A general route for the N-hydroxysuccinimidyl (NHS) ester functionalization of poly(ferrocenyldimethylsilane)-b-polyvinylsiloxane copolymers, which should be readily transferrable to other vinyl containing polymers, has been developed using a simple two step approach. Facile reaction of the NHS ester functionalized polymers with primary amines enables the incorporation of a range of functionalities previously inaccessible using standard thiol-ene “click” reactions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 245–252

The crystallization-driven self-assembly (CDSA) of crystalline-coil polyselenophene diblock copolymers represents a facile approach to nanofibers with distinct optoelectronic properties relative to those of their polythiophene analogs. The synthesis of an asymmetric diblock copolymer with a crystallizable, π-conjugated poly(3-heptylselenophene) (P3C7Se) block and an amorphous polystyrene (PS) coblock is described. CDSA was performed in solvents selective for the PS block. Based on transmission electron microscopy (TEM) analysis, P3C7Se₁₈-b-PS₁₂₅ formed very long (up to 5 μm), highly aggregated nanofibers in n-butyl acetate (nBuOAc) whereas shorter (ca. 500 nm) micelles of low polydispersity were obtained in cyclohexane. The micelle core widths in both solvents determined from TEM analysis (≈ 8 nm) were commensurate with fully-extended P3C7Se₁₈ chains (estimated length = 7.1 nm). Atomic force microscopy (AFM) analysis provided characterization of the micelle cross-section including the PS corona (overall micelle width ≈ 60 nm). The crystallinity of the micelle cores was probed by UV–vis and photoluminescence (PL) spectroscopy and wide-angle X-ray scattering (WAXS).

Mild thermolysis of Lewis base stabilized phosphinoborane monomers R¹R²PBH₂⋅NMe₃ (R¹,R²=H, Ph, or tBu/H) at room temperature to 100 °C provides a convenient new route to oligo- and polyphosphinoboranes [R¹R²P-BH₂]_n. The polymerization appears to proceed via the addition/head-to-tail polymerization of short-lived free phosphinoborane monomers, R¹R²P-BH₂. This method offers access to high molar mass materials, as exemplified by poly(tert-butylphosphinoborane), that are currently inaccessible using other routes (e.g. catalytic dehydrocoupling).

The creation of synthetic 2D materials represents an attractive challenge that is ultimately driven by their prospective uses in, for example, electronics, biomedicine, catalysis, sensing, and as membranes for separation and filtration. This Review illustrates some recent advances in this diverse field with a focus on covalent and non-covalent 2D polymers and frameworks, and self-assembled 2D materials derived from nanoparticles, homopolymers, and block copolymers.

The catalyst loading is the key to control the molecular weight of the polymer in the iron-catalyzed dehydropolymerization of phosphine–borane adducts. Studies showed that the reaction proceeds through a chain-growth coordination–insertion mechanism.

Die milde Thermolyse der Lewis-Base-stabilisierten Phosphanylboran-Monomere R¹R²P-BH₂⋅NMe₃ (R¹,R²=H, Ph oder tBu/H) von Raumtemperatur bis 100 °C ist eine bequeme Synthesemethode für Oligo- und Poly(phosphanylborane) [R¹R²P-BH₂]_n. Die Polymerisation scheint über eine Additions-/Kopf-Schwanz-Polymerisation kurzlebig, freier Phosphanylboran-Monomere, R¹R²P-BH₂, zu verlaufen. Diese Methode liefert hochmolekulare Materialien, wie durch Poly(tert-butylphosphanylborane) veranschaulicht, die gegenwärtig auf anderen Wegen (z. B. katalytische dehydrierende Kupplung) nicht zugänglich sind.

Die Herstellung synthetischer zweidimensionaler (2D-)Materialien ist eine faszinierende, aber schwierige Aufgabe, angetrieben durch Anwendungsmöglichkeiten in der Elektronik, Biomedizin, Katalyse und Sensorik sowie in Form von Membranen für die Trennung und Filtration. Unser Aufsatz beleuchtet aktuelle Fortschritte auf diesem breiten Gebiet, mit Schwerpunkten auf kovalenten und nichtkovalenten 2D-Polymeren und Gerüsten sowie auf selbstorganisierten 2D-Materialien aus Nanopartikeln, Homopolymeren und Blockcopolymeren.

The catalyst loading is the key to control the molecular weight of the polymer in the iron-catalyzed dehydropolymerization of phosphine–borane adducts. Studies showed that the reaction proceeds through a chain-growth coordination–insertion mechanism.

Hard ferromagnetic (L1₀ phase) FePt alloy nanoparticles (NPs) with extremely high magnetocrystalline anisotropy are considered to be one of the most promising candidates for the next generation of ultrahigh-density data storage system. The question of how to generate ordered patterns of L1₀-FePt NPs and how to transform the technology for practical applications represents a key current challenge. Here the direct synthesis of L1₀ phase FePt NPs by pyrolysis of Fe-containing and Pt-containing metallopolymer blend without post-annealing treatment is reported. Rapid single-step fabrication of large-area nanodot arrays (periodicity of 500 nm) of L1₀-ordered FePt NPs can also be achieved by employing the metallopolymer blend, which possesses excellent solubility in most organic solvents and good solution processability, as the precursor through nanoimprint lithography (NIL). Magnetic force microscopy (MFM) imaging of the nanodot pattern indicates that the patterned L1₀ phase FePt NPs are capable of exhibiting decent magnetic response, which suggests a great potential to be utilized directly in the fabrication of bit patterned media (BPM) for the next generation of magnetic recording technology.

The reaction of R¹R²PCl (R¹ = Me, Ph; R² = Ph, oTol) with N,N′-bis(trimethylsilyl)sulfur diimide in the presence of GaCl₃ yields Lewis acid/base adducts of the corresponding cyclodiphosph(V)azenes: [MePhPN]₂·(GaCl₃)₂, [Me(dmp)PN]₂·(GaCl₃)₂ (dmp = 2,6-dimethylphenyl), and [Ph(oTol)PN]₂·(GaCl₃)₂. The same synthetic protocol was applied for the model compound Ph₂AsCl. All isolated products were characterized spectroscopically and by single-crystal X-ray diffraction studies. Their ability to form oligomers/polymers induced by abstraction of the Lewis acid was investigated with the model compounds [MePhPN]₂·(GaCl₃)₂ and [Ph₂PN]₂·(GaCl₃)₂.

Reactivity studies of dicarba[2]ferrocenophanes and also their corresponding ring-opened oligomers and polymers have been conducted in order to provide mechanistic insight into the processes that occur under the conditions of their thermal ring-opening polymerisation (ROP) (300 °C). Thermolysis of dicarba[2]ferrocenophane rac-[Fe(η⁵-C₅H₄)₂(CHPh)₂] (rac-14; 300 °C, 1 h) does not lead to thermal ROP. To investigate this system further, rac-14 was heated in the presence of an excess of cyclopentadienyl anion, to mimic the postulated propagating sites for thermally polymerisable analogues. This afforded acyclic [(η⁵-C₅H₅)Fe(η⁵-C₅H₄)-CH₂Ph] (17) through cleavage of both a FeCp bond and also the CC bond derived from the dicarba bridge. Evidence supporting a potential homolytic CC bond cleavage pathway that occurs in the absence of ring-strain was provided through thermolysis of an acyclic analogue of rac-14, namely [(η⁵-C₅H₅)Fe(η⁵-C₅H₄)(CHPh)₂-C₅H₅] (15; 300 °C, 1 h), which also afforded ferrocene derivative 17. This reactivity pathway appears general for post-ROP species bearing phenyl substituents on adjacent carbons, and consequently was also observed during the thermolysis of linear polyferrocenylethylene [Fe(η⁵-C₅H₄)₂(CHPh)₂]_n (16; 300 °C, 1 h), which was prepared by photocontrolled ROP of rac-14 at 5 °C. This afforded ferrocene derivative [Fe(η⁵-C₅H₄CH₂Ph)₂] (23) through selective cleavage of the H(Ph)CC(Ph)H bonds in the dicarba linkers. These processes appear to be facilitated by the presence of bulky, radical-stabilising phenyl substituents on each carbon of the linker, as demonstrated through the contrasting thermal properties of unsubstituted linear trimer [(η⁵-C₅H₅)Fe(η⁵-C₅H₄)(CH₂)₂(η⁵-C₅H₄)Fe(η⁵-C₅H₄)(CH₂)₂(η⁵-C₅H₄)Fe(η⁵-C₅H₅)] (29) with a H₂CCH₂ spacer, which proved significantly more stable under analogous conditions. Evidence for the radical intermediates formed through CC bond cleavage was detected through high-resolution mass spectrometric analysis of co-thermolysis reactions involving rac-14 and 15 (300 °C, 1 h), which indicated the presence of higher molecular weight species, postulated to be formed through cross-coupling of these intermediates.

In contrast to ruthenocene [Ru(η⁵-C₅H₅)₂] and dimethylruthenocene [Ru(η⁵-C₅H₄Me)₂] (7), chemical oxidation of highly strained, ring-tilted [2]ruthenocenophane [Ru(η⁵-C₅H₄)₂(CH₂)₂] (5) and slightly strained [3]ruthenocenophane [Ru(η⁵-C₅H₄)₂(CH₂)₃] (6) with cationic oxidants containing the non-coordinating [B(C₆F₅)₄]⁻ anion was found to afford stable and isolable metalmetal bonded dicationic dimer salts [Ru(η⁵-C₅H₄)₂(CH₂)₂]₂[B(C₆F₅)₄]₂ (8) and [Ru(η⁵-C₅H₄)₂(CH₂)₃]₂[B(C₆F₅)₄]₂ (17), respectively. Cyclic voltammetry and DFT studies indicated that the oxidation potential, propensity for dimerization, and strength of the resulting RuRu bond is strongly dependent on the degree of tilt present in 5 and 6 and thereby degree of exposure of the Ru center. Cleavage of the RuRu bond in 8 was achieved through reaction with the radical source [(CH₃)₂NC(S)SSC(S)N(CH₃)₂] (thiram), affording unusual dimer [(CH₃)₂NCS₂Ru(η⁵-C₅H₄)(η³-C₅H₄)C₂H₄]₂[B(C₆F₅)₄]₂ (9) through a haptotropic η⁵–η³ ring-slippage followed by an apparent [2+2] cyclodimerization of the cyclopentadienyl ligand. Analogs of possible intermediates in the reaction pathway [C₆H₅ERu(η⁵-C₅H₄)₂C₂H₄][B(C₆F₅)₄] [E=S (15) or Se (16)] were synthesized through reaction of 8 with C₆H₅EEC₆H₅ (E=S or Se).

With the aim of accessing colloidally stable, fiberlike, π-conjugated nanostructures of controlled length, we have studied the solution self-assembly of two asymmetric crystalline–coil, regioregular poly(3-hexylthiophene)-b-poly(2-vinylpyridine) (P3HT-b-P2VP) diblock copolymers, P3HT₂₃-b-P2VP₁₁₅ (block ratio=1:5) and P3HT₄₄-b-P2VP₁₁₅ (block ratio=ca. 1:3). The self-assembly studies were performed under a variety of solvent conditions that were selective for the P2VP block. The block copolymers were prepared by using Cu-catalyzed azide–alkyne cycloaddition reactions of azide-terminated P2VP and alkyne end-functionalized P3HT homopolymers. When the block copolymers were self-assembled in a solution of a 50 % (v/v) mixture of THF (a good solvent for both blocks) and an alcohol (a selective solvent for the P2VP block) by means of the slow evaporation of the common solvent; fiberlike micelles with a P3HT core and a P2VP corona were observed by transmission electron microscopy (TEM). The average lengths of the micelles were found to increase as the length of the hydrocarbon chain increased in the P2VP-selective alcoholic solvent (MeOH<iPrOH<nBuOH). Very long (>3 μm) fiberlike micelles were prepared by the dialysis of solutions of the block copolymers in THF against iPrOH. Furthermore the widths of the fibers were dependent on the degree of polymerization of the chain-extended P3HT blocks. The crystallinity and π-conjugated nature of the P3HT core in the fiberlike micelles was confirmed by a combination of UV/Vis spectroscopy, photoluminescence (PL) measurements, and wide-angle X-ray scattering (WAXS). Intense sonication (iPrOH, 1 h, 0 °C) of the fiberlike micelles formed by P3HT₂₃-b-P2VP₁₁₅ resulted in small (ca. 25 nm long) stublike fragments that were subsequently used as initiators in seeded growth experiments. Addition of P3HT₂₃-b-P2VP₁₁₅ unimers to the seeds allowed the preparation of fiberlike micelles with narrow length distributions (L_w/L_n <1.11) and lengths from about 100-300 nm, that were dependent on the unimer-to-seed micelle ratio.

Stable colloidal dispersions of polyaniline (PAni) nanofibers with controlled lengths from about 200 nm–1.1 μm and narrow length distributions (L_w/L_n<1.04; L_w=weight average micelle length, L_n=number average micelle length) were prepared through the template-directed synthesis of PAni using monodisperse, solution-self-assembled, cylindrical, block copolymer micelles as nanoscale templates. These micelles were prepared through a crystallization-driven living self-assembly method from a poly(ferrocenyldimethylsilane)-b-poly(2-vinylpyridine) block copolymer (PFS₂₅-b-P2VP₄₂₅). This material was initially self-assembled in iPrOH to form cylindrical micelles with a crystalline PFS core and a P2VP corona and lengths of up to several micrometers. Sonication of this sample then yielded short cylinders with average lengths of 90 nm and a broad length distribution (L_w/L_n=1.32). Cylindrical micelles of PFS₂₅-b-P2VP₄₂₅ with controlled lengths and narrow length distributions (L_w/L_n<1.04) were subsequently prepared using thermal treatment at specific temperatures between 83.5 and 92.0 °C using a 1D self-seeding process. These samples were then employed in the template-directed synthesis of PAni nanofibers through a two-step procedure, where the micellar template was initially stabilised by deposition of an oligoaniline coating followed by addition of a polymeric acid dopant, resulting in PAni nanofibers in the emeraldine salt (ES) state. The ES–PAni nanofibers were shown to be conductive by scanning conductance microscopy, whereas the precursor PFS₂₅-b-P2VP₄₂₅ micelle templates were found to be dielectric in character.

The metallation of the cyclopentadienyl (Cp) ligands of poly(ferrocenyldimethylsilane) (PFDMS) can be performed by reaction with the Schlosser's base pair t-BuLi/KOt-Bu in THF. Subsequent treatment with a series of electrophiles affords a range of Cp-substituted polymers with up to an average of 1.8 new substituents per repeating unit. NMR studies on polymers containing trimethylsilyl groups and deuterium on the Cp rings are indicative of high regioselectivity with selective metallation at the β-carbon.

Recent advances in polymer synthesis have significantly enhanced the ability to rationally design block copolymers with tailored functionality. The self-assembly of these macromolecules in the solid state or in solution allows the formation of nanostructured materials with a variety of properties and potential functions. This Review illustrates recent progress in the field of block copolymer materials by highlighting selected emerging applications.

We demonstrate the synthesis and characterization of star-shaped crystalline-coil block copolymers with four arms consisting of an inner block of poly(ethylene oxide) and an outer semicrystalline compartment of poly(ferrocenyldimethylsilane), [PEO₅₀-b-PFDMS₃₅]₄. The materials were synthesized by transition-metal-catalyzed ring-opening polymerization of dimethylsila[1]ferrocenophane in the presence of silane-functionalized four-arm PEO stars as macroinitiators and they exhibited a moderate polydispersity (PDI≅1.4). Self-assembly in mixtures of THF and different alcohols as selective solvents for the PEO block resulted in the formation of semicrystalline vesicles (ethanol, 1-butanol) or large, rather ill-defined, spherical structures (methanol). Further, both the rate of addition of the selective co-solvent and the overall solvent/non-solvent ratio drastically affected the size and stability of the self-assembled particles. We could also show that a photoacid generator, as a model for an active substance, can be encapsulated and the UV-induced generation of HCl resulted in a straightforward degradation of the organometallic vesicles.

The dehydrocoupling/dehydrogenation behavior of primary arylamine–borane adducts ArNH₂⋅BH₃ (3 a–c; Ar=a: Ph, b: p-MeOC₆H₄, c: p-CF₃C₆H₄) has been studied in detail both in solution at ambient temperature as well as in the solid state at ambient or elevated temperatures. The presence of a metal catalyst was found to be unnecessary for the release of H₂. From reactions of 3 a,b in concentrated solutions in THF at 22 °C over 24 h cyclotriborazanes (ArNH-BH₂)₃ (7 a,b) were isolated as THF adducts, 7 a,b⋅THF, or solvent-free 7 a, which could not be obtained via heating of 3 a–c in the melt. The μ-(anilino)diborane [H₂B(μ-PhNH)(μ-H)BH₂] (4 a) was observed in the reaction of 3 a with BH₃⋅THF and was characterized in situ. The reaction of 3 a with PhNH₂ (2 a) was found to provide a new, convenient method for the preparation of dianilinoborane (PhNH)₂BH (5 a), which has potential generality. This observation, together with further studies of reactions of 4 a, 5 a, and 7 a,b, provided insight into the mechanism of the catalyst-free ambient temperature dehydrocoupling of 3 a–c in solution. For example, the reaction of 4 a with 5 a yields 6 a and 7 a. It was found that borazines (ArN-BH)₃ (6 a–c) are not simply formed via dehydrogenation of cyclotriborazanes 7 a–c in solution. The transformation of 7 a to 6 a is slowly induced by 5 a and proceeds via regeneration of 3 a. The adducts 3 a–c also underwent rapid dehydrocoupling in the solid state at elevated temperatures and even very slowly at ambient temperature. From aniline–borane derivative 3 c, the linear iminoborane oligomer (p-CF₃C₆H₄)N[BH-NH(p-CF₃C₆H₄)]₂ (11) was obtained. The single-crystal X-ray structures of 3 a–c, 5 a, 7 a, 7 b⋅THF, and 11 are discussed.

Conjugates of poly(ferrocenyldimethylsilane) (PFDMS) with Ac-(GA)₂-OH, Ac-A₄-OH, Ac-G₄-OH and Ac-V₄-OH have been prepared by reaction of the tetrapeptide units with the amino-terminated metallopolymer. The number average degree of polymerisation (DP_n) of the PFDMS was approximately 20 and comparable materials with shorter (DP_n≈10) and/or amorphous chains have been prepared by the same procedure. Poly(ferrocenylethylmethylsilane) (PFEMS) was employed for the latter purpose. All conjugates were characterised by GPC, MALDI-TOF MS, NMR and IR spectroscopy. With the exception of Ac-V₄-PFDMS₂₀, all materials exhibited some anti-parallel β-sheet structure in the solid state. The self-assembly of the conjugates was studied in toluene by DLS. The vast majority of the materials, irrespective of peptide sequence or chain crystallinity, afforded fibres consisting of a peptidic core surrounded by a PFS corona. These fibres were found in the form of cross-linked networks by TEM and AFM. The accessibility of the chemically reducing PFS corona has been demonstrated by the localised formation of silver nanoparticles on the surface of the fibres.

Moderne Methoden der Polymersynthese eröffnen eine Vielzahl an Möglichkeiten zur zielgerichteten Herstellung von Blockcopolymeren mit maßgeschneiderter Funktionalität. Die Selbstaggregation solcher Makromoleküle in fester Phase oder in Lösung führt zur Bildung nanostrukturierter Materialien mit unterschiedlichen Eigenschaften und möglichen Funktionen. Dieser Aufsatz beschäftigt sich mit jüngsten Entwicklungen auf dem Gebiet der Blockcopolymer-basierten Materialien und behandelt eine Auswahl sich entwickelnder Anwendungsfelder.

The catalytic dehydrocoupling of Me₂NH·BH₃ (1) by Rh/Al₂O₃ (2) has been shown to act as an efficient hydrogenation and reduction system for a variety of organic substrates. A range of functional groups have been reduced, but chloro, bromo and iodo substituents, epoxide and nitrile groups were found to be stable under the reaction conditions, allowing chemoselective hydrogenation reactions to be performed. This reduction has also been shown to proceed cleanly under atmospheric air for a few representative examples of alkene and nitro functional groups.

The amine–borane adduct iPr₂NH·BH(C₆F₅)₂ (1) and the aminoborane iPr₂N=B(C₆F₅)₂ (2) have been prepared and crystallographically characterised. Interconversion between the two compounds has been attempted using thermal and transition-metal-catalysed dehydrogenation and hydrogenation protocols and the overall reaction thermodynamics were probed by computational methods. Thermal dehydrogenation of 1 was found to yield 2, together with uncharacterised by-products. Treatment of 1 with the carbene 1,3-di-tert-butyl-4,5-dihydroimidazol-2-ylidene (3) under ambient conditions did not lead to the elimination of hydrogen, but instead to the loss of C₆F₅H to afford iPr₂N=B(H)C₆F₅ (4). Attempts to hydrogenate aminoborane 2 were unsuccessful with no reaction observed either thermally or in the presence of transition-metal catalysts. A computational study of the interconversion between compounds 1 and 2 indicated a thermodynamically unfavourable hydrogenation reaction, which was inverse to that demonstrated for the analogous phosphane–borane/phosphanylborane pair, iPr₂PH·BH(C₆F₅)₂ (5) and iPr₂P–B(C₆F₅)₂ (6). The contrasting reactivity was attributed to the different N–B and P–B π-bond strengths in 2 and 6, respectively.

An improved protocol for the selective dilithiation of [V(η⁵-C₅H₅)(η⁷-C₇H₇)] has been developed, which afforded [V(η⁵-C₅H₄Li)(η⁷-C₇H₆Li)]⋅PMDTA (5; PMDTA=N,N,N′,N′′,N′′-pentamethyldiethylenetriamine) in almost quantitative yield (98 %). In the solid state, the species features a dimeric structure with two terminal and two bridging lithium atoms, with the latter connecting both sandwich subunits. Reaction with suitable Group 4 dihalide compounds enabled the isolation of highly strained silicon- and germanium-bridged [1]trovacenophanes 6 and 7. Similarly, reaction of 5 with Cl₂Sn₂tBu₄ afforded the rather unstrained complex [V(η⁵-C₅H₄)(η⁷-C₇H₆)Sn₂tBu₄] (8), which together with 7 represent the first trovacenophanes to incorporate heavier analogues of silicon in the ansa-bridge. Ring-opening polymerization reactions of [V(η⁵-C₅H₄)(η⁷-C₇H₆)SiRR′] (2 a: R=R′=Me; 6: R=Me, R′=iPr) were performed by heating in a solution of toluene in the presence of the Karstedt catalyst, which resulted in the formation of the corresponding soluble poly(trovacenylsilanes) in yields of 41 and 33 %, respectively. As estimated by gel permeation chromatography (GPC), the macromolecules possess molecular weights of M_n=10 010 and 5580 g mol⁻¹ with polydispersity indices of 2.31 and 1.64 for 9 and 10, respectively. ESR spectroscopic studies on 9 and 10 revealed only a single broad resonance in each case without any identifiable ⁵¹V hyperfine coupling.

The ability of trialkyl Group 14 triflates in combination with amine and pyridine bases to dehydrogenate amine– and phosphane–borane adducts has been investigated. By using multinuclear NMR spectroscopy, it has been shown that Me₂NH·BH₃ (11) is efficiently converted to [Me₂N–BH₂]₂ (12) by the so-called “frustrated Lewis pair” (FLP) of nBu₃SnOTf (4, ^–OTf = ^–OSO₂CF₃) and 2,2,6,6-tetramethylpiperidine (6). Within the scope of the study, exchange of the Lewis acid effects the rate of dehydrogenation in the order: 4 > Me₃SiOTf (2) > Et₃SiOTf (3). Exchange of the Lewis base for 2,6-di-tert-butylpyridine (5) has also been shown to reduce the rate of reaction, whereas 1,3-di-tert-butylimidazol-2-ylidene (7) reacted directly with 2 to afford 1,3-bis-tert-butyl-4-(trimethylsilyl)imidazolium triflate (8[OTf]). For FLP combinations for which dehydrogenation reaction times are longer, detectable quantities of [H₂B(μ-H)(μ-NMe₂)BH₂] (14) are observed. Both the dehydrogenation reaction and competitive formation of this product are proposed to proceed by initial hydride abstraction by the Lewis acid, followed by deprotonation by the Lewis base, or combination with further dimethylamine–borane and elimination of [Me₂NH₂]OTf (18[OTf]), respectively. In contrast to 11, MeNH₂·BH₃ (22) was not found to cleanly dehydrogenate to either [MeNH–BH₂]₃ or [MeN–BH]₃ under the same conditions. An alternative reaction pathway was observed with either 2 or 4 and 6 with Ph₂PH·BH₃ (23), resulting in P-silylation or P-stannylation of the phosphane–borane, respectively.

Phosphorus-bridged strained [1]ferrocenophanes [Fe{(η-C₅H₄)₂P(CH₂CMe₃)}] (2) and [Fe{(η-C₅H₄)₂P(CH₂SiMe₃)}] (3) with neopentyl and (trimethylsilyl)methyl substituents on phosphorus, respectively, have been synthesized and characterized. Photocontrolled living anionic ring-opening polymerization (ROP) of the known phosphorus-bridged [1]ferrocenophane [Fe{(η-C₅H₄)₂P(CMe₃)}] (1) and the new monomers 2 and 3, initiated by Na[C₅H₅] in THF at 5 °C, yielded well-defined polyferrocenylphosphines (PFPs), [Fe{(η-C₅H₄)₂PR}]_n (R=CMe₃ (4), CH₂CMe₃ (5), and CH₂SiMe₃ (6)), with controlled molecular weights (up to ca. 60×10³ Da) and narrow molecular weight distributions. The PFPs 4–6 were characterized by multinuclear NMR spectroscopy, DSC, and by GPC analysis of the corresponding poly(ferrocenylphosphine sulfides) obtained by sulfurization of the phosphorus(III) centers. The living nature of the photocontrolled anionic ROP allowed the synthesis of well-defined all-organometallic PFP-b-PFS_F (7 a and 7 b) (PFS_F=polyferrocenylmethyl(3,3,3,-trifluoropropyl)silane) diblock copolymers through sequential monomer addition. TEM studies of the thin films of the diblock copolymer 7 b showed microphase separation to form cylindrical PFS_F domains in a PFP matrix.

The ring-opening polymerization (ROP) behavior of a variety of substituted 1,1′-ethylenylferrocenes, or dicarba[2]ferrocenophanes, is reported. The electronic absorption spectra and tilted solid-state structures of the monomers rac-[Fe(η⁵-C₅H₄)₂(CHiPr)₂] (7), [Fe(η⁵-C₅H₄)₂(C(H)MeCH₂)] (8), and rac-[Fe(η⁵-C₅H₄)₂(CHPh)₂] (9) are consistent with the presence of substantial ring strain, which was exploited to synthesize soluble, well-defined polyferrocenylethylenes (PFEs) [Fe(η⁵-C₅H₄)₂(C(H)MeCH₂)]_n (12) and [Fe(η⁵-C₅H₄)₂(CHPh)₂]_n (13) through photocontrolled ROP. Polymer chain lengths could be controlled by the monomer-to-initiator ratio up to about 50 repeat units and, consistent with the “living” nature of the polymerizations, sequential block copolymerization with a sila[1]ferrocenophane led to polyferrocenylethylene–polyferrocenylsilane (PFE-b-PFS) block copolymers (14 and 15). PFE polymers 12 and 13 showed two reversible oxidation waves, indicative of appreciable Fe⋅⋅⋅Fe interactions along the polymer backbone. The diblock copolymers were characterized by NMR spectroscopy, GPC analysis, and cyclic voltammetry.

A new type of metallopolymer-polypeptide block copolymer poly(ferrocenyldimethylsilane)-b-poly (ε-benzyloxycarbonyl-l-lysine) was synthesized by ring-opening polymerization of ε-benzyloxycarbonyl-l-lysine N-carboxyanhydride initiated by using a primary amino-terminated poly(ferrocenyldimethylsilane). Studies on the self-organization behavior of this polypeptide block copolymer in both the bulk state and in solution were performed. In the bulk state, a cylindrical-in-lamellar structure was observed in a compositionally asymmetric sample. Rod-like micelles with a polyferrocenylsilane core formed in a polypeptide-selective solvent alone or in the presence of a common solvent. Significantly, an additional small quantity of the common solvent assisted the formation of longer micelles and micelles with better shape-regularity. This is attributed to a decrease in the number of nucleation events and PFS core reorganization effects.

The photochemical reactions of the moderately strained sila[1]ferrocenophane [Fe(η-C₅H₄)₂SiPh₂] (1) and the highly strained thia[1]ferrocenophane [Fe(η-C₅H₄)₂S] (8) with transition-metal carbonyls ([Fe(CO)₅], [Fe₂(CO)₉] and [Co₂(CO)₈]) have been studied. The use of metal carbonyls has allowed the products of photochemically induced Fe-cyclopentadienyl (Cp) bond cleavage reactions in the [1]ferrocenophanes to be trapped as stable, characterisable products. During the course of these studies the synthesis of 8 from [Fe(η-C₅H₄Li)₂⋅TMEDA] (TMEDA=N,N,N′,N′-tetramethylethylenediamine) and S(SO₂Ph)₂ has been significantly improved by a change of reaction solvent and temperature. Photochemical reaction of 1 with excess [Fe(CO)₅] in THF gave the dinuclear complex [Fe₂(CO)₂(μ-CO)₂(η-C₅H₄)₂SiPh₂] (9). The analogous photolytic reaction of 8 with [Fe(CO)₅] in THF gave cyclic dimer [Fe(η-C₅H₄)₂S]₂ (10) and [Fe₂(CO)₂(μ-CO)₂(η-C₅H₄)₂S] (11), with the former being the major product. Photolysis of 1 with [Co₂(CO)₈] afforded the remarkable tetrametallic dimer [(CO)₂Co(η-C₅H₄)SiPh₂(η-C₅H₄)Fe(CO)₂]₂ (13). The corresponding photochemical reaction of 8 with [Co₂(CO)₈] gave a trimetallic insertion product in high conversion, [Co(CO)₄(CO)₂Fe(η-C₅H₄)S(η-C₅H₄)Co(CO)₂] (14). These reactivity studies show that UV light promotes FeCp bond cleavage reactions of both of the [1]ferrocenophanes 1 and 8. We have found that, whereas the less strained sila[1]ferrocenophane 1 requires photoactivation for FeCp bond insertions to occur, the highly strained thia[1]ferrocenophane 8 undergoes both irradiative and non-irradiative insertions, although the latter occur at a slower rate. Our results suggest that such photoinduced bond cleavage reactions may be general and applicable to other related strained organometallic rings with π-hydrocarbon ligands.