A method for the synthesis of well-defined mono-, di-, and mixed-telechelic polyphosphazenes produced via a living cationic polymerization of phosphoranimines is described. Amino phosphoranimines R−NH(CF3CH2O)2PNSiMe3 (R = Ph−, p-BrPh−, p-H3CPh−, CH2CHCH2−, and CH2CHPh−) were synthesized via a reaction between a bromophosphoranimine and the appropriate organic amine. Ditelechelic polymers [R−NH]2−[Cl2PN] n were prepared by quenching living poly(dichlorophosphazene) chains, [Cl3PN(Cl2PN) n −PCl3]+[PCl6]- with small quantities of the amino phosphoranimines. Cationic initiators of the amino phosphoranimines were also generated using PCl5 and were used to polymerize Cl3PNSiMe3, to give monotelechelic poly(dichlorophosphazenes). In addition, a mixed telechelic system was produced by the termination of an allylamino monotelechelic poly(dichlorophosphazene) chain with a bromoanilino phosphoranimine. In all cases, displacement of the chlorine atoms with sodium trifluoroethoxide yielded hydrolytically stable telechelic polymers with controlled molecular weights and low polydispersities.

Mono- and ditelechelic linear polyphosphazenes, functionalized with a norbornene end group, were synthesized through the termination of living poly(dichlorophosphazene) with norbornenyl phosphoranimines. These materials were employed as macromonomers for the synthesis of graft copolymers via the ring-opening metathesis polymerization (ROMP) of the terminal norbornenyl component. Norbornenyl monotelechelic polyphosphazenes with various molecular weights yielded un-cross-linked graft copolymers when subjected to ROMP. The ditelechelic polyphosphazenes yielded branched or cross-linked materials due to the multiple reactive sites. In addition, the 5-norbornene-2-methoxy phosphoranimine was polymerized via ROMP to yield materials that consisted of a polynorbornene backbone with phosphoranimine pendent side groups.

A new approach to the synthesis of poly(dichlorophosphazene) and poly(organophosphazenes) has been developed via the cationic condensation polymerization of phosphoranimines. The effects of solvent, temperature, concentration, and initiator on the cationic condensation polymerization of Cl3PNSiMe3 and PhCl2PNSiMe3 are described. The ambient temperature polymerization of PhCl2PNSiMe3 is faster in toluene, benzene, and dioxane than in methylene chloride or chloroform. The polymerizations of Cl3PNSiMe3 and PhCl2PNSiMe3 were monitored by both NMR (31P and 1H) and GPC methods. The initial polymerization rates are slow, presumably because of the precipitation of phosphazene short chain salts, RCl2PN−[PR(Cl)N] n −PCl3 +PCl6 - (where R = Cl or Ph; n = 0, 1, 2, ...). After the chains redissolve (∼15−60 min), polymerization proceeds, with the propagation rates following pseudo-first-order kinetics for both monomers. The reactions in toluene, benzene, or dioxane yielded polymers with controlled molecular weights in the range of 105, with narrow polydispersities (<1.3). The usefulness of this approach for the synthesis of a biomedically important polyphosphazene has also been demonstrated.

Synthetic strategies for the design of oligomeric ethers with pendant cyclopentadienyliron moieties have been developed. A wide range of these materials have been prepared via nucleophilic aromatic substitution reactions of a mono-or di-hydroxyaromatic nucleophiles and a variety of chloroarene complexes under mild experimental conditions. The mono-and bis-(cyclopentadienyliron) arene complexes were used as building blocks for the larger systems. The crystal stuctures of three bis(cyclopentadieny1iron) arene dications, [ (q5-C5H5) Fe(q6-C6H5) -0-XC6H,X-(q6-C,H5) Fe(q5-C5H5)I2+ (X = 0 or S) and [ (q5-C5H5) Fe(q6-C6H5) -m-OC,H,O-(q6-C,H5) Fe(q5-C5H5)I2+, have been determined by X-ray crystal structure analysis. A number of routes to the synthesis of the oligomeric species (tri-, tetra-and hexa-iron moieties) have been investigated to determine the flexibility and efficiency of the proposed strategies, and these materials have been fully characterized using spectroscopic and analytical techniques. To prove further the structures of these complexes, some of them have been prepared using different starting materials, giving the same proposed products. A series of polyiron complexes containing terminal hydroxy groups have also been prepared and used a s dinucleophiles.

A new development in the chemistry of arenes activated toward SNAr reactions by the cyclopentadienyliron (FeCp+) moiety is presented in this work. A class of diiron complexes of diphenoxybenzenes was prepared in a highly efficient and very mild fashion. Dihydroxy aromatic compounds served as dinucleophiles, allowing for the formation of the diiron complexes. This could be achieved in either a one or two step procedure. A wide variety of dinucleophiles were incorporated into this study, as well as a number of FeCp+ activated arenes. It is shown that these reactions are not inhibited by bulky substituents on either the dinucleophiles or activated arenes. The diiron complexes themselves could also undergo SNAr reactions, provided that the complexed arenes contained a chlorine substituent. This allowed for the functionalization of the complexes with species that could not be introduced directly in their syntheses. The carbon nucleophiles generated from ethyl cyanoacetate or (phenylsulfony1)acetonitrile could be attached to the complexed ethers in this manner. The FeCp+ moieties were removed easily by photolytic demetalation which allowed for the recovery of a wide range of functionalized diphenoxybenzenes. This methodology is advantageous over all those previously reported and should be a practical route to the synthesis of aromatic ethers.

A modification of the method for synthesis of well-defined mono- and ditelechelic polyphosphazenes via the living, cationic polymerization of phosphoranimines has been developed. This process provides access to phosphazene block, comb, and graft copolymers that contain organic or organosilicon macromolecules. Several alkoxy and aryloxy phosphoranimines, RO(CF3CH2O)2PNSiMe3 (R = Ph, MeOPh, C10H7, BOC−NH−CH2CH2, t-BuMe2SiO(CH2)5, C8H11, and CH2CH−C6H4), were synthesized via the reaction between a bromophosphoranimine and the appropriate sodium alkoxide or aryl oxide. These species are potential initiators or terminators, useful for the synthesis of telechelic polyphosphazenes with etheric linkages rather than the amino linkages used previously. Ditelechelic polymers, RO[(CF3CH2O)2PN] n −P(OCH2CF3)3OR, were prepared by terminating living poly(dichlorophosphazene) chains, [Cl3PN−(Cl2PN) n −PCl3]+[PCl6]-, with these alkoxy or aryloxy phosphoranimines. Alternatively, monotelechelic polyphosphazenes were produced through the termination of the polymer [(CF3CH2O2)3PN−(Cl2PN) n −PCl3]+[PCl6]- with the appropriate alkoxy or aryloxy phosphoranimines. In all cases, hydrolytically stable telechelic polymers with controlled molecular weights and low polydispersities were obtained in good yield after macromolecular replacement of labile chlorine atoms with sodium trifluoroethoxide.

Abstract:The electrochemical investigation of a number of polyarene-iron complexes ([3]"-[915+) containing etheric, sulphide, and sulphone bridges indicated that there were various degrees of interaction based on the nature of the bridging heteroatoms. While the electrochemical investigation of all etheric complexes showed that the metallic moieties behaved as isolated redox centers, it was found that there was electronic communication (ca. 70-80 mV) for the isomeric sulphide complexes [412+ and [612+. The rate constant of the following chemical reaction (k,) was calculated for some of these complexes and it was found that these rates were affected by the nature of the solvent, the bridging ligand, and the temperature. At various temperatures, kfindicated a higher degree of stability for complexes containing sulphide bridges than for those containing etheric bridges, especially at room temperature. The effect of a strong coordinating solvent, such as acetonitrile, on the k, of complex [3]'+ indicated that the substitution of the arene ligand with acetonitrile molecules proceeded as a dissociative mechanism. Controlled potential coulometry was also used to verify the transfer of two electrons in the first reduction process of the di-iron complexes.Key words: cyclopentadienyliron, cyclic voltammetry, arene complexes, isolated and interacting redox centers.

No abstract