Metall‐π‐Komplexe von Benzolderivaten, 36. Zur Kenntnis der Struktur von μ(η⁶:η⁶‐Biphenyl)bis[(η⁶‐benzol)metall]‐Komplexen in starrer Lösung und im Kristall

Abstract

Metal .re-Complexes of Benzene Derivatives, 36'). -

Multidecker Bis(benzene)chromium: Opportunities for Design of Rigid and Highly Flexible Molecular Wires

“…The binding energy between the Cr atoms and the arene subunits of (class- 2 ) 8 and (class- 3 ) 8 wires is 90.5 and 88.9 kcal/mol, respectively, making both of them strongly bonded and realistic. This is also in line with previous syntheses of class- 2 and class- 3 dimers. − …”

“…If the arene ligands of two adjacent repeat units in addition are strongly coupled electronically, good conduction through the −(arene−metal−arene) n − motifs should result. Three classes of oligomers 1 − 3 with such motifs were considered (Figure A), and it is noteworthy that a few of the shortest class- 2 and class- 3 oligomers previously have been generated and found to be persistent. − For example, the class- 3 dimer, μ-(η 6 :η 6 -biphenyl)-bis[(η 6 -biphenyl)chromium], was stable when sublimed at 180 °C …”

Metal−Metal Interactions in Linked Metallocenes

“…60°, whereas in the crystal structure of [(biphenyl){Cr(benzene)} 2 the biphenyl is planar. 136 also been shown to be a triplet by ESR spectroscopy. 137 The paramagnetism of {(biphenyl) 2 Cr 2 } 2+ may be contrasted with the diamagnetism of (Fv 2 -Fe 2 ) 2+ ; important factors determining the different behavior may include the greater M-M separation in the former species and the differing electronic configurations of bis(arene)chromium and ferrocenium cations (e 2 4 a 1 1 and a 1 2 e 2 3 configurations for the respective frontier orbitals 138 ).…”

“…In the case of ([(biphenyl){Cr(benzene)} 2 ] 2+ , the zero-field splitting parameter in the ESR spectra suggest the two rings of the central biphenyl ligand are twisted with a dihedral angle of ca. 60°, whereas in the crystal structure of [(biphenyl){Cr(benzene)} 2 the biphenyl is planar .…”

[7−7]- versus [5−5]Bitrovacene: How Linkage Isomerism Affects Exchange Coupling and Redox Splitting1

“…Obviously, a planar structure of the bridging heptafulvalenediyl ligand is avoided, a fact that we trace to ortho-hydrogen compression strain. Whereas this strain is tolerated in the case of the planar μ-η 5 :η 5 -fulvalenediyl ( 7 • • ) and μ-η 6 :η 6 -biphenyl ( 3 ) bridges, the more obtuse intra-ring CCC bond angle in the μ-η 7 :η 7 -heptafulvalenediyl bridge brings the ortho hydrogen atoms of the neighboring rings into closer proximity, thereby causing a twist distortion. If for the C−H bond length the X-ray crystallographic value of 1.00 Å is chosen, in the planar conformations of the C n H n −C n H n bridges nonbonded H···H distances between ortho/ortho‘ hydrogen atoms would amount to 2.52 Å ( n = 5), 1.93 Å ( n = 6), and 1.44 Å ( n = 7).…”