Activity For Copolymerization Research Articles

Rigid-Flexible Binuclear Catalysts: Boosting Activity for Copolymerization of CO2 and Propylene Oxide

Rigid-Flexible Binuclear Catalysts: Boosting Activity for Copolymerization of CO₂ and Propylene Oxide

A hybrid steric ligand modification strategy promotes propylene (co)polymerization

Recently, a Hybrid Steric Ligand Modification (HSLM) strategy has been shown to significantly increase the polymerization activity and the branching degree of the resulting (co)polymers in the ethylene (co)polymerization via α-diimine catalysts. In this study, the HSLM strategy was employed for propylene (co)polymerization using a group of α-diimine Pd(II) catalysts with bulky hybrid ligands. The HSLM catalysts (Pd1-4) produced polypropylene with high molecular weights (45.4–156.9 kg/mol) and resulted in significantly high levels of activity (105 g mol−1 h−1). Additionally, nearly half of the propylene underwent chain straightening (1,3-enchainment = 43–46 %). Our findings suggest that Pd1-4 catalysts are more effective than the symmetrical catalysts Pd5-6 in producing high molecular weight polypropylene with high activity. Among all the catalysts tested, Pd4 with 4-tert-butylphenyl displayed the highest polymerization activity and molecular weight, although with lowest branching densities. It is suggested that the HSLM may provide a more open spatial configuration around the metal center, which facilitates the coordination and insertion of propylene molecules as well as chain walking. The hybrid Pd(II) catalysts showed moderate activity during the copolymerization of propylene with MA. The copolymers produced had low molecular weights (3.1–11.2 kg/mol), high branching densities (120–211/1000C), and high incorporation ratios (8.82–18.08 mol%). The copolymerization activity was highest with 4-tert-butylphenyl Pd4. The resulting P-MA copolymers had the highest molecular weight, the largest branching degree, and the lowest incorporation ratios.

Synthesis of Polar-functionalized Isotactic Polypropylenes Using Commercial Heterogeneous Ziegler-Natta Catalyst.

The efficient synthesis of polar-functionalized polypropylenes with high molecular weight and high stereoregularity represents a challenging task. This challenge becomes even more daunting when pursuing an industrially preferred heterogeneous process. This study demonstrated the realization of these goals through the use of commercial heterogeneous Ziegler-Natta catalysts in the copolymerization of propylene with ionic cluster polar monomers. The results revealed high copolymerization activity (∼1.1 × 107 g mol-1 h-1), moderate polar monomer incorporation ratios (∼4.9 mol %), high copolymer molecular weight (Mw > 105 g mol-1), high stereoregularity ([mmmm] ∼ 96%), and high melting temperature range (150-162 °C). The utilization of ionic cluster polar monomers improved the thermal stability as well as stereoselectivity of the catalyst. Moreover, the Ziegler-Natta catalyst can homopolymerize ionic cluster polar monomers with high activities (>104 g mol-1 h-1). The resulting polar-functionalized isotactic polypropylenes (iPP) exhibited superior tensile strength, impact strength, creep resistance, transparency, and crystallinity compared with nonpolar iPP. This enhancement was attributable to the dual roles of the ionic cluster polar monomer unit, serving as both a transparent nucleating agent and a dynamic cross-linking functionality. Furthermore, the polar-functionalized iPP exhibited improved compatibility with polar materials, offering benefits for applications in composites, recycling of mixed plastic wastes, 3D printing, and other fields. This study offered a comprehensive solution for the future industrial production of polar-functionalized iPP via copolymerization, bridging the gap between an efficient and practical copolymerization process from a synthetic chemistry perspective and enhanced material properties from an application perspective.

Synthesis of vanadium (V) complex with bulky phenoxy ligand and the study of catalysis behavior in ethylene (co)polymerization

A series of imido-vanadium complexes containing bulky aryloxo ligand have been isolated and employed as catalyst in ethylene (co)polymerization. The introduction of bulky ligand in the vanadium complex structure could promote the thermal stability of catalyst in ethylene polymerization. Especially the corresponding catalysts remain good activity in the ethylene copolymerization with polar monomers such as 10-undecen-1-ol (UOH) and methyl 10-undecenoate (UA). In the attempted copolymerization with acrylate monomer, the vanadium catalysts still show moderate activity but only afford polyethylene.

Synthesis, kinetic study and characterization of C5‐dienes/styrene copolymers via living anionic polymerization in cyclopentyl methyl ether solvent

Abstract1,3‐Dienes/styrene sequence‐controlled copolymers are widely used as thermoplastic elastomers, transparent impact resin and synthetic rubber and other materials. In this work, the binary anionic copolymerization of styrene (S) and C5‐dienes including 1,3‐pentadiene (P, E/Z = 65/35) and isoprene (I) were studied in cyclopentyl methyl ether (CPME) ‘green’ solvent using n‐BuLi as initiator, and the effects of copolymerization monomer ratio and polar additive (PA) on the copolymerization kinetics and monomer sequence distributions were investigated. The kinetic analysis results showed that all copolymerization systems were the first‐order reaction and the C5‐dienes/S could be quantitatively consumed. The addition of S or I was conducive to the efficient conversion of P. Although the addition of PAs had little effect on the polymerization rate, it had a great influence on the microstructure and sequence distribution of the copolymer. 1H NMR tracking analysis showed that, for S/P copolymerization with different feeding ratios 1/3 < fP < 2/3, the instant composition FP in the copolymer remained relatively constant at 15% < FP < 35% when the monomer conversion rate was below 60%, and thus the inevitable formation of P microblocks in subsequent polymerization sequences was observed. Additionally, similar sequence distributions were obtained in the case of I/P copolymerization systems. By contrast, S/I copolymerization conformed to the typical random copolymerization pattern, and the copolymerization activity of S was slightly higher than that of the I in CPME. The use of strong PAs such as 2,2‐di(2‐tetrahydrofuran)propane directly resulted in a change of monomer sequence from a random pattern to a gradual block pattern. Moreover, the 3,4‐isoprene branch units were much more sensitive to solvent and PA than 1,2‐pentadiene units for C5‐dienes; also Fourier transform infrared and DSC analysis verified the microstructure and sequence analysis results mentioned above. In addition, the results of gel permeation chromatography showed that the copolymerization process in CPME had excellent controllable characteristics. © 2023 Society of Industrial Chemistry.

Synthesis, characterization and ethylene (Co)polymerization of binuclear Vanadium(IV) catalysts based on xanthene-bridged bis-salicylaldiminato ligands

Bimetallic complexes have attracted much attention due to their excellent catalytic performances in many fields. Herein six xanthene-bridged bis-salicylaldiminato [ON] bidentate binuclear vanadium(IV) complexes V2L1-V2L6 were synthesized and characterized by MALDI-TOF-MS, FTIR spectroscopy and elemental analysis, and the crystal structures of V2L1 and V2L2 were further characterized by XRD, in which each vanadium atom was found coordinated with three O, one Cl and one N atoms to form a twisted trigonal bipyramidal configuration. Under Et2AlCl and ethyl trichloroacetate (ETA) activation, all the binuclear vanadium(IV) complexes exhibited high activity over 106 g/mol(V)·h·atm towards ethylene polymerization and copolymerization with 1-hexene. The activity of binuclear V2L4 for ethylene polymerization was much higher than that of its mononuclear counterpart VL, indicating that strong bimetallic synergetic effect existed in these binuclear vanadium complexes. The substituents on the ligands have a great influence on the catalytic performances of the vanadium complexes. The introduction of bulky isopropyl group into the ligand had little effect on the activity, but the introduction of electron-withdrawing fluorine atoms could significantly increase the activity, suggesting that the electronic, rather than the steric factors had a greater impact. As the amount of fluorine substituent on the iminophenyl moiety of the complex increased, the catalytic activity increased appreciably. With five fluorine atoms on the benzene ring of the imine moiety, the complex V2L6 showed the highest activity of 1.10 × 107 g/mol(V)·h·atm for ethylene polymerization to produce the highest molecular weight of polyethylene. Furthermore, the introduction of fluorine atoms into ligands could also increase the catalytic activity of vanadium complexes, comonomer incorporation and molecular weight of obtained copolymer towards ethylene/1-hexene copolymerization. The highest copolymerization activity of V2L6 was 4.13 × 106 g/molV·h·atm, which was more than three time that of the fluorine-free complex V2L1. The insertion rate of 1-hexene for the fluorine-containing complex V2L3-V2L6 was also higher than that for V2L1.

Mechanistic Studies on Aluminum-Catalyzed Ring-Opening Alternating Copolymerization of Maleic Anhydride with Epoxides: Ligand Effects and Quantitative Structure-Activity Relationship Model.

Previous work has indicated that aluminum (Al) complexes supported by a bipyridine bisphenolate (BpyBph) ligand exhibit higher activity in the ring-opening copolymerization (ROCOP) of maleic anhydride (MAH) and propylene oxide (PO) than their salen counterparts. Such a ligand effect in Al-catalyzed MAH-PO copolymerization reactions has yet to be clarified. Herein, the origin and applicability of the ligand effect have been explored by density functional theory, based on the mechanistic analysis for chain initiation and propagation. We found that the lower LUMO energy of the (BpyBph)AlCl complex accounts for its higher activity than the (salen)AlCl counterpart in MAH/epoxide copolymerizations. Inspired by the ligand effect, a structure-energy model was further established for catalytic activity (TOF value) predictions. It is found that the LUMO energies of aluminum chloride complexes and their average NBO charges of coordinating oxygen atoms correlate with the catalytic activity (TOF value) of Al complexes (R2 value of 0.98 and '3-fold' cross-validation Q2 value of 0.88). This verified that such a ligand effect is generally applicable in anhydride/epoxide ROCOP catalyzed by aluminum complex and provides hints for future catalyst design.

Synthesis of degradable polyacetals via an intramolecular phosphonium bisborane Lewis pair catalyzed copolymerization of epoxides with o‐phthaladehyde

AbstractAn intramolecular phosphonium bisborane Lewis pair (PBB‐Br) was used for the copolymerization of o‐phthalaldehyde (OPA) with epoxides under mild conditions. In particular, poly(o‐phthalaldehyde‐alt‐propylene oxide) termed as (poly(OPA‐alt‐PO)), having high molecular weight (Mn = 42.5 kg/mol) with Đ = 1.12 was generated at 25 °C using PBB‐Br as a highly efficient catalyst. The purity of OPA, temperature and monomer/comonomer feeding ratio effects on the copolymerization were investigated. Subsequently, the degradability and thermal stability of generated polyacetals were studied. Using alcohol as chain transfer agent, random or block polyacetal‐polyethers with different structures can be obtained in one‐pot synthesis. The cooperation of the two boron centers plays a pivotal role in boosting the activity of copolymerization of OPA and PO.

Ni(II) and Pd(II) complexes bearing novel chiral bis(β-ketoamino) ligand and their catalytic activity toward copolymerization of norbornene and polar norbornene derivatives

A series of novel Ni(II) and Pd(II) complexes bearing chiral bis(β-ketoamino) ligand were synthesized and characterized. The Ni(II) and Pd(II) complexes exhibited high activities for norbornene homopolymerization with only B(C6F5)3 as cocatalyst, for Ni(II) complex even up to 1.38 ×106 gpolymer/molNi·h. All the complexes had good thermal stability. Most importantly, the complexes also displayed high activities of 105 gpolymer/molmetal·h toward the copolymerization of norbornene and 5-norbornene-2-yl acetate with high molecular weights and tunable norbornene and 5-norbornene-2-yl acetate content. The copolymerization activity, molecular weight, and norbornene and 5-norbornene-2-yl acetate feed ratio of the Ni complex were higher than those of the Pd complex.

Impact of Labile Ligands on Catalyst Initiation and Chain Propagation in Ni-Catalyzed Ethylene/Acrylate Copolymerization

Polar polyolefin synthesis by coordination polymerization is of high interest, but the catalysts’ low activity limits industrial implementation. Herein, we demonstrate how the nature of the labile ligand, L, impacts the performance of neutral nickel catalysts supported by bidentate phosphine-phenoxide and phosphine-enolate ligands in ethylene/acrylate copolymerization. By tuning L, the copolymerization activity reaches ∼24000 kg/(mol h). In situ studies indicate that a weaker L leads to faster chain propagation and more efficient catalyst initiation. Overall, this work highlights the potential of a strategy to improve catalyst activity in polar polyolefin synthesis complementary to design optimization for the bidentate ligand.

Progress in the catalyst for ethylene/α‐olefin copolymerization at high temperature

AbstractEthylene/α‐olefin copolymers are one of the most widely‐used polyolefin materials. With the continuous improvement of polyolefin catalysts, high‐performance polyolefin materials were synthesized by adjusting the chain microstructure, changing the comonomer type and comonomer insertion amount, among which the ethylene/α‐olefin random copolymer elastomer (POE) and olefin block copolymer elastomer (OBC) are the most famous and well accepted by the market. The excellent properties of POE and OBC first depend on their polymer chain microstructure. The chain microstructure of polyolefins is fundamentally determined by the catalysts, polymerization conditions, comonomer feed policies, and reaction engineering. High‐performance ethylene/α‐olefin copolymer elastomers are currently prepared by high‐temperature solution polymerization process, which needs to be carried out at a temperature above the melting point of the polymer and is beneficial to speed up the polymerization reaction rate and control the polyolefin chain microstructure. However, the high‐temperature solution polymerization process launched more stringent requirements for the olefin coordination polymerization catalyst. Systematic reports on catalysts for high‐temperature solution copolymerization of ethylene and α‐olefins are lacking. In this review, we screened some catalysts suitable for the controllable copolymerization and high‐temperature solution copolymerization of ethylene/α‐olefin based on the catalyst's heat resistance, copolymerization activity, comonomer insertion ability, molecular weight, and distribution of the copolymer, including traditional Z–N catalysts, metallocene catalysts, and post‐metallocene catalysts. And the future development of catalysts for high‐temperature solution copolymerization of olefins, catalysts for precise control of polyolefin chain microstructures, and catalysts for olefin copolymerization with polar monomers at high temperature are envisaged.

Mechanistic Basis for the High Enantioselectivity and Activity in the Multichiral Bimetallic Complex-Mediated Enantioselective Copolymerization of meso-Epoxides

The desymmetric ring-opening copolymerization of meso-epoxides with cyclic anhydrides or carbon dioxide (CO2) constitutes a straightforward route to diverse isotactic polymers with two contiguous stereogenic centers. Both high enantioselectivity and excellent activity have been observed in catalyst systems based on biaryl-linked bimetallic complexes with multiple chiralities. In this study, we analyzed the basis for the high enantioselectivity and activity of multichiral bimetallic catalysts by combining experimental observations and theoretical calculations. More specifically, density functional theory calculations of the entire catalytic cycles for the copolymerization of cyclohexene oxide (CHO) and phthalic anhydride (PA) or CO2 demonstrated that ligand exchange was required for CHO coordination, while the ring-opening stage was the rate-determining step. Notably, the M···M separation and the endo dihedral angle of the bimetallic complex changed continuously during copolymer propagation, wherein the cleft opened and closed alternately, demonstrating that a flexible phenol–phenol (biphenol) axis is essential. The carboxylate anion coordinated simultaneously with both metal ions in the dinuclear catalyst reduces the reaction energy barrier during the ligand exchange process significantly. Calculation of the optimal routes for the coordination of CHO to Al(III) or Co(III) ions indicated three possible states. The energy barriers for CHO ring-opening mediated by the (R,R,Ra,R,R)- and (R,R,Sa,R,R)-isomers were calculated in each state, and it was found that epoxide ring-opening was sensitive to the absolute stereochemistries of the biphenol linker and the cyclohexyl diamine skeletons, as well as the phenolate ortho-substituents. The two diastereoisomers have opposite stereoselectivities in the epoxide ring-opening stage, wherein the (R,R,Ra,R,R)-isomer-mediated CHO ring-opening process at the (S)-C–O bond in the most stable CHO coordination state exhibited the lowest energy barrier, therefore determining the enantiomer preference and the copolymerization rate.

Propylene Polymerization Performance with Ziegler-Natta Catalysts Combined with U-Donor and T01 Donor as External Donor

In propylene (C3) polymerization with Ziegler-Natta catalyst, not only internal donor but also external donor is very important to make isotactic polypropylene (PP) with higher yield. Most propylene-based polymers have been commercially produced with Ziegler-Natta catalysts combined with dialkyl-dialkoxy silane compounds (R2Si(OR)2) such as C-donor, P-donor, and D-donor as external donors. In this paper, we will introduce the propylene polymerization performance with aminosilane compounds, i.e., diethylamino triethoxy silane (U-donor) and bis(ethylamino) di-cyclopentyl silane (T01 donor), as external donor in Ziegler–Natta catalyst. The polymerization screening experiments were conducted using some triethoxyalkylsilanes compounds (1–7) and performances were compared with U-donor. The polymerization results of the binary donor system show improvement in stereoregularity. These aminosilane compounds exhibit high hydrogen response in propylene polymerization and high copolymerization performance of propylene (C3) and ethylene (C2) in ICP production compared with dialkyl-dialkoxy silane compounds. While using methanol as an additive along with external electron donor, as a serendipitous, the copolymerization activity, block ratio, EPR (ethylene-propylene rubber) content improve significantly for U-donor as compared with T01 donor and C-donor.

Performance regulation of lignin-based flocculant at the practical molecular level by fractionation

Lignin, an inedible yet sustainable aromatic resource, has great commercial prospects as raw material to prepare flocculants with efficient flocculation coupled with sterilization. However, the troublesome heterogeneity of lignin is the bottleneck for the large-scale production of highly efficient flocculants. In this study, an easy to operate organic solvent fractionation approach was first applied to separate industrial lignin and generate several homogeneous fractions, and the polydispersity of lignin improved from 2.80 to 1.30–1.85. Subsequently, a series of lignin-based flocculants were synthesized in a UV-induced biphasic polymerization system using different lignin fractions (F0-F4). Surprisingly, the lignin-based flocculants LF1 and LF2, which were prepared from lignin F1 and lignin F2 fractionated by ethyl acetate and ethanol, respectively, exhibited over 99% removal rate and excellent sterilization efficiency on E. coli suspensions. The improved efficiency could be attribute to the more homogeneous structure of the fractionated lignin. Moreover, more G units and phenolic hydroxyl groups in lignin contributed to the increase of its copolymerization activity, while the low molecular weight and excellent hydrophilicity led to superior dispersibility and reactivity accessibility in biphasic polymerization. The purification test of E. coli suspensions showed that the flocculation performance of lignin-based flocculants was not only affected by charge density and molecular weight, but also by the balance of amphiphilicity, and its sterilization ability was mainly determined by charge density. The effect of lignin structure on the preparation and performance of lignin-based flocculants was fully explored at the actual molecular level, which has important enlightening significance for the application of lignin in wastewater recycling.

Investigating the Ring-Opening Polymerization Activity of Niobium and Tantalum Ethoxides Supported by Phenoxyimine Ligands.

A variety of metal catalysts from around the periodic table have been studied for the ring-opening polymerization (ROP) of cyclic esters. Within this field, group V catalysts have been rarely explored. To better understand the effect the choice of metal and ligand has on ROP activity, a series of 10 niobium and tantalum alkoxide catalysts, supported by a range of phenoxyimine ligands, were synthesized. The electronics and steric bulk of the ligands were varied on the phenoxy group (tBu, Cl, and OMe) and the imine group (Ph; 2,6-diMePh; 2,6-diiPrPh; and 2,4,6-tritBuPh) to probe their effect on the catalyst structure and activity. Catalysts were characterized with 1D, 2D, and variable-temperature NMR techniques to determine their structure in solution. Single crystal X-ray diffraction studies were conducted to establish their solid-state structure. The 10 catalysts are pseudo-octahedral, and each shows ligand coordination through phenoxy-oxygen and imine-nitrogen (O,N). In the case of the o-vanillin ligand set, however, evidence was found for O,O-coordination of the ligand when the steric encumbrance of the imine-nitrogen was increased. Each catalyst was active for the ring-opening polymerization of both rac-lactide (LA) and ε-caprolactone (CL) in the absence of solvent at 140 °C. In the case of CL, the catalysts supported by chloro-containing ligands showed the most polymerization control based on final polymer molecular weight and dispersity. Ligand trends were less clear for the polymerization of LA, though in all cases the catalysts were more controlled than the parent homoleptic alkoxide [M(OEt)5; M = Nb or Ta]. The most promising catalyst in the family was tested for copolymerization activity of LA and CL in one pot. Copolymerization of the two monomers was successful and yielded random poly(caprolactone-co-lactide).

Inside Cover: Master of Chaos and Order: Opposite Microstructures of PCL‐co‐PGA‐co‐PLA Accessible by a Single Catalyst (Angew. Chem. Int. Ed. 11/2022)

The iron guanidine catalyst shows extraordinary copolymerization activity towards lactide, glycolide, and ϵ-caprolactone, as reported by Sonja Herres-Pawlis, Moshe Kol, and co-workers in their Research Article (e202112853). Depending on the reaction temperature and the mode of monomer addition, it either forms up to pentablock copolymers in a highly defined way or promotes transesterifications to such a high degree that random copolymers are produced. Therefore, it is a rare example of a catalyst mastering both microstructures: ordered and chaotic.

Design and synthesis of binuclear vanadium catalysts for copolymerization of ethylene and polar monomers

Binuclear vanadium complexes exhibited higher activity than monometallic complexes in ethylene polymerization and afforded UHMWPE. The binuclear catalysts also showed moderate activity in copolymerization with 10-undecen-1-ol and methyl 10-undecenoate.

The preparation of cross-linkable polyethylene via coordination copolymerization of ethylene with alkene-derived chlorosilane

A facile and controllable way to prepared silane-crosslinked polyethylene by coordination polymerization was proposed in this article. Four alkene-derived chlorosilanes, trichloro(oct-7-en-1-yl)silane (Oct-TriSi), dichloro(methyl)(oct-7-en-1-yl)silane (Oct-DiSi), chlorodimethyl(oct-7-en-1-yl)silane (Oct-MoSi) and (2-(bicyclo[2.2.1]hept-5-en-2-yl)ethyl)dichloro(methyl)silane (Nor-DiSi) were first synthesized by hydrosilylation and copolymerized with ethylene to prepare cross-linkable polyethylene. The copolymerization results of ethylene/octenyl-silanes indicated monochloro-substituted silane showed lowest crosslinking ability while trichloro-substituted silane showed the lowest copolymerization ability, therefore, their ability to prepare cross-linkable polyethylene was: Oct-DiSi > Oct-TriSi > Oct-MoSi, moreover, Nor-DiSi outcompeted Oct-DiSi as comonomer to obtain higher copolymerization activity, comonomer proportion in copolymer, comonomer conversion and gel content. The crosslinking process was simply finished via alcoholysis with methanol and subsequent hydrolysis catalyzed with DBTDL. Even with a slight addition of Nor-DiSi, the polyethylene was able to be crosslinked, with the gel content ranging from 42.0 to 98.0%. The TGA and DMA tests demonstrated the crosslinked copolymers showed better thermal stability and heat deformation resistance than polyethylene. After crosslinking, the copolymers with an appropriate gel content would have higher yield stress, tensile modulus and tensile stress.

Synthesis of mono- and bis- benzimidazolin-2-iminato titanium complexes and their catalytic performances in ethylene homo- and co- polymerizations

A series of mono- and bis- benzimidazolin-2-iminato titanium complexes (Ti1–Ti6) were synthesized herein. All the complexes were isolated in high yields and confirmed by 1H and 13C NMR spectra. Molecular structures of complexes Ti1, Ti3, and Ti4 were further determined by single-crystal X-ray diffraction, which gave comprehensive bond properties as well as structural differences with the previously reported imidazolin-2-iminato titanium analogs. Being activated by methylaluminoxane (MAO), all the complexes showed moderate activities for ethylene homopolymerization and copolymerization with α-olefins. In all the cases, the resultant polymers had narrow molecular weight distributions. The catalysts still possessed acceptable polymerization activities even at a temperature of 90 °C, implying the uniqueness of the benzimidazolin-2-iminato ligand.

Synthesis, Characterization, and Catalytic Study of Amine-Bridged Bis(phenolato) Co(II) and Co(II/III)-M(I) Complexes (M = K or Na).

Co(II) complexes 1-3 bearing amine-bridged bis(phenolato) complexes have been synthesized through reactions of bis(phenols) with CoCl2 or Co(OAc)2. Oxidation of the Co(II) complex with air resulted in partial oxidation, generating mixed valence Co(II/III) complexes 4 and 5. In addition, due to the presence of alkali compounds (KOAc and NaOMe), 4 and 5 formed as Co-alkali metal heterometallic complexes, which are the first example of mixed valence Co(II/III)-M(I) (M = K or Na) complexes. Complexes 1-5 showed good activity in the cycloaddition of epoxides and CO2 under atmospheric pressure, generating cyclic carbonates in 40-99% yields. Co(II/III)-Na(I) complex 5 performed better in reactions of bulkier substrates, underlining the enhanced activity of mixed valence Co-alkali metal heterometallic complexes. On the contrary, complex 5 showed limited activity in copolymerization of epoxide and CO2.