DFT calculations were performed to gain insight of possible dihydrogen uptake by the electron-deficient metallaborane (CpRe)2B 6H6 (A). Results first revealed a possible H-H insertion in A, giving rise to the formation of (CpRe)2B6H 8 isomers accompanied with an opening of B-B bonds in the B 6H6 ring and Re-B bonds breaking. A two-step pathway was calculated to be the lowest-energy route with the highest activation barrier at ca. 25 kcal/mol at the B3LYP/6-311G++(d,p) level of theory. Addition of a second dihydrogen molecule to A is also found possible leading to the hydrogen-saturated species (CpRe)2B6H10. © 2012 Elsevier Ltd. All rights reserved.

Sundargopal Ghosh

Department Of Chemistry

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

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

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

Polyhedron

Ruthenaborane clusters have been modelled by performing density functional theory calculations using the B3LYP functional. The calculations gain insights into hydrogen storage and the H-H bond activation by ruthenaboranes. To study the nature of the chemical bond of H2 molecules attached to ruthenaboranes, we carried out structural optimizations for different ruthenaborane clusters and determined transition state structures for their hydrogenation addition/elimination reactions. Calculations of the reaction pathways yielded different transition-state structures involving molecular hydrogen bonded to the cluster or formation of metal hydrides. The H-H bond of H2 seems to be activated by the ruthenaborane clusters as activation energies of 24-42 kcal/mol were calculated for the H2 addition reaction. The calculated Gibbs free energy for the H2 addition reaction is 14-27 kcal/mol. The calculated activation energies and the molecular structures of the [(C5Me5)Ru2B 10H16], [(C5Me5)Ru2B 8H14] and [(C5Me5)Ru 2B8H12] clusters with different degree of hydrogenation are compared. The mechanisms of the H2 addition and elimination reactions of the studied clusters suggest that they might be useful as hydrogen storage materials due to their ability to activate the H-H bond. They also serve as an example of the ability of hypoelectronic metallaboranes to reversibly or irreversibly bind hydrogen. © 2014 Elsevier B.V. All rights reserved.

Fulltext

Journal of Organometallic Chemistry

Addition and elimination reactions of H2 in ruthenaborane clusters: A computational study

Molecular metallaboranes, which feature complexes with M-B rather than M-C bonds, constitute a class of compounds which has revealed new possibilities for the way metal and borane fragments interact to generate novel structures, demonstrating an important role for the transition metal in the structural arrangement. Early transition-metal dimetallaboranes in particular adopt deltahedra with the same total connectivities as the borane anions or late transition-metal metallaboranes but with flattened geometries rather than spherical shapes. They are characterised by high metal coordination numbers, M-M cross-cluster distances within the single bond range, and formal (apparent) cluster electron counts three skeletal electron pairs short of that required for a canonical structure of the same nuclearity. A selection of these boron-rich dimetallaboranes is theoretically investigated and compared to illustrate the role of the transition metal in their cluster bonding. © 2012 Elsevier Masson SAS. All rights reserved.

Solid State Sciences

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Journal	Polyhedron
ISSN	02775387
Open Access	No