Enantiopure Ruthenocenes Cp*Ru(1,2-C5H3R1R2) with a Planar Chiral Cyclopentadienyl Ligand and a Pentamethylcyclopentadienyl Spectator Ligand

Diastereoselective synthesis, structure and reactivity studies of ferrocenyloxazoline gold(i) and gold(ii) complexes

In the last few decades, gold complexes have demonstrated huge potential for soft Lewis acid catalysis. Despite the intensive research on Au complexes and planar chiral metallacycles, enantiopure ferrocenylgold complexes have - surprisingly - not been reported until the studies presented in this article. Herein, we report the asymmetric synthesis of planar chiral ferrocenyl Au(i) complexes. These dinuclear species form helically chiral ten-membered (NCCCAu)₂ rings stabilized by aurophilic interactions. In supramolecular solid state structures, linear, zigzag or helical Au(i) wires with regular AuAu separations were observed. The dissolved dinuclear entities could be oxidized by Au(i) to unique ferrocenyl Au(ii) complexes featuring short Au(ii)-Au(ii) bonds, while the ferrocene core remained intact. However, our initial studies revealed the issue of configurational lability of the ferrocenyl Au(ii) complexes in terms of the element of planar chirality in the presence of the gold source, (Me₂S)AuCl. This was successfully addressed by a systematic study implementing permanent σ-donor ortho-protecting groups such as methyl and trimethylsilyl, which impede an epimerization event. Oxidation of the dinuclear Au(i) complexes was also accomplished by oxidative addition reactions with halogenated solvents, preferably CHCl₃. Additional reactivity studies revealed that dinuclear Au(ii) dihalide complexes are also formed with reactive alkylhalides such as iodomethane, benzylbromide and benzyliodide. Interestingly, the whole spectral range of colors (violet, blue, green, yellow, and red) is covered by the title complexes depending on the Au oxidation state and the anionic ligands in the Au(ii) complexes. This appears to be quite unusual for ferrocenes, which typically adopt orange to red colors in a non-oxidized state.

Asymmetric Pentafulvene Carbometalation--Access to Enantiopure Titanocene Dichlorides of Biological Relevance

Unprecedented asymmetric copper-catalyzed addition of ZnEt2 (ZnBu2) to the exocyclic C=C bond of pentafulvenes C5H4(=CHAr) (Ar=2-MeOPh and related species) results in enantiomerically enriched (up to 93:7 e.r.) cyclopentadienyl ligands (C5H4CHEtAr; abbreviated Cp(R)). Copper catalyst promotion with both chiral phosphoramidite ligands and a phosphate additive is vital in realizing both acceptable enantioselectivities and reaction rates. Enantiomeric Cp(R)2TiCl2 complexes have been prepared; the (S,S) isomer is twice as active towards pancreatic, breast, and colon cancer cell lines as its (R,R) enantiomer at 24 h.

Dinuclear planar chiral ferrocenyl gold(i) & gold(ii) complexes

The first scalemic ferrocenyl gold(i) and gold(ii) complexes have been prepared and structurally analysed by X-ray, (spectro)electrochemical and DFT studies.

Synthesis and characterization of 1,2,3,4,5-pentafluoroferrocene

Starting from ferrocene, pentafluoroferrocene [Fe(C5F5)(C5H5)] can be prepared in five steps via a one-pot lithiation-electrophilic fluorination strategy. Pentafluoroferrocene was characterized by multinuclear NMR and IR spectroscopy, by cyclovoltammetry as well as X-ray (solid) and electron diffraction (gas) and the experimental results compared with DFT calculations.

A new double-cube nitride complex containing titanium and potassium

The reaction of the imide-nitride complex [{Ti(η(5)-C(5)Me(5))(μ-NH)}(3)(μ(3)-N)] with potassium iodide in pyridine at room temperature affords the adduct di-μ-iodido-1:1'κ(4)I-bis{tri-μ(3)-imido-1:2:3κ(3)N;1:2:4κ(3)N;1:3:4κ(3)N-μ(3)-nitrido-2:3:4κ(3)N-tris[2,3,4(η(5))-pentamethylcyclopentadienyl](pyridine-1κN)-tetrahedro-potassiumtrititanium(IV)}, [K(2)Ti(6)(C(10)H(15))(6)I(2)N(2)(NH)(6)(C(5)H(5)N)(2)] or [(C(5)H(5)N)(μ-I)K{(μ(3)-NH)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)}](2). The crystal structure contains two [KTi(3)N(4)] cube-type units held together by two bridging I atoms. There is a centre of inversion located in the middle of this unprecedented discrete K(2)I(2) unit. The geometry around K is best described as distorted trigonal prismatic, with three imide groups, two bridging I atoms and one pyridine ligand.