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Impact of the 2-R-Allyl and Chloride Ligands on the Cathodic Paths of [Mo(η3-2-R-allyl)(α-diimine)(CO)2Cl] (R = H, CH3; α-diimine = 6,6ʹdimethyl-2,2ʹ-bipyridine and bis(p-tolylimino)acenaphthene)

Taylor, J. O., Culpeck, R., Chippindale, A., Calhorda, M. J. and Hartl, F. (2021) Impact of the 2-R-Allyl and Chloride Ligands on the Cathodic Paths of [Mo(η3-2-R-allyl)(α-diimine)(CO)2Cl] (R = H, CH3; α-diimine = 6,6ʹdimethyl-2,2ʹ-bipyridine and bis(p-tolylimino)acenaphthene). Organometallics. ISSN 1520-6041 (In Press)

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Abstract/Summary

ABSTRACT: A new series of formally Mo(II) complexes, [Mo(η3-2-R-allyl)(6,6ʹ-dmbipy)(CO)2Cl] (6,6ʹ-dmbipy = 6,6ʹ-dimethyl-2,2ʹbipyridine; 2-R-allyl = allyl for R = H, 2-methallyl for R = CH3) and [Mo(η3-2-methallyl)(pTol-bian)(CO)2Cl] (pTol-bian = bis(ptolylimino)acenaphthene) belong, in this rare case, to the same structural type. The impact of the anionic π-donor ligand X (Cl‒ vs. NCS‒) and the 2-R-allyl substituents on the cathodic behavior was explored. Both ligands play a significant role at all stages of the reduction path. While 2e– reduced [Mo(η3-allyl)(6,6ʹ-dmbipy)(CO)2]– is inert when ECE-generated from [Mo(η3-allyl)(6,6ʹdmbipy)(CO)2(NCS)], the Cl– ligand promotes Mo‒Mo dimerization by facilitating the nucleophilic attack of [Mo(η3-allyl)(6,6ʹdmbipy)(CO)2]– at the parent complex at ambient temperature. The replacement of the allyl ligand with 2-methallyl has a similar effect. The Cl‒/2-methallyl ligand assembly destabilizes even primary radical anions of the complex containing the strongly πaccepting pTol-bian ligand. Under argon, the cathodic paths of [Mo(η3-2-R-allyl)(6,6ʹ-dmbipy)(CO)2Cl] terminate at ambient temperature with 5-coordinate [Mo(6,6ʹ-dmbipy)(CO)3]2‒ instead of [Mo(η3-2-R-allyl)(6,6ʹ-dmbipy)(CO)2]– that is stabilized in chilled electrolyte. [Mo(η3-allyl)(6,6'-dmbipy)(CO)2]– catalyses CO2 reduction only when generated at the second cathodic wave of the parent complex while [Mo(η3-2-methallyl)(6,6ʹ-dmbipy)(CO)2]– is already moderately active at the first cathodic wave. This behavior is fully consistent with absent dimerization under argon on the cyclovoltammetric time scale. The electrocatalytic generation of CO and formate is hampered by irreversible formation of anionic tricarbonyl complexes replacing reactive [Mo(η3-2methallyl)(6,6ʹ-dmbipy)(CO)2]2 along the cathodic route.

Item Type:Article
Refereed:Yes
Divisions:Life Sciences > School of Chemistry, Food and Pharmacy > Department of Chemistry
ID Code:97654
Publisher:American Chemical Society

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