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

Glen Berenger Deacon, Michael Guy Gardiner, Peter Courtney Junk, Josh Phillip Townley, Jun Wang

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21 Citations (Scopus)

Abstract

The redox transmetalation/protolysis (RTP) reactions of ytterbium or neodymium metal with calix[4]H-4 (5,11,17,23-tetra-tert-butylcalix[4]arene-25,26,27,28-tetrol) in the presence of bis(pentafluorophenyl)mercury under ultrasonication yielded [Ln(III)(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 [Yb-2(N4Et8)(thf)(4)] (3) in good yield. Subsequent oxidation of 3 by dioxygen generated the novel tetranuclear ytterbium(III) complex [Yb-4(mu-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 eta(1) bound by nitrogen and eta(5) 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 beta-position) macrocyclic complex [La-2(HN3N Et-8)(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 [ K-3(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.
Original languageEnglish
Pages (from-to)3857 - 3864
Number of pages8
JournalOrganometallics
Volume31
Issue number10
DOIs
Publication statusPublished - 2012

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