12427-78-0Relevant academic research and scientific papers
Enantioselective synthesis and application to the allylic imidate rearrangement of amine-coordinated palladacycle catalysts of cobalt sandwich complexes
Cassar, Doyle J.,Ilyashenko, Gennadiy,Ismail, Muhammad,Woods, James,Hughes, David L.,Richards, Christopher J.
, p. 17951 - 17962 (2014/01/17)
The reaction of (η5-(N,N-dimethylaminomethyl)cyclopentadien- yl)(η4-tetraphenylcyclobutadiene)cobalt with sodium tetrachloropalladate and (R)-N-acetylphenylalanine gave planar chiral palladacycle di-μ-chloridebis[(η5-(Ssu
The preparation, spectroscopy, structure and electrochemistry of some [Co(η4-C4Ph4)(η5-C 5H4R)] complexes
O'Donohue, Paul,McAdam, C. John,Courtney, Donagh,Ortin, Yannick,Müller-Bunz, Helge,Manning, Anthony R.,McGlinchey, Michael J.,Simpson, Jim
, p. 1496 - 1509 (2011/05/07)
[Co(η4-C4Ph4)(η5-C 5H4R)] (R = CO2Me, 2; and CHO, 3), prepared by the reactions of [Co(η5-C5H4R)(PPh 3)2] with Ph2C2, were used as precursors for complexes where R = CH2OH, 4; CH2Cl, 5; CH2P(O)(OEt)2, 6; CH2PPh3 +, [7]+; C(O)Fc, 8 (Fc = ferrocenyl); CFc2OH, 9; CHC(CN)2, 10; syn and anti-CHNNH-C6H 3(NO2)2-2,4, 11; CH(Fc)OH, 12; CHFc +, [13]+; and CFc2+, [14] +. Most new compounds have been characterised by elemental analyses, and all by spectroscopy. Their spectra are consistent with their formulae; of particular interest is the UV-Vis spectrum of [14]+ which shows two very strong absorption bands at 389 and 835 nm. X-ray diffraction techniques were used to determine the structures of 1 (R = Me), 4, 6, [7]Cl, 8, 9, 10, 11a (syn isomer), and 12. All have the same basic structure with the Co atom sandwiched between ca. planar η5-C5H4R and η4-C4Ph4 rings. The Ph groups do not lie in the C4 planes, and the C4Ph4 ligands constitute four-bladed propellers. The two rings are close to parallel with interplanar angles of 0.4-4.4° except where R = CH(Fc)OH (6.6°) and CFc2OH (12°) which is attributed to steric crowding though this does not affect the ferrocenyl groups to the same extent. When the C atom α to the C5H4 ligand is sp3 hybridised, it is usually displaced out of the C5 plane away from Co, but when Cα is sp2 hybridised (in 8 and 10) it is displaced out of the C5 plane towards Co. This is attributed to the contribution that η6-fulvene mesomers make towards a description of the structure of the latter compounds but not the former. In the primary and secondary alcohols 4 and 12 there is H-O?H-O hydrogen bonding, but in the tertiary alcohol 9 there is evidence of an intramolecular Fe?HO bond to one ferrocenyl group Fe?H = 2.965(1) and an angle of 5.1° between its two cyclopentadienyl ligands. Electrochemical studies are reported for 8-11 and the known compound triferrocenylcarbinol; this last is compared with the mixed cobalt/ferrocenyl systems 8 and, particularly, 9. The Co(η4- C4Ph4)(η5-C5H4-) centre is always more difficult to oxidise than Fe(η5-C 5H5)(η5-C5H4-).
Synthesis and 1H NMR spectroscopic properties of substituted (η4-tetraarylcyclobutadiene)(η5-cyclopentadienyl)cobalt metallocenes
Nguyen, Huy V.,Yeamine, Mebuba R.,Amin, Jahangir,Motevalli, Majid,Richards, Christopher J.
, p. 3668 - 3676 (2009/03/11)
The reaction of diarylacetylenes with CoCl(PPh3)3 and sodium cyclopentadienylide or sodium carbomethoxycyclopentadienylide gave (η4-tetra-arylcyclobutadiene)(η5-cyclopentadienyl)cobalt and (η4-tetra-arylcyclobutadiene)(η5-carbomethoxycyclopentadienyl)cobalt, respectively, where aryl = para-XC6H4 (X = CF3, F, MeO). The reaction was unsuccessful for the synthesis of (η4-tetra(para-methoxyphenyl)cyclobutadiene)(η5-cyclopentadienyl)cobalt, which was synthesised instead from dicarbonyl(η5-cyclopentadienyl)cobalt. In all of the examples starting with CoCl(PPh3)3 an intermediate (η5-cyclopentadienyl)- or (η5-carbomethoxycyclopentadienyl)(triphenylphosphine)-2,3,4,5-tetraarylcobaltacyclopentadiene complex was isolated, and two examples were characterised by X-ray crystallography. Heating the (η5-cyclopentadienyl)- or (η5-carbomethoxycyclopentadienyl)(triphenylphosphine)-2,3,4,5-tetraarylcobaltacyclopentadiene complexes resulted in clean conversion to the corresponding metallocenes. The influence of the para-aryl substituents on the 1H NMR of the cyclopentadienyl moiety is tabulated, together with the influence of a range of R substituents in (η4-tetraphenylcyclobutadiene)(η5-RC5H4)cobalt (R = CO2Me, CH2OH, Me, CHO, CCH, CO2H, CN, CONHR1, 2-oxazolinyl, NH2, NHAc, HgCl, Br, I, SiMe3, SnMe3, Ph).
(η4-Tetraarylcyclobutadiene)(η5-formylcyclopentadienyl)cobalt(I) complexes: Facilities to finetune the electron-donating capability in dipolar organometallics
Dabek, Sven,Prosenc, Marc Heinrich,Heck, Jürgen
, p. 2216 - 2226 (2007/10/03)
Five different (η4-tetraarylcyclobutadiene)(η5-formylcyclopentadienyl)cobalt(I) complexes (1a-1e) were synthesized in reasonable yields in a one-pot reaction of CoCl(PPh3)3, formylcyclopentadienyl sodium and the appropriate diarylethyne. The aryl groups of the ethyne were modified by various para-substituents X (X = Cl, H, Me, OMe, NMe2), which were intended to alter the redox potentials of the synthesized cobalt sandwich complexes. A cyclic voltammetry study revealed a linear dependence of the first oxidation potential to the Hammett parameter σp. X-ray structure analyses performed for two complexes (X = Me and NMe2) demonstrate only subtle changes in the solid state structure despite the large differences in electrochemical properties. A theoretical analysis by the density functional theory method has been performed on the geometries and electronic structures of the complex (η4-cyclobutadiene)(η5-cyclopentadienyl)Co(I), its cation and dication.
An NMR study of the rotational barriers in cobalt-stabilized carbocations: X-ray crystal structures of (η4-C4Ph4)Co-(η5 -C5H4R), where R is CH3C=O, CH=O, CH(tBu)OH
Ortin, Yannick,Ahrenstorf, Kirsten,O'Donohue, Paul,Foede, Daniel,Müller-Bunz, Helge,McArdle, Patrick,Manning, Anthony R.,McGlinchey, Michael J.
, p. 1657 - 1664 (2007/10/03)
Treatment of the aldehyde (η4-C4Ph4) Co(η5-C5H4-CH=O) (4b) with tert-butyllithium or phenyllithium yields the secondary alcohols (η4-C4Ph4)Co(η5- C5H4-CH(R)OH), where R=tert-butyl (5) or phenyl (6 . Protonation of 5 and 6 at -80 °C furnishes the deep purple, cobalt-stabilized cations, 7 and 8, respectively, both of which exhibit restricted rotation about the external C5H4 -CHR+ linkage on the NMR time-scale. These data indicate a minimum value for the barrier to rotation of 15 kcal mol-1, but it is certainly much higher, indicating a considerable degree of C-C double bond character. X-ray crystal structures of 4b, 5 and also of the ketone (η4-C4Ph4 Co(η5 -C5H4-C(=O)CH3 (4a) are reported. The secondary alcohol 5 exhibits disorder in the solid state because of the presence of diastereomers as a consequence of the stereogenic center at the α-carbon and the clockwise or anticlockwise propeller orientations of the tetraphenylcyclobutadiene ligand.
Oligoalkyne-bridged (η4-cyclobutadiene)(η5-cyclopentadienyl)cobalt fragments - Syntheses and properties
Classen, Joerg,Gleiter, Rolf,Rominger, Frank
, p. 2040 - 2046 (2007/10/03)
The syntheses of (η5-cyclopentadienyl)(η4 -tetraphenylcyclobutadiene)cobalt units bridged by buta-1,3-diyne, octa-1,3,5,7-tetrayne, and dodeca-1,3,5,7,9,11-hexayne units (15, 18, 21) are reported. All three species could be obtained by Hay coupling of the corresponding mono-, di-, and triyne units 14, 17, and 20. In the case of 14-17 and 21, the molecular structures were confirmed on the basis of X-ray studies on single crystals. Cyclic voltammetry revealed a weak interaction between the metal centers of 15 and no interaction between the metal centers of 18 and of 21. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
