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Rare-earth metalation of calix[4]pyrrole/calix[4]arene free of alkali-metal companions

journal contribution
posted on 2023-05-17, 12:28 authored by Deacon, GB, Michael GardinerMichael Gardiner, Junk, PC, Townley, JP, Wang, J

The redox transmetalation/protolysis (RTP) reactions of ytterbium or neodymium metal with calix[4]H4 (5,11,17,23-tetra-tert-butylcalix[4]arene-25,26,27,28-tetrol) in the presence of bis(pentafluorophenyl)mercury under ultrasonication yielded [LnIII(calix[4]H)(thf)]2 (1, Ln = Yb; 2, Ln = Nd). The characterization of both 1 and 2, including an X-ray single-crystal structural determination for 2, suggests triple deprotonation of the macrocyclic ligand on metalation. The related RTP reaction of H4N4Et8 (meso-octaethylcalix[4]pyrrole) with ytterbium metal and Hg(C6F5)2 at ambient temperature, however, resulted in quadruple deprotonation and afforded the ytterbium(II) calix[4]pyrrolide complex [Yb2(N4Et8)(thf)4] (3) in good yield. Subsequent oxidation of 3 by dioxygen generated the novel tetranuclear ytterbium(III) complex [Yb4(μ-O)2(N4Et8)2(thf)2] (4). The structures of the ytterbium(II) complex 3 and the ytterbium(III) complex 4 incorporate endo (3) and endo/exo (4) pyrrolide sandwich and half-sandwich units, respectively, with metal centers η1 bound by nitrogen and η5 bonded by pyrrolide rings. The RTP reaction of lanthanum metal using diphenylmercury in place of bis(pentafluorophenyl)mercury gave the triply deprotonated and N-confused pyrrolide (with an alkyl substituent of one pyrrolide ring migrated to a β-position) macrocyclic complex [La2(HN3N'Et8)2] (5). The triple deprotonation of the macrocyclic ligand H4N4Et8 was also achieved through its reaction with 3 molar equiv of potassium metal, giving colorless crystals of [{K3(HN4Et8)(thf)(PhMe)2}n] (6). However, an attempt to isolate the corresponding partially deprotonated calix[4]pyrrolide ytterbium(III) complex through the metathesis reaction of potassium precursor 6 with ytterbium triiodide was unsuccessful.


History

Publication title

Organometallics

Volume

31

Issue

10

Pagination

3857-3864

ISSN

0276-7333

Department/School

School of Natural Sciences

Publisher

American Chemical Society

Place of publication

Washington

Rights statement

Copyright 2012 American Chemical Society

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the chemical sciences

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