from first principles PP-I-1

PP-II-11Selectivity of the Nickel (0) Species in the Synthesis of thePolyphenylene-Based Block-CopolymersMatveeva O.A., Ilitchev I.S., Grishin D.F.Research Institute of Chemistry, Lobachevsky State University, Nizhny Novgorod, Russiailis@uic.nnov.ruThe catalytic system NiBr 2 (PPh 3 ) 2 (5 mol%)/ Zn/ Ph-X are capable of providing both thecontrolled polymerization of styrene and methyl methacrylate [1] and the synthesis ofbiphenyls [2]. It was also reported that the nickel complexes with the monodentate phospineligands catalyzed the synthesis of fluorescent polyphenylene-b-PMMA copolymers via thepolycondensation of p-dibromobenzene and polymerization of MMA [3].Two approaches to study the reactivity of Ni(0) species in the copolymerization of MMA withpolyphenylene were applied. First approach was the one-pot nickel-catalyzed synthesis ofpolyphenylenes from p-dibromobenzene and block-copolymers of PMMA initiated by theformed oligophenylenes. The reaction of p-dibromobenzene and MMA in the presence ofNiBr 2 (PPh 3 ) 2 /zinc dust results in polymers with yields of 38 – 97% in 5 hours (M n ~3500).The reaction with the separately synthesized Ni(PPh 3 ) 4 complex was the second one. Thiscatalyst was prepared from NiBr 2 (PPh 3 ) 2 by reduction with zinc dust in THF, followed bydecantation of its solution from zinc and the addition to the p-dibromobenzene solution ofMMA in THF. This reaction affords polymers with the yield of 35% in 5 hours.THFNiBr 2 + nPPh 3 + ZnBrC25 0 [Ni(PPh 3 ) n ] + ZnBr 6 H 4 Br2[BrC 6 H 4 NiBr(PPh 3 ) 2 ]+ (n-2)PPh 3C, 15 min25 0 C, 20 min[BrC 6 H 4 NiBr(PPh 3 ) 2 ]MMA + BrC 6 H 4 Br-(C65 0 6 H 4 ) n -(CH 2 C(CH 3 )COOCH 3 ) m - + PMMAC, 5 hAddition of the bipy ligand to MMA on the second stage reduces the polymer yield but causesthe growth of its molecular weight.Analysis of MALDI-TOF spectra of the polymers preparedwith bipy clearly indicates the presence of the three types of macromolecules with various endgroups compared to that obtained only with Ph 3 P. These facts confirm the difference inmechanisms in both cases.This work was financially supported by the Russian Foundation for Basic Research (project #11-03-00074) and the scientific program ”UMNIK” (GK No.154-U/14130)References:[1] D. Grishin, N.Valetova, I. Ilitchev, M. Prokhorova, I.Beletskaya, Russ.Chem.Bull. 55 (2006) 2106.[2] J. Hassan, M. Sevignon, C. Gozzi, E. Schulz, M. Lemaire, Chem.Rev., 102 (2002) 1359.[3] I.Ilitchev, O.Matveeva, XIX Mendeleev Conference, Volgograd, 2011, 25-30 Sept.Proc. v.2, p.327142