A homologous series of regioselectively tetradeprotonated group 8 metallocenes: New inverse crown ring compounds synthesized via a mixed sodium-magnesium tris(diisopropylamide) synergic base

Andrikopoulos, P.C. and Armstrong, D.R. and Clegg, W. and Gilfillan, C.J. and Hevia, E. and Kennedy, A.R. and Mulvey, R.E. and O'Hara, C.T. and Parkinson, J.A. and Tooke, D.M. (2004) A homologous series of regioselectively tetradeprotonated group 8 metallocenes: New inverse crown ring compounds synthesized via a mixed sodium-magnesium tris(diisopropylamide) synergic base. Journal of the American Chemical Society, 126 (37). pp. 11612-11620. ISSN 0002-7863

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(C5H3)(2)}Na4Mg4(i-Pr2N)(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(C5H3)(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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