Amine‐bis(phenolato)cobalt(II) Catalysts for the Formation of Organic Carbonates from Carbon Dioxide and Epoxides

Abstract

New monometallic amine-bis(phenolato)cobalt(II) [(ONNO) R -Co II ] (R = CMe 2 Ph; Cl; Br) complexes have been synthesized and fully characterized including X-ray crystallographic analysis. These Co II complexes show good activity for the formation of cyclic propylene carbonate in combination with tetrabutylammonium bromide (TBAB) as a co-catalyst. The reaction parameters such as carbon dioxide pressure, co-catalyst loadings and temperature were varied to determine the ideal reaction conditions. These catalysts were also employed in copolymerization reactions of cyclohexene oxide/[a] WACKER-Lehrstuhl für Makromolekulare Chemie, CO 2 and propylene oxide/CO 2 . [(ONNO) Cl Co II ]*(MeOH) was found to effectively copolymerize cyclohexene oxide (CHO) and CO 2 . This is the first reported amine-bis(phenolato) cobalt(II) complex to be active in the copolymerization of CO 2 and CHO. In-depth stability studies were conducted (Evan's method) to validate Co II as the active species required for copolymerization. End-group analysis via NMR, ESI-MS and MALDI-TOF revealed the presence of 4-(dimethylamino)pyridine (DMAP) and methoxy terminated chains.

Chemical fixation of carbon dioxide catalyzed via cobalt (III) ONO pincer ligated complexes

“…Cobalt complexes have been extensively studied for this reaction and recently reviewed by Lu and Darensbourg 32 . Among them, salen 33,34 , chiral Co [35][36][37] , bis(phenoxyiminato) 38 , amine-bis(phenolato) 39 , porphyrin 40 ligand based cobalt complexes are more frequently studied. Moreover, Wani et al investigated some di-nuclear transition metal complexes/nBu 4 NI as catalyst/co-catalysts for the cycloaddition of CO 2 to epoxides exhibiting a low turnover frequency of 167 h −1 at high pressure of 10 bar 41 .…”

Cyclohexene oxide/carbon dioxide copolymerization by chromium(iii) amino-bis(phenolato) complexes and MALDI-TOF MS analysis of the polycarbonates

“…6 Also, CO 2 can be considered a renewable resource, 7 so its utilization is preferred over dwindling fossil fuels that are still the main basis for commercial polycarbonate synthesis. For example, complexes with Zn, [10][11][12] Al, 13 Co, [14][15][16][17][18][19][20][21] Fe, [22][23] Mg, 24 and Cr [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] have proven to be active in CO 2 /epoxide copolymerization. 9 Recently, a large number of complexes have been developed as active catalyst precursors for the copolymerization of CO 2 and epoxides.…”

Versatile cobalt complexes for initiating immortal ring‐opening polymerization (ROP) of lactide (LA), mediating living radical polymerization of t‐butyl acrylate (tBA) and catalyzing copolymerization of LA and tBA by combination of ROP and organometallic‐mediated radical polymerization

“…The cobalt complexes in the solid state are stable at room temperature. Recently, Rieger and co‐workers reported cobalt complexes of similar structure to be active in the copolymerization of CO 2 and cyclohexene oxide (CHO), which show good activity for the formation of cyclic propylene carbonate in combination . The crystal structures of the ligands L 3 H 2 and L 4 H 2 ⋅C 2 H 5 OH as well as complexes 3 –CH 3 OH and 4 –2CH 3 OH were obtained from single‐crystal X‐ray diffraction studies (Figures S1 and S2; Figures and ).…”