Synthesis of New Ferrocenylenesilylene Polymers by Direct Hydrosilylation/Polymerization of [FC–SiRH], FC?=?(η5-C5H4)Fe(η5-C5H4), Using Organometallic Alkenes and Alkynes

Synthesis of new ferrocenylenesilylene polymers was effected by direct hydrosilylation/polymerization of 1,1′-methylsilyl-ferrocenophane [FC–SiMeH] (FC = (η⁵-C₅H₄)Fe(η⁵-C₅H₄) with acetylenes and organometallic olefins using a Pt⁰ catalyst. The reaction of [FC–SiMeH] with HC₂Ph, HC₂SiMe₃, CH₂=CHSiMe₂Fp, Fp = (η⁵-C₅H₅)Fe(CO)₂ and CH₂=CHCH₂SiMe₂Fp in the presence of a platinum catalyst resulted in high yields of the corresponding hydrosilylated polymers. In the case of the acetylenes only β products were obtained, both E and Z isomers, whereas for the olefins both α and β-isomers were noted. Only in the case of the more bulky allylsilicon material was any unreacted SiH functionality retained in the polymer, an effect also noted when using [FCSiPhH] as the starting ferrocenophane. Cyclic voltammetric studies on these polymers revealed metal–metal interaction with two redox processes associated with the ferrocenylene Fe center along with an irreversible oxidation at higher potential for the Fp Fe atom. Ian: A pleasure to contribute; keep up the good work-aptp, cheers, Keith.     

Synthesis and Redox Properties of an Electropolymerizable Amido Ferrocenyl Pyrrole-functionalized Dendrimer

A novel diaminobutane-based poly(propyleneamine) ferrocenyl dendrimer functionalized with electrochemically polymerizable pyrrole substituents, DAB-dend-[{η⁵-C₅H₄CONH}Fe{η⁵-C₅H₄C(O)NH(CH₂)₃NC₄H₄}]₄ (1), has been prepared and characterized. A secondary reaction product, the dipyrrole derivative [Fe{η⁵-C₅H₄C(O)NH(CH₂)₃NC₄H₄}₂] (2) has been also isolated and used as a model to facilitate the characterization of 1. The molecular structure of 2 has been determined by single crystal X-ray diffraction studies. Glassy carbon electrodes have been successfully modified by electropolymerization of the pyrrole-functionalized derivatives 1 and 2, in dichloromethane/acetonitrile solutions, resulting in visually detectable electroactive ferrocenyl polymer films persistently attached to the electrode surfaces. Osteryoung square wave voltammetry experiments (OSWV) showed that films of the electropolymerized amidoferrocenylpyrrole functionalized dendrimer 1 (poly-1) senses H₂PO₄⁻ in aqueous solution using Li[B(C₆F₅)₄] as supporting electrolyte. This paper is dedicated to Professor Didier Astruc in “recognition” of his outstanding contributions to so many fields of inorganic and organic chemistry. Furthermore, CMC and BA thank him for his counsel and friendship during and after their post doctoral stages in his lab.     

Organometallic–Inorganic Conjugated Unsymmetrical Schiff-Base Hybrids. Synthesis,Characterization, Electrochemistry and X-ray Crystal Structures of Functionalized Trinuclear Iron–Nickel–Ruthenium Dipolar Chromophores

The synthesis of neutral dinuclear iron–nickel unsymmetrical Schiff base complexes 3 and 4 was achieved via a template reaction involving equimolar amounts of alkyl or aryl “half-unit” precursors, respectively, Fc–C(O)CH=C(CH₃)N(H)R (1: R = CH₂CH₂NH₂; 2: R = o-C₆H₄NH₂; Fc = CpFe(η⁵-C₅H₄); Cp = η⁵-C₅H₅), 5-bromosalicylaldehyde and nickel(II) acetate tetrahydrate in a refluxing CH₂Cl₂/MeOH (1:1) mixture. The ionic trinuclear unsymmetrical complex 5 was prepared by reacting its dinuclear precursor 3 with the arenophile source, [Cp*Ru(NCCH₃)₃]PF₆ (Cp* = η⁵-C₅(CH₃)₅), in refluxing CH₂Cl₂ for 2 h, whereas the trinuclear species 6 was formed upon regioselective π-complexation of the 5-bromosalicylidene ring of 4 by [Cp*Ru]⁺ at room temperature overnight. All the new compounds were adequately characterized by analytical and spectroscopic techniques and, in addition, the crystal and molecular structures of the “half-unit” 1, the binuclear complex 4 and its hemisolvate adduct 4 · 0.5CH₃OH, the trinuclear Schiff base compound 5 · 2(CH₃)₂CO, and the mixed sandwich metalloligand 7 have been determined by X-ray crystallography. Both organometallic–inorganic hybrids 5 and 6 contain the neutral electron-releasing ferrocenyl group, and the cationic electron-withdrawing ruthenium mixed sandwich, linked through the unsymmetrical tetradentate Schiff base complex {Ni(ONNO)}. UV–vis, ¹H and ¹³C NMR as well as electrochemical data clearly indicate a mutual donor–acceptor electronic influence between the organometallic termini. Furthermore, X-ray crystal structure analysis of 5 · 2(CH₃)₂CO reveals the partial delocalization of bonding electron density throughout the dinucleating nickel Schiff base ligand. Dedicated to Prof. Didier Astruc, a true friend, an outstanding lecturer and scientist, in honor of his pioneering research efforts and accomplishments in the fields of organometallic chemistry, dendrimers and their applications in nanocatalysis.     

Silyl group mediated linkage of closo-C2B10-cage to nido-C2B4-carborane: synthesis of the novel carborane ligand, 1-R-2-[5′-(SiMe2CH2)-2′,3′-(SiMe3)2-2′,3′-C2B4H5]-1,2-C2B10H10 (R=Me,Ph)

The reaction of the sodium salt of the monoanion, nido-[2,3-(Si(CH₃)₃)₂-2,3-C₂B₄H₅]⁻, with (chloromethyl)dimethylchlorosilane in a 1:1 molar ratio produced the B_(cage)-substituted cluster, nido-5-ClCH₂Si(CH₃)₂-2,3-(Si(CH₃)₃)₂-2,3-C₂B₄H₅ (1), in 81% yield. This product (1) was reacted further with the lithium salt of [closo-1-R-1,2-C₂B₁₀H₁₀]⁻ monoanion (R=Me, Ph) to give the novel linked and mixed C₂B₄/C₂B₁₀ carborane species, 1-Me-2-[5^′-SiMe₂CH₂-2^′,3^′-(SiMe₃)₂-2^′,3^′-C₂B₄H₅]-1,2-C₂B₁₀H₁₀ (2), 1-Ph-2-[5^′-SiMe₂CH₂-2^′,3^′-(SiMe₃)₂-2^′,3^′-C₂B₄H₅]-1,2-C₂B₁₀H₁₀ (3), in yields of 76% and 81%, respectively.     

Synthesis,Characterization, and Reactivity of Lanthanide Complexes with Bulky Silylallyl Ligands

The synthesis of new lanthanide allyl complexes of enhanced stability and solubility in saturated hydrocarbons based on silyl-substituted allyl ligands is reported. Thus the potassium salt K(CH₂CHCHSiMe₃) ( 1 ) reacts with YCl₃ in tetrahydrofuran to give the tris-allyl complex Y(CH₂CHCHSiMe₃)₃ ( 2 ), while K(CH₂CHCHSiMe₂^tBu) ( 3 ) affords Y(CH₂CHCHSiMe₂^tBu)₃(THF)_1.5 ( 4 ). Slow re-crystallization of 4 from light petroleum in the presence of tert-butylcyanide led to multiple insertion to give the sec-amido complex Y{NHC(^tBu)(CH)₃SiMe₂^tBu}₂{η₂-NHC(^tBu)CH=CHCH₂SiMe₂^tBu)CH(CHCHSiMe₂^tBu)C^tBuNH}(THF)·(CH₃CH(Me)(CH₂)₂CH₃) ( 5 ), which was crystallographically characterized. The reaction of ScCl₃(THF)₃ with two equivalents of Li{1,3-C₃H₃(SiMe₃)₂} in tetrahydrofuran gives the bis-allyl complex {1,3-C₃H₃(SiMe₃)₂}₂Sc(μ-Cl)₂Li(THF)₂ ( 6 ), while the analogous reaction of K{1,3-C₃H₃(SiMe₃)₂} ( 7 ) with either LaCl₃ or YCl₃ in tetrahydrofuran affords the bis-allyl complexes MCl{1,3-C₃H₃(SiMe₃)₂}₂(THF)_x (8, M = La, x = 1; 9, M = Y, x = 0). An attempt to prepare the similar neodymium complex gave the mono-allyl complex NdI₂{1,3-C₃H₃(SiMe₃)₂}(THF)_1.25 ( 10 ). The reactions of 8 and 9 with triisobutyl aluminum in benzene-d₆ show allyl exchange between lanthanide and aluminum. Complexes 8 , 9 , and 10 have been tested with a variety of activator systems as catalysts for the polymerization of 1,3-butadiene.     

Synthesis of Poly(propargyl esters) with Rhodium Catalysts and Their Characterization

Summary Propargyl esters (HC≡CCH₂OC(=O)R; 1: R = n-C₅H₁₁, 2: R = CH₃, 3: R = CHBrCH₃, 4: R = C₆H₅, 5: R = C(C₆H₅)₃) were polymerized by using (nbd)Rh⁺(η⁶-Ph-B^-Ph₃) (nbd = 2,5-norbornadiene) to produce poly(1)–poly(5) with molecular weights in the range of M_n = 4,900–40,000. Poly(1), poly(3) and poly(4) were readily soluble in common organic solvents such as toluene, THF and CHCl₃, and poly(2) showed similar solubility behavior except that it was insoluble in THF. Poly(5) did not dissolve in any organic solvent. Poly(1) was yellow oil, while poly(2)–poly(5) were yellow solids. Poly(1)–poly(4) exhibited UV-vis absorptions in a range of 300–425 nm, which are attributed to the conjugation of the main chain. All the polymers were thermally stable up to 150–200 °C.     

Synthesis, Characterization and Photoluminescence of Dimeric and Polymeric Metallaynes of Group 10–12 Metals Containing Conjugation-breaking Diphenylmethane Unit

A novel approach based on conjugation interruption was developed for a luminescent and thermally stable platinum(II) polyyne polymer trans-[–Pt(PBu₃)₂C≡C(C₆H₄)CH₂(C₆H₄)C≡C–] _n (1) containing the diphenylmethane chromophoric spacer. Particular attention was focused on the photophysical properties of this group 10 polymetallayne and comparison was made to its binuclear model complex trans-[Pt(Ph)(PEt₃)₂C≡C(C₆H₄)CH₂(C₆H₄)C≡CPt(Ph)(PEt₃)₂] (2) and their closest group 11 gold(I) and group 12 mercury(II) neighbors, [MC≡C(C₆H₄)CH₂(C₆H₄)C≡CM] (M = Au(PPh₃) (3), HgMe (4)). The regiochemical structures of these angular-shaped compounds were studied by various spectroscopic analyses. Upon photoexcitation, each of them emits an intense purple-blue fluorescence emission in the near UV region in dilute fluid solutions at room temperature. Harvesting of organic triplet emissions harnessed through the strong heavy-atom effects of group 10–12 transition metals was examined. These metal-containing phenyleneethynylenes spaced by the conjugation-breaking CH₂ unit were found to have high optical gaps and high-energy triplet states. The influence of metal and sp³-hybridized methylene conjugation-interrupters on the intersystem crossing rate and the spatial extent of the lowest singlet and triplet excitons was fully elucidated. Our investigations indicate that high-energy triplet states in these materials intrinsically give rise to very efficient phosphorescence with fast radiative decays. Dedicated to Professor Didier Astruc in recognition of his outstanding contribution to metallodendrimers and polymers.     

Gas permeation properties of poly(2,5-dialkyl-p-phenyleneethynylene) membranes

Dipropynylbenzenes with alkyl groups (CH₃C ≡ CRC₆H₂RC≡CCH₃, R=n-C₆H₁₃, n-C₈H₁₇, n-C₁₀H₂₁, 1a–c, respectively) were polymerized with Mo(CO)₆ to afford solvent-soluble poly(2,5-dialkyl-p-phenyleneethynylene)s (2a–c). The polymers (2a–c) had high molecular weight over 3×10⁴, and gave free-standing membranes by solution casting method. According to thermogravimetric analysis (TGA), these poly(p-phenyleneethynylene)s showed high thermal stability (T₀ ≥380 °C). The densities of membranes of poly(2,5-dialkyl-p-phenyleneethynylene)s (2a–c) were 0.936–0.965, and their fractional free volume (FFV) were relatively large (ca. 0.14–0.15). The oxygen permeability coefficients (PO₂) of membranes of 2a–c were 4.88, 7.06, and 16.6 barrers, respectively.     

Polyphosphazenes as Solid Templates for the Formation of Monometallic and Bimetallic Nanostructures

A simple synthetic route to monometallic and bimetallic nanostructured materials is presented. Pyrolysis of the organometallic iron co-polyphosphazenes, [{[N = P(R₁)₂]_0.8[N = P(OC₆H₄CH₂CN[Fe])₂]_0.15}{PF₆}_0.32]_n (1) and [{[N = P(R₁)₂]₀₅₅[N = P(OC₆H₄CH₂CN[Fe])₂]_0.2}{PF₆}_0.32]_n (2) with R₁ = OC₁₂H₈ [Fe] = CpFe(dppe)⁺ Cp = η−C₅H₅, dppe = PPh₂(CH₂)₂PPh₂ in air affords nanoparticles of the iron pyrophosphate Fe₂Fe₅(P₂O₇)₄, while the pyrolysis of both copolymers in air and in the presence of TlPF₆ yield bimetallic Tl, Fe nanostructures. The polyphosphazene acts as a hybrid organic–inorganic template. By carbonization, the organic part of the polymer provides holes where the metallic centers grow while the inorganic P = N acts as precursor for the formation of phosphorus oxides, which form the metal pyrophosphates or the stabilizing matrix. Pyrolysis of organometallic polyphosphazene polymers containing two organometallic fragments is discussed as a new and general method for obtaining bimetallic nanostructured materials.     

Preparation of Polymers Containing Metal–Metal Bonds along the Backbone Using Click Chemistry

The [(η⁵-C₅H₄(CH₂)₃OC(O)(CH₂)₂C≡CH)Mo(CO)₃]₂ complex (1) was synthesized and used to explore the feasibility of using the Huisgen cycloaddition reaction (a click reaction) to incorporate molecules with metal–metal bonds into polymer backbones. In a model reaction, coupling of 1 with benzyl azide was observed in 24 h using Cp*Ru(PPh₃)₂Cl as a catalyst. In contrast, the reaction of 1 with benzyl azide using a CuBr/ligand catalyst (where the ligand is either PMDETA or bipyridine), resulted in disproportionation of the Mo–Mo unit in 1. Complex 1 was also coupled with telechelic azide-terminated polystyrene oligomers. With either the CuBr/PMDETA or CuBr/bipyridine catalyst, disproportionation of the Mo–Mo bonded unit occurred before complete coupling was observed. The reaction was also slow when the Cp*Ru(PPh₃)₂Cl catalyst was used; however, no disproportionation products were observed and a high molecular weight polymer (M _n = 120,000 g/mol) was produced. The Cp*Ru(PPh₃)₂Cl catalyst was also used to couple 1 with azide-terminated poly(ethylene glycol). After 15 h, this reaction produced a polymer with M _n = 73,000 g mol⁻¹. It is concluded that, although somewhat slow, click chemistry using the Cp*Ru(PPh₃)₂Cl catalyst is an excellent method for synthesizing high molecular weight polymers with metal–metal bonds along the backbone.     

Developing a fulvene route to C1-bridged “constrained geometry” Ziegler catalyst systems

6-dimethylamino-6-methylfulvene (7) was converted to the [(C₅H₄)–CMe₂–NMe₂]⁻ ligand system (8) by treatment with methyllithium. Its reaction with MCl₄ (M = Zr, Ti) followed by treatment with CH₃Li gave the respective [(C₅H₄)–CMe₂–NMe₂]₂M(CH₃)₂ complexes (12). Their reaction with B(C₆F₅)₃ led to reactive metallocene cation complexes that instantaneously underwent CH activation at a N–CH₃ group to yield the metallacyclic cation complexes 15. (tert-butylaminomethyl)fluorene was prepared by the addition of tert-butylisocyanate to fluorenyllithium followed by hydride reduction. Deprotonation by a variety of bases gave rise to a series of competing and consecutive reactions to yield several unusually structured products, among them a fluorenyl-anellated η⁵-1-azapentadienyl anion equivalent (25) and [(flu)-CH₂–NCMe₃]Li₂ (23). An improved way of generating synthetically useful C₁-linked [Cp–C₁(R) _n –NR¹]^2- dianion equivalents was developed starting from 6-amino-6-methylfulvene (26). N-silylation followed by double deprotonation with, e.g., lithium diisopropylamide cleanly furnished the respective [(C₅H₄)–C(=CH₂)–NSiMe₃]^2- dianion 33 (isolated as the dilithio derivative). Its reaction with Cl₂Zr(NEt₂)₂ in THF gave [η⁵:κ-N-(C₅H₄)–C(=CH₂)–NSiMe₃]Zr(NEt₂)₂ 36. Activation of 36 with methylalumoxane in toluene led to the formation of a C₁-linked “constrained geometry” Ziegler catalyst that polymerized ethylene similarly as the [(C₅Me₄)SiMe₂NCMe₃]ZrCl₂ derived literature system. This revised version was published online in June 2006 with corrections to the Cover Date.     

General aspects of ethylene polymerization by d0 and d0f n transition metals

We present a generalized view of d⁰and d⁰f ⁿ metal complexes as olefin polymerization catalysts from computational studies of the {L}M–C₂H₅ ^(0,+,2+)-fragments (M = Sc(III), Y(III), La(III), Lu(III), Ti(IV), Zr(IV), Hf(IV), Ce(IV), Th(IV) and V(V); L = NH–(CH)₂–NH^2- {1}, N(BH₂)–(CH)₂–(BH₂)N^2- {2}, O–(CH)₃–O^- {3}, Cp₂ ^2- {4}, NH–Si(H₂)–C₅H₄ ^2- {5}, {(oxo)(O–(CH)₃–O)}^3- {6}, (NH₂)₂ ^2- {7}, (OH)₂ ^2- {8}, (CH₃)₂ ^2- {9}, NH–(CH₂)₃–NH^2- {10} and O–(CH₂)₃–O^2- {11}). This revised version was published online in June 2006 with corrections to the Cover Date.     

A convenient method for the synthesis of [Pd{[(η5-C5H3)–CHN–(CH2)2–NMe2]Fe(η5-C5H5)}Cl] and the study of its reactivity with diphosphines

A one-pot method for the preparation of [Pd{[(η⁵-C₅H₃)–CHN–(CH₂)₂–NMe₂]Fe(η⁵-C₅H₅)}Cl] is described. Its X-ray crystal structure and its reactions with the diphosphines Ph₂P–(CH₂)_n–PPh₂ {with n=1 (ddpm) or 2 (dppe)} are also reported.     

Polyferrocenylsilanes as Protective Charge Migration Coatings for Dielectrics

Polyferrocenylsilanes [Fe(η-C₅H₄)₂SiMePh] _n (3) and [Fe(η-C₅H₄)₂SiMe₂] _n (4) were prepared by transition metal-catalyzed ring-opening polymerization (ROP) and thin films of these materials were studied to investigate their potential utility as protective charge migration coatings for dielectrics. Films ( 15 μm) of 3 or 4 cast from a concentrated toluene solution coated on Mylar did not experience any arc discharging when exposed to a beam of low energy (20 keV) electrons for a 1 h time period. In order to further investigate the charge migration properties of polyferrocenylsilanes, thick shapes and films of 3 were prepared by mold-extrusion and solution-casting onto a Teflon substrate, respectively. Charge accumulation measurements on 3 using a nonintrusive electrostatic probe showed that even after a 1 h exposure to a 25 keV electron flux, no appreciable charge accumulation existed. The direction of current flow was explored by constructing a device consisting of a film (thickness ca. 100–130 μm) of polymer 3 coating a layer of copper. When positioned beneath a circular mask and exposed to a low energy electron flux (5–25 keV), measurements of the current at the surface of the polymer film either exposed to or not exposed to the electron flux were not significantly different, and the current recorded from the bare copper connection to the ground was significantly (100–1000 times) higher. Although the mechanism of charge migration in polyferrocenylsilanes is not fully understood, these experiments indicated it may arise from a conduction mechanism, however electron scattering may also be involved.Dedicated to Professor Richard J. Puddephatt in recognition of his outstanding and scholarly contributions to chemistry.     

Synthesis and Redox Properties of a π-Conjugated Cyclobutadienecobalt Polymer Containing Ferrocenyl Groups

The reaction of CpCo(PPh₃)₂, in which Cp= ⁵-cyclopentadienyl, with a -conjugated diacetylene, FcCC–o-C₆H₄–CCFc, in which Fc=ferrocenyl, was found to give a cyclobutadienecobalt mononuclear complex, { ⁴-C₄Fc₂(o-FcC₆H₄)₂}CoCp (1), the crystal structure of which was determined by X-ray crystallography. In contrast, the reaction of CpCo(PPh₃)₂ with FcCC–p-C₆H₄–CCFc affords a cyclobutadienecobalt polymer, [p-C₆H₄( ⁴-C₄Fc₂)CoCp] _n (2). The monocobalt complex 1 shows reversible 1e^– and 3e^– redox waves at E ⁰=0.116 and 0.350 V vs Ag/Ag⁺, and the polymer complex 2 shows two chemically reversible redox waves at E ⁰=0.143 and 0.219 V for the oxidation of the ferrocenyl moieties in the cyclic voltammogram. Crystal data are as follows: (1, C₆₅H₄₉CoFe₄), triclinic, space group P\={1} (No. 2), a=13.547(4), b=16.197(4), c=11.763(4) Å, =106.79(2), =97.93(3), =97.12(3), V=2410(1) ų, Z=2.     

Synthesis of pyrrole-bridged constrained geometry complexes and their application for olefin polymerization

In this article, four constrained geometry complexes 4a [(η⁵-C₅H₄)CH₂(α-C₄H₃N)]Ti(NMe₂)₂, 7a [(η⁵-C₉H₆)CH₂(α-C₄H₃N)]Ti(NMe₂)₂, 4b [(η⁵-C₅H₄)CH₂(α-C₄H₃N)]Zr(NEt₂)₂, 7b [(η⁵-C₉H₆)CH₂(α-C₄H₃N)]Zr(NEt₂)₂ with pyrrole-bridged fragment were synthesized and characterized by ¹H NMR, ¹³C NMR, MASS, and EA. When combined with MAO, complex 4b given the highest activity, the activity of copolymerizing ethylene and 1-hexene reached 2.48 × 10⁶ g polymer/mol·M·h. The effects of temperature, pressure, and ratio of Al/Metal on the polymerization reaction and properties of polymers had been investigated. The polymers with these complexes were characterized by ¹³C NMR and DSC, and the results shown that polymer with 4a had the highest α-olefin incorporation, the incorporation of 1-hexene reached up to 9.81 mol%, and the 1-octene was 8.84 mol%. Actually, there was no [HH] or [OO] sequence in the copolymer, according to the formula of reactivity ratio, rE • rH = 0, all these results suggested that the copolymerization mode is alternating copolymerization. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48620.     

Study of the cytotoxic activity of alkenyl-substituted ansa-titanocene complexes

The cytotoxic activity on tumour cell lines, human adenocarcinoma HeLa, human myelogenous leukemia K562, human malignant melanoma Fem-x and normal immunocompetent cells, was tested for four different ansa-titanocene dichloride derivatives with potentially reactive substituents [Ti{Me(CH₂CH)Si(η⁵-₅Me₄) (η⁵-C₅H₄)}Cl₂] (1), [Ti{Me(H)Si(η⁵-C₅Me₄)₂}Cl₂] (2), [Ti{Me{(CH₂CH)Me₂SiCH₂CH₂}Si(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] (3) and [Ti{Me₂Si(η⁵-C₅Me₄)(η⁵-C₅H₃(CMe₂(CH₂CH₂CHCH₂)))}Cl₂] (4), showing a very promising activity and opening up the possibility of extensive investigation in this field.     

Structural differences of half-sandwich complexes of scandium and yttrium containing bulky substituents

Scandium and yttrium half-sandwich chloride complexes (η⁵-C₅Me₄R)ScCl₂(THF)₂ R = CH₂Ph (3) or SiMe₂CH₂CH₂Ph (5) and (η⁵-C₅Me₄R)YCl₂(THF)₂ R = CH₂Ph (4) or SiMe₂CH₂CH₂Ph (6) were prepared by metathetic reactions of the corresponding substituted lithium or potassium cyclopentadienides with scandium or yttrium trichloride. A mutual comparison of the determined solid state structures of 4 and 5 revealed the tetranuclear character in the case of scandium complex containing C₅Me₄SiMe₂CH₂CH₂Ph ligand, while a formation of the trinuclear ate-complex 4 incorporating lithium was observed for the combination of yttrium and the benzyl substituted tetramethyl cyclopentadienyl. Moreover, the steric effect of addition of another differently substituted cyclopentadienyl ring into the molecule was evaluated.     

Semi-rigid N-para-ferrocenyl(benzoyl)amino-acid esters for biomaterials: synthesis and characterization of Fc-C6H4CONHCH(R)CO2Me where Fc = (η5-C5H5)Fe(η5-C5H4) and R=H,CH3,CH2CH(CH3)2,CH2C6H5 and the X-ray crystal structures of Fc-C6H4CO2Me and the l-alanine derivative Fc-C6H4CONHCH(CH3)CO2Me

A series of N-para-(ferrocenyl)benzoyl amino-acid esters, para-Fc(C₆H₄)CONHCH(R)CO₂CH₃ {Fc = (η⁵-C₅H₅)Fe(η⁵-C₅H₄); R = H, CH₃, CH₂CH(CH₃)₂, CH₂C₆H₅}, 3–6 have been prepared by coupling para-(ferrocenyl)benzoic acid to the amino-acid esters (gly, l-Ala, l-Leu, l-Phe) using the standard 1,3-dicyclohexylcarbodiimide (DCC), 1-hydroxybenzotriazole (HOBt) protocol. The compounds were fully characterized by a range of spectroscopic techniques including FAB-MS. The X-ray crystal structures of the parent para-(ferrocenyl)benzoyl methyl ester, Fc-C₆H₄CO₂Me, 1 and a chiral derivative N-{para-(ferrocenyl)benzoyl}-l-alanine methyl ester, Fc-C₆H₄CONHCH(CH₃)CO₂Me, 4 have been determined.