Abstract
The role of 2‐iminopyrrolyl copper(I) complexes in the Reversible‐Deactivation Radical Polymerization (RDRP) of methyl methacrylate (MMA) is described. Mononuclear 2‐iminopyrrolyl copper(I) complexes [Cu{κ2N,N′‐NC4H3‐2‐C(H)=NR′}Ln] 1–7 (R′ = C6H5, Ln = (PPh3)2 (1); R′ = 2,6‐Me2C6H3, Ln = (PPh3)2 (2); R′ = 2,6‐iPr2C6H3, Ln = (PPh3)2 (3); R′ = 4‐NMe2C6H4, Ln = (PPh3)2 (4); R′ = CH3, Ln = (PPh3)2 (5); R′ = CH3, Ln = (PMe3)2 (6); R′ = CH3, Ln = PiPr3 (7)) were synthesized by the reaction of the in situ prepared sodium salts of precursors HL1–5 with [Cu(NCMe)4]BF4 with the respective phosphines. In their absence, the binuclear complex [Cu{κN,κN'‐NC4H3‐2‐C(H)=NCH3}]2 8 was formed instead, which, when treated with one equivalent of PR3 yielded the binuclear complexes [Cu2{κN,κN'‐NC4H3‐2‐C(H)=NCH3}2PR3] 9 (R = Ph) and 10 (R = Me).All complexes, except 8, were active in the RDRP of MMA using the initiator tert‐butyl‐α‐bromoisobutyrate (tBiB‐Br), achieving apparent propagation kinetic constants (kp') in the range of 0.5–7.5 × 10−5 s−1, at 90 °C and with a [MMA]0:[complex]0:[tBiB‐Br]0 ratio of 500:1:1. All reactions yielded poly (methyl methacrylate)s with molecular weights ( ) and dispersities higher than expected for Controlled Radical Polymerization processes. Complex 7 achieved the best results, with values being only 1.2‐fold higher than theoretically expected. Experimental and density functional theory (DFT) studies suggest that this system operates via Atom Transfer Radical Polymerization/Organometallic Mediated Radical Polymerization (ATRP/OMRP) mechanisms interplay.
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