Metal-.pi.-complexes of benzene derivatives. 37. Redox behavior of the sandwich complexes C12H12M (C12H12 = C6H6 + C6H6, C5H5 + C7H7; M = vanadium, chromium). A comparative study

A journey into the electrochemistry of vanadium compounds

“…It is well known that multiple unsaturated bonds as components of molecular wires (double and triple C C bonds, triple C N bond) can efficiently transmit along the molecular line from one center (donor) to another one (acceptor). At first, [5]trovacene itself was investigated by cyclic voltammetry and compared with bis( 6 -benzene)vanadium [242] in order to gain insight into the factors that govern the redox processes (Table 11). Then, the substitution of benzene with arsenabenzene was accomplished, trying to solve the question of whether interannular "secondary bonding" between the heavier group 15 elements could stabilize the synperiplanar conformation of bis-arene complexes [243] Results are in Scheme 15).…”

Cyclopentadienyl Complexes of Chromium, Molybdenum and Tungsten

“…1370 shown that the oxidation potentials correlate with ionization energies f r o m photoelectron spectra. 1374 A well-defined Rydberg structure has been observed in the gas-phase absorption spectrum of the latter chromium complex. 1375 One-pot syntheses o f [M(T|-C 7 H 7 )(T|-C 7 H 9 )] f r o m MoCl 5 or WC1 6 have been developed, which in turn lead to improved access to [M(t|-C 7 H 7 )Cp] via the dihalides [MI 2 (NCMe)(r|-C 7 H 7 )].…”

Trovacenyl-based organometallic triradicals: Spin frustration, competing interactions and redox splitting

“…Conversely, taking into account the sensitivity of the exchange interaction to a substitution at bridging atoms, a through-bond mechanism appears plausible. Through-bond coupling most likely proceeds vŸ the combined action of spin polarization and superexchange [9,[18][19][20][21][22][23]. Yet, both mechanisms lack efficiency [37], which manifests itself in the small hyperfine coupling constants of the hydrogen nuclei at the coordinated rings, Aiso(tHcp) = 1.8 G [38].…”

“…Ir was, however, found in some cases that meta-phenylene derivatives can also display antiferromagnetically coupled ground states [15][16][17], pointing to the fact that the acquired knowledge does not yet allow an unequivocal understanding of the magneto-structural correlations. In a series of studies on these correlations we used the sandwich complex 1 as the spin-bearing group [18][19][20][21][22][23]. Compared with other organometallic bis(arene)metal compounds 1 has the following advantages: (1) the redox potentiat E1/2(+/0 ) = +0.26 V renders 1 almost air-stable, whereas its isomer bis(rl6-benzene)vanadium with Ev2(+/O) = -0.35 Vis much more sensitive to oxygen [22], (2) 1 is easily functionalized since it can be selectively lithiated at the cyclopentadienyl ring (meaning a proton is substituted by a lithium ion) [24] and (3) the neutral V(d 5) complex has an orbitally nondegenerate ground state 2A~ in which the nonbonding singly occupied molecular orbital (SOMO) is constituted to over 90% by the vanadium 3d: orbital [22].…”

“…In a series of studies on these correlations we used the sandwich complex 1 as the spin-bearing group [18][19][20][21][22][23]. Compared with other organometallic bis(arene)metal compounds 1 has the following advantages: (1) the redox potentiat E1/2(+/0 ) = +0.26 V renders 1 almost air-stable, whereas its isomer bis(rl6-benzene)vanadium with Ev2(+/O) = -0.35 Vis much more sensitive to oxygen [22], (2) 1 is easily functionalized since it can be selectively lithiated at the cyclopentadienyl ring (meaning a proton is substituted by a lithium ion) [24] and (3) the neutral V(d 5) complex has an orbitally nondegenerate ground state 2A~ in which the nonbonding singly occupied molecular orbital (SOMO) is constituted to over 90% by the vanadium 3d: orbital [22]. This contrasts with the isoelectronic ferricenium ion (Fe(dS), 2Ex) [25] and leads to well-resolved electron paramagnetic resonance (EPR) spectra even at room temperature.…”