Controlled/“Living” Radical Polymerization of MMA Catalyzed by Cobaltocene

Cobalt(I)‐mediated living radical polymerization of methyl methacrylate

“…In the case of cobaltocene, an equilibrium between cobaltocene and alkyl halide to form an ionic pair as a prior step for radical generation was explained as managing the catalyst/ initiator ratio. 12 Thus, there might be some equilibrium reaction between 1c and CCl 4 ; however, no evidence such as a solvent acceleration effect or side reactions was observed in our case. The living nature of this polymerization was sensitive to the reaction temperature and solvents, as shown in entries 11-18; when the reaction was carried out over 80 8C, a well-defined polymer was not available, and the polymerization in other solvents, dichloromethane or toluene, resulted in lower yield formation of the living polymer.…”

“…Although in principle there is no relationship between the amounts of the initiator and the catalyst, sometimes their ratio becomes a significant factor in the control of ATRP, especially that catalyzed by palladium acetate, 11 the Wilkinson catalyst, 9(b) and cobaltocene. 12 More than 2 equiv of 1c added to the initiator was required to obtain PMMA with a narrow polydispersity (M w /M n < 1.4). In the case of cobaltocene, an equilibrium between cobaltocene and alkyl halide to form an ionic pair as a prior step for radical generation was explained as managing the catalyst/ initiator ratio.…”

“…Some studies clearly have shown that a complex containing other metal centers can catalyze controlled polymerization. 12,13 One example was reported by Wang et al 12 using cobaltocene(II) as a catalyst, which, well known as a 19-electron compound, reportedly reduced the initiator and was oxidized from Co(II) to Co (III) to initiate the radical polymerization. In contrast, we took notice that stable cobalt(I) species were readily oxidized to cobalt(II) species.…”

Iron compounds in controlled radical polymerization: Ferrocenes, (clathro)chelates, and porphyrins

“…The detailed studies of the metallocenes effect on the radical polymerization have been reported in [22][23][24][30][31][32][33][34][35][36][37][38][39][40][41][42][43], the considered metallocenes including complexes of iron [22, 23, 30-35, 39, 43], titanium [23, 36-38, 40, 41], zirconium [24,38,42,43], molybdenum [44,45], cobalt [46], ruthenium [47,48], etc.…”

Mn2(CO)10-Induced RAFT Polymerization of Vinyl Acetate, Methyl Acrylate, and Styrene

“…Among the numerous initiating systems, there are now three representatives in terms of wide applicability and good controllability; i.e., the nitroxide-mediated radical polymerization (NMP), 1,2 metal-catalyzed living radical polymerization or atom transfer radical polymerization (ATRP), [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] and reversible addition-fragmentation chain transfer (RAFT) 18 polymerization or macromolecular design via interchange of xanthate (MADIX). 19 Although the components and the mechanisms are different, they are all based on the reversible transient activation of the dormant covalent species into the growing radical species.…”