title: 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.
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.
authors.affiliation: Dipartimento di Chimica Fisica e Inorganica, Università di Bologna, Viale Risorgimento 4, 40136 Bologna, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Femoni
authors.forename: Maria Carmela
authors.initials: MC
authors.lastname: Iapalucci
authors.forename: Giuliano
authors.initials: G
authors.lastname: Longoni
authors.forename: Stefano
authors.initials: S
authors.lastname: Zacchini
authors.forename: Salvatore
authors.initials: S
authors.lastname: Zarra