Dinitrogen Reduction Chemistry with Scandium Provides a Complex with Two Side-on (N=N)2− Ligands Bound to One Metal: (C5Me5)Sc[(µ-η2:η2-N2)Sc(C5Me5)2]2

Abstract

Although there are few reduced dinitrogen complexes of scandium, this metal has revealed a new structural type in reductive dinitrogen chemistry by reduction of bis(pentamethylcyclopentadienyl) scandium halides under N2. Reduction of Cp*2ScI (Cp* = C5Me5) with potassium graphite (KC8) under dinitrogen generates the dark blue paramagnetic complex (Cp*2Sc)2(µ-η1:η1-N2), 1. This end-on bridging (N=N)2− complex is a diradical with a magnetic moment of 2.8 µB. Upon further reduction of 1 with KC8, the orange diamagnetic trimetallic complex Cp*Sc[(µ-η2:η2-N2)ScCp*2]2, 2, is obtained. This complex has an unprecedented structure in which two side-on bridging (N=N)2− ligands are bound to the central (Cp*Sc)2+ moiety. Complex 2 can also be obtained directly from reduction of Cp*2ScI or a mixture of Cp*2ScCl and Cp*2ScCl(THF) with KC8. The reaction of Cp*2ScI with KC8 in the presence of 18-crown-6 or 2.2.2-cryptand affords 2 along with small amounts of Cp*2Sc(µ-η2:η2-N2)ScCp*I(THF), 3, which is green a room temperature and purple at low temperature and displays a mixture of side-on and end-on bridging isomers in the crystal structure collected at −180 °C. Density functional theory (DFT) calculations are consistent with a triplet ground state for the end-on complex 1 and singlet ground states for the side-on complexes 2 and 3.

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Article information

Article type
Edge Article
Submitted
17 Jun 2024
Accepted
29 Aug 2024
First published
30 Aug 2024
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., 2024, Accepted Manuscript

Dinitrogen Reduction Chemistry with Scandium Provides a Complex with Two Side-on (N=N)2− Ligands Bound to One Metal: (C5Me5)Sc[(µ-η2:η2-N2)Sc(C5Me5)2]2

J. D. Queen, A. Rajabi, Q. E. Goudzwaard, Q. Yuan, D. K. Nguyen, J. W. Ziller, F. Furche, Z. Xi and W. J. Evans, Chem. Sci., 2024, Accepted Manuscript , DOI: 10.1039/D4SC03977G

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