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Sundargopal Ghosh
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Sundargopal Ghosh
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Sundargopal Ghosh
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Ghosh, S.
Ghosh, Sundargopal
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33 results
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- PublicationSynthesis and Characterization of Bis(sigma)borate and Bis–zwitterionic Complexes of Rhodium and Iridium(16-08-2016)
;Roy, Dipak Kumar ;Borthakur, Rosmita ;De, Anangsha ;Varghese, Babu ;Phukan, Ashwini K.Building upon the chemistry of Rh–N,S-heterocyclic carbene complex, [(Cp*Rh)(L2)(1-benzothiazol-2-ylidene)], 2 (Cp*=η5-C5Me5; L=C7H4NS2) with various monoboranes-Lewis adducts, we explored the chemistry of 2 with BH3⋅thf at elevated temperature. As a result, mild thermolysis of 2 with BH3⋅thf led to the formation of bis(sigma)borate [(η4-C5Me5H)Rh(η2-H3BL)], 3 and a bis-zwitterionic species [Cp*RhS(BH2L2)], 4 with the concomitant release of BH3⋅bt (bt=benzothiazole). The RhS3C2N2B2 atoms in 4 generates two six membered rings fused by a common Rh−S bond, which may be considered as a bicycle [4.4.0] cage at the rhodium center. In an effort to generate the iridium analogue of 3, reaction of [Cp*IrCl2]2 with Na[H3B(mbt)] (mbt=2-mercaptobenzothiazole) was carried out that produced bis(sigma)borate complex [(η4-C5Me5H)Ir(η2-H3BL)], 1. The solid state X-ray structures of 1 and 3 showed that the Cp*H ligand coordinated to the metal center in a η4-fashion. In compound 3, the methyl group is oriented towards rhodium center, whereas it is away from Ir center in 1. In addition, the DFT computations were performed to shed light on the bonding and electronic structures of these compounds. - PublicationReactivity of dirhodium analogues of octaborane-12 and decaborane-14 towards transition-metal moieties(25-03-2013)
;Roy, Dipak Kumar ;Anju, R. S. ;Varghese, BabuBuilding upon the key results of our earlier work on rhodaboranes, we continue to explore the chemistry of two nido-rhodaborane clusters, [(Cp*Rh)2B8H12] (1) and [(Cp*Rh)2B6H10] (2) with [Au(PPh 3)Cl] that yielded [(Cp*Rh)2(AuPPh3) 2B8H10] (3) and isomeric [(Cp*Rh) 2(AuPPh3)2B6H8] (4a,b) respectively. The reactivity of 2 with [Au(PPh3)Cl] was rather unusual. In 3 Au exhibits a regular μ2-bonding mode, while in 4a,b there is a μ3-bonding with a Au-Rh bond. Further, the reactivity of 2 was performed with [Fe2(CO)9] that permitted the isolation of 12-vertex [(Cp*Rh)2B6H 6{Fe(CO)2}2{Fe(CO)3}2] (5), 7-vertex [(Cp*Rh)2{Fe(CO)3}2B 3H3] (6), and the heterometallic compound [(Cp*Rh)2{Fe(CO)3}2(μ3-CO) 2] (7) in moderate to good yields. The cluster core of 5 consists of a 10-vertex isocloso geometry with two additional {Fe(CO)3} vertices capping two trigonal faces. Cluster 6 contains a capped-octahedral geometry, where one of the boron atoms is in the capping position. All of the compounds have been characterized by IR and 1H, 11B, and 13C NMR spectroscopy in solution, and the solid-state structures were established by crystallographic analysis of 3-7. © 2013 American Chemical Society. - PublicationHypoelectronic 8-11-Vertex Irida- and Rhodaboranes(16-05-2016)
;Roy, Dipak Kumar ;Borthakur, Rosmita ;Prakash, Rini ;Bhattacharya, Somnath ;Jagan, RajamonyA series of novel isocloso-diiridaboranes [(Cp∗Ir)2B6H6], 1, 2; [1,7-(Cp∗Ir)2B8H8], 4; [1,4-(Cp∗Ir)2B8H8], 5; [(Cp∗Ir)2B9H9], 8; isonido-[(Cp∗Ir)2B7H7], 3; and 10-vertex cluster [5,7-(Cp∗Ir)2B8H12], 6 (Cp∗ = η5-C5Me5) have been isolated and structurally characterized from the pyrolysis of [Cp∗IrCl2]2 and BH3·thf. On the other hand, the corresponding rhodium system afforded 10- and 11-vertices clusters [5-(Cp∗Rh)B9H13)], 7, and [(Cp∗Rh)2B9H9], 9, respectively. Clusters 1 and 2 are topological isomers. The geometry of 1 is dodecahedral, similar to that of its parent borane [B8H8]2-, in which two of the [BH] vertices are replaced by two [Cp∗Ir] fragments. The geometry of 2 can be derived from a nine-vertex tricapped trigonal prism by removing one of the capped vertices. Compounds 4 and 5 are 10-vertex isocloso clusters based on a 10-vertex bicapped square antiprism structure. The only difference between them is the presence of a metal-metal bond in 5. The solid-state structures of 8 and 9 attain an 11-vertex geometry in which a unique six-membered B6H6 moiety is bonded to the metal center. In addition, quantum-chemical calculations have been used to provide further insight into the electronic structure and stability of the clusters. All the compounds have been characterized by IR and 1H, 11B, and 13C NMR spectroscopy in solution, and the solid-state structures were established by X-ray crystallographic analysis. - PublicationFused metallaborane clusters of group 9 and 8 transition metals(01-12-2014)
;Roy, Dipak Kumar ;Jagan, R.Building on our earlier results, the condensation of rhodium polychlorides with borane reagents (LiBH4·thf, BH3·thf, BHCl2·SMe2 etc.), we continue to explore the chemistry of the same system with metal carbonyl compounds. As a result, the reaction of [(Cp∗Rh)2B2H6], generated from fast metathesis of [Cp∗RhCl2]2 and LiBH4, with heavier group 8 metal carbonyl compounds, yielded [(Cp∗Rh)2B4H4Rh{Cp∗RhB3H8}], 1, [(Cp∗Rh)B3H7{Ru(CO)2}(Cp∗RhCO)2], 2 [(Cp∗Rh)2B3H3{Ru(CO)3}2], 3 and [(Cp∗Rh)2{Os4(CO)12}(B)H], 4. Further, these reaction also generated two mixed-metal tetrahedral hydrido clusters [(Cp∗Rh){Os(CO)3}3(μ-H)4], 5 and [(Cp∗Rh)2{Os(CO)3}2(μ-CO) (μ-H)2], 6 as minor products. Compound 1 is an octahedra and a square pyramid fused cluster, whereas for 2 a square pyramid and a triangle are fused through a vertex. Both 1 and 2 follow Mingos's formalism for fused clusters. Cluster 4 is an interstitial boride composed of one boron, two rhodium and four osmium atoms. Based on its compositions, compound 4 is a rare example of heteronuclear borides. All the compounds have been characterized by IR, 1H, 11B, 13C NMR spectroscopy in solution and the solid state structures were established by crystallographic analysis of 1-5. - PublicationHomometallic Cubane Clusters: Participation of Three-Coordinated Hydrogen in 60-Valence Electron Cubane Core(08-09-2015)
;Yuvaraj, K. ;Roy, Dipak Kumar ;Mondal, Bijan ;Varghese, BabuThis work describes the synthesis, structural characterizations, and electronic structures of a series of novel homometallic cubane clusters [(Cp∗Ru)2{Ru(CO)2}2BH(μ3-E)(μ-H)B(μ-H)3M], (2, M = Cp∗Ru, E = CO; 3, M = Ru(Cp∗Ru)2(μ-CO)3(μ-H)BH), E = BH), [(Cp∗Ru)3(μ3-CO)(BH)3(μ3-H)3], 4, and [(Cp∗Ru)2(μ3-CO){Ru(CO)3}2(BH)2(μ-H)B], 5 (Cp∗ = η5-C5Me5). These cubane clusters have been isolated from a thermally driven reaction of diruthenium analogue of pentaborane(9) [(Cp∗RuH)2B3H7], 1, and [Ru3(CO)12]. Structural and spectroscopic studies revealed the existence of triply bridged hydrogen (μ3-H) atoms that participate as a vertex in the cubane core formation for compounds 2, 3, and 4. In addition, the crystal structure of these clusters clearly confirms the presence of an electron precise borane ligand (borylene fragment) which is triply bridged to the trimetallic units. Bonding of these novel complexes has been studied computationally by DFT methods, and the studies demonstrate that the cubane clusters 2 and 3 possess 60 cluster valence electrons (cves) with six metal-metal bonds. All the new compounds have been characterized in solution by mass spectrometry; IR; and 1H, 11B, and 13C NMR studies, and the structural types were unequivocally established by crystallographic analysis of compounds 2-5. (Figure Presented). - PublicationMixed-metal chalcogenide tetrahedral clusters with an exo-polyhedral metal fragment(07-12-2014)
;Yuvaraj, K. ;Roy, Dipak Kumar ;Anju, V. P. ;Mondal, Bijnaneswar ;Varghese, BabuThe reaction of metal carbonyl compounds with group 6 and 8 metallaboranes led us to report the synthesis and structural characterization of several novel mixed-metal chalcogenide tetrahedral clusters. Thermolysis of arachno-[(Cp∗RuCO)2B2H6], 1, and [Os3(CO)12] in the presence of 2-methylthiophene yielded [Cp∗Ru(CO)2(μ-H){Os3(CO)9}S], 3, and [Cp∗Ru(μ-H){Os3(CO)11}], 4. In a similar fashion, the reaction of [(Cp∗Mo)2B5H9], 2, with [Ru3(CO)12] and 2-methylthiophene yielded [Cp∗Ru(CO)2(μ-H){Ru3(CO)9}S], 5, and conjuncto-[(Cp∗Mo)2B5H8(μ-H){Ru3(CO)9}S], 6. Both compounds 3 and 5 can be described as 50-cve (cluster valence electron) mixed-metal chalcogenide clusters, in which a sulfur atom replaces one of the vertices of the tetrahedral core. Compounds 3 and 5 possess a [M3S] tetrahedral core, in which the sulfur is attached to an exo-metal fragment, unique in the [M3S] metal chalcogenide tetrahedral arrangements. All the compounds have been characterized by mass spectrometry, IR, and 1H, 11B and 13C NMR spectroscopy in solution, and the solid state structures were unequivocally established by crystallographic analysis of compounds 3, 5 and 6. - PublicationReactivity of diruthenium and dirhodium analogues of pentaborane(9): Agostic versus boratrane complexes(10-03-2014)
;Anju, R. S. ;Roy, Dipak Kumar ;Mondal, Bijan ;Yuvaraj, K. ;Arivazhagan, C. ;Saha, Koushik ;Varghese, BabuA series of novel Cp*-based (Cp*=η5-C 5Me5) agostic, bis(σ-borate), and boratrane complexes have been synthesized from diruthenium and dirhodium analogues of pentaborane(9). The synthesis and structural characterization of the first neutral ruthenadiborane(6) analogue are also reported. This new route offers a very efficient method for the isolation of bis(σ-borate) and agostic complexes from diruthenapentaborane(9). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. - PublicationNew Routes to a Series of σ-Borane/Borate Complexes of Molybdenum and Ruthenium(23-11-2015)
;Ramalakshmi, Rongala ;Saha, Koushik ;Roy, Dipak Kumar ;Varghese, Babu ;Phukan, Ashwini K.A series of agostic σ-borane/borate complexes have been synthesized and structurally characterized from simple borane adducts. A room-temperature reaction of [Cp∗Mo(CO)3Me], 1 with Li[BH3(EPh)] (Cp∗=pentamethylcyclopentadienyl, E=S, Se, Te) yielded hydroborate complexes [CpMo(CO)2(μ-H)BH2EPh] in good yields. With 2-mercapto-benzothiazole, an N,S-carbene-anchored σ-borate complex [Cp∗Mo(CO)2BH3(1-benzothiazol-2-ylidene)] (5) was isolated. Further, a transmetalation of the B-agostic ruthenium complex [Cp Ru(μ-H)BHL2] (6, L=C7H4NS2) with [Mn2(CO)10] affords a new B-agostic complex, [Mn(CO)3(μ-H)BHL2] (7) with the same structural motif in which the central metal is replaced by an isolobal and isoelectronic [Mn(CO)3] unit. Natural-bond-orbital analyses of 5-7 indicate significant delocalization of the electron density from the filled σB-H orbital to the vacant metal orbital. - PublicationChemistry of Rh-N,S heterocyclic carbene complexes(01-06-2016)
;Roy, Dipak Kumar ;Yuvaraj, K. ;Jagan, R.Chloro-rhodaboratrane [(Cp∗Rh)(L2)BCl] 4 has been synthesized from rhodium N,S-heterocyclic carbene complex [(Cp∗Rh)(L2)(1-benzothiazol-2-ylidene)], 1, (L = C7H4NS2) and borane reagent BHCl2.SMe2. The Rh-B bond in 4 is buttressed between two benzothiazolyl units in [3.3.0] fashion. The presence of B-Cl bond allowed us to explore the chemistry of boratrane 4 at the boron centre. The reaction of ethynylmagnesium bromide with 4 yielded η1-vinyl complex [Cp∗RhBr(C2H2)L] 5, containing a five membered metallaheterocycle. In an objective to abstract the chloride, alike borylene synthesis from haloboryl, we performed the reaction of 4 with NaBArF4 that resulted the thiolato bridged bimetallic compound [Cp∗Rh(μ-L)3RhCp∗][BArF4] 6 (ArF: C6H3(CF3)2-3,5). - PublicationSynthesis and structural characterization of group 5 dimetallaheteroboranes(01-01-2013)
;Shankhari, Pritam ;Roy, Dipak Kumar ;Geetharani, K. ;Anju, R. S. ;Varghese, BabuTreatment of group 5 metal polychlorides such as [CpnMCl 4-x] (M = Nb: n = 1, x = 0; M = V: n, x = 2), (Cp = η5-C5H5) with [LiBH4·THF] followed by thermolysis in presence of diphenyl dichalcogenide ligands, E 2Ph2 (E = Se or Te) yielded dimetallaheteroborane clusters [(CpNb)2BH(Se)4], 1 and [(CpV)2B 3H9(μ3-Te)], 2 in modest yields. Compound 1 can be considered as an edge fused cluster in which a trigonal bipyramidal unit [Nb2Se2B] has been fused with a tetrahedral core [Nb 2Se2] by means of a common [Nb2] edge. Compound 2 can be described as a dimetallaheteroborane built from two edge-fused V 2B2 tetrahedra, in which one of the BH3 units is replaced by an isoelectronic Te ligand. All the compounds have been characterized by mass spectrometry, 1H, 11B, 13C, 51V and 77Se NMR spectroscopy. In addition the geometry of compound 1 has been established by crystallographic analysis. © 2012 Elsevier B.V. All rights reserved.