New findings in the chemistry of iron carbonyls: the previously unreported [H(4-n)Fe4(CO)12]n- (n = 1, 2) series of clusters, which fills the gap with ruthenium and osmium

Cristina Femoni; Maria Carmela Iapalucci; Giuliano Longoni; Stefano Zacchini; Salvatore Zarra

doi:10.1021/ic802015f

New findings in the chemistry of iron carbonyls: the previously unreported [H(4-n)Fe4(CO)12]n- (n = 1, 2) series of clusters, which fills the gap with ruthenium and osmium

Inorg Chem. 2009 Feb 16;48(4):1599-605. doi: 10.1021/ic802015f.

Authors

Cristina Femoni¹, Maria Carmela Iapalucci, Giuliano Longoni, Stefano Zacchini, Salvatore Zarra

Affiliation

¹ Dipartimento di Chimica Fisica e Inorganica, Università di Bologna, Viale Risorgimento 4, 40136 Bologna, Italy.

PMID: 19159238
DOI: 10.1021/ic802015f

Abstract

The new [HFe(4)(CO)(12)](3-) cluster anion has been obtained in high yields by reduction of [Fe(4)(CO)(13)](2-) or [HFe(3)(CO)(11)](-) with a 6 M methylalcoholic KOH solution under a nitrogen atmosphere and isolated with miscellaneous tetrasubstituted ammonium salts. The [NEt(4)](3)[HFe(4)(CO)(12)] salt has been characterized by IR, (1)H and (13)C NMR, electrospray ionization mass spectrometry, and X-ray studies. Investigation of its protonation reaction afforded spectroscopic proof for the existence of its unstable isomeric [HFe(4)(CO)(11)(CO-H)](2-) and [H(2)Fe(4)(CO)(12)](2-) conjugated acids. The latter is probably isostructural with the [H(2)Ru(4)(CO)(12)](2-) congener. The nature of the first protonation product as a [HFe(4)(CO)(11)(CO-H)](2-) adduct, involving an oxygen-bound proton, has been corroborated by the preparation and spectroscopic characterization of the corresponding [HFe(4)(CO)(11)(CO-Me)](2-) dianion. The above findings demonstrate that protonation of a CO-shielded polynuclear metal anion initially occurs on one oxygen atom and then the oxygen-bound proton migrates to the metal cage. Finally, [HFe(4)(CO)(12)](3-) and its [H(2)Fe(4)(CO)(12)](2-) conjugate acid fill the previously existing gap between the chemistry of iron carbonyls and ruthenium and osmium congeners.