We report a new K⊂[Fe4Co4] cyanide box: a true soluble model of the photomagnetic FeCo Prussian blue analogues, which also shows photo-switchable SMM properties and remarkable redox versatility.

The synthesis, structure, and full characterization of a redox-switchable germylene based on a [3]ferrocenophane ligand arrangement, [Fc(NMes) Ge] (4), is presented. The mesityl (Mes)-substituted title compound is readily available from Fc(NHMes) (2) and Ge{N(SiMe ) } , or from the dilithiated, highly air- and moisture-sensitive compound Fc(NLiMes) ⋅3 Et O (3) and GeCl . Cyclic voltammetry studies are provided for 4, confirming the above-mentioned view of a redox-switchable germylene metalloligand. Although several 1:1 Rh and Ir complexes of 4 (5-7) are cleanly formed in solution, all attempts to isolate them in pure form failed due to stability problems. However, crystalline solids of [Mo(κ Ge-4) (CO) ] (8) and [W(κ Ge-4) (CO) ] (9) were isolated and fully characterized by common spectroscopic techniques (8 by X-ray diffraction). DFT calculations were performed on a series of model compounds to elucidate a conceivable interplay between the metal atoms in neutral and cationic bimetallic complexes of the type [Rh(κ E-qE)(CO) Cl] (qE=[Fc(NPh) E] with E=C, Si, Ge). The bonding characteristics of the coordinated Fc-based metalloligands (qE/qE ) are strongly affected upon in silico oxidation of the calculated complexes. The calculated Tolman electronic parameter (TEP) significantly increases by approximately 20 cm (E=C) to 25 cm (E=Si, Ge) upon oxidation. The change in the ligand-donating abilities upon oxidation can mainly be attributed to Coulombic effects, whereas an orbital-based interaction appears to have only a minor influence.

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The synthesis and characterization of two bulky ferrocenyl-functionalized amidinates and their lithium, potassium, rhodium­(I), and iridium­(I) complexes are reported. The ferrocenyl mono­(amidine) [Fc­{C­(NDipp)­(NHDipp)}] (1) (Fc = ferrocenyl; Dipp = 2,6-diisopropylphenyl) and its potassium complex [Fc­{C­(NDipp)2K}·3THF] (2) as well as the 1,1′-ferrocendiyl-bridged bis­(amidinate) [fc­{C­(NMes)2Li}2·3THF] (3) (fc = ferrocene-1,1′-diyl; Mes = mesityl) were synthesized. Salt metathesis reactions with the metal precursors [Rh­(cod)­Cl]2 (cod = 1,5-cyclooctadiene) and [Ir­(cod)­Cl]2 gave the rhodium­(I) and iridium­(I) complexes [Fc­{C­(NDipp)2Rh­(cod)}] (4), [fc­{C­(NMes)2Rh­(cod)}2] (5), and [fc­{C­(NMes)2Ir­(cod)}2] (6), as well as the ortho-metalated compound [(Cp)­Fe­(C5H3)­{C­(NHDipp)­(NDipp)­Ir­(cod)}] (7). As complex 7 showed an ortho-metalation on the ferrocene backbone, we investigated this reaction in more detail. It was found that the rhodium­(I) complexes 4 and 5 also undergo ortho-metalation upon treatment with carbon monoxide (CO). After the carbonylation, the first known ortho-metalation of rhodium­(I) on ferrocene complexes was observed for [(Cp)­Fe­{(C5H3)­C­(NHDipp)­(NDipp)­Rh­(CO)2}] (8) and [Fe­(C5H3)2{C­(NHMes)­(NMes)­Rh­(CO)2}2] (9). A combined electrochemical and quantum chemical study revealed that depending on both the metal-bound ligand (CO vs cod) and the bonding mode (κ2 N vs ortho-metalated), the highest occupied molecular orbital is located more on iron or on rhodium/iridium.

A series of bimetallic silyl halido cuprates consisting of the new tripodal silicon-based metalloligand [κ(3)N-Si(3,5-Me2pz)3Mo(CO)3](-) is presented (pz = pyrazolyl). This metalloligand is straightforwardly accessible by reacting the ambidentate ligand tris(3,5-dimethylpyrazolyl)silanide ({Si(3,5-Me2pz)3}(-)) with [Mo(CO)3(η(6)-toluene)]. The compound features a fac-coordinated tripodal chelating ligand and an outward pointing, "free" pyramidal silyl donor, which is easily accessible for a secondary coordination to other metal centers. Several bimetallic silyl halido cuprates of the general formula [CuX{μ-κ(1)Si:κ(3)N-Si(3,5-Me2pz)3Mo(CO)3}](-) (X = Cl, Br, I) have been synthesized. The electronic and structural properties of these complexes were probed in detail by X-ray diffraction analysis, electrospray mass spectrometry, infrared-induced multiphoton dissociation studies, cyclic voltammetry, spectroelectrochemistry, gas-phase photoelectron spectroscopy, as well as UV/Vis and fluorescence spectroscopy. The heterobimetallic complexes contain linear two-coordinate copper(I) entities with the shortest silicon-copper distances reported so far. Oxidation of the anionic complexes in methylene chloride and acetonitrile solutions at E(1/2)(0( = -0.60 and -0.44 V (vs. ferrocene/ferrocenium (Fc/Fc(+))), respectively, shows substantial reversibility. Based on various results obtained from different characterization methods, as well as density functional theory calculations, these oxidation events were attributed to the Mo(0)/Mo(I) redox couple.