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A tridentate and dianionic N-heterocyclic olefin (NHO) with two unsymmetrically-tethered aryloxide sidearms on bismuth: a fortuitous followed by systematic discovery.

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Title: A tridentate and dianionic N-heterocyclic olefin (NHO) with two unsymmetrically-tethered aryloxide sidearms on bismuth: a fortuitous followed by systematic discovery.
Authors: Goswami, Santu1 (AUTHOR), Sarkar, Subham1,2 (AUTHOR), Guha Roy, Anisha1 (AUTHOR), Mallick, Dibyendu2 (AUTHOR) dibyendu.chem@presiuniv.ac.in, Mukherjee, Debabrata1 (AUTHOR) d.mukherjee@iiserkol.ac.in
Source: Dalton Transactions: An International Journal of Inorganic Chemistry. 5/28/2025, Vol. 54 Issue 20, p8142-8151. 10p.
Subjects: Bismuth compounds, Ligands (Chemistry), Heterocyclic compounds, Chemical reactions, Ab-initio calculations, Imidazoles, Aryl group
Abstract: Herein, we report our previously developed bifunctional imidaozlium-phenol LH2Br ([HO-4,6-tBu2-C6H2-2-CH2{CH(NCH = CHNAr)}]Br; Ar = Dipp = 2,6-iPr2-C6H3), leading to three distinct outcomes with bismuth by simply altering the relative ratios of the reacting components. Treating LH2Br and Bi(HMDS)3 (HMDS = N(SiMe3)2) in a 1 : 1 ratio gives the NHC-Bi complex [(L)BiBr(HMDS)] (1). In contrast, LH2Br , Bi(HMDS)3, and KHMDS in a 2 : 1 : 1 ratio serendipitously result in an unprecedented NHO-Bi complex [(DippNHO2ArO)BiBr] (2), featuring a novel dianoinic and tridentate NHO ligand with two unsymmetric aryloxide sidearms. A tri-acidic imidazolium salt L′H3I ([HO-4,6-tBu2-C6H2-2-CH2{C(HO-4,6-tBu2-C6H2-2-CH2)(NCH = CHNMe)}]I) is synthesized independently as a potential precursor to such an NHO framework, and the corresponding NHO-BiI complex [(MeNHO2ArO)Bi(μ-I)]2 (32) is made as proof of concept. Lastly, treating LH2Br and Bi(HMDS)3 in a 2 : 1 ratio also unexpectedly leads to an 'abnormal' NHC-Bi complex [(aL)BiBr2(DippImd)] (4; DippImd = Dipp-imidazole). The multi-component and essentially multi-step reactions leading to 2 and 4 are challenging to fully elucidate mechanistically. Still, control experiments indicate 1 as a possible intermediate in both cases. Based on these results and prior insights into LH2Br and an intermediate LH , plausible routes for both 2 and 4 are hypothesized. DFT calculations are also performed to analyze the bonding in 2 and 32 and to justify an NHC to aNHC isomerization towards the formation of 4. [ABSTRACT FROM AUTHOR]
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Abstract:Herein, we report our previously developed bifunctional imidaozlium-phenol LH2Br ([HO-4,6-tBu2-C6H2-2-CH2{CH(NCH = CHNAr)}]Br; Ar = Dipp = 2,6-iPr2-C6H3), leading to three distinct outcomes with bismuth by simply altering the relative ratios of the reacting components. Treating LH2Br and Bi(HMDS)3 (HMDS = N(SiMe3)2) in a 1 : 1 ratio gives the NHC-Bi complex [(L)BiBr(HMDS)] (1). In contrast, LH2Br , Bi(HMDS)3, and KHMDS in a 2 : 1 : 1 ratio serendipitously result in an unprecedented NHO-Bi complex [(DippNHO2ArO)BiBr] (2), featuring a novel dianoinic and tridentate NHO ligand with two unsymmetric aryloxide sidearms. A tri-acidic imidazolium salt L′H3I ([HO-4,6-tBu2-C6H2-2-CH2{C(HO-4,6-tBu2-C6H2-2-CH2)(NCH = CHNMe)}]I) is synthesized independently as a potential precursor to such an NHO framework, and the corresponding NHO-BiI complex [(MeNHO2ArO)Bi(μ-I)]2 (32) is made as proof of concept. Lastly, treating LH2Br and Bi(HMDS)3 in a 2 : 1 ratio also unexpectedly leads to an 'abnormal' NHC-Bi complex [(aL)BiBr2(DippImd)] (4; DippImd = Dipp-imidazole). The multi-component and essentially multi-step reactions leading to 2 and 4 are challenging to fully elucidate mechanistically. Still, control experiments indicate 1 as a possible intermediate in both cases. Based on these results and prior insights into LH2Br and an intermediate LH , plausible routes for both 2 and 4 are hypothesized. DFT calculations are also performed to analyze the bonding in 2 and 32 and to justify an NHC to aNHC isomerization towards the formation of 4. [ABSTRACT FROM AUTHOR]
ISSN:14779226
DOI:10.1039/d5dt00706b