Well-Controlled Polymerization of Phenylacetylenes with Organorhodium(I) Complexes:  Mechanism and Structure of the Polyenes

ABSTRACT:Polymerization of various mono-and disubstituted acetylenes was investigated by using GrubbsHoveyda catalyst (1). Hexyl propiolate (2) and 1-phenyl-2-(p-trimethylsilyl)phenylacetylene (3) Substituted polyacetylenes have been gathering much attention due to their potential applications to material-separation membranes, and optoelectronic and related fields.1 These polymers have been obtained by polymerization of corresponding acetylenic monomers in the presence of transition metal catalysts. Catalysts including group 5 and 6 transition metal and Rh have traditionally been employed to induce their polymerization. Among them, halides of early transition metals such as TaCl 5 , NbCl 5 , MoCl 5 , and WCl 6 in conjunction with organometallic cocatalysts polymerize various mono-and disubstituted acetylenes to give high molecular weight polymers in good yield. Some well-defined Ta, Mo, and W carbenes, so-called Schrock carbenes, induce living polymerization of substituted acetylenes. [2][3][4][5] This implies that the group 5 and 6 transition metal-catalyzed polymerization proceeds by the metathesis mechanism. One of the drawbacks of the early transition metal is that they are readily deactivated by polar groups in the monomer and polymerization solvents because of their high oxophilicity.Another type of catalysts frequently used for the polymerization of substituted acetylenes are rhodium (Rh) catalysts. Rh catalysts can polymerize only monosubstituted acetylenes such as phenylacetylene and its ring-substituted derivatives, 6-11 N-propargylamides, 12-17 and propiolic esters. [19][20][21][22][23] The Rh-catalyzed polymerization proceeds by the insertion mechanism, and features excellent tolerance to polar subsituents in the monomer 24,25 and protic solvents. 26 The Rh-based polymers generally possess high cis stereoregularity, which is indispensable for the formation of helical structures of poly(N-propargylamide)s. 12-17A huge number of studies on the synthesis and catalysis of ruthenium (Ru) carbene complexes have been reported in these several years. Ru carbene complexes represented by Grubbs' first-and secondgeneration catalysts exhibit high activity in olefin metathesis reactions such as ring-opening metathesis polymerization (ROMP), ring-closing metathesis (RCM), cross metathesis (CM). 27 Compared to early transition metal-based metathesis catalysts, Ru carbene complexes display tolerance against protic functional groups in these metathesis reactions as well as considerable stability to oxygen and moisture. It should also be noted that many Ru complexes have well-defined carbene structures, which enables to directly generate carbene-type active species without adding cocatalysts. The Grubbs' second-generation complex reportedly reacts with diphenylacetylene stoichiometrically to afford 3 -vinylcarbene complex, which is regarded as an intermediate of the polymerization of acetylenes.28 Ru-catalyzed polymerizations of acetylene 29 and diyne compounds 30,31 have recently been reported. Though an Ru carbene ...

Section: Structure and Properties Of Poly(2)mentioning

confidence: 96%

Polymerization of Substituted Acetylenes by the Grubbs–Hoveyda Ru Carbene Complex

Katsumata

Shiotsuki

Kuroki

et al. 2005

“…These matters depend mainly on the low polymerizability of the rotaxane-containing monomer due to the wheel component working as a sterically hindered group toward the growing end; competitive occurrence of the dethreading of the wheel component during polymerization when a pseudorotaxane monomer is used; and a nonstereoregular main chain polymer being formed by the polymerization of vinylic monomer. 9 Polymerization of a vinylic rotaxane monomer but not pseudorotaxane monomer has been reported only by Osakada et al 11 To overcome such issues, we have noticed and studied the synthesis of ethynyl-functionalized rotaxane monomer for high polymerization and its derivation to polyacetylene, because the high polymerization of bulky acetylenes is readily achieved with appropriate catalysts, [22][23][24][25][26][27][28][29] and polyacetylenes usually have a stable main chain conformation. In this paper, we wish to disclose the synthesis of phenylacetylene monomers tethering rotaxane moieties and their polymerization to novel side chain-type polyrotaxanes.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of acetylene-functionalized [2]rotaxane monomers directed toward side chain-type polyrotaxanes

Nakazono

Fukasawa

Sato

et al. 2010

A crown ether-ammonium salt-type rotaxane monomer was synthesized in a high yield using dibenzo-24-crown-8-ether and sec-ammonium salt having a hydroxy terminal by means of an end-capping reaction with an ethynyl benzoic acid. Its N-acetylated derivative was also synthesized in a quantitative yield using excess acetic anhydride and triethylamine. Novel side chain-type polyrotaxanes, that is, ammonium-type and neutral polyphenylacetylenes tethering rotaxane moieties in side chains with high molecular weights, were obtained in high yields by polymerizations with an Rh catalyst. The structures of the polymers were characterized by infrared, ultraviolet-visible (UV-vis) spectra and size exclusion chromatography. N-acetylation of the rotaxane moieties of the ammonium salt-type polymer resulted in the formation of a reddish-colored neutral polymer showing red-shifted UV-vis absorptions around 500 nm based on the conjugated main chain, according to the structural change of rotaxane side chains, that is, the change of the distance of the wheel component to the polyacetylene main chain. The solubility of the polymers was evaluated.

“…29 The stereoregularity of the poly-1 was confirmed to be a highly cis-transoidal by NMR spectroscopy. [39][40][41][42][43] The number-average molecular weight (M n ) and molecular weight distribution (M w =M n ) of poly-1 were 9:5 Â 10 4 and 5.6, respectively, as determined by sizeexclusion chromatography (SEC) using poly(ethylene oxide) and poly(ethylene glycol) standards in wateracetonitrile ( …”

Section: Methodsmentioning

confidence: 99%

Helicity Induction on a Poly(phenylacetylene) Derivative Bearing a Sulfonic Acid Pendant with Chiral Amines and Memory of the Macromolecular Helicity in Dimethyl Sulfoxide

Hasegawa

Maeda

Ishiguro

et al. 2006

ABSTRACT:A stereoregular poly(phenylacetylene) derivative bearing a sulfonic acid residue (poly-1) as the pendant was found to form a predominantly one-handed helix upon complexation with various chiral amines through noncovalent acid-base interactions in dimethyl sulfoxide (DMSO). In sharp contrast to analogous poly(phenylacetylene)s bearing relatively weak carboxy and phosphonic acid residues as the pendants, the poly-1-amine complexes exhibited a weak induced circular dichroism (ICD) in the UV-visible region of the polymer backbone. However, in the presence of a strong acid, such as p-toluenesulfonic acid (TosOH), the ICD intensity significantly increased, resulting from a favorable ion pair formation between the sulfonic acid residues of the poly-1 and chiral amines, leading to an increase in the helical sense excess of poly-1. Moreover, the macromolecular helicity of poly-1 induced by chiral amines in the presence of TosOH was ''memorized'' after the chiral amines and their salts were completely removed and replaced with an achiral diamine, i.e., ethylene diamine, in DMSO, while no memory effect was observed for a helical poly-1 induced by the same chiral amines in the absence of TosOH.