The condensation of 1,1′-diaminoferrocene (1) with a range of chloroformamidinium salts [(R′RN) 2 CCl]X (2) afforded the corresponding bis(guanidines) [Fe{(η 5 -C 5 H 4 )−NC(NRR′) 2 } 2 ] (3; five examples). The two guanidine units present in 3 are able to chelate a proton or a water molecule. The structures of 3 and of the corresponding hydrates were determined by single-crystal X-ray diffraction. Cyclic voltammetry revealed that the ferrocene moiety of 3 is exceptionally electron rich, with E 1/2 values down to −0.90 V vs the ferrocenium/ ferrocene couple. According to the results of DFT calculations, these bis-(guanidines) are superbases with proton affinities considerably higher than that of the classic "Proton Sponge" 1,8-bis(dimethylamino)naphthalene. Furthermore, they are able to act as tridentate ligands, giving rise to Fe→M dative bonds, as is shown by chelates of the type [PdCl(3-κFe,κ 2 N)] + , which were obtained by reaction of 3 with [PdCl 2 (MeCN) 2 ]. The unusual N,Fe,N-chelating mode leads to exceptionally short Fe−Pd bonds (ca. 2.69 Å) and causes an enormous coordination-induced anodic shift of the half-wave potential of ca. 0.6 V.

Two homoleptic copper(I) complexes of the bidentate isocyanide 1,1′‐diisocyanoferrocene (1) were prepared and structurally characterised. The dications present in [Cu2(μ‐1)3][PF6]2 exhibit a paddle‐wheel‐like structure with trigonal‐planar CuI. These dications are connected in a chain‐like fashion by bridging ligands 1 in the coordination polymer [{Cu2(μ‐1)3}(μ‐1)]n(OTf)2n, which contains tetracoordinate CuI in a distorted tetrahedral coordination environment. The hexafluorophosphate analogue of the latter compound was also prepared.