Bulky cyclopentadienyl chromium complexes as ethene trimerisation catalyst precursors

The process of ethene trimerisation to 1-hexene, has recently attracted considerable interest, in light of the usefulness of 1-hexene industrially. In this project the process of catalytic ethene trimerisation, using bulky cyclopentad ienyl chromium complexes was investigated. Firstly, a series of known and novel bulky cyclopentadiene ligands, of the type, C₅Ph₄RH (R = H, alkyl, aromatic or substituted aromatic group) were synthesised. Four routes were investigated. (i) Making use of an in situ generated bis-lithium intermediate, resulting in the formation of 1 ,2,3,4,5-pentaphenyl cyclopenta-1 ,3-diene and 1 ,2,3,4-tetraphenylcyclopenta-1 ,3-diene. (ii) The attempted use of a metallation I alkylation route which was unsuccessful. (iii) The use of tetracyclone as starting material, reacted with alkyl likthium reagents, or alkyl Grignard reagents which resulted in the formation of ligands, of the type C₅Ph₄R, with R in the 5 position of the ring (R = n-butyl, tertbutyl, hexyl). Unexpected side reactions afforded the isolation of two ligands of the type C₅Ph₄R, R = 1-propeneyl and ethyl, both with the terminal alkene function, saturated. (iv) The use of a Pd catalysed route, making use of Cp₂ZrCI₂ as source of cyclopentadiene, resulted in the successful isolation of the cyclopentadiene, C₅Ar₅H (Ar = C₆Me₂H₃). All new compounds were successfully characterised using NMR, IR, MS and elemental analysis. A stable Fe(II) model complex, bis-tetraphenylcyclopentadienyl iron, was prepared and cyclic voltametry conducted on it, to investigate the effect of phenyl substituents on a Cp ligand in the reduction I oxidation potential of the iron(II) centre. This study showed that phenyl rings on a cyclopentadiene ligand have a significant effect on the redox potential of Fe(II); this trend could possibly be expected with other metals, in particular chromium

Mechanistic studies of CO2 reduction to methanol mediated by an N-heterocyclic germylene hydride

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.The labile germylene hydride LCyGeH is capable of activating CO2 affording the corresponding formate LCyGeOCH([double bond, length as m-dash]O) (2) (LCy = cyclo-C6H8-1-NAr-2-C(Ph)NAr, Ar = 2,6-iPr2C6H3). Compound 2 and the previously reported LGeOCH([double bond, length as m-dash]O) (L = CH(MeC[double bond, length as m-dash]NAr)2, Ar = 2,6-iPr2C6H3) (2′) could be further converted to methanol with the AlH3·NMe3 alane-amine adduct as a hydrogen source upon workup with water. A plausible mechanism for the conversion of the formate complexes to methanol is proposed based on additional results from the conversion of 2′ with the milder hydride delivery agent LAlH2.DFG, EXC 314, Unifying Concepts in Catalysi

Unprecedented silicon(II)-> calcium complexes with N-heterocyclic silylenes

The first N-heterocyclic silylene (NHSi) complexes of any s-block element to date are reported for calcium: [(eta(5)-C5Me5)(2)Ca<--:Si(O-C6H4-2-Bu-t){((NBu)-Bu-t)(2)CPh}] (6) and [(eta(5)-C5Me5)(2)Ca<--:Si((NBuCH)-Bu-t)(2)] (7). Complexes 6 and 7 are isolable in a facile way upon reaction of the corresponding free N-heterocyclic silylenes (NHSis) with [(eta(5)-C5Me5)(2)Ca] (2). Complexes 6 and 7 were fully characterised by spectroscopic means and the single crystal X-ray diffraction analysis of 6 is also reported. Analysis of the bonding situation by DFT methods including a Bader Atoms in molecules (AIM) analysis is also reported. The bonding interaction between the Si and Ca centres in complexes 6 and 7 can best be viewed as sigma-donor-acceptor interactions, with a considerable ionic contribution in the bond. The reactivity towards the oxygen containing substrates THF and benzophenone is also discussed.DFG, EXC 314, Unifying Concepts in Catalysi

From elusive thio- and selenosilanoic acids to copper(I) complexes with intermolecular Si=E -> Cu-O-Si coordination modes (E = S, Se)

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.The facile synthesis of the first stable selenosilanoic acid–base adduct LSi([double bond, length as m-dash]Se)OH(dmap) 3 (L = CH[C(Me)NAr]2, Ar = 2,6-iPr2C6H3, dmap = 4-dimethylaminopyridine), the heavier analogue of the thiosilanoic acid adduct LSi([double bond, length as m-dash]S)OH(dmap) 1, is reported. Both adducts 1 and 3 react readily with MesCu (Mes = 2,4,6-trimethylphenyl) to form the novel dimeric Cu(I) complexes [LSi([double bond, length as m-dash]E)OCu]2 (4: E = S; 5: E = Se) with unprecedented intermolecular Si[double bond, length as m-dash]E → Cu–O–Si coordination modes. The latter are efficient pre-catalysts for the Cu(I)-mediated aziridination of styrene with PhI[double bond, length as m-dash]N(Ts) (Ts = tosyl)

Residual Energy Harvesting from Light Transients Using Hematite as an Intrinsic Photocapacitor in a Symmetrical Cell

Hematite as a sustainable photoabsorber material offers a band gap close to 2 eV and photoanode characteristics, but usually requires additional catalysts to enhance surface redox chemistry during steady state light energy harvesting for water splitting. Here, for a highly doped hematite film, sufficient intrinsic photocapacitor behavior is reported for the conversion of light transients into energy. Residual energy is harvested in a symmetric architecture with two opposing mesoporous hematite films on conductive glass. Transient light energy harvesting is shown to occur without the need for water splitting

Synthesis and In Vitro (Anticancer) Evaluation of eta(6)-Arene Ruthenium Complexes Bearing Stannyl Ligands

Treatment of the known half-sandwich complexes of the type [(eta(6)-C6H6)RuCl2(P(OR)(3))] (R = Me or Ph) with SnCl2 yielded three new half-sandwich ruthenium complexes (C1-C3): [(eta(6)-C6H6)RuCl(SnCl3)(P(OMe)(3))] (C1), [(eta(6)-C6H6)RuCl(SnCl3)(P(OPh)(3))] (C2) and the bis-stannyl complex [(eta(6)-C6H6)Ru(SnCl3)(2)(P(OMe)(3))] (C3) by facile insertion of SnCl2 into the Ru-Cl bonds. Treatment of the known complexes [(eta(6)-C6H6)RuCl(SnCl3)(PPh3)] and [(eta(6)-C6H6)RuCl2(PPh3)] with 4-dimethylaminopyridine (DAMP) and ammonium tetrafluoroborate afforded the complex salts: [(eta(6)-C6H6)Ru(SnCl3)(PPh3)(DAMP)]+BF4- (C4) and [(eta(6)-C6H6)RuCl(PPh3)(DAMP)]+BF4- (C5) respectively. Complexes C1-C5 have been fully characterized by spectroscopic means (IR, UV-vis, multinuclear NMR, ESI-MS) and their thermal behaviour elucidated by thermal gravimetric analysis (TGA). Structural characterization by single crystal X-ray crystallography of the novel complex C2 and [(eta(6)-C6H6)RuCl2(P(OPh)(3))], the latter having escaped elucidation by this method, is also reported. Finally, the cytotoxicity of the complexes was determined on the A2780 (human ovarian cancer), A2780cisR (human ovarian cis-platin-resistant cancer), and the HEK293 (human embryonic kidney) cell lines and discussed, and an attempt is made to elucidate the effect of the stannyl ligand on cytotoxicity

25th Anniversary of Molecules—Recent Advances in Inorganic Chemistry

Celebrating the “25th Anniversary of Molecules” with a Special Issue dedicated to “Recent Advances in Inorganic Chemistry” strengthens the renewed role that inorganic chemistry, one of the oldest chemistry divisions, has lately earned thanks to cutting-edge perspectives and interdisciplinary applications, eventually receiving the veneration and respect which its age might require [...

Synthesis, structure and anti-cancer activity of osmium complexes bearing π-bound arene substituents and phosphane Co-Ligands: A review: A review

While many examples of osmium complexes, as anti-cancer agents, have been reported and some reviews have been devoted to this topic, a particularly interesting and synthetically accessible sub-class of these compounds namely those bearing a π– bound arene and phosphane co-ligand have escaped review. These complexes have made a surprisingly late entry in the literature (2005) in terms of anti-cancer investigations. This is somewhat surprising considering the plethora of analogous complexes that have been reported for the lighter analogue, ruthenium. Herein we review all complexes, neutral and ionic, bearing the “(ƞ6-arene)Os(PR3)” moiety focusing on their synthesis, reactivity, structural features (by X-ray diffraction analysis) as well as anti-cancer biological activity. An attempt is made throughout the article to contrast these to each other and to analogous Ru systems, and a full summary of all existing in vitro biological data is presented