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      Volume 131, Issue 12

      December 2019

    • Table of Contents

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    • Special issue on 150 years of the periodic table

      ELUVATHINGAL D JEMMIS J N MOORTHY R MURUGAVEL

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    • Probing the Lewis acidity of heavier pnictogen trichlorides

      JOBHA A JOHNSON AJAY VENUGOPAL

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      Lewis acidity of SbCl3 and BiCl3 has been investigated in the solid as well as in solution state. Two b-ketoimine ligands, [O=C(Me)]CH[C(Me)NHAr] (L1, Ar=2,6-diisopropylphenyl) and [(CH2)2{-N(H)C(Me)CHC(Me)=O}2] (L2) are used to prepare the complexes [(L1)(THF)SbCl3]2 (1),[(L1)(THF)BiCl3]2 (2), [L2SbCl3]2 (3) and [(L2)3(BiCl3)2] (4), which are characterized by multinuclear NMR spectroscopy, elemental analysis and single-crystal X-ray diffraction experiments. Solid-state structural analysis of 1–4 and solution studies on SbCl3 and BiCl3 using the Gutmann-Beckett method reveal the higher Lewis acidity of BiCl3 compared to SbCl3

    • BINOL accelerated Ru(II)-catalyzed regioselective C-H functionalization of arenes with disulfides and diselenides

      RAGHUNATH BAG TANUMAY SARKAR SUNDARAVEL VIVEK KUMAR KANGKAN TALUKDAR THARMALINGAM PUNNIYAMURTHY

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      A BINOL accelerated Ru-catalyzed ortho-selective C-H coupling of arenes tethered to 7-azaindoles is described with disulfides and diselenides under air. The thioether can be readily oxidized to sulfoxide and sulfone. The use of less expensive Ru-catalysis, substrate scope and scale-up are the important practical features.

    • Influence of periodic table in designing solid-state metal chalcogenides for thermoelectric energy conversion

      EKASHMI RATHORE MOINAK DUTTA KANISHKA BISWAS

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      With the apparent burgeoning energy crisis, alternative sources of energies are in a greater need for a sustainable future. Thermoelectrics which can convert waste heat arising from industries, power plants and automobiles into a usable form, electricity; have the potential to be a game-changer in this critical energyshortage. The efficiency of thermoelectric materials which is given by the figure of merit is tricky to manipulate due to the complicated interrelationships of its parameters. But with proper understanding of a material and with the aid of periodic table, one can manoeuvre the shortcomings which hinder its efficiency.In this perspective, we discuss how the properties of materials can be manipulated just by understanding the elements of the periodic table and how each element in their respective position in the periodic table influencesthe outcome of high performing thermoelectric material.

    • Designing M-bond (X-M...Y, M 5 transition metal): r-hole and radial density distribution

      JYOTHISH JOY ELUVATHINGAL D JEMMIS

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      Following the ubiquitous H-bond, there is a growing interest in weak non-covalent interactions involving other elements, viz., the Z-bonds (X-Z...Y, Z = halogens, chalcogens, etc.). Although almost all the main group elements can act as Z bond donors, the search for a similar role for transition metals in X-M...Y,(M = transition metal) interaction, called the Metal-bond, is still in its infancy. This article summarizes our attempts to understand the participation of transition metal elements as electron acceptors in a weak interaction with electron-rich species Y. Cambridge Structural Database analysis revealed that except Group 11and 12 transition metal complexes (Type-II), electron-saturated (18 electron) metal complexes having partly filled d orbitals (Group 3–10; Type-I) hesitate to form Metal-bonds. This is attributed to the partial r-hole screening by core electron density and diminished stabilization from charge polarization in Type I complexes. We also show that Type-I complexes could be forced to form Metal-bonds by employing extreme ligand conditions, thereby opening new areas of research where Metal-bonds can act as emerging non-covalent interaction in designing supramolecular architectures

    • Catalytic dearomative hydroboration of heteroaromatic compounds

      BASUJIT CHATTERJEE CHIDAMBARAM GUNANATHAN

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      This review offers a comprehensive discussion on literature concerning the development of catalytic protocols for the dearomative hydroboration of heteroaromatic compounds. The importance of selective dearomatization of heteroarenes, their remarkable applications along with the development ofdifferent catalytic methods and their synthetic scopes are emphasized.

    • Rhodium-catalyzed synthesis of C4-chalcogenoalkylated oxindoles via Sommelet-Hauser type rearrangement of 3-diazoindolin-2-ones

      ANGULA CHANDRA SHEKAR REDDY BHOJKUMAR NAYAK PAZHAMALAI ANBARASAN

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      Efficient rhodium-catalyzed Sommelet-Hauser type rearrangement of 3-diazoindolin-2-ones with a-thioesters has been accomplished for the synthesis of C4-thioalkylated oxindoles. The developed reaction offers the selective functionalization of C4-position of oxindole via generation of S-ylide and [2, 3]-sigmatropic rearrangement and allows access to diverse C4-thioalkylated oxindoles in good to excellent yield. Furthermore, the method was successfully extended to the synthesis C4-selenoalkylated oxindoles employingthe corresponding a-selenoester.

    • Chemical bonding in Period 2 homonuclear diatomic molecules: a comprehensive relook

      A DAS E ARUNAN

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      Theoretical and experimental studies of bonding in the main group homonuclear diatomic molecules have been pursued for many years, and they possess serious challenges for scientists. Most of the early experimental work have been carried out by Herzberg.1,2 We take a relook at the bonding motifs of Period 2 homonuclear diatomic molecules (from Li2 to Ne2) using varieties of quantum chemical tools, commonly used for intermolecular bonding/interactions now. The methods employed include Atoms in Molecules (AIM), Non-covalent Index plot (NCI), Electrostatic potential (ESP), and Potential Acting on oneElectron in a Molecule (PAEM). The spectroscopic constants i.e., equilibrium bond distances (re), harmonic frequencies (x), bond dissociation energies (De) have all been evaluated using high-level ab initio methods and critically compared with the experimental results. Multi-reference calculations (CASSCF) on B2 and C2 have been carried out as they have a large number of low lying electronic states. Bonding within these homonuclear diatomic molecules show all the diversities that are encountered in inter/intra-molecular bonding in chemistry. Based on the AIM analysis, these 8 homonuclear diatomic molecules could be divided into three different groups, based on the correlation between binding energy and the electron density at the bond critical point. However, PAEM/ESP analysis allows us to analyse all eight of them as one group havinga good correlation between binding energy and the PAEM/ESP at the critical point between the two atoms. Our results highlight the arbitrariness in relying on some computational tools to characterize a bond as covalent (shared) or ionic/electrostatic (closed). In contrast, they also show the usefulness of the various methods in exploring similarities and differences in bonding. We propose that from Li2 to Ne2, all homonuclear diatomic molecules are bound by ‘chemical bonds’.

    • Solvent-assisted monomeric molecular structure of the phosphate diester and the synthesis of menthol-based phosphate diesters

      DEBDEEP MANDAL VIVEK GUPTA BISWAJIT SANTRA NICOLAS CHRYSOCHOS VIVEK W BHOYARE AVIJIT MAITI ABHISEK KAR SUMAN ANKU GUHA PALLAVI THAKUR RAMAKIRUSHNAN SURIYA NARAYANAN NITIN T PATIL CAROLA SCHULZKE VADAPALLI CHANDRASEKHAR ANUKUL JANA

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      Phosphate diesters are well known to form intermolecular H-bonded dimeric structures in their solid-state. Recently, we reported 2,6-(CHPh)2-4-iPr-phenyl substituted phosphate diester exists as H-bonded monomeric molecular structure along with water dimer in the solid-state. Herein we report 2,6-(CHPh)2-4-iPr-phenyl substituted phosphate diester forms a monomeric molecular structure in the solid-state upon cocrystallization with dimethylformamide, DMF(Me2NCHO). The -CHO group of DMF simultaneously acts as an H-bond acceptor to P-OH and an H-bond donor to P=O moieties. We also used the alcohols, ROH (R = Me, Et, iPr, and tBu), for crystallisation of 2,6-(CHPh)2-4-iPr-phenyl substituted phosphate diester. In these instances, solvent-incorporated dimeric structures are found in the solid-state. We also report the syntheses and molecular structures of anionic phosphate diesters of 2,6-(CHPh)2-4-iPr-phenyl substitutedphosphate diester possessing various counter cations. Moreover, we also report the syntheses and molecular structures of phosphate diesters based on (-)-menthol, (?)-menthol and (?)/(-)-menthol. These exist as H-bonded dimers in the solid-state.

    • On the position of La, Lu, Ac and Lr in the periodic table: a perspective

      ADITI CHANDRASEKAR MEENAKSHI JOSHI TAPAN K GHANTY

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      The periodic table of elements, organised as blocks of elements that contain similar properties, occupies a central role in chemistry. However, the position of some of the elements in the periodic table is a debate that has been ensuing over the past one and a half long centuries. Particularly, the positions oflanthanum (La), lutetium (Lu), actinium (Ac) and lawrencium (Lr) in the periodic table have been quite controversial. Different kinds of studies carried out by various research groups have yet left the fate of these elements undecided as the results of these investigations suggested that these elements could potentially be placed in the d-block, p-block or all four in the f-block. Our recent work looked into this question from a new perspective, involving encapsulation of La, Lu, Ac and Lr into Zintl ion clusters, Pb122- and Sn122-. These clusters were chosen as they provide a fitting environment for the determination of structural, thermodynamic and electronic properties of the encapsulated species. Various results that have been evaluated and subsequently analysed (Joshi et al. in Phys. Chem. Chem. Phys. 20:15253–15272, 2018) in order to seek outsimilarities and differences for making justified conclusions about the placement of all these four elements in the periodic table are the subject matter of this review article

    • Syntheses and structures of chalcogen-bridged binuclear group 5 and 6 metal complexes

      MOULIKA BHATTACHARYYA RINI PRAKASH CHANDAN NANDI MONOJIT GHOSAL CHOWDHURY BEESAM RAGHAVENDRA THIERRY ROISNEL SUNDARGOPAL GHOSH

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      Syntheses and structural elucidations of a series of chalcogen stabilized binuclear complexes of group 5 and 6 transition metals have been described. Room temperature reaction of [Cp*CrCl]2 (Cp* = h5- C5Me5) with Li[BH3(SePh)] afforded a Se inserted binuclear chromium complex, [(Cp*Cr)2(m-Se2SePh)2], 1.In an attempt to make the analogous complexes with heavier group 6 metals, reactions of [Cp*MCl4] (M = Mo and W) with Li[BH3(SePh)] were carried out that yielded Se inserted binuclear complexes [(Cp*M)2(m-Se)2(m-SePh)2], 2 and 3 (2: M = Mo and 3: M = W) along with known [(Cp*M)2B5H9], 4a–b (4a: M = Mo and 4b: M = W). Similarly, the reactions of [Cp*NbCl4] with Li[BH3(EPh)] (E = S or Se)followed by thermolysis led to the formation of binuclear chalcogen complexes [(Cp*Nb)2(m-E2)2], 5 and 6 (5: E = S and 6: E = Se) and known [(Cp*Nb)2(B2H6)6], 7. All these complexes have been characterized by 1H and 13C NMR spectroscopy and mass spectrometry. The structural integrity of complexes 1, 3, 5 and 6 was established by the X-ray diffraction studies. The DFT studies further exemplify the bonding interactions present in these complexes, especially the multiple bond character between the metals in 1–3.

    • In silico design of pseudo D5h actinide based molecular magnets: role of covalency in magnetic anisotropy

      SOURAV DEY GOPALAN RAJARAMAN

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      Actinide molecular magnets are of great interest in the area molecular magnetism as they possess strong covalency and spin-orbit coupling that their 4f congeners lack. Despite these known advantages, the actinide based molecular magnets have not been explored in detail due to the limited availability of actinidesalts. While theoretical tools are proven to be useful in lanthanide chemistry towards prediction, they are still at an infant stage in actinide chemistry. In this manuscript, we have attempted to utilise CASSCF/RASSI-SO calculations to predict suitable pseudo D5h molecules possessing attractive magnetic properties. To begin with, we have undertaken an extensive benchmarking of the methodology employed by studying two sets of isostructural, [NdTp3], [UTp3], [Nd(COT²)2]-, [U(COT²)2]- {Tp- = trispyrazolylborate, COT² = bis(trimethylsilyl)cyclooctatetraenyl dianion} complexes. The method assessment reveals that the methodology employed is reliable as this has reproduced the experimental observables. With this, we have moved forward with prediction where pseudo-D5h symmetric [L2M(H2O)5][I]3L2.(H2O) {M = Nd, U, Pu; L =tBuPO(NHiPr)2} systems are modelled from their Nd(III) X-ray structure. Our calculations reveal that the Uranium complex studied possess superior SIM characteristics compared to its lanthanide analogue. Plutonium complex has prolate electron density at the ground state, and hence the ligand environment isunsuitable for yielding SIM behaviour. The role of solvent molecules, counter anions and equatorial and axial ligand are explored and tantalizing prediction with a barrier height of 1403.3 and 989.5 cm-1 are obtained for [tBuPO(NHiPr)2-U-tBuPO(NHiPr)2]3+ and [Pu(H2O)5]3+ models, respectively and this paves the way for synthetic chemist to target such geometries in actinide based SIMs.

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