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Issue 11, 2019
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Bimetallic nickel-lutetium complexes: tuning the properties and catalytic hydrogenation activity of the Ni site by varying the Lu coordination environment

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Abstract

We present three heterobimetallic complexes containing an isostructural nickel center and a lutetium ion in varying coordination environments. The bidentate iPr2PCH2NHPh and nonadentate (iPr2PCH2NHAr)3tacn ligands were used to prepare the Lu metalloligands, Lu(iPr2PCH2NPh)3 (1) and Lu{(iPr2PCH2NAr)3tacn} (2), respectively. Reaction of Ni(COD)2 (where COD is 1,5-cyclooctadiene) and 1 afforded NiLu(iPr2PCH2NPh)3 (3), with a Lu coordination number (CN) of 4 and a Ni–Lu distance, d(Ni–Lu), of 2.4644(2) Å. Complex 3 can further bind THF to form 3-THF, increasing both the Lu CN to 5 and d(Ni–Lu) to 2.5989(4) Å. On the other hand, incorporation of Ni(0) into 2 provides NiLu{(iPr2PCH2NAr)3tacn} (4), in which the Lu coordination environment is more saturated (CN = 6), and the d(Ni–Lu) is substantially elongated at 2.9771(5) Å. Cyclic voltammetry of the three Ni–Lu complexes shows an overall ∼410 mV shift in the Ni(0/I) redox couple, suggesting tunability of the Ni electronics across the series. Computational studies reveal polarized bonding interactions between the Ni 3dz2 (major) and the Lu 5dz2 (minor) orbitals, where the percentage of Lu character increases in the order: 4 (6.0% Lu 5dz2) < 3-THF (8.5%) < 3 (9.3%). All three Ni–Lu complexes bind H2 at low temperatures (−30 to −80 °C) and are competent catalysts for styrene hydrogenation. Complex 3 outperforms 4 with a four-fold faster rate. Additionally, adding increasing THF equivalents to 3, which would favor build-up of 3-THF, decreases the rate. We propose that altering the coordination sphere of the Lu support can influence the resulting properties and catalytic activity of the active Ni(0) metal center.

Graphical abstract: Bimetallic nickel-lutetium complexes: tuning the properties and catalytic hydrogenation activity of the Ni site by varying the Lu coordination environment

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Supplementary files

Article information


Submitted
23 Oct 2018
Accepted
03 Feb 2019
First published
04 Feb 2019

This article is Open Access
All publication charges for this article have been paid for by the Royal Society of Chemistry

Chem. Sci., 2019,10, 3375-3384
Article type
Edge Article

Bimetallic nickel-lutetium complexes: tuning the properties and catalytic hydrogenation activity of the Ni site by varying the Lu coordination environment

B. L. Ramirez, P. Sharma, R. J. Eisenhart, L. Gagliardi and C. C. Lu, Chem. Sci., 2019, 10, 3375 DOI: 10.1039/C8SC04712J

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