Issue 29, 2022

Cooperative B–H bond activation: dual site borane activation by redox active κ2-N,S-chelated complexes

Abstract

Cooperative dual site activation of boranes by redox-active 1,3-N,S-chelated ruthenium species, mer-[PR32-N,S-(L)}2Ru{κ1-S-(L)}], (mer-2a: R = Cy, mer-2b: R = Ph; L = NC7H4S2), generated from the aerial oxidation of borate complexes, [PR32-N,S-(L)}Ru{κ3-H,S,S′-BH2(L)2}] (transmer-1a: R = Cy, transmer-1b: R = Ph; L = NC7H4S2), has been investigated. Utilizing the rich electronic behaviour of these 1,3-N,S-chelated ruthenium species, we have established that a combination of redox-active ligands and metal–ligand cooperativity has a big influence on the multisite borane activation. For example, treatment of mer-2a–b with BH3·THF led to the isolation of fac-[PR3Ru{κ3-H,S,S′-(NH2BSBH2N)(S2C7H4)2}] (fac-3a: R = Cy and fac-3b: R = Ph) that captured boranes at both sites of the κ2-N,S-chelated ruthenacycles. The core structure of fac-3a and fac-3b consists of two five-membered ruthenacycles [RuBNCS] which are fused by one butterfly moiety [RuB2S]. Analogous fac-3c, [PPh3Ru{κ3-H,S,S′-(NH2BSBH2N)(SC5H4)2}], can also be synthesized from the reaction of BH3·THF with [PPh32-N,S-(SNC5H4)}{κ3-H,S,S′-BH2(SNH4C5)2}Ru], cisfac-1c. In stark contrast, when mer-2b was treated with BH2Mes (Mes = 2,4,6-trimethyl phenyl) it led to the formation of trans- and cis-bis(dihydroborate) complexes [{κ3-S,H,H-(NH2BMes)Ru(S2C7H4)}2], (trans-4 and cis-4). Both the complexes have two five-membered [Ru–(H)2–B–NCS] ruthenacycles with κ2-H–H coordination modes. Density functional theory (DFT) calculations suggest that the activation of boranes across the dual Ru–N site is more facile than the Ru–S one.

Graphical abstract: Cooperative B–H bond activation: dual site borane activation by redox active κ2-N,S-chelated complexes

Supplementary files

Article information

Article type
Edge Article
Submitted
12 Febr. 2022
Accepted
22 Jūn. 2022
First published
23 Jūn. 2022
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2022,13, 8567-8575

Cooperative B–H bond activation: dual site borane activation by redox active κ2-N,S-chelated complexes

M. Zafar, A. Ahmad, S. Saha, R. Ramalakshmi, T. Roisnel and S. Ghosh, Chem. Sci., 2022, 13, 8567 DOI: 10.1039/D2SC00907B

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