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

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