1 research outputs found
Influence of the Metal (Al, Cr, and Co) and Substituents of the Porphyrin in Controlling Reactions Involved in Copolymerization of Propylene Oxide and Carbon Dioxide by Porphyrin Metal(III) Complexes. 3. Cobalt Chemistry
A series of cobaltÂ(III)
complexes LCoX, where L = 5,10,15,20-tetraphenylporphyrin (TPP), 5,10,15,20-tetrakisÂ(pentafluorophenyl)Âporphyrin
(TFPP), and 2,3,7,8,12,13,17,18-octaethylporphyirn (OEP) and X = Cl
or acetate, has been investigated for homopolymerization of propylene
oxide (PO) and copolymerization of PO and CO<sub>2</sub> to yield
polypropylene oxide (PPO) and polypropylene carbonate (PPC) or propylene
carbonate (PC), respectively. These reactions were carried out both
with and without the presence of a cocatalyst, namely, 4-dimethylaminopyridine
(DMAP) or PPN<sup>+</sup>Cl<sup>–</sup> (bisÂ(triphenylphosphine)Âiminium
chloride). The PO/CO<sub>2</sub> copolymerization process is notably
faster than PO homopolymerization. With ionic PPN<sup>+</sup>Cl<sup>–</sup> cocatalyst the TPPCoOAc catalyst system grows two
chains per Co center and the presence of excess [Cl<sup>–</sup>] facilitates formation of PC by two different backbiting mechanisms
during copolymerization. Formation of PPC is dependent on both [Cl<sup>–</sup>] and the CO<sub>2</sub> pressure employed (1–50
bar). TPPCoCl and PO react to form TPPCoÂ(II) and ClCH<sub>2</sub>CHÂ(Me)ÂOH,
while with DMAP, TPPCoCl yields TPPCoÂ(DMAP)<sub>2</sub><sup>+</sup>Cl<sup>–</sup>. The reactions and their polymers and other
products have been monitored by various methods including react-IR,
FT-IR, GPC, ESI, MALDI TOF, EXAFS, and NMR (<sup>1</sup>H, <sup>13</sup>CÂ{<sup>1</sup>H}) spectroscopy. Notable differences are seen in these
reactions with previous studies of (porphyrin)ÂMÂ(III) complexes (M
= Al, Cr) and of the (salen)ÂMÂ(III) complexes where M = Cr, Co