Building 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.

Sundargopal Ghosh

Department Of Chemistry

Babu Varghese

Bonding modes

BORON ATOM

CLUSTER CORES

CRYSTALLOGRAPHIC ANALYSIS

DIRHODIUM

HETEROMETALLIC COMPOUNDS

Solid-state structures

Chemical bonds

Nuclear magnetic resonance spectroscopy

Rhodium

Iron compounds

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It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Organometallics

Treatment of a dirhodium analogue of pentaborane(9), [(Cp*Rh)2B3H7] (nido-1; Cp* = η5-C5Me5), with [Fe2(CO)9] at room temperature led to the formation of [(Cp*Rh)2Fe(CO)3(µ-CO)B3H2Cl] (2) and the metal-rich metallaborane [(Cp*Rh)2Fe(CO)3Fe(CO)2(µ-CO)2B2H2] (3). When the same reaction was carried out at moderate temperature, two metal-rich metallaboranes, [(Cp*Rh)3Fe(CO)2(µ3-CO)2B2HX] 4 (X = H) and 5 (X = Cl), and a heterometallic µ9-boride cluster, [(Cp*Rh)3(RhCO)3Fe(CO)3(µ-CO)3B3H2] (6), were obtained. Compounds 4 and 5 can be viewed as cubane clusters with 62 cluster valence electrons (cves) and five metal–metal bonds. In another reaction, the treatment of nido-1 with [Mn2(CO)10] yielded the heterometallic µ9-boride cluster [(Cp*Rh)3Rh(CO)2{Mn(CO)3}2B4H3] (7). The cluster cores of both 6 and 7 are comprised of tricapped trigonal prisms containing a µ9-B atom bonded to seven/six metals and two/three boron atoms, respectively. All the new compounds have been characterized by mass spectrometry, IR, 1H, 11B{1H}, and 13C{1H} NMR spectroscopy, and X-ray crystallographic analysis. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

European Journal of Inorganic Chemistry

Metal-Rich Metallaboranes: Structures and Geometries of Heterometallic µ9-Boride Clusters

We report the synthesis and structural characterization of moderately air stable metal rich metallaboranes of iridium. Treatment of [Cp*IrCl2]2with BH3·thf at high temperature led to the isolation of a trimetallic [nido-5-(Cp*Ir)3B7H11], 1. Compound 1 is isoelectronic and isostructural with decaborane-14 where three BH units in [B10H14] have been replaced by Cp*Ir fragments. As far as we are aware, 1 is the first example of a iridadecaborane having three metals. In addition to the formation of 1, a change in the reaction conditions enabled us to isolate a 7 sep [(Cp*Ir)3B4H4], 2. The geometry of 2 can be viewed as a condensed polyhedron composed of Ir3B3octahedron capped by a BH unit. All the compounds have been characterized by IR and1H,11B, and13C NMR spectroscopy in solution, and the solid-state structures were established by X-ray crystallographic analysis. Quantum-chemical calculations by DFT methods for compounds 1 and 2 showed reasonable agreement with the experimentally observed structural parameters. The large HOMO–LUMO gaps are consistent with the high stabilities of the iridium clusters compared to their known Rh and Co analogues. © 2016 Elsevier B.V.

Journal of Organometallic Chemistry

Metal rich metallaboranes of group 9 transition metals

We report the synthesis, isolation and structural characterization of several crystalline, moderately air stable nido-metallaboranes which represent novel metal rich open cage systems.The reaction of [Cp*CoCl]2, (Cp* = ν5-C5Me5), with [LiBH 4·thf] in toluene at-78 °C, followed by thermolysis with [BH3·thf] in boiling toluene yielded clusters, [(Cp*Co)3B6H8O] (1) and [(Cp*Co)2B8H11Me] (2). Under the similar reaction condition, [Cp*RhCl2]2 yielded [(Cp*Rh)3B7H11] (3) and [(Cp*Rh)2B8H12] (4). All the new compounds, 1-4 have been characterized by elemental analysis, IR, 1H, 11B, 13C NMR spectroscopy, and the geometric structures were unequivocally established byX-ray diffraction analysis of compound 1-4. Quantum chemical calculation by using density functional theory method is implemented on model compounds 10-40 (10-40 are the Cp analogs of 1-4 respectively, Cp = C5H5) and yields geometries in agreement with the X-ray detaermined geometries. Large HOMO-LUMO gaps are in tally with the higher stabilities of 10 and 30. © The National Academy of Sciences, India 2014.

Proceedings of the National Academy of Sciences India Section A - Physical Sciences

Synthesis, characterization and electronic structures of Rh and co analogs of decaborane-14

The recent achievements and progress in the field of high-nuclearity supraicosahedral metallaborane chemistry are reviewed and compared to those made in borane, carborane and metallacarborane chemistry. In contrast to metallacarboranes, characterized large supraicosahedral metallaboranes only adopt isocloso deltahedral structural arrangements with n vertices and a non-Wadean n skeletal-electron-pair count. This anomaly can be rationalized by the preference of metal atoms for 6-connect vertices present in the cluster cages. © 2013 Springer Science+Business Media New York.

Journal of Cluster Science

Beyond the Icosahedron: The Quest for High-Nuclearity Supraicosahedral Metallaboranes

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. © 2014 Elsevier B.V.

Fused metallaborane clusters of group 9 and 8 transition metals

A neutral metallaborane comprising a Rh4B12 polyhedron with icosioctahedron geometry with 16 vertices and 28 triangular faces was prepared (see structure; Rh: red, B: green). The cage has the shape of a 12-membered truncated tetrahedron with four capped hexagonal faces. © 2013 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.

Angewandte Chemie - International Edition

Boron beyond the icosahedral barrier: A 16-vertex metallaborane

The reaction of nido-[1,2-(Cp*RuH)2B3H 7] (1 a, Cp*=Î·5-C5Me 5) with [Mo(CO)3(CH3CN)3] under mild conditions yields the new metallaborane arachno-[(Cp*RuCO) 2B2H6] (2). Compound 2 catalyzes the cyclotrimerization of a variety of internal- and terminal alkynes to yield mixtures of 1,3,5- and 1,2,4-substituted benzenes. The reactivities of nido-1 a and arachno-2 with alkynes demonstrates that a change in geometry from nido to arachno drives a change in the reaction from alkyne-insertion to catalytic cyclotrimerization, respectively. Density functional calculations have been used to evaluate the reaction pathways of the cyclotrimerization of alkynes catalyzed by compound 2. The reaction involves the formation of a ruthenacyclic intermediate and the subsequent alkyne-insertion step is initiated by a [2+2] cycloaddition between this intermediate and an alkyne. The experimental and quantum-chemical results also show that the stability of the metallacyclic intermediate is strongly dependent on the nature of the substituents that are present on the alkyne. Everything changes but Ru: The reactivities of nido-[1,2-(Cp*RuH)2B3H7] and arachno-[(Cp*RuCO)2B2H6] with alkynes show that a change in geometry (nido to arachno) drives a change from alkyne-insertion to catalytic cyclotrimerization, respectively. Copyright © 2012 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.

Chemistry - A European Journal

A mechanistic study of the utilization of arachno-diruthenaborane [(Cp*RuCO)2B2H6] as an active alkyne-cyclotrimerization catalyst

We present the results of our investigation of a thermally driven cluster expansion of rhodaborane systems with BH 3·THF. Four novel rhodaborane clusters, for example, nido-[(CpRh) 2B 6H 10], 1; nido-[(CpRh)B 9H 13], 2; nido-[(CpRh) 2B 8H 12], 3; and nido-[(CpRh) 3B 8H 9(OH) 3], 4 (Cp* = η 5-C 5Me 5), have been isolated from the thermolysis of [CpRhCl 2] 2 and borane reagents in modest yields. Rhodaborane 1 has a nido geometry and is isostructural with [B 8H 12]. The low temperature 11B and 1H NMR data demonstrate that compound 1 exists in two isomeric forms. The framework geometry of 2 and 3 is similar to that of [B 10H 14] with one BH group in 2 (3-position), and two BH groups in 3 (3, 4-positions) are replaced by an isolobal {CpRh} fragment. The 11 vertex cluster 4 has a nido structure based on the 12 vertex icosahedron, having three rhodium and eight boron atoms. In addition, the reaction of rhodaborane 1 with [Fe 2(CO) 9] yielded a condensed cluster [(CpRh) 2{Fe(CO) 3} 2B 6H 10], 5. The geometry of 5 consists of [Fe 2B 2] tetrahedron and an open structure of [(CpRh) 2B 6], fused through two boron atoms. The accuracy of these results in each case is established experimentally by spectroscopic characterization in solution and structure determinations in the solid state. © 2012 American Chemical Society.

Inorganic Chemistry

Synthesis and structure of dirhodium analogue of octaborane-12 and decaborane-14

The reaction of [CpnMCl4-x] (M=V: n=2, x=2; M=Nb: n=1, x=0; Cp=Î·5-C5H5) with LiBH4·THF followed by thermolysis in the presence of dichalcogenide ligands E2R2 (E=S, Te; R=2,6-(tBu) 2-C6H2OH, Ph) and 2-mercaptobenzothiazole (C7H5NS2) yielded dimetallaheteroboranes [{CpV(μ-TePh)}2(μ3-Te)BH·thf] (1), [(CpV)2(BH3S)2] (2), [(CpNb)2B 4H10S] (3), [(CpNb)2B4H 11S(tBu)2C6H2OH] (4), and [(CpNb)2B4H11TePh] (5). In cluster 1, the V2BTe atoms define a tetrahedral framework in which the boron atom is linked to a THF molecule. Compound 2 can be described as a dimetallathiaborane that is built from two edge-fused V2BS tetrahedron clusters. Cluster 3 can be considered as an edge-fused cluster in which a trigonal-bipyramidal unit (Nb2B2S) has been fused with a tetrahedral core (Nb2B2) by means of a common Nb2 edge. In addition, thermolysis of an in-situ-generated intermediate that was produced from the reaction of [Cp2VCl2] and LiBH 4·THF with excess BH3·THF yielded oxavanadaborane [(CpV)2B3H8(μ3- OEt)] (6) and divanadaborane cluster [(CpV)2B5H 11] (7). Cluster 7 exhibits a nido geometry with C2v symmetry and it is isostructural with [(Cp*M)2B 5H9+n] (M=Cr, Mo, and W, n=0; M=Ta, n=2; Cp*=Î·5-C5Me5). All of these new compounds have been characterized by 1H NMR, 11B NMR, and 13C NMR spectroscopy and elemental analysis and the structural types were established unequivocally by crystallographic analysis of compounds 1-4, 6, and 7. Group 5 alive: Divanadatellura- and divanadathiaboranes were obtained from the treatment of Group 5 metal polychlorides with dichalcogenides and monoboranes. The treatment of [Cp2VCl2] with monoboranes yielded an oxavanadaborane and a divanadaborane (see structures). Copyright © 2012 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.

Synthesis and structural characterization of new divanada- and diniobaboranes containing chalcogen atoms

C-H activation of arenes and heteroarenes has been achieved by a hydrogen rich tantalaborane cluster [(Cp*Ta)2B5H 11] that leads to the formation of C-H functionalized products. Furthermore, we examined the reaction of substituted thiophene and pyrrole derivatives with tantalaborane which provided a convenient and efficient route to regio-defined C-H functionalized heteroarenes. © 2011 The Royal Society of Chemistry.

Journal	Organometallics
ISSN	02767333
Open Access	No