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

Deacon, Glen B., Gardiner, Michael G., Junk, Peter C., Townley, Josh P., and Wang, Jun (2012) Rare-earth metalation of calix[4]pyrrole/calix[4]arene free of alkali-metal companions. Organometallics, 31 (10). pp. 3857-3864.

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View at Publisher Website: http://dx.doi.org/10.1021/om2011134
 
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Abstract

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.

Item ID: 29650
Item Type: Article (Refereed Research - C1)
Keywords: rich lanthanide clusters; calix-tetrapyrrole ring; meso-octaalkylporphyrinogen; porphyrinogen complexes; aryloxo-lanthanoids; molecular-structure; crystal-structures; redox chemistry; ligands; reactivity
ISSN: 1520-6041
Funders: Australian Research Council (ARC), Education Bureau of Hubei Province, People's Republic of China
Date Deposited: 02 Oct 2013 10:34
FoR Codes: 03 CHEMICAL SCIENCES > 0302 Inorganic Chemistry > 030202 f-Block Chemistry @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970103 Expanding Knowledge in the Chemical Sciences @ 100%
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