Ring‐Opening Polymerization Reactions of Propylene Oxide Catalyzed by Porphyrin Metal (3+) Complexes of Aluminum, Chromium and Cobalt

Abstract

In today's world, a major scientific challenge is preserving the delicate balance between industrial growth and a pollutant free terrestrial environment. Thus, "greener" syntheses of commodity materials, capture and utilization of gaseous industrial by-products have become research areas of increasing significance. The pioneering work of Inoue showed a potential utilization of CO2, a major petrochemical by-product, and opened a new field of research. Inoue discovered the (porphyrin)Al(III)X catalyst systems, (X=Cl(-) or alkoxide) which copolymerize CO2 with epoxides to produce polycarbonates. This catalyst can also copolymerize epoxides and cyclic anhydrides to form polyesters. The current record describes our research aimed towards mechanistic understanding and further developments of (porphyrin)M(III)X catalyst systems. This detailed account shows the influence of the porphyrin ligands (tetraphenylporphyrin (TPP), octaethylporphyrin (OEP), tetrakis-pentafluorophenylporphyrin (TFPP)), metal centers (Al, Cr, and Co) and Lewis base co-catalysts on the individual reaction steps and equilibria involved in the copolymerization processes.

Metal–Cocatalyst Interaction Governs the Catalytic Activity of MII-Porphyrazines for Chemical Fixation of CO2

“…In their work, they propose that under high concentrations of PPNC there must be a competition between Cl – and the epoxide for the p orbital of the organoboranes catalysts, decreasing their conversions. Other examples include metallic systems, such as Mn III (acacen)­X, Al III (P)Cl (P = TPP, TFPP, or OEP), and Mn III (T2,3DCPP)­X; nevertheless, this is the first time that a remarkable inactivation was noted even at a low ratio of catalyst/TBAX (X = Br – or Cl – ). Our experiments strongly suggest that this behavior is linked to the high electrophilicity of the metals in the Pz core, as shown by the atomic charges (Table S5).…”

“…Our experiments strongly suggest that this behavior is linked to the high electrophilicity of the metals in the Pz core, as shown by the atomic charges (Table S5). , …”

Cycloaddition of CO2 and epoxides catalyzed by imidazolium bromides under mild conditions: influence of the cation on catalyst activity

“…[11][12][13] For the copolymerization of PO and CO 2 , a wide variety of molecular transition metal catalysts is known. [14][15][16][17][18] Furthermore, the carbonate synthesis can be carried out without a metal catalyst as well, using nucleophilic reagents, such as halides or N-donor bases. 19 The use of halides is well documented, and meanwhile, ILs containing halides as anions or functionalized ILs are known to catalyze the cycloaddition, bearing the advantage of facilitated product separation due to the low volatility of the ILs.…”

Overcoming NHCs neutrality: installing tetracarbenes on group 13 and 14 metals

“…Tetradentate ligands that bind in an equatorial manner about the metal centre are a mainstay for developing successful main group catalysts. [1][2][3][4][5][6] Although a plethora of examples abound, perhaps the most important auxiliary ligands of this type are salen and porphyrin derivatives (Fig. 1A).…”

“…1A). [2][3][4][5] Aluminium complexes that feature both of these classes of ligands are highly reactive Lewis acids that can efficiently perform ring opening polymerization and phospho-transfer catalysis. 3,7 In a similar manner, gallium and indium salen complexes have been used…”