Initiator Control of Conjugated Polymer Topology in Ring-Opening Alkyne Metathesis Polymerization

Abstract

Molybdenum carbyne complexes [RC≡Mo(OC(CH3)(CF3)2)3] featuring a mesityl (R = Mes) or an ethyl (R = Et) substituent initiate the living ring-opening alkyne metathesis polymerization of the strained cyclic alkyne, 5,6,11,12-tetradehydrobenzo[a,e][8]annulene, to yield fully conjugated poly(o-phenylene ethynylene). The difference in the steric demand of the polymer end-group (Mes vs Et) transferred during the initiation step determines the topology of the resulting polymer chain. While [MesC≡Mo(OC(CH3)(CF3)2)3] exclusively yields linear poly(o-phenylene ethynylene), polymerization initiated by [EtC≡Mo(OC(CH3)(CF3)2)3] results in cyclic polymers ranging in size from n = 5 to 20 monomer units. Kinetic studies reveal that the propagating species emerging from [EtC≡Mo(OC(CH3)(CF3)2)3] undergoes a highly selective intramolecular backbiting into the butynyl end-group.

Well‐Defined Alkyne Metathesis Catalysts: Developments and Recent Applications

“…[10] The 2,4,6-trimethylbenzylidyne complex MoF6 yielded fully conjugated poly(o-phenyleneethynylene) polymers 62 with PDIs of 1.3-1.7 and neither branching nor backbiting was observed. [171] On the contrary,t he corresponding propylidyne complex 60 formed mainlyc yclic polymers 63 under the same conditions in isolatedy ields of more than 60 %. The different selectivity of both catalystsw as rationalized by NMR studies with 13 C-labeled cyclodiyne 61:w hile am esityl group attached to the chain end of the polymer afforded a stable propagatingc omplex, an ethyl group in the end position resulted in backbiting of the alkylidyne moiety into the end-group and subsequently to the formation of cyclic polymers.…”

“…[170] Shortly after that, Fischers howed the impact of the alkylidyne moiety of ROAMP catalystso nthe topology of the resulting polymer when he compared the catalysts [MesC Mo{OC(CF 3 ) 2 Me} 3 ]( MoF6) [60] and [EtCMo{OC(CF 3 ) 2 Me} 3 (dme)] (60)( Scheme 22). [171] Using the ring-strained monomer 5,6,11,12-tetradehydrobenzo[a,e] [8]annulene ( 61), fully conjugated poly(o-phenyleneethynylene)s (PPEs) were produced, which were typically synthesized via ADIMET or transition metal catalyzed cross-coupling reaction of aryl halidesa nd aromatic alkynes. [10] The 2,4,6-trimethylbenzylidyne complex MoF6 yielded fully conjugated poly(o-phenyleneethynylene) polymers 62 with PDIs of 1.3-1.7 and neither branching nor backbiting was observed.…”

C3−C3′ and C6−C6′ Oxidative Couplings of Carbazoles

“…[82] The design and synthesis of well-defined polymers with controllable architectures and topologies have been ac entral theme in the research area of polymer science in the past three decades. [83] For general step-growthp olymerization, al inear polymer is prepared from monomers with two reactive sites, and a branchedp olymer is prepared from monomersw ith more than two reactives ites. With control of the reactive sites on the C3À C3' and C6ÀC6' positions, the carbazole can be used as ac ontrolled junction for topological polymerizations tartingf rom an identicalm onomer ( Figure 10).…”

Alkenylcarbyne Complexes Derived from the Reactions of OsXCl-(PPh3)3(X=H,Cl) with Propargyl Chloride and Phosphine Ligand-Controlled Transformation of Hydride-Carbyne to Carbene

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Abstract Reactions of the simple osmium precursors OsHCl(PPh 3 ) 3 (1) or OsCl 2 (PPh 3 ) 3 (2) with 3-chloro-3-methylbut-1-yne afforded OsHCl 2 (≡CCH＝CMe 2 )(PPh 3 ) 2 (3) or OsCl 3 (≡CCH＝CMe 2 )(PPh 3 ) 2 (4), respectively. Treatment of 3 with Ph 2 PC≡ CPh led to the formation of the tris-diphenyl(phenylethynyl)phosphine alkenylcarbene complex OsCl 2 (＝CHCH＝CMe 2 )(Ph 2 PC ≡CPh) 3 (5), while complex 4 underwent simple phosphine ligand substitution with Ph 2 PC≡CPh to give OsCl 3 (≡CCH＝ CMe 2 )(Ph 2 PC≡CPh) 2 (6).

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“…然而, 目前具有炔烃复分解活性的催化剂还仅限于前过渡金 属(主要为 Schrock 型的钼、钨的卡拜配合物或其前 体) [2,3] . 作为目前研究得最多的后过渡金属卡拜配合物, 锇卡拜也因其丰富的反应性质以及人们对探索后过渡 金属卡拜配合物的炔烃复分解活性的兴趣而越来越受 到关注 [4] , 近年来涌现了相当多锇卡拜配合物的报道, 并发现了许多有趣的反应性质 [4a,4b,5～8] .…”