12126-50-0Relevant articles and documents
Zinc-Containing Radical Anions via Single Electron Transfer to Donor–Acceptor Adducts
Cao, Levy L.,Bamford, Karlee L.,Liu, Liu Leo,Stephan, Douglas W.
, p. 3980 - 3983 (2018)
Reactions of [Cp*2Fe] with the Lewis acid [Zn(C6F5)2] in the presence of [(PhC(S)S)2], 9,10-phenanthrenedione or 4,5-pyrenedione yield the salt [Cp*2Fe][(PhC(S)S)Zn(C6F5/su
Unusual electronic effects imparted by bridging dinitrogen: An experimental and theoretical investigation
Hoffert, Wesley A.,Rappe, Anthony K.,Shores, Matthew P.
, p. 9497 - 9507 (2010)
We describe the preparation, structural and magnetic characterizations, and electronic structure calculations for a redox-related family of dinitrogen-bridged chromium acetylide complexes containing the [RC 2Cr(μ-N2)CrC2R]n+ (R = Ph-, iPr3Si-; n = 0, 1,2) backbone: [(dmpe)4Cr 2(C2Ph)2(μ-N2)] (1), [(dmpe) 4Cr2(C2SiiPr3) 2(μ-N2)] (2), [(dmpe)4Cr 2(C2SiiPr3)2(μ-N 2)]BArF4 (3), and [(dmpe)4Cr 2(C2SiiPr3)2(μ-N 2)](BArF4)2 (4). Compounds 3 and 4 are synthesized via chemical oxidation of 2 with [Cp2Co]+ and [Cp*2Fe]+, respectively. X-ray structural analyses show that the alteration of the formal Cr oxidation states does not appreciably change the Cr-N-N-Cr skeletal structures. Magnetic data collected for 2 and 4 are consistent with high-spin triplet and quintet ground states, respectively. The mixed-valent complex 3 exhibits temperature dependent magnetic behavior consistent with a quartet ? doublet twocenter spin equilibrium. Electronic structure calculations (B3LYP) performed on the full complexes in 2 and 4 suggest that the high-spin states arise from singly occupied orthogonal π* orbitals coupled with a variable occupation of dδ orbitals. Significant N-N and Cr-N π-bonding pins the occupation of the π manifold, leading to variable occupation of the dδ space. In contrast, mixed-valent 3 is not well described by a B3LYP hybrid density functional model. A [9,11] CAS-SORCI study on a simplified model of 3 reproduces the observed Hund's rule violation for the S = 1/2 ground state and places the lowest quartet 1.45 kcal/mol above the doublet ground state.
Self-exchange reaction kinetics of metallocenes revisited: Insights from the decamethylferricenium-decamethylferrocene reaction at variable pressure
Zahl, Achim,Van Eldik, Rudi,Matsumoto, Mitsuru,Swaddle, Thomas W.
, p. 3718 - 3722 (2003)
Rate constants kex and volumes of activation ΔVex? have been obtained using 1H NMR for the self-exchange reaction of the [(η5-C5(CH3)5)2 Fe]+ hexafluorophosphate and tetrafluoroborate with [(η5-C5(CH3)5)2Fe] in acetone-d6 (ΔVex? = -8.6 ± 0.3 cm3 mol-1), dichloromethane-d2, and (semiquantitatively) in acetonitrile-d3. Under the experimental conditions, ion pairing was significant only in CD2Cl2, but even that produced only a minor reduction in kex and so had a negligible effect on ΔVex? (= -6.4 ± 0.2 cm3 mol-1 with PF6-). In all cases, ΔVex? is negative and consistent with a simple two-sphere activation model, rather than with that of Weaver et al. (Nielson, R. M.; McManis, G. E.; Safford, L. K.; Weaver, M. J. J. Phys. Chem. 1989, 93, 2152) in which the barrier crossing rate is limited by solvent dynamics. Similarly, the ～5-fold increase in kex on going from [(η5-C5H5)2Fe]+/0 to [(η5-C5(CH3)5)2 Fe]+/0 in acetone can be explained with the two-sphere model on the basis of the effects of reactant size on the solvent reorganization energy, without reference to solvent dynamics.
ORGANOMETALLIC DERIVATIVES OF THE TRANSITION ELEMENTS IV. FERROCENES VIA THE REACTION OF IRON ATOMS WITH ALKYNES
Simons, L. H.,Lagowski, J. J.
, p. 195 - 204 (1983)
Iron atoms react with disubstituted alkynes to produce iron complexes and alkyne oligomers.The oligomers are cyclic trimers and/or cyclic tetramers of the starting alkynes.Structural characterization of iron complexes shows an unusual rearrangement to sub
Catalytic photodefluorination of perfluoroalkanes to perfluoroalkenes with a ferrocene photosensitizer
Burdeniuc, Juan,Crabtree, Robert H.
, p. 1582 - 1586 (1998)
Perfluoroalkenes are obtained from perfluoroalkanes by photoinduced electron transfer from an organometallic photosensitizer, decamethylferrocene, in the polar solvent thf. In the presence of Zn, the reaction becomes catalytic in ferrocene because the dec
Solvent Dynamical Effects in Electron Transfer: Comparisons of Self-Exchange Kinetics for Cobaltocenium-Cobaltocene and Related Redox Couples with Theoretical Predictions
Nielson, Roger M.,McManis, George E.,Golovin, Neal M.,Weaver, Michael J.
, p. 3441 - 3450 (1988)
Rate constants, Kex, and activation parameters for the self-exchange of cobaltocenium-cobaltocene Cp2Co+/0, and the decamethyl derivative Cp'2Co+/0, in 13 organic solvents have been evaluated by using the proton NMR line-broadening technique with the objective of probing the influence of solvent dynamics upon the electron-transfer kinetics.Together with some corresponding measurements reported earlier for ferrocenium-ferrocene Cp2Fe+/0, additional measurements for the decamethyl derivative, Cp'2Fe+/0, and with corresponding data for Cp2Co+/0 electrochemical exchange, these results enable a systematic comparative examination to be made of the effects of solvent dielectric relaxation on the barrier-crossing frequency for such simple outer-sphere reactions.For the facile Cp'2Co+/0 couple the solvent dependence of the observed frequency factors, νn(obsd), extracted from the kex values by correcting for the solvent-dependent barrier height, ΔG*, is in approximate accordance with the relative frequency factors νos(calcd), predicted from the continuum model of overdamped solvent relaxation.The subunity (ca. 0.7-0.8) slope of the logarithmic νn(obsd) - ??os(calcd) plot for Cp'2C0+/0 self-exchange is consistent with a recent theoretical prediction of the combined effect of overdamped solvent motion and reactant vibrations (ref 2g).In a given solvent, the sequence of kex values is Cp'2Co+/0 > Cp2Co+/0 ca.Cp'2Fe+/0 > Cp2Fe+/0, with Cp2Co+/0 and Cp2Fe+/0 being about 10- and 100-folds lower, respectively, than Cp'2Co+/0 self-exchange.While these reactivity differences can be traced to variations in donor-acceptor orbital overlap, the solvent dependencies of kex for Cp2Co+/0 and Cp2Fe+/0 electron exchange nevertheless exhibit a strong influence from overdamped solvent relaxation.Marked deviations from the dielectric continuum predictions are seen, however, in several solvents.Thus the barrier-crossing frequencies in propylene carbonate, N-methylformamide, and especially methanol are substantially (4-100-fold) larger than expected from νos(calcd), implicating the presence of surprisingly rapid relaxation modes in these solvents.The solvent-dependent activation parameters also differ significantly from the expectations of conventional theoretical modes.
Tunable Band Gaps in MUV-10(M): A Family of Photoredox-Active MOFs with Earth-Abundant Open Metal Sites
Fabrizio, Kevin,Lazarou, Konstantinos A.,Payne, Lillian I.,Twight, Liam P.,Golledge, Stephen,Hendon, Christopher H.,Brozek, Carl K.
, p. 12609 - 12621 (2021)
Titanium-based metal-organic frameworks (Ti-MOFs) have attracted intense research attention because they can store charges in the form of Ti3+ and they serve as photosensitizers to cocatalysts through heterogeneous photoredox reactions at the MOF-liquid interface. Both the charge storage and charge transfer depend on the redox potentials of the MOF and the molecular substrate, but the factors controlling these energetic aspects are not well understood. Additionally, photocatalysis involving Ti-MOFs relies on cocatalysts rather than the intrinsic Ti reactivity, in part because Ti-MOFs with open metal sites are rare. Here, we report that the class of Ti-MOFs known as MUV-10 can be synthetically modified to include a range of redox-inactive ions with flexible coordination environments that control the energies of the photoactive orbitals. Lewis acidic cations installed in the MOF cluster (Cd2+, Sr2+, and Ba2+) or introduced to the pores (H+, Li+, Na+, K+) tune the electronic structure and band gaps of the MOFs. Through the use of optical redox indicators, we report the first direct measurement of the Fermi levels (redox potentials) of photoexcited MOFs in situ. Taken together, these results explain the ability of Ti-MOFs to store charges and provide design principles for achieving heterogeneous photoredox chemistry with electrostatic control.
Influence of the redox active ligand on the reactivity and electronic structure of a series of Fe(TIM) complexes
Hess, Corinna R.,Weyhermueller, Thomas,Bill, Eckhard,Wieghardt, Karl
, p. 5686 - 5700 (2010)
The redox properties of Fe and Zn complexes coordinated by an α-diimine based N4-macrocyclic ligand (TIM) have been examined using spectroscopic methods and density functional theory (DFT) computational analysis. DFT results on the redox series of [Zn(TIM*)]n and [Fe(TIM*)]n molecules indicate the preferential reduction of the α-diimine ligand moiety. In addition to the previously reported [Fe(TIM*)]2 dimer, we have now synthesized and characterized a further series of monomeric and dimeric complexes coordinated by the TIM ligand. This includes the five-coordinate monomeric [Fe(TIM*)I], the neutral and cationic forms of a monomeric phosphite adduct, [Fe(TIM*)(P(OPh) 3)] and [Fe(TIM*)(P(OPh)3)](PF6), as well as a binuclear hydroxy-bridged complex, [{Fe(TIM*)}2(μ-OH)] (PF6). Experimental and computational data for these synthetic compounds denote the presence of ferrous and ferric species, suggesting that the α-diimine based macrocycles do not readily support the formation of formally low-valent (M0 or MI) metal complexes as previously speculated. Magnetochemical, Moessbauer, electron paramagnetic resonance (EPR), and electronic spectral data have been employed to experimentally determine the oxidation state of the central metal ion and of the macrocyclic ligand (TIM*) in each compound. The series of compounds is described as follows: [FeII(TIM0)(CH3CN 2)]2+, SFe = ST = 0; [Fe 2.5(TIM2.5-)]2, ST = 1; [{Fe III(TIM2-)}2(μ-OH)]+, S Fe = 3/2, ST = 0; [FeIII(TIM2-)I], SFe = 3/2, ST = 1/2; [FeII(TIM 2-)(P(OPh3))], SFe = ST = 0; and [FeII(TIM1-)(P(OPh3))]1+/[Fe I(TIM0)(P(OPh3))]1+, ST = 1/2. The results have been corroborated by DFT calculations.
Ferro and Antiferromagnetic Exchange in Decamethylbimetallocenes
Hilbig, Harald,Hudeczek, Peter,K?hler, Frank H.,Xie, Xiulan,Bergerat, Pierre,Kahn, Olivier
, p. 4246 - 4257 (1998)
With the aim of studying next-neighbor magnetic interactions in polymeric metallocenes the paramagnetic decamethylbimetallocenes (M′M′) have been chosen as most simple model compounds. They have been synthesized for vanadium, cobalt, and nickel (to yield V′V′, Co′Co′, and Ni′Ni′, respectively) by starting from dilithium and dithallium salts of the fulvalene dianion. The latter have been characterized by 13C NMR spectroscopy. Decamethylbiferrocene has been synthesized as a diamagnetic standard compound, and decamethylbicobaltocenium hexafluorophosphate, as a precursor to Co′Co′. While the methylated M′M′ species were stable when protected from air, the synthesis of the parent binickelocene (Ni′Ni′) was accompanied by the formation of the ternickelocene NiNiNi. According to 1H NMR spectroscopy NiNi and NiNiNi were antiferromagnetic and underwent ligand exchange to nickelocene and bisfulvalenedinickel. Unlike the usually green nickelocenes Ni′Ni′ was deep redviolet owing to a new band at 528 nm. Measurements of the magnetic susceptibility (Χm) and the magnetization established a rare example of ferromagnetic interaction within a purely organometallic compound for Co′Co′. By contrast. V′V′ and Ni′Ni′ were antiferromagnetic (J = -1.6 and -180 cm-1, respectively, with H = -JSA· SB). The 1H and 13C NMR spectra confirmed the expected structures of Co′Co′ and Ni′Ni′. while the synthesis of V′V′-d8 and 2H NMR spectroscopy were necessary to fully establish the vanadium compound, Temperature-dependent measurements of the 1H NMR signal shifts and of Χm yielded similar J values for Ni′Ni′. MO calculations were carried out for M′M′, and the results were converted into theoretical NMR spectra of the bridging fulvalene ligand depending on the spin-carrying MO. This allowed the full assignment of the NMR signals and showed that the spin is delocalized to more than one MO. The MOs were shown to have different magnetic coupling capabilities, and the different magnetic behavior of M′M′ was attributed to the near-degeneracy of the magnetic orbitals.
CONVERSION OF THE DIAMAGNETIC NONAMETHYLFERROCENYLCARBENIUM SALTS INTO THE PARAMAGNETIC SALTS OF BIS(NONAMETHYLFERROCENIUMYL)ETHANE
Fedin, E. I,Blumenfeld, A. L.,Petrovskii, P. V.,Kreindlin, A. Z,Fadeeva, S. S.,Rybinskaya, M. I.
, p. 257 - 268 (1985)
Conversion of the diamagnetic salt of nonamethylferrocenylcarbenium primary cation into the paramagnetic salt of bis(nonamethylferroceniumyl)ethane has been studied by high-resolution NMR in solution and, mainly, by spin-lattice and spi-spin relaxation in
