Zur Molekülstruktur des Tris‐2,2′‐Dipyridyl‐Vanadin(0) sowie der isomorphen Titan (0)‐ und Chrom(0)‐Komplexe

Electronic Structures of the [V(tbpy)3]z (z = 3+, 2+, 0, 1−) Electron Transfer Series

“…The intraligand bond lengths are virtually identical between the three ligands, with an average C py –C py ′ distance of 1.438 Å and an average C py –N distance of 1.378 Å. Although [V(bpy) 3 ] has been previously crystallographically characterized, comparison of the computed and experimental bond distances is dubious due to the limited structure resolution. Indeed, the crystal structure itself gives conflicting information about the extent of bpy ligand reduction, with long C py –C py ′ bonds (avg.…”

“…The reason for choosing the t bpy ligand in contrast to unsubstituted bpy was the observation that in the corresponding suite of chromium complexes, diffraction quality crystals were obtained where the site symmetry of the respective central chromium ion did not involve a threefold axis rendering the three t bpy ligands equivalent in the solid state for crystallographic reasons . This was in contrast to the corresponding crystal structures of salts of the tri-, di-, and monocations of the [Cr(bpy) 3 ] z series which all displayed C 3 symmetry with accompanying static disorder problems of the bpy ligands for the di- and monocations. , …”

“…Surprisingly, from the [V(bpy) 3 ] z ( z = 3+, 2+, 1+, 0) series only the neutral complex has been targeted by X-ray crystallography . The low quality of this 1963 structure determination only allows for the atom connectivity to be unequivocally established for the octahedral VN 6 polyhedron.…”

Electronic and Molecular Structures of the Members of the Electron Transfer Series [Cr(tbpy)3]n (n = 3+, 2+, 1+, 0): An X-ray Absorption Spectroscopic and Density Functional Theoretical Study

“…The electronic structure of the neutral diamagnetic complex 4 has, in the past, often been discussed but controversially with respect to questions like (a) how much electron density resides in the π*-LUMO of the (bpy 0 ) ligands, (b) if one or more of the bpy ligands are reduced, is it localized or delocalized, and (c) can one assign an oxidation state to the central Cr ion or not? The molecular structure of [Cr­(bpy) 3 ] 0 has not been solved by X-ray crystallography , due to the fact that it crystallizes as a merohedric twin (space group P 3̅ c 1). We have also not been able to solve the crystal structure of 4 .…”

“…In this paper, we will establish the electronic structures of four members of the electron transfer series [Cr­( t bpy) 3 ] n ( n = 3+, 2+, 1+, 0) (complexes 1 – 4 in Chart ), where use of ( t bpy) allowed us to access higher-quality X-ray crystal structures than had been obtained using the unsubstituted (bpy) ligand (see below). The complexes containing unsubstituted (bpy) (Table ), namely, [Cr­(bpy) 3 ]­(PF 6 ) 3 , [Cr­(bpy) 3 ]­(PF 6 ) 2 , [Cr­(bpy) 3 ]­(PF 6 ), and [Cr­(bpy) 3 ] 0 , have been investigated previously by X-ray crystallography − and electronic spectroscopy and many contradictory electronic structures have been proposed ranging from a completely metal-centered redox series involving Cr III (d 3 , S = 3/2), Cr II (d 4 , S = 1), Cr I (d 5 , S = 1/2), and Cr 0 (d 6 , S = 0) and three neutral (bpy 0 ) ligands in each case to a series where the reducing electrons occupy, at least partly, the π* LUMOs of the (bpy 0 ) ligands. The electronic structure of the dication has been most widely described as a low-spin Cr II species, namely [Cr II (bpy 0 ) 3 ]­(PF 6 ) 2 ( S = 1), as is evidenced by its appearance as such in multiple advanced inorganic chemistry textbooks .…”