An N‐Heterocyclic Germylene and Stannylene with a 1,1’‐Ferrocenylene Backbone and Dimesitylboryl N‐Substituents

The diaminoferrocene derivative fc[NH(BMes2)]2 (1H2; fc = 1,1’‐ferrocenylene, Mes = mesityl) was prepared from fc(NH2)2 and Mes2BCl and used for the preparation of the N‐heterocyclic tetrylenes fc{[N(BMes2)]2E} (1E, E = Ge, Sn) via the sodium amide fc[NNa(BMes2)]2 (1Na2), which was obtained from 1H2 and NaN(SiMe3)2. 1H2 is inert towards LiN(SiMe3)2 or nBuLi. Its reaction with nBuLi in the presence of TMEDA afforded the TMEDA‐coordinated lithium amide 1Li2(TMEDA)2. Crystallisation of 1Na2 from THF furnished the adduct 1Na2(THF)3. The reaction of 1Na2 with Me3SiCl afforded 1(SiMe3)2. Attempts to obtain the thiourea fc{[N(BMes2)]2C=S} (1C=S) from 1Na2 and Cl2C=S were not successful. 1C=S is accessible from fc(NH3)Cl2, which is transformed to fc[(NH)2C=S] (2) by reaction with Cl2C=S and NEt3 (4 equiv.), followed by conversion of 2 to fc{[N(SiMe3)]2C=S} (3) with Me3SiCl and NEt3 (2 equiv.) and subsequent reaction of 3 with Mes2BCl. All new compounds except 1Na2 and 2 were structurally characterised by single‐crystal X‐ray diffraction. The N‐boryl substituents of 1E compete efficiently with the EII atom for nitrogen π‐donation, causing comparatively long EII–N bonds and small EII bond angles. 1C=S contains a four‐membered BNCS ring due to intramolecular adduct formation involving the Lewis basic S atom and a Lewis acidic B atom.