Andrikopoulos PC, Armstrong DR, Clegg W, Gilfillan CJ, Hevia E, Kennedy AR, Mulvey RE, O'Hara CT, Parkinson JA, Tooke DM. A Homologous Series of Regioselectively Tetradeprotonated Group 8 Metallocenes: New Inverse Crown Ring Compounds Synthesized via a Mixed Sodium−Magnesium Tris(diisopropylamide) Synergic Base.
J Am Chem Soc 2004;
126:11612-20. [PMID:
15366908 DOI:
10.1021/ja0472230]
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Abstract
Subjecting ferrocene, ruthenocene, or osmocene to the synergic amide base sodium-magnesium tris(diisopropylamido) affords a unique homologous series of metallocene derivatives of general formula [(M(C(5)H(3))(2))Na(4)Mg(4)(i-Pr(2)N)(8)] (where M = Fe (1), Ru (2), or Os (3)). X-ray crystallographic studies of 1-3 reveal a common molecular "inverse crown" structure comprising a 16-membered [(NaNMgN)(4)](4+) "host" ring and a metallocenetetraide [M(C(5)H(3))(2)](4-) "guest" core, the cleaved protons of which are lost selectively from the 1, 1', 3, and 3'-positions. Variable-temperature NMR spectroscopic studies indicate that 1, 2, and 3 each exist as two distinct interconverting conformers in arene solution, the rates of exchange of which have been calculated using coalescence and EXSY NMR measurements.
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