An Environmentally Benign and Cost-Effective Synthesis of Aminoferrocene and Aminoruthenocene

Metallocenium incorporated charge-enhanced thiourea catalysts

Several metallocenium derivatives were prepared including N-ferrocenium-N'-phenylthiourea tetrakis-[3,5-bis(trifluoromethyl)phenyl]borate (BArF4, 4a), N-methylferrocenium-N'-phenylthiourea BArF4 (4b) and N-cobaltocenium-N'-phenylthiourea BArF4 (5). These compounds are competent catalysts for the Friedel-Crafts alkylation of indoles with trans-β-nitrostyrenes, and are much more active than their reduced non-charged forms. The iron derivatives are less stable than the cobalt analog and were generated and used in situ whereas the cobalt-containing thiourea was isolated and characterized by X-ray crystallography. All three of these metallocenium salts have Lewis and Brønsted acidic sites which were exploited in tandem to afford charge-activated catalysts.

Influence of Rare-Earth Ion Radius on Metal-Metal Charge Transfer in Trinuclear Mixed-Valent Complexes

We report the synthesis and characterization of a highly conjugated bisferrocenyl pyrrolediimine ligand, Fc₂PyrDIH (1), and its trinuclear complexes with rare earth ions─(Fc₂PyrDI)M(N(TMS)₂)₂ (2-M, M = Sc, Y, Lu, La). Crystal structures, nuclear magnetic resonance (NMR) spectra, and ultraviolet/visible/near-infrared (UV/vis-NIR) data are presented. The latter are in good agreement with DFT calculations, illuminating the impact of the rare earth ionic radius on NIR charge transfer excitations. For [2-Sc]⁺, the charge transfer is at 11,500 cm^-1, while for [2-Y]⁺, only a d-d transition at 8000 cm^-1 is observed. Lu has an ionic radius in between Sc and Y, and the [2-Lu]⁺ complex exhibits both transitions. From time-dependent density functional theory (TDDFT) analysis, we assign the 11,500 cm^-1 transition as a mixture of metal-to-ligand charge transfer (MLCT) and metal-to-metal charge transfer (MMCT), rather than pure metal-to-metal CT because it has significant ligand character. Typically, the ferrocenes moieties have high rotational freedom in bis-ferrocenyl mixed valent complexes. However, in the present (Fc₂PyrDI)M(N(TMS)₂)₂ complexes, ligand-ligand repulsions lock the rotational freedom so that rare-earth ionic radius-dependent geometric differences increasingly influence orbital overlap as the ionic radius falls. The Marcus-Hush coupling constant H_AB trends as [2-Sc]⁺ > [2-Lu]⁺ > [2-Y]⁺.

Forever young: the first seventy years of ferrocene

The discovery of ferrocene, [Fe(η5-C5H5)2], seventy years ago has significantly influenced chemical research and provided a key impetus for establishing and rapidly expanding organometallic chemistry, which has continued at a...

The self-indicating preparation of bromoferrocenes from stannylferrocenes and an improved synthesis of di-iodoferrocene

A simple method for the preparation of bromoferrocenes from stannylferrocenes is described: the preparation of 1,1′-dibromoferrocene is used as an example. Stannylferrocenes are reacted with bromine directly in dichloromethane to give bromoferrocenes in a self-indicating titration reaction. Also, an enhanced method of removal of the highly soluble organotin tin by-products formed in the preparation of 1,1′-diiodoferrocene from 1,1′-tri-n-butylstannylferrocene is reported allowing the preparation of large-scale quantities of 1,1′-diiodoferrocene, which is one of the most important starting materials in ferrocene chemistry.

Scalable Synthesis of Functionalized Ferrocenyl Azides and Amines Enabled by Flow Chemistry

A scalable access to functionalized ferrocenyl azides has been realized in flow. By halogen-lithium exchange of ferrocenyl halides and trapping with tosyl azide, a variety of functionalized ferrocenyl azides were obtained in high yields. To allow a scalable preparation of these potentially explosive compounds, a flow protocol was developed accelerating the reaction time to minutes and circumventing accumulation of potentially hazardous intermediates. The corresponding ferrocenyl amines were then prepared by a reliable reduction process.

Synthesis and characterization of 1'-(diphenylphosphino)-1-isocyanoferrocene, an organometallic ligand combining two different soft donor moieties, and its Group 11 metal complexes

The development of a practical synthesis of 1'-(diphenylphosphino)-1-aminoferrocene (2) and its P-borane adduct (2B) allowed the facile preparation of 1'-(diphenylphosphino)-1-isocyanoferrocene (1). This compound combining two specific soft-donor moieties was studied as a ligand for univalent Group 11 metal ions. The reactions of 1 with AgCl at 1 : 1 and 2 : 1 molar ratios only led to the coordination polymer [Ag₂(μ-Cl)₂(μ(P,C)-1)]_n (6), while those with Ag[SbF₆] provided the dimer [Ag₂(Me₂CO-κO)₂(μ(P,C)-1)₂][SbF₆]₂ and the quadruply-bridged disilver complex [Ag₂(μ(P,C)-1)₄][SbF₆]₂ (8), respectively. Addition of 1 to [AuCl(tht)] (tht = tetrahydrothiophene) afforded the mono- and the digold complex, [AuCl(1-κP)] (9) and [(μ(P,C)-1)(AuCl)₂] (10), depending on the reaction stoichiometry. Finally, the reaction of 1 with [Au(tht)₂][SbF₆] or halogenide removal from 9 with AgNTf₂ led to cationic dimers [Au₂(μ(P,C)-1)₂]X₂ (11, X = SbF₆ (a) or NTf₂ (b)). Catalytic tests in the Au-mediated isomerization of (Z)-3-methylpent-2-en-4-yn-1-ol to 2,3-dimethylfuran revealed that 11a and 11b are substantially less catalytically active than their analogues containing 1'-(diphenylphosphino)-1-cyanoferrocene as the ligand, most likely due to a stronger coordination of the isonitrile moiety, which prevents dissociation of the dimeric complexes into catalytically active monomeric species.

Aminophosphine ligands as a privileged platform for development of antitumoral ruthenium(ii) arene complexes

The potential utility of aminophosphine ligands in both high-throughput testing and rational design of new anticancer metallodrugs.

Syntheses and purification of the versatile synthons iodoferrocene and 1,1'-diiodoferrocene

This paper describes the improved synthesis and purification of iodoferrocene (FcI) and 1,1'-diiodoferrocene (FcI2). FcI and FcI2 were prepared by mono- and dilithiation of ferrocene followed by conversion into iodoferrocenes by reaction with iodine. Purification was accomplished by a simple sublimation/distillation procedure, affording FcI and FcI2 in high yields (74 and 72%) and high purity (>99.9%). We determined the molecular structures of FcI and FcI2 by X-ray single crystal diffraction.