W. A. Braunecker, T. Pintauer, N. Tsarevsky, G. Kickelbick, K. Matyjaszewski:
"Towards understanding monomer coordination in atom transfer radical polymerization: synthesis of [CuI(PMDETA)(π -M)][BPh4] (M=methyl acrylate, styrene, 1-octene, and methyl methacrylate) and structural studies by FT-IR and 1H NMR spectroscopy and X-ray crystallography.";
Journal of Organometallic Chemistry,
CuI complexes of the form [CuI(PMDETA)(π-M)][BPh4] (where PMDETA = N,N,N',N",N"-pentamethyldiethylenetriamine, and M = vinyl monomer) were synthesized and isolated from soln. as crystals with Me acrylate (MA), styrene (Sty), and 1-octene (Oct). The interaction of the C=C double bond of the vinyl monomer with CuI was characterized via FT-IR and 1H NMR spectroscopy and single crystal X-ray crystallog. A fourth complex with Me methacrylate (MMA) was synthesized and characterized spectroscopically, but no crystals suitable for X-ray structure anal. could be obtained. In all complexes, PMDETA acts as a tridentate ligand, while the pseudotetrahedral coordination geometry around CuI is completed by a π-interaction with the C=C double bond of M in the presence of a non-coordinating counter-ion. A decrease in C=C IR stretching frequencies of Δν(C=C) = -110, -80, -109, and -127 cm-1 for complexes with MA, Sty, Oct, and MMA, resp., was obsd. upon coordination. No significant change in C=C bond length was seen in the crystal structure for complexes with MA and Oct while a slight lengthening was obsd. for the Sty complex. The upfield shift of the vinyl proton resonances indicated the presence of significant π-back-bonding.
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