Cationic organoiron mixed-sandwich hydrazine complexes: Reactivity toward aldehydes, ketones, β-diketones and dioxomolybdenum complexes

This review covers comprehensively the authors work during the present decade based on the chemistry of ionic organometallic hydrazines formulated as [(eta(5)-Cp')Fe(eta(6)-Ar-NHNH2)]+PF6- (Cp'=C5H5, C5Me5; Ar = aryl), that could be considered as a new generation of hydrazines owing to the changes provoked by the coordination of the 12-electron Cp'Fe+ fragment both in the electronic properties of the aromatic ring and in the hydrazine group. The reactivity of this new class of hydrazine is obviously centered, as in the classic Fischer's organohydrazines, Ar-NHNH2, on the -NHNH2 functional unit which is able to react with alclehydes. RCH(=O) (R = alkyl, aryl, ferrocenyl (Fc)) and ketones, RR'C=O (R = alkyl, aryl: R'=alkyl, aryl, Fc), to afford ionic organometallic hydrazones. Likewise, the mixed-sandwich hydrazine precursors react with beta-diketones Me-C(=O)-CH2-C(=O)-Me to afford ionic organometallic pyrazoles, and with cis-dioxo-molybdenum complexes, e.g. [MoO2(S2CNEt2)(2)], to afford ionic organometallic mono-organodiazenido complexes in which the two metal centers are connected by a mu,eta(6):eta(1)-aryldiazenido bridge. While some ionic hydrazones exhibit NLO properties, the ionic organodiazenido hybrid complexes exhibit charge-transfer features. (C) 2009 Elsevier B.V. All rights reserved.