Functionalized ferrocenes

N-Metallocenyl Ynamides: Preparation, Reactivity, and Synthesis of ansa[3]-Ferrocenylamides

The first synthesis of various N-metallocenyl ynamides has been developed, and two strategies for the oxidative cyclization of N-ferrocenyl ynamide into ansa[3]-ferrocenylamide are also reported. The mechanism for the iodine(III)-triggered transformation has been studied by means of DFT calculations, showing that it proceeds through a concerted iodination deprotonation step.

Controllable access to P-functional [3]ferrocenophane and [4]ferrocenophane frameworks

Condensation of secondary 1,1'-diaminoferrocenes with phosphorus trihalides (PCl3 or PBr3) yielded either P-halo-1,3-diaza-2-phospha[3]ferrocenophanes or 1,1'-diaminoferrocenediyl-bis(dichlorophosphines), respectively. The latter provide controlled access to both [3]- and [4]ferrocene frameworks. Thus, reductive coupling with magnesium gave diaza-diphospha[4]ferrocenophane-annelated tetraphosphetanes, while a reaction with LiNMe2 produced a P-chloro-diazaphospha[3]ferrocenophane. Condensation of diaminoferrocenes and aminodichlorophosphines were mostly unselective, but afforded in one case a 3-amino[3]ferrocenophane. All reaction products were characterised by spectroscopic and single-crystal XRD studies. DFT studies indicate that the product selectivity in the reactions studied depends on a combination of kinetic and thermodynamic effects, which correlate subtly with the steric bulk of the N-substituents. Cyclic voltammetry measurements revealed that the ferrocenophanes can undergo multiple oxidation events, the first of which may according to DFT studies be located in both the ferrocene and aminophosphine units. The quantum chemical studies provided also insight into stereochemical aspects like ring strain in the ferrocenophane units.

Electrophilic Carboxamidation of Ferrocenes with Isocyanates

Ferrocenes undergo one-step carboxamidation by reaction with isocyanates in CF₃SO₃H solution. The chemistry is most efficient in excess superacid, and it has been accomplished with aryl and aliphatic isocyanates. In conversions with ferrocene carboxylic acids, isocyanates provide imides in good yields. A mechanism for this conversion is suggested involving carbamic acid anhydride formation and subsequent intramolecular reaction at the substituted cyclopentadienyl ring.

Cationic and Neutral Rotaxanes Having Different Functional Groups in the Axle Molecule and Their Coordination to PtII

Dibenzo[24]crown-8 (DB24C8) forms rotaxanes with a linear molecule having a dialkylammonium group and a triazole group as well as with the acetylation product of a cationic axle molecule. The former cationic rotaxane is stabilized by multiple intermolecular hydrogen bonds between the NH₂⁺ and oxyethylene groups. The neutral rotaxane contains the macrocycle in the vicinity of the terminal aryl group. The co-conformation of both the cationic and neutral rotaxanes can be fixed by coordination of the triazole group of the axle molecule to PtCl₂ (dmso)₂ . A ¹ H NMR spectroscopic study on the thermodynamics of the Pt coordination revealed a larger association constant for the rotaxanes than for the corresponding axle molecules and a larger value for the neutral rotaxane than for the cationic rotaxane.

New 1,1'-Ferrocene Bis(sulfonyl) Reagents

Several new 1,1'-bis(sulfonyl)ferrocenes designed for the synthesis of sulfonamide linked biological conjugates have been prepared. 1,1'-Bis(sulfonylbromide)ferrocene can be produced from the corresponding sulfonylchloride via a bis(sulfonylhydrazide) intermediate. Bis(sulfonyl-N-hydroxybenzotriazole)ferrocene can also be synthesized from the sulfonyl chloride, and reaction of glycine methyl ester with the sulfonyl chloride affords a [3]ferrocenophane complex. All new compounds have been structurally characterized by X-ray crystallography.

Ferrocene-containing non-interlocked molecular machines

Ferrocene is chemically robust and readily functionalized which enables its facile incorporation into more complex molecular systems. This coupled with ferrocene's reversible redox properties and ability to function as a “molecular ball bearing” has led to the use of ferrocene as a component in wide range of non-interlocked synthetic molecular machine systems.

Recent progress in ferrocene- and azobenzene-based photoelectric responsive materials

Ferrocene- and azobenzene-based derivatives are commonly used photoelectric responsive materials and possess wide range of applications.

The palladium(ii) complex of N,N-diethyl-1-ferrocenyl-3-thiabutanamine: synthesis, solution and solid state structure and catalytic activity in Suzuki–Miyaura reaction

A novel phosphine-free ferrocene-containing Pd complex is an excellent precatalyst for Suzuki–Miyaura coupling.

Electrochemistry of redox-active self-assembled monolayers

Redox-active self-assembled monolayers (SAMs) provide an excellent platform for investigating electron transfer kinetics. Using a well-defined bridge, a redox center can be positioned at a fixed distance from the electrode and electron transfer kinetics probed using a variety of electrochemical techniques. Cyclic voltammetry, AC voltammetry, electrochemical impedance spectroscopy, and chronoamperometry are most commonly used to determine the rate of electron transfer of redox-activated SAMs. A variety of redox species have been attached to SAMs, and include transition metal complexes (e.g., ferrocene, ruthenium pentaammine, osmium bisbipyridine, metal clusters) and organic molecules (e.g., galvinol, C(60)). SAMs offer an ideal environment to study the outer-sphere interactions of redox species. The composition and integrity of the monolayer and the electrode material influence the electron transfer kinetics and can be investigated using electrochemical methods. Theoretical models have been developed for investigating SAM structure. This review discusses methods and monolayer compositions for electrochemical measurements of redox-active SAMs.

Selective lithiation and phosphane-functionalization of [(eta(7)-C7H7)Ti(eta(5)-C5H5)] (troticene) and its use for the preparation of early-late heterobimetallic complexes

The cycloheptatrienyl-cyclopentadienyl sandwich complex [(eta(7)-C(7)H(7))Ti(eta(5)-C(5)H(5))] (troticene) can be dilithiated (once at each ring) or selectively monolithiated, either at the seven- or five-membered ring, depending on the reaction conditions. Treatment of the resulting lithiotroticenes with ClPPh(2) afforded the corresponding troticenyl-phosphanes [(eta(7)-C(7)H(6)PPh(2))Ti(eta(5)-C(5)H(4)PPh(2))] (1), [(eta(7)-C(7)H(6)PPh(2))Ti(eta(5)-C(5)H(5))] (2), or [(eta(7)-C(7)H(7))Ti(eta(5)-C(5)H(4)PPh(2))] (3). The use of nBuLi/N,N',N',N'',N"-pentamethyldiethylenetriamine (pmdta) allowed us to isolate the lithium complexes [(eta(7)-C(7)H(6)Li)Ti(eta(5)-C(5)H(4)Li)] x pmdta (4) and [(eta(7)-C(7)H(7))Ti(eta(5)-C(5)H(4)Li)] x pmdta (5), which were structurally characterized by X-ray diffraction analyses. Reaction of the monophosphane 3 with Mo(CO)(6) and [(tht)AuCl] (tht = tetrahydrothiophene) afforded the heterobimetallic complexes [(3)Mo(CO)(5)] (6) and [(3)AuCl] (7) and also the trimetallic species [(3)(2)AuCl] (8). The reaction of trans-[PtCl(2)(SEt(2))(2)] with the diphosphane 1 led to the formation of cis-[(1)PtCl(2)] (9), whereas the complexes trans-[(2)(2)PtCl(2)] (10) and trans-[(3)(2)PtCl(2)] (11) were isolated by reaction of two equivalents of the monophosphanes 2 and 3 with trans-[PtCl(2)(SEt(2))(2)]. The X-ray crystal structures of 6-11 are also reported.

Ferrocenylbutadiyne

The title compound, [Fe(C₅H₅)(C₉H₅)], crystallizes in a form of a π–π-stacked assembly formed as a result of strong inter­molecular π–π inter­actions between (a) the triple bonds of two neighboring butadiyne substituents overlapping in a ‘head-to-tail’ fashion [characterized by C⋯C short contacts of 3.622 (5), 3.567 (6) and 3.556 (6) Å] and (b) the triple bonds of the butadiyne substituent and substituted cyclo­pendadiene ring of neighboring mol­ecules [C⋯C = 3.474 (5) and 3.492 (6) Å]. The linear butadiyne substituent has alternating C—C triple and single bonds, while the unsubstituted cyclo­penta­diene ring is slightly positionally disordered (although the structure reported here was solved as non-disordered) and retains a close to eclipsed conformation.

Synthesis and reactivity of functionalized cycloheptatrienyl-cyclopentadienyl sandwich complexes

This feature article provides an overview of the synthesis and reactivity of functionalized cycloheptatrienyl-cyclopentadienyl transition metal sandwich complexes of the type [(eta(7)-C(7)H(7))M(eta(5)-C(5)H(5))] (M = group 4, 5 or 6 metal), which can be used as building blocks for the preparation of metallopolymers and polymetallic complexes. Emphasis is placed on 16-electron group 4 complexes (M = Ti, Zr, Hf) and their reactivity towards sigma-donor/pi-acceptor ligands, which indicates that these complexes bear a close resemblance to Lewis acidic M(+IV) complexes. Based on theoretical calculations, this behavior can be mainly attributed to the strong and appreciably covalent metal-cycloheptatrienyl interaction with the cycloheptatrienyl ring acting more as a -3 ligand than as a +1 ligand in these mixed ring complexes.