We describe ferrocene-based N-heterocyclic germylenes and stannylenes of the type [Fe{(η -C H )NR} E:] (1 RE; E=Ge, Sn; R=neopentyl (Np), mesityl (Mes), trimethylsilyl (TMS)), which constitute the first examples of redox-functionalised N-heterocyclic tetrylenes (NHTs). These compounds are thermally stable and were structurally characterised by means of X-ray diffraction studies, except for the neopentyl-substituted stannylene 1 NpSn, the decomposition of which afforded the aminoiminoferrocene [fc(NHCH tBu)(N=CHtBu)] (2) and the spiro tin(IV) compound (1 Np) Sn (3). DFT calculations show that the HOMO of the NHTs of our study is localised on the ferrocenylene backbone. A one-electron oxidation process affords ions of the type 1 RE . In contrast to the NHC system 1 RC, the localised ferrocenium-type nature of the oxidised form does not compromise the fundamental tetrylene character of 1 RE .

The N‐heterocyclic silylene [{Fe(η5‐C5H4‐NDipp)2}Si] (1DippSi, Dipp=2,6‐diisopropylphenyl) shows an excellent combination of pronounced thermal stability and high reactivity towards small molecules. It reacts readily with CO2 and N2O, respectively affording (1DippSiO2)2C and (1DippSiO)2 as follow‐up products of the silanone 1DippSiO. Its reactions with H2O, NH3, and FcPH2 (Fc=ferrocenyl) furnish the respective oxidative addition products 1DippSi(H)X (X=OH, NH2, PHFc). Its reaction with H3BNH3 unexpectedly results in B−H, instead of N−H, bond activation, affording 1DippSi(H)(BH2NH3). DFT results suggest that dramatically different mechanisms are operative for these H−X insertions.

Three new N-heterocyclic germylenes of the type [Fe{(η 5 -C 5 H 4 )NR} 2 Ge] (1RGe) containing particularly bulky alkyl [R = 2-adamantyl (Ad), 1,1,2,2-tetramethylpropyl (Pr*)] or aryl substituents [R = 2,6-diisopropylphenyl (Dipp)] were prepared and structurally characterized, in two cases (R = Ad, Dipp), by singlecrystal X-ray diffraction. Together with the previously described homologues with R = trimethylsilyl (TMS), tert-butyl (tBu), and mesityl (Mes) their oxidative addition reactions with S 8 and Se 8 were studied, which afforded compounds of the type [1RGe(μ-E)] 2 (E = S, Se). The low solubility of most of these products severely hampered * Prof. Dr. U. Siemeling

The diaminoferrocene derivatives [Fe{(η5‐C5H4)NHR}2] (1H2, a: R = SiMe2tBu, b: R = CMe2tBu, c: R = C6H3‐2,6‐iPr2) were converted into the lithium amides 1aLi2 – 1cLi2 by treatment with nBuLi. The reaction of these amides with AlI3 furnished 1aAlI – 1cAlI. The reduction of 1aAlI with KC8 afforded 1aAl–Al1a, which is a new stable dialumane(4) with exclusively tricoordinate Al atoms and only the second example so far of a tetraamino‐substituted compound of this kind. 1bH2, 1cH2, 1aLi2, [1c{Li(THF)3}2], [1aAlI(OEt2)], 1cAlI, 1aAl–Al1a·½Et2O and 1aAl–Al1a·½C7H8 were structurally characterized by single‐crystal X‐ray diffraction.

The reaction of a stable silylene with Ph2CCO and OCCCO respectively afforded the first silaallene oxide and a silylketene, whose hydrolysis furnished a stable methyleneketene.