Catalytic Hydrosilylation of Alkenes by Iron Complexes Containing Terpyridine Derivatives as Ancillary Ligands
摘要:
Iron complexes formulated as Fe(terpy)X-2 (terpy = 2,2':6',2 ''-terpyridine derivatives; X = Cl, Br) were prepared and their catalytic activities for hydrosilylation of olefin with hydrosilane were examined. Although Fe(terpy)X-2 did not show catalytic activity, the treatment of Fe(terpy)X-2 with NaHBEt3 caused catalytic activity. The influence of substituents in terpy on the catalytic activity was examined, and it was found that some complexes with an unsymmetrically disubstituted terpy selectively produced 1-silylalkane with quite high catalytic activity. In the reaction of 1-octene with PhSiH3, the double-hydrosilylation product Ph(1-octyl)(2)SiH was selectively obtained.
Iron-Catalyzed Hydrogen Production from Formic Acid
摘要:
Hydrogen represents a clean energy source, which can be efficiently used in fuel cells generating electricity with water as the only byproduct. However, hydrogen generation from renewables under mild conditions and efficient hydrogen storage in a safe and reversible manner constitute important challenges In this respect formic acid (HCO2H) represents a convenient hydrogen storage material, because it is one of the major products from biomass and can undergo selective decomposition to hydrogen and carbon dioxide in the presence of suitable catalysts. Here, the first light-driven iron-based catalytic system for hydrogen generation from formic acid is reported By application of a catalyst formed in situ from inexpensive Fe-3(CO)(12), 2,2'.6'2"-terpyridine or 1,10-phenanthroline, and triphenylphosphine, hydrogen generation is possible under visible light irradiation and ambient temperature. Depending on the kind of N-ligands significant catalyst turnover numbers (>100) and turnover frequencies (up to 200 h(-1)) are observed, which are the highest known to date for nonprecious metal catalyzed hydrogen generation from formic acid NMR, IR studies, and DFT calculations of iron complexes, which are formed under reaction conditions, confirm that PPh3 plays an active role in the catalytic cycle and that N-ligands enhance the stability of the system It is shown that the reaction mechanism includes iron hydride species which are generated exclusively under irradiation with visible light
Several phenyl-substituted 2,2â²:6â²,2â³-terpyridines (tpy) were synthesized and it was found that 4â²-phenyl tpy (ptp, 3) exhibited the most effective fluorescence, whose quantum yield was up to 0.64 in cyclohexane. For further study on tuning the fluorescence properties of ptp, different substituents were introduced into the p-position of the phenyl group. While Br- 10, Cl- 11, and CH3-ptp 12 showed their absorption and fluorescence in the same region as 3, those of NH2- 14 and Me2N-ptp 15 were observed at much longer wavelengths. In addition, fluorescence maxima of 14 and 15 showed large (>130 nm) solvent dependence. The difference between ground and excited state dipole moment (Îμ) for 15 was estimated to be 15.2 D by the LippertâMataga equation, indicating the intramolecular charge transfer (ICT) process. Semi-empirical MO calculation (MOPAC/AM1) demonstrated that the HOMO-1, HOMO and LUMO of 3, 10â12 were mainly localized on the phenyl (Ïph), tpy (Ïtpy) and tpy (Ï*tpy) part, respectively, indicating that the lowest energy absorption band of 3, 10â12 was the local excitation (ÏtpyâÏ*tpy). In the
case of 14 and 15, which have an electron-donating substituent, Ïph instead of Ïtpy became the HOMO. Thus, the lowest energy absorption of 14 and 15 was an ICT transition (ÏphâÏ*tpy), and a large red shift of the fluorescence occurred. In these compounds, the energy level of Ïph is controlled without affecting that of Ïtpy and Ï*tpy, suggesting a novel approach for tuning the color of fluorescence.
Double-helical complexes from simple 2,2′ : 6′,2″-terpyridines; the crystal and molecular structure [Cu<sub>2</sub>(Ph<sub>2</sub>tpy)<sub>2</sub>][PF<sub>6</sub>]<sub>2</sub>(Ph<sub>2</sub>tpy = 6,6″-diphenyl-2,2′ : 6′,2″-terpyridine)
作者:Edwin C. Constable、Andrew J. Edwards、Michael J. Hannon、Paul R. Raithby
DOI:10.1039/c39940001991
日期:——
2,2â²:6â²,2â³-Terpyridines from dinuclear complexes with copper(I) which are double-helical; the introduction of 6-phenyl substituents stabilises the helicate, and the crystal and molecular structure of [Cu2(Ph2tpy)2][PF6]2 described.
Silver(I)-2,2′:6′2′-terpyridine complexes: X-ray structure of [{Ag(tpy)(MeCN)}2][PF6]2 and [Ag(dptpy)(MeCN)][BF4]·MeCN (tpy = 2,2′: 6′2′-terpyridine; dptpy = 6,6′-diphenyl-2,2′:6′,2′-terpyridine)
作者:Edwin C. Constable、Andrew J. Edwards、Geoffrey R. Haire、Michael J. Hannon、Paul R. Raithby
DOI:10.1016/s0277-5387(97)00333-1
日期:1998.1
silver(I) acetate with 2,2′: 6′,2′-terpyridine (tpy) and 6,6′-diphenyl-2,2′: 6′, 2′-terpyridine (dptpy) has been investigated. In contrast to the behaviour with copper(I), no dinuclear double-helical species have been unambiguously isolated although there is evidence that double-helical [Ag2L2]2+ complexes exist in weakly-coordinating solvents. In the case of 2,2′ : 6′,2′-terpyridine, a species containing
The reaction of an alkyl- or aryl-lithium with 1,10-phenanthroline followed by hydrolysis and rearomatisation with manganese dioxide gives good yields of the 2,9-disubstituted product. This synthetic method has been extended to other polyimines such as 2,2′-bipyridine, 2,2′,6′, 2″-terpyridine and 1,8-naphtyridine.