Stereoregular Polymerization of Alkyl Propiolate Catalyzed by Rh Complex

Induced Helix of an Aliphatic Polyacetylene Detected by Circular Dichroism

“…Poly-4 also complexed with other a-hydroxy acids such as (S)-hexahydromandelic acid (6) and (S)-2-hydroxy-3-methylbutyric acid (7) in THF to show ICDs; molar ellipticities ([0] x 10-2 (degree cm 2 d mol-1 ) and Jc (nm)) of the first Cotton for the complexes with (S)-6 and (S)-7 were -2.2 (473) and -1.3 (467), respectively. The sign of the Cotton effects appears to reflect the absolute configuration of the chiral acids.…”

Precise synthesis of monosubstituted polyacetylenes using Rh complex catalysts. Control of solid structure and π-conjugation length

“…On the other hand, using the [Rh(NBD)Cl] 2 catalyst at room temperature produces the cis-isomer almost quantitatively, forming light yellow and amorphous material bearing a fairly high molecular weight when poor solvents such as alcohol or amine were used in the polymerization. We found that the most outstanding features of the resulting polyacetylene, which was stereospecifically prepared using the simple Rh complex catalyst, are first: 1 H and 13 C NMR spectra of the resulting polymers have extremely sharp line widths compared with those of the trans-isomers 16,18,20) , which makes an unequivocal assignment of each signal impossible and may be correlated with the polymer structures and/or the concentration of p-radicals involved in the trans-conjugated polymer [23][24] and second: the formation of a pseudohexagonal, columnar structure, representing self-assembly or a superstructure, which is associated with useful and anisotropic physicochemical properties 19,20) . Therefore, these characteristics may be a proof of the highly stereospecific polymerization of monosubstituted acetylenes.…”

“…However, except for the precise control of the molecular weight and its dispersity, there has been no clear and unequivocal assignment (Scheme 1) of the geometry and/ or regularity of the resulting polymers regarding the C2C bond in the main chain of the polymer, including few stereospecific polymerizations of cis-and/or transmonosubstituted polyacetylenes (i), copolymerization (ii), isomerization (iii) of cis-to-trans geometrical isomer with its mechanism (iv), generation of p-conjugated radicals as solitons through the rotational scission of the cisdouble-bond, and the role of the radical in the conductivity and/or magnetism of the polymer (v). In this report, we describe the stereospecific polymerization to yield selectively the cis-form using the [Rh(norbornadiene)Cl] 2 ([Rh(NBD)Cl] 2 ) catalyst [12][13][14][15][16][17][18] , leading to a control method of molecular orientation and/or spin order in solid polymers, i. e., the formation of pseudohexagonal structures [19][20][21] , aggregation of the radical spins as a source of magnetism [20][21] , pressure-induced cis-trans isomerization [14][15][16] , and generation of the p-radical through rotational scission of the cis-double-bonds (Scheme 1).…”

Pressure-inducedcis totrans isomerization of aromatic polyacetylenes prepared using a Rh complex catalyst: A control of ?-conjugation length

“…2 It has been proposed that the effect of the solvents is to promote In a previous article we reported that phenylacetthe efficient dissociation of the dimer complex ylene (PA), 1 its homologues, 2 a-naphthylacety-[Rh(NBD)Cl] 2 into the monomeric species, which lene, 3 and alkylpropiolates, 4,5 and pentynoate 6 may be an important initiation species for this can be stereospecifically polymerized in the prespolymerization, 1,7 as shown in Scheme 1. Further, ence of a Rh complex, [Rh(norbornadiene)Cl] 2 , the structural differences observed between poly-[Rh(NBD)Cl] 2 , when triethylamine (TEA) or an pentynoates prepared with the Rh complex cataalcohol is used as the polymerization solvent and lyst and with metathesis catalysts such as WCl 6 that the helical cis-transoid isomer were selecwas interpreted in terms of the difference in geotively formed in high yields under mild conditions.…”