RESUMEN
The synthesis, structure, and full characterization of a redox-switchable germylene based on a [3]ferrocenophane ligand arrangement, [Fc(NMes)2 Ge] (4), is presented. The mesityl (Mes)-substituted title compound is readily available from Fc(NHMes)2 (2) and Ge{N(SiMe3 )2 }2 , or from the dilithiated, highly air- and moisture-sensitive compound Fc(NLiMes)2 â 3 Et2 O (3) and GeCl2 . Cyclic voltammetry studies are provided for 4, confirming the above-mentioned view of a redox-switchable germylene metalloligand. Although several 1:1 RhI and IrI 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(κ1 Ge-4)2 (CO)4 ] (8) and [W(κ1 Ge-4)2 (CO)4 ] (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(κ1 E-qE)(CO)2 Cl]0/+ (qE=[Fc(NPh)2 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 20â cm-1 (E=C) to 25â cm-1 (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.
RESUMEN
The synthesis and characterisation of two aluminium diphosphamethanide complexes, [Al(tBu)2 {κ(2) P,P'-Mes*PCHPMes*}] (3) and [Al(C6 F5 )2 {κ(2) P,P'-Mes*PCHPMes*}] (4), and the silylated analogue, Mes*PCHP(SiMe3 )Mes* (5), are reported. The aluminium complexes feature four-membered PCPAl core structures consisting of diphosphaallyl ligands. The silylated phosphine 5 was found to be a valuable precursor for the synthesis of 4 as it cleanly reacts with the diaryl aluminium chloride [(C6 F5 )2 AlCl]2 . The aluminium complex 3 reacts with molecular dihydrogen at room temperature under formation of the acyclic σ(2) λ(3) ,σ(3) λ(3) -diphosphine Mes*PCHP(H)Mes* and the corresponding dialkyl aluminium hydride [tBu2 AlH]3 . Thus, 3 belongs to the family of so-called hidden frustrated Lewis pairs.
RESUMEN
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 -0.44â 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.