Syntheses, reactivities, molecular structures, and physical properties of paramagnetic bis(tetraphenylcyclopentadienyl) complexes of vanadium, chromium, cobalt, and nickel

Six‐coordinated vanadium(IV) complexes with tridentate task‐specific ionic liquid Schiff base ligands: Synthesis, characterization and effect of ionic nature on catalytic activity

“…The low symmetry of complexes VO(acac)L 1–4 removes the orbital degeneracy so the experimental magnetic moment values ( μ eff ) for paramagnetic vanadium complexes VO(acac)L 1–4 at 292 K are very close to the spin‐only value expected for one unpaired electron with S = 1/2 for uncoupled spin systems (1.73). Thus these measurements confirm the oxidation state of complexes VO(acac)L 1–4 …”

“…Hence, if μ eff = 1.73, then n = 1. Matching of μ eff to the nearest value to find n and comparison of this value with the theoretical one predicted knowing the element and its oxidation state such as the emphasis on vanadium in oxidation states +4 or +5 . As one‐electron system of six‐coordinated V(IV) complexes with 3d 1 electron configuration and S = 1/2 possesses an orbitally nondegenerate ground state ( 2 B 2 g), by the static Jahn–Teller distortion (z‐in), partially quenched orbital contributions to the magnetic moment and also g || and g ⊥ are not substantially different from 2.…”

Synthesis, characterization and catalytic behaviour of ansa-zirconocene complexes containing tetraphenylcyclopentadienyl rings: X-ray crystal structures of [Zr{Me2Si(η5-C5Ph4)(η5-C5H3R)}Cl2] (R=H, But)

“…13 C{ 1 H} NMR (100 MHz, CDCl 3 ): d 2.8 (SiMe 2 ), 100.3, 101.2 (C 1 -Cp), 109.2, 114.3 (C 5 H 4 ), 123.1, 125.7 (C 5 Ph 4 ), 127. 3,128.4,129.7,130.5,131.2,133.9,141.1,143.2 (Ph). MS electron impact (m/e (relative intensity)): 652 (90) 4.9.…”

“…These reports have shown that the presence of these bulky cyclopentadienyl ligands greatly reduce the reactivity of their complexes, when compared with the unsubstituted metallocene analogues [2]. Solid-state and solution studies have allowed a greater understanding of the influence of the phenyl groups and of the interaction between and within the cyclopentadienyl rings of the metallocene complex [2,3]. Further work dealing with the stability and conformation of bis(tetraphenylcyclopentadienyl) metal complexes, such as [M(g 5 -C 5 HPh 4 ) 2 ] (M = V, Cr, Co, and Ni), has also been carried out although the bent metallocene conformation was never observed [2].…”

The Elusive Chemistry of Bent-Sandwich Chromocene

“…Cp* 2 Cr (Cp* = C 5 Me 5 ) also coordinates two CO ligands at elevated CO pressures to form a stable, isolable ( 3 -Cp*)( 5 -Cp*)Cr(CO) 2 complex [22]. By contrast (C 5 Ph 4 H) 2 Cr does not coordinate CO in the presence of an atmosphere of the gas at room temperature [23].…”