Experimental Electron Density of the Complex Carbides Sc₃[Fe(C₂)₂] and Sc₃[Co(C₂)₂]

Abstract

The nature of chemical bonding in the complex carbides Sc3[Fe(C2)2] (1) and Sc3[Co(C2)2] (2) has been explored by combined experimental and theoretical charge density studies. The structures of these organometallic carbides contain one-dimensional infinite TC4 (T = Fe, Co) ribbons embedded in a scandium matrix. Bonding in 1 and 2 was studied experimentally by multipolar refinements based on high-resolution X-ray data and compared to scalar-relativistic electronic structure calculations using the augmented spherical wave method. Besides substantial covalent T-C bonding within the TC4 ribbons, one also observes discrete Sc-C bonds of noticeable covalent character. Furthermore, our study highlights that even tiny differences in the electronic band structure of solids might be faithfully recovered in the properties of the Laplacian of the experimental electron density. In our case, the increase of the Fermi level in the organometallic Co(d9) carbide 2 relative to its isotypic Fe(d8) species 1 is reflected in the charge density picture by a significant change in the polarization pattern displayed by valence shell charge concentrations of the transition metal centers in the TC4 units. Hence, precise high-resolution X-ray diffraction data provide a reliable tool to discriminate and analyze the local electronic structures of isotypic solids, even in the presence of a severe coloring problem (Z(Fe)/Z(Co) = 26/27).

On the Electronic Structure of NiII Complexes That Feature Chelating Bisguanidine Ligands

“…Since experimental charge-density distributions do not suffer from an insufficient treatment of relativistic effects and electron correlation, they might serve as reference densities for theoretical studies. [33] Finally, the analysis of the topology of our experimental charge-density distribution of [(btmgb)NiCl 2 ] will allow for the quantification of electron donation from the btmgb ligand to the Ni atom and thus an estimate of the degree of any competing NIL behavior in this benchmark system. Figure 6 shows an ORTEP plot of [(btmgb)NiCl 2 ] displaying 50 % probability ellipsoids based on high-order X-ray data at 7 K and subsequent multipolar refinements.…”

45Sc Solid State NMR Spectroscopy – A Complementary Tool to X‐ray Crystallography for Structure Determination of Intermetallic Compounds

“…The carbides Sc 3 TC 4 (T = Mn, Fe, Co, Ni, Ru, Rh, Os, Ir) [52,[62][63][64][65][66] have complex structural behavior. They crystallize with a pronounced subcell structure which was first refined for the cobalt compound [67].…”

Was Chemiker aus der Elektronendichte lernen

“…Die Anhebung des Fermi‐Niveaus der Co‐Verbindung findet seine Entsprechung in einem anderen Polarisationsmuster des Übergangsmetalls der MC4‐Baugruppe. Die Polarisation des Eisenatoms orthogonal zur FeC4‐Ebene ist am Cobaltatom der ansonsten isostrukturellen Verbindung nicht zu finden 14…”