Copper(I/II) and cobalt(II) coordination chemistry of relevance to controlled radical polymerization processes

Abstract

The reaction of various alkyl halides (1-bromoethylbenzene, BEB; 1-chloroethylbenzene, CEB; methyl iodide; 1-bromoethylacetate, BEA; and ethyl-2-bromopropionate, EBP) with CuBr/L (L = bipy, Me 6TREN) has been investigated in the presence of [Co(acac) 2] or [Co(acac) 2]/py, with the goal of generating radicals by halogen atom transfer to Cu I for subsequence trapping by Co II and generation of an alkylcobalt(III) product. No evidence for the formation of the target product has been obtained. The various reactions, carried out under different conditions, have led to the crystallization of the following compounds: {[Cu(bipy) 2Br] +} 2{[Cu 2Br 4] 2−} ( 1); [Cu(Me 6TREN)Br]Br; [Cu(Me 6TREN)Br 0.37Cl 0.63]Br ( 2); trans-[Co(acac) 2(THF) 2] ( 3); [Co(Me 6TREN)Br]Br ( 4); [Cu(Me 7TREN)I]{[Cu 2I 2(Br 0.628I 0.372) 2] 0.9[I] 0.2} ( 5); [C 6H 8N] 2[CoI 4] ( 6); [Co(acac) 3]; and [Co(acac) 2(THF) 2CoBr 2] ( 7). The structures of 1– 7 have been determined by single-crystal X-ray diffraction.