Special Chemistry Seminar with Professor Sundargopal Ghosh (IIT–Madras)

About

Professor Sundargopal Ghosh

Indian Institute of Technology, Madras

"Planar Boron Rings as Next-Generation Ligands for Sandwich Complexes”

Abstract: The discovery of sandwich complexes with ferrocene, I shown in Chart 1, highlighted the fundamental role of cyclopentadienyl (Cp) ligands in sandwich complexes.¹ The tunability of Cp ligands has inspired chemists to explore isoelectronic planar main-group rings (P₅, As₅, Sb₅, Bi₅, Si₅ or B₅) as alternative ligand frameworks aiming to achieve greater electronic versatility. Notably, in 2002, the isolation of the fully inorganic metallocene, [Ti(P5)2]2- (II), marked the first 16e carbon-free sandwich complex.²In contrast, boron rings remained largely unexplored for decades due to the intrinsic electron deficiency of boron and its preference for polyhedral cluster geometries.^3-4 This perception was overturned by transition-metal templation strategies. Grimes first reported the pentaborane ring complex [(CpFe)B5H10], which was later extended to Ru and Ir analogues by Fehlner. Recently, we have synthesized the Os analogue (III) using a Cp-based metal precursor.⁵ Encouraged by this result, we attempted to access carbon-free sandwich complexes using various metal precursors, for example, [M2(μ-Cl)2(COD)2] (M = Ir, Rh), [M(PPh3)3Cl2] (M = Ru, Os), [Cp*Fe(dppe)Cl] and [Fe(dppe)Cl2]n; however,

these efforts were unsuccessful.^6-7 In one case, the use of a PPh3-based precursor led to the formation of a tetraborane [B4H8]2- ring stabilized by a monometallic Os template (IV).⁵ Remarkably, employing a COD-based Os-precursor afforded the 18e [Os(B5H10)2] (V), a true carbon-free analogue of ferrocene.⁸ The journey to synthesize these sandwich complexes will be discussed.

References:

T. J. Kealy and P. L. Pauson, Nature, 1951, 168, 1039−1040.

E. Urnėžius, W. W. Brennessel, C. J. Cramer, J. E. Ellis and P. v. R. Schleyer, Science, 2002, 295, 832–834.

K. Saha, D. K. Roy, R. D. Dewhurst, S. Ghosh and H. Braunschweig, Acc. Chem. Res., 2021, 54, 1260–1273.

S. Kar, S. Bairagi, G. Joshi, E. D. Jemmis, H. Himmel and S. Ghosh, Acc. Chem. Res., 2024, 57, 2901–2914.

S. Shyamal, D. Chatterjee, K. Kar and S. Ghosh, Inorg. Chem., 2024, 63, 21838–21848.

K. Bakthavachalam, K. Yuvaraj, M. Zafar and S. Ghosh, Chem. Eur. J., 2016, 22, 17291–17297.

F. Assanar, S. Gayen, D. K. Patel, T. Pradeep and S. Ghosh, Chem. Sci., 2026, 17, 3129–3140.

S. Mohapatra, S. Saha, G. Joshi, U. Gupta, D. K. Patel, E. D. Jemmis and S. Ghosh, Science, 2026, 392, 411.

Bio: Prof. Sundargopal Ghosh received his B.Sc. and M.Sc. degrees from the University of Calcutta and obtained his Ph.D. from the Indian Institute of Technology (IIT) Bombay in 1998. He subsequently carried out postdoctoral research with Prof. Thomas P. Fehlner at the University of Notre Dame, USA. In 2005, he joined the Department of Chemistry at the Indian Institute of Technology Madras, where he is currently a Professor.

Prof. Ghosh's research focuses on transition metal–boron chemistry, with particular emphasis on the synthesis, structural diversity, electronic structure, chemical bonding, and reactivity of boron-containing organometallic compounds. His work has significantly advanced the understanding of boron-rich molecular architectures and their applications in catalysis and small-molecule activation.

He has authored more than 320 research articles in leading international peer- reviewed journals. In recognition of his scientific contributions, he has received several prestigious honors, including the CRSI Bronze Medal (2013), the IIT Madras Institute Research and Development Award (2014), and election as Fellow of the Indian Academy of Sciences (FASc, 2017), the National Academy of Sciences, India (FNASc, 2017), and the Indian National Science Academy (INSA, 2025).

Prof. Ghosh has supervised 39 Ph.D. and 45 MSc students, many of whom have established successful careers in academia and research institutions worldwide, reflecting his enduring commitment to excellence in research and mentorship.