)C=N(C6H3-2,6-iPr2))-6-(OMe)C5H3N]AlMe2}+{Me2AlCl2}-(5) jako produkt spontánní disociace Me2AlCl iniciované ligandem L1. Vzhledem k faktu, že sloučeniny 2-5 obsahují alkyl-kovový fragment, byly tyto sloučeniny použity jako katalyzátory v ROP -kaprolaktonu, stejně jako sloučenina 1·(THF)2.

Carbonic anhydrase IX (CAIX) is an enzyme expressed on the surface of cells in hypoxic tumors. It plays a role in regulation of tumor pH and promotes thus tumor cell survival and occurrence of metastases. Here, derivatives of the cobalt bis(dicarbollide)(1-) anion are reported that are based on substitution at the carbon sites of the polyhedra by two alkylsulfonamide groups differing in the length of the aliphatic connector (from C1 to C4, n=1-4), which were prepared by cobalt insertion into the 7-sulfonamidoalkyl-7,8-dicarba-nido-undecaborate ions. Pure meso- and rac-diastereoisomeric forms were isolated. The series is complemented with monosubstituted species (n=2). Synthesis by a direct method furnished similar derivatives (n=2, 3), which are chlorinated at the B(8,8') boron sites. All compounds inhibited CAIX with subnanomolar inhibition constants and showed high selectivity for CAIX. The best inhibitory properties were observed for the compound with n= 3 and two substituents present in rac-arrangement with K

Invited for the cover of this issue is the group of Michal Straka and Martin Dračínský (IOCB Prague, Czech Academy of Sciences). The image depicts a neutron star, which is used to represent the relativistic effects between a heavy element and a hydrogen atom reported in this work. Read the full text of the article at 10.1002/chem.202001532.

Although 1-Ph-2-X-closo-1,2-C2B10H10 (X = F, Cl, Br, I) derivatives had been computed to have positive values of the heat of formation, it was possible to prepare them. The corresponding solid-state structures were computationally analyzed. Electrostatic potential computations indicated the presence of highly positive &sigma, holes in the case of heavy halogens. Surprisingly, the halogen&bull, &bull, &pi, interaction formed by the Br atom was found to be more favorable than that of I.

Ring cleavage of cyclic ether substituents attached to a boron cage via an oxonium oxygen atom are amongst the most versatile methods for conjoining boron closo-cages with organic functional groups. Here we focus on much less tackled chemistry of the 11-vertex zwitterionic compound [10-(O-(CH2-CH2)2O)-nido-7,8-C2B9H11] (1), which is the only known representative of cyclic ether substitution at nido-cages, and explore the scope for the use of this zwitterion 1 in reactions with various types of nucleophiles including bifunctional ones. Most of the nitrogen, oxygen, halogen, and sulphur nucleophiles studied react via nucleophilic substitution at the C1 atom of the dioxane ring, followed by its cleavage that produces six atom chain between the cage and the respective organic moiety. We also report the differences in reactivity of this nido-cage system with the simplest oxygen nucleophile, i.e., OH−. With compound 1, reaction proceeds in two possible directions, either via typical ring cleavage, or by replacement of the whole dioxane ring with -OH at higher temperatures. Furthermore, an easy deprotonation of the hydrogen bridge in 1 was observed that proceeds even in diluted aqueous KOH. We believe this knowledge can be further applied in the design of functional molecules, materials, and drugs.

Six novel oxazaborines based on 7-aminocoumarin substituted by either fluoride or phenyl group on the boron atom were prepared from the corresponding enaminones. The compounds were characterized by means of 1H, 13C, 19F, and 11B NMR in solution, X-ray diffraction in crystal, UV–Vis spectroscopy, and electrochemistry. The observed optical properties were compared to the DFT calculations. Dynamic behaviour of selected oxazaborines was studied by means of 19F and 1H VT NMR and 2D EXSY. Both the enaminones and oxazaborines exhibit relatively strong fluorescence both in solid state and in frozen 2-methyltetrahydrofuran at 77 K, but none in solution. In some cases, phosphorescence was observed as well. Preliminary aggregation tests revealed aggregation induced emission (AIE) properties of the studied molecules. Concerning the electrochemical properties, the first reduction of all the oxazaborines studied proceeds as transport controlled one-electron (quasi)reversible process whereas the first oxidation of BPh2 oxazaborines proceeds as a two-electron irreversible process most probably of the ECE type. The oxidation of BF2 compounds was not possible to obtain within the given potential window. Analysis of frontier orbitals showed that change from BF2 to BPh2 leads to decrease of energy gap. .

Organometallic molybdenum compounds bearing poly[(methylthio)methyl]borates, [(η3-C3H5)Mo(CO)2(κ3-PhTt)] and [Bu4N][{(η3-C3H5)Mo(CO)2Cl}2(κ2:κ2-RTt)], where PhTt = phenyltris[(methylthio)methyl]borate and RTt = tetrakis[(methylthio)methyl]borate, have been obtained by ligand exchange reaction from [(η3-C3H5)Mo(CO)2(NCMe)2Cl] and appropriate borate. The PhTt ligand provides tridentate face-capping coordination to the central metal while the RTt acts as a bridging ligand and connects two [(η3-C3H5)Mo(CO)2Cl] monomeric units by unusual κ2:κ2-coordination mode. Both compounds were fully characterized by spectroscopic methods and X-ray crystallography.

This work describes a procedure giving cyclopentadienyl molybdenum(II) compounds bearing carboxylic acid function group. It involves synthesis of carboxylic acid ester functionalized cyclopentadienides, their coordination to molybdenum(II) precursor and saponification of ester function groups. The method is not limited only to compounds with the function group directly attached in the cyclopentadienyl ring but also to those functionalized in the side chain. The attempts to synthesize the indenyl analogues were only partially successful due to low stability in the saponification step. All reported structure types were elucidated from spectroscopic measurements and verified by X-ray crystallography. The second part of the work describes an effect of the outer-coordination sphere on cytotoxicity of the cationic molybdenum(II) compounds bearing N,N-chelating ligands. The cytotoxicity of the modified species bearing phenanthroline ligand toward human leukemia cells MOLT-4 (IC50 = 10.5 ± 0.5 μmol l−1) is higher than reported for cisplatin (IC50 = 15.8 ± 1.9 μmol l−1).

We report the modification of the 2-ammonio group at halogenated decaborate ions with 2,3-epoxypropane, the product of which reacts readily with nucleophiles to form previously inaccessible coupling of polyhedra with organic molecules and materials. We demonstrate that these ions present a good binding motif in supramolecular chemistry.

New preparative methods for halogenation of the cage producing the corresponding [2-NH3-B10X9]- species (2- to 4-, X = Cl, Br, I) have been developed using halogenations by elemental halogens in a glass pressure vessel. Compared to similar icosahedral species of formulation [1-H3N-B12X11]- (X = Cl, Br), the N-alkylation reactions in 10-vertex series proceed significantly more easily. The reason for this difference is conceivably due to the two orders of magnitude lower basicity of the amino group, with pKa values in the interval from 9.27 to 8.37, and slightly lower steric strain around the reaction centre. Thus methylations with MeI under mild conditions provided the whole series of corresponding quarternary amines of the formulation [2-Me3N-B10X9]- (5- to 7-, X = Cl, Br, I). The effect of the steric strain of the surrounding halogens on the reactivity at the NH3- centre could then be better seen from reactions with bulkier benzyl bromide. Under comparable conditions, these reactions resulted in the ready formation of disubstituted compounds in case of X = Cl (8-), mixture of mono and disubstituted derivatives for X = Br (9-, 10-) or in monosubstited product for X = I (11-) only. Dibenzyl derivative of the nonaiodinated products (12-) could be still obtained, however only under more forcing conditions. The single-crystal X-ray diffraction structures of all three polyhalogenated derivatives 2- to 4- are presented along with that for benzyl derivative 10-, spectral and physicochemical properties of these polyhalogenated systems are outlined along with specific insights into specific properties of the NH3 group.

Nicotinamide has been employed as a supramolecular reagent in the synthesis of ten copper(II) chloro-, bromo-, fluoro-, iodo-, and dichlorobenzoate complexes. Compound structures were determined by single-crystal X-ray diffraction structural analysis. All ten compounds are monomeric complexes with a square-bipyramidal coordination sphere around the Cu2+ ion. The two polymorphs of [Cu(2,6-Cl2bz)2(nia)2] are examples of coordination compounds which are conformation and supramolecular isomers. The molecules of all compounds are connected by N–H…O and O–H…O hydrogen bonds from NH2 groups of nicotinamide and water molecules which create supramolecular hydrogen-bonding-coordination chains and networks.

Reported are procedures leading to the first types of methyl camouflaged dicarbadecaboranes with fewer than eleven vertices. The compounds contain the closo-1,6-C2B8 scaffolding inside the egg-shaped hepta – decamethyl sheath, which imparts unusually high air and solvolytic stability to all of these compounds.

Currently the whole area of polyhalogenated polyhedral anions undergoes renaissance due to their high stability, the kinetic inertness of cage-B-X (X= F, Cl, Br, I) bonds and facile tuning of physicochemical properties (stability, polarity, lipophilicity, pKa, solubility, electrochemical potentials, etc.). Herein, we report on specific procedures that facilitate polyhalogenation of basic 10- and 12-vertex borate anions. New preparative methods for perhalogenation of the [B10H10]2- ion in aqueous solution that easily and almost quantitatively produce [B10X10]2- species (X= Cl, Br, I) have been developed using halogenations by elemental halogens in a glass pressure vessel. Moreover, attention is also paid to similar reactions leading to derivatives with mixed substitutions with heavier halogens and ammonium group, i.e. on the series of [1-NH3-B12X11]- (X= Cl, Br, I). The X-ray structure of the [1-NH3-B12I11]- derivative is presented and spectral, electrochemical and physicochemical properties of these polyhalogenated systems are outlined along with specific insights into properties of NH3 group and its substitution chemistry.

A series of tri- and diorganotin(IV) nitrates and nitrites bearing the 2-( N,N -dimethylaminomethyl)phenyl-as a C,N -chelating ligand (L CN ) has been prepared and structurally characterized. Air-stable triorganotin(IV) nitrates and nitrites of the type L CN R 2 SnX (for X = NO 3 : R = n -Bu ( 1 ), R = Ph ( 2 ); for X = NO 2 : R = n -Bu ( 7 ), R = Ph ( 8 )) and (L CN ) 2 ( n -Bu)SnX (X = NO 3 ( 3 ), NO 2 ( 9 )) are monomeric both in solution and solid state with distorted trigonal bipyramidal geometry around the central tin atom. These species were prepared in biphasic systems (water/organic solvent) using AgNO 3 and NaNO 2 , respectively. Diorganotin(IV) dinitrates ( i.e. L CN ( n -Bu)Sn(NO 3 ) 2 ( 4 ), L CN PhSn(NO 3 ) 2 ( 5 ) and (L CN ) 2 Sn(NO 3 ) 2 ( 6 )) and dinitrites ( i.e. L CN ( n -Bu)Sn(NO 2 ) 2 ( 10 ), L CN PhSn(NO 2 ) 2 ( 11 ) and (L CN ) 2 Sn(NO 2 ) 2 ( 12 )) are monomeric species due to the bidentate bonding fashion of the nitrato, nitrito and/or L CN substituents. Compounds 4–6 and 10–12 were prepared under an inert atmosphere using AgNO 3 in acetonitrile and KNO 2 in THF/benzene mixture of solvents, respectively. All these extraordinary stable compounds have been characterized by IR and NMR spectroscopy. In addition, solid-state structures of 2 , 4 , 5 , 6 , 8 , 11 , 12 and one decomposition product of 10 ( i.e. [L CN ( n -Bu)Sn(NO 3 )(μ-OH)] 2 ; 4a ) were determined by the SC-XRD techniques.

The reaction of N,C,N -chelated pnictinidenes ArE(I) [where Ar = C 6 H 3 -2,6-(CH=N t -Bu) 2 , E = As ( 1 ) and Sb ( 2 )] with dimeric complexes [(COD)M(μ-Cl)] 2 (where COD = 1,5-cyclooctadiene, M = Rh or Ir) gave pnictinidene complexes [ArEM(Cl) (COD)] [where E = As, M = Ir ( 3 ) and E = Sb, M = Ir ( 4 ), Rh ( 6 )] that were characterized by the help of 1 H and 13 C NMR spectroscopy and in the case of 3 and 6 also with the single-crystal X-ray diffraction analysis. However, the complex [ArAsRh(Cl) (COD)] ( 5 ) could not be isolated and exists only in an equilibrium with starting compounds in solution. The treatment of other Rh(I) precursors, such as [(COT) 2 Rh (μ-Cl)] 2 (COT = cyclooctene), with 1 or 2 led to the rhodium (III) pincer complex ArRhCl 2 ( 7 ) as a results of a transmetalation. Complex 7 was completely characterized including the single-crystal X-ray diffraction analysis. Finally, the reactivity toward the rhodium(I) carbonyl complex [(CO) 2 Rh (μ-Cl)] 2 was studied. In the case of the stibinidene 1 , an insoluble material was obtained, while the arsinidine derivative cis -[ArAsRh(Cl) (CO) 2 ] ( 8 ) could be isolated and characterized by NMR and IR spectroscopy.

The synthesis of the monomeric organogermanium(II) hydrides {(LGeH)M(CO)5} (M = Cr (4), W (5)) utilizing the C,N-chelated ligand L (L is [2-(CH2NEt2)-4,6-tBu2-C6H2]-) is reported. The stabilization of the GeH terminal bond in 4 and 5 is accompanied by the combination of the electronic and steric protection of the ligand L. The reactivity of the GeH terminal bond was also investigated and attempts to reduce the polar C≡N bond in tBuNC provided unexpected N-C bond cleavage reaction yielding organogermanium(II) cyanides {(LGeCN)M(CO)5} (M = Cr (6), W (7)) instead of hydrogermylation reaction

The small differences in synthesis condition led to formation of four new copper(II) salicylatocomplexes – two differently polymeric [Cu(4-MeOSal)2(μ-H2O)2]n 1, [Cu(μ-3,5-Br2Sal)2(H2O)2]n 2 and two dimeric [Cu(5-MeSal)2(MeOH)]2⋅2MeOH 3 [Cu(4-MeSal)2(EtOH)2]2 4 compounds, where 4-MeOSal = 4-methoxysalicylate, 3,5-Br2Sal = 3, 5-dibromsalicylate, 5-MeSal = 5-methylsalicylate, and 4-MeSal = 4-methoxysalicylate monoanion. Complexes were characterized by elemental analysis, UV–Vis, infrared, EPR spectra and single crystal X-ray analysis. Spectral properties are in good agreement with structural information. Intermolecular interactions are responsible for building supramolecular structure. The complexes 1 and 2 build up 2D supramolecular structures by the O–H⋯O hydrogen bonds formation while the complexes 3 and 4 are forming 1D supramolecular chain of paddle wheel units and coordinated solvent molecules.

Based on the 2-(N-piperidinyl)thiophene central donor, 32 model push–pull molecules with systematically varied malonic acid-derived peripheral acceptors have been prepared. Further property tuning has been achieved by modifying the π-linker and the structural arrangement (linear vs. quadrupolar D–π–A systems). Malonic acid derivatives such as cyanoacetic acid, malondinitrile, diethyl malonate, Meldrum′s acid, and N,N′-dibutyl(thio)barbituric acid as well as 1,3-diketo analogues dimedone and indan-1,3-dione were employed as acceptor moieties. Knoevenagel condensation with four thiophene aldehydes afforded the target chromophores in satisfactory yields. The electron-withdrawing abilities of malonic acid acceptors were examined both by experiment including X-ray analysis, differential scanning calorimetry, electrochemistry, and UV/Vis absorption spectroscopy, and by DFT calculations. Details of the structure–property relationships have been elucidated. According to the increasing electron-withdrawing ability, the widely used malonic acid acceptor units can be ordered: diethyl malonate ≤ cyanoacetic acid < malondinitrile < Meldrum's acid < dimedone ≤ N,N′-dibutylbarbituric acid < indan-1,3-dione ≤ N,N′-dibutylthiobarbituric acid.