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.

Sundargopal Ghosh

Department Of Chemistry

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IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

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IIT Madras

Journal of Cluster Science

In an attempt to synthesize expanded-cage metallaheteroboranes containing heavier chalcogen atoms, the reaction of diruthenaborane analogue of pentaborane(9), nido-[1,2-(Cp*RuH)2B3H7] (1) with phenyl-chalcogenoborates Li[BH3(EPh)] (E = S, Se or Te) was carried out. Thermolysis of nido-1 with Li[BH3(SPh)] led to the formation of the dimetalla-pentaborane(11) analogue arachno-[(Cp*Ru)2B3H8(SPh)] (2). In parallel to the formation of 2, the reaction also yielded three B-H functionalized compounds, namely [(Cp*Ru)2B4H7(Ph)] (3), [(Cp*Ru)2B4H7(Cl)] (4) and [(Cp*Ru)2B4H6(SPh)(Cl)] (5). On the other hand, reaction of 1 with Li[BH3(SePh)] led to the formation of the diruthenium analogue of hexaborane(10) nido-[(Cp*Ru)2B4H9(SePh)] (6), whereas Li[BH3(TePh)] yielded the capped nido-pentagonal-pyramidal [(Cp*Ru)2B4H6Te] (7). Compound 7 is a rare ruthenaborane cluster containing a heavier chalcogen element (Te). All the compounds were characterized by mass spectrometry and 1H, 1H{11B}, 11B{1H} and 13C{1H}NMR spectroscopy. The solid state X-ray structures of all the compounds were unequivocally established by crystallographic analysis. Additionally, the electronic properties of compound 2 were analyzed. © 2017 Elsevier B.V.

Fulltext

Journal of Organometallic Chemistry

Synthesis and characterization of diruthenaborane analogues of pentaborane(11) and hexaborane(10)

In an effort to synthesize supraicosahedral iridaboranes, pyrolysis of [Cp∗IrCl2]2 with excess [BH3·THF] was carried out, and this synthesis afforded the isomeric iridaborane [(Cp∗Ir)2B6H6] clusters 1 and 2. The geometry of 1 was determined to be dodecahedral, i.e., similar to that of [B8H8]2-, whereas 2 was found to exhibit a cluster shape that can be derived from a nine-vertex tricapped trigonal prism by removing one of the capped vertices. The calculation of a large HOMO-LUMO gap further rationalized the isocloso structures for these isomers. © The Royal Society of Chemistry 2016.

Chemical Communications

Hypoelectronic isomeric diiridaboranes [(Cp∗Ir)2B6H6]: The "rule-Breakers"(Cp∗ = η5-C5Me5)

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

Reaction of [Cp*CoCl]2 (Cp* = η5-C5Me5) with [LiBH4· THF] in toluene at -70 C, followed by thermolysis with 2-mercaptobenzothiazole (C7H5NS2) in boiling toluene led to the isolation of a range of cobaltaborane clusters, [(Cp*Co) 2B7H6OMe], 1; [(Cp*Co) 3B8H7R], 2a, b (2a: R = H; 2b: R = Me); [(Cp*Co)3B8H8S], 3 and [(Cp*Co)2B4H4RR′], 4a-d (4a: R, R′ = H; 4b: R = Me, R′ = H; 4c: R = H, R′ = Me and 4d: R, R′ = Me). In parallel to the formation of compounds 1-4, the reaction also yielded known [(Cp*Co)3B4H 4] in good yield. Compound 1 may be considered as 9-vertex hypoelectronic cluster with C1 symmetry, where cobalt atoms occupy the degree 5 vertices. All the dicobaltaboranes 4a-d contains two μ3-H protons and found to be very reactive. As a result, one of them (4a) when reacted with Fe2(CO)9 and sulfur powder yielded, almost immediately, [(Cp*Co)2B 4H5SFe3(CO)9], 5 and [(Cp *Co)2B3H3(μ-CO)Fe(CO) 3], 6. All the new compounds have been characterized in solution by mass, 1H, 11B, 13C NMR spectroscopy and elemental analysis. The structural types were unequivocally established by X-ray crystallographic analysis of compounds 1-6. Density functional theory (DFT) calculations on the model compounds 1′ and 2′ (1′, and 2′ are the Cp analog of 1, and 2a respectively, Cp = C5H 5) yield geometries in agreement with the structure determinations. The existence of large HOMO-LUMO gap of these molecules rationalizes the isocloso description for 2a. Bonding patterns in the structure have been analyzed on the grounds of DFT calculations. © 2013 Elsevier B.V. All rights reserved.

Hypoelectronic metallaboranes: Synthesis, structural characterization and electronic structures of metal-rich cobaltaboranes

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.

Organometallics

Reactivity of dirhodium analogues of octaborane-12 and decaborane-14 towards transition-metal moieties

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

Syntheses and structural characterization of supraicosahedral rhodaborane clusters are reported. Reaction of [(Cp*RhCl2)2], (Cp* = η5-C5Me5) with [LiBH 4·thf] followed by thermolysis with excess of [BH 3·thf] afforded 16-vertex closo-[(Cp*Rh) 3B12H12Rh{Cp*RhB4H 9}], 1, 15-vertex [(Cp*Rh)2B13H 13], 2, 12-vertex [(Cp*Rh)2B10H n(OH)m], (3a: n = 12, m = 0; 3b: n = 9, m = 1; 3c: n = 8, m = 2) and 10-vertex [(Cp*Rh)3B7H7], 4, and [(Cp*Rh)4B6H6], 5. Cluster 1 is the unprecedented 16-vertex cluster, consists of a sixteen-vertex {Rh 4B12} with an exo-polyhedral {RhB4} moiety. Cluster 2 is the first example of a carbon free 15-vertex supraicosahedral metallaborane, exhibits icosihexahedron geometry (26 triangular faces) with three degree-six vertices. Clusters 3a-c have 12-vertex isocloso geometry, different from that of icosahedral one. Clusters 4 and 5 are attributed to the 10-vertex isocloso geometry based on 10-vertex bicapped square antiprism structure. In addition, quantum-chemical calculations with DFT methods at the BP86 level of theory have been used to provide further insight into the electronic structure and stability of the optimized structures which are in satisfactory agreement with the structure determinations. 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 compounds 1-5. © 2013 American Chemical Society.

Journal	Journal of Cluster Science
ISSN	10407278
Open Access	No