Pentafluorophenylcobalt(II) complexes

Royo, Pascual; Vazquez, A.

doi:10.1016/s0022-328x(00)84590-8

Cited by 10 publications

(4 citation statements)

References 8 publications

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“…Anhydrous cobalt(II) halides, CoX 2 , or solvates thereof, are known to react with a number of Grignard reagents, RMgX, giving rise to organocobalt(II) compounds of general formula “CoR 2 ” . The precise formulation of the resulting compounds is largely dependent on the reaction conditions and on the nature of the R group but, in most cases, they may be considered as solvates CoR 2 (solv) x or higher aggregates (CoR 2 ) n . Except for extremely bulky R groups, organocobalt(II) compounds with higher R contents can be obtained by treatment of the same precursors with organolithium reagents, LiR.…”

Section: Resultsmentioning

confidence: 99%

Homoleptic Organocobalt(III) Compounds with Intermediate Spin

et al. 2014

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Homoleptic organocobalt(III) compounds with formula [NBu4][Co(III)(C6X5)4] [X = F (3), Cl (4)] were obtained in reasonable yields by chemical oxidation of the corresponding divalent species [NBu4]2[Co(II)(C6X5)4] [X = F (1), Cl (2)]. The [Co(III)(C6X5)4](-)/[Co(II)(C6X5)4](2-) couples are electrochemically related by quasi-reversible, one-electron exchange processes at moderate potential: E1/2 = -0.29 (X = F) and -0.36 V (X = Cl) versus saturated calomel electrode. The [Co(III)(C6X5)4](-) anions in salts 3 and 4 show an unusual square-planar geometry as established by single-crystal X-ray diffraction methods. According to their stereochemistry, these Co(III) derivatives (d(6)) are paramagnetic non-Kramers systems with a large zero-field splitting contribution and no observable electron paramagnetic resonance (EPR) spectrum. The thermal dependence of their magnetic susceptibilities can be explained in terms of a spin-Hamiltonian formalism with S = 1 ground state (intermediate spin) and substantial spin-orbit contribution. The magnetic properties of the square-planar d(7) parent species [NBu4]2[Co(II)(C6X5)4] were also thoroughly studied both at microscopic (EPR) and macroscopic levels (alternating current and direct current magnetization measurements). They behave as S = 1/2 (low spin) systems with mainly (dz(2))(1) electron configuration and a certain degree of s-orbital admixture that has been quantified. The electronic structures of all four open-shell [Co(C6X5)4](q-) compounds (q = 1, 2) accounting for their respective magnetic properties are based on a common orbital energy-level diagram.

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Section: Resultsmentioning

confidence: 99%

Homoleptic Organocobalt(III) Compounds with Intermediate Spin

et al. 2014

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“…The new organometallic Mg(II)Co(II) catalyst, 1 , was prepared with pentafluorophenyl groups as the hydrolyzable non-initiating coligands. To make the catalyst, the macrocyclic ligand [LH 2 ] was first reacted with [Mg{N(SiMe 3 ) 2 } 2 ], followed by a reaction with cobalt(II) bis(pentafluorophenyl) ([Co(C 6 F 5 ) 2 (THF) 2 ]) and stirring the mixture for 24 h. , Complex 1 , [LMgCo(C 6 F 5 ) 2 ], was isolated by cooling the reaction solution to −30 °C, as a purple crystalline solid, in 53% yield. Complex 2 was prepared following literature methods .…”

Section: Resultsmentioning

confidence: 99%

High Molar Mass Polycarbonates as Closed-Loop Recyclable Thermoplastics

Rosetto,

Vidal,

McGuire

et al. 2024

J. Am. Chem. Soc.

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Using carbon dioxide (CO 2 ) to make recyclable thermoplastics could reduce greenhouse gas emissions associated with polymer manufacturing. CO 2 /cyclic epoxide ring-opening copolymerization (ROCOP) allows for >30 wt % of the polycarbonate to derive from CO 2 ; so far, the field has largely focused on oligocarbonates. In contrast, efficient catalysts for high molar mass polycarbonates are underinvestigated, and the resulting thermoplastic structure−property relationships, processing, and recycling need to be elucidated. This work describes a new organometallic Mg(II)Co(II) catalyst that combines high productivity, low loading tolerance, and the highest polymerization control to yield polycarbonates with number average molecular weight (M n ) values from 4 to 130 kg mol −1 , with narrow, monomodal distributions. It is used in the ROCOP of CO 2 with bicyclic epoxides to produce a series of samples, each with M n > 100 kg mol −1 , of poly(cyclohexene carbonate) (PCHC), poly(vinyl-cyclohexene carbonate) (PvCHC), poly(ethyl-cyclohexene carbonate) (PeCHC, by hydrogenation of PvCHC), and poly(cyclopentene carbonate) (PCPC). All these materials are amorphous thermoplastics, with high glass transition temperatures (85 < T g < 126 °C, by differential scanning calorimetry) and high thermal stability (T d > 260 °C). The cyclic ring substituents mediate the materials' chain entanglements, viscosity, and glass transition temperatures. Specifically, PCPC was found to have 10× lower entanglement molecular weight (M e ) n and 100× lower zero-shear viscosity compared to those of PCHC, showing potential as a future thermoplastic. All these high molecular weight polymers are fully recyclable, either by reprocessing or by using the Mg(II)Co(II) catalyst for highly selective depolymerizations to epoxides and CO 2 . PCPC shows the fastest depolymerization rates, achieving an activity of 2500 h −1 and >99% selectivity for cyclopentene oxide and CO 2 .

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“…27 The new organometallic Mg(II)Co(II) catalyst, 1, was prepared with pentafluorophenyl groups as the hydrolysable noninitiating co-ligands. To make the catalyst, the macrocyclic ligand [LH2] was first reacted with [Mg{N(SiMe3)2}2], followed by a reaction with cobalt(II) bis(pentafluorophenyl) ([Co(C6F5)2(THF)2]) and stirring the mixture for 24 h. [76][77] Complex 1, [LMgCo(C6F5)2], was isolated, by cooling the reaction solution to -30 ˚C, as a purple crystalline solid, in 53 % yield. Complex 2 was prepared following literature methods.…”

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confidence: 99%

High Molar Mass Polycarbonates as Closed-Loop Recyclable Thermoplastics

Rosetto,

Vidal,

McGuire

et al. 2024

Preprint

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Using carbon dioxide (CO2) to make recyclable thermoplastics could reduce greenhouse gas emissions associated with polymer manufacturing. CO2/cyclic epoxide ring-opening copolymerization (ROCOP) allows for >30 wt% of the polycarbonate to derive from CO2; so far, the field has focused on oligocarbonates. In contrast, efficient catalysts for high molar mass polycarbonates are under-investigated and the resulting thermoplastic structure-property relationships, processing and recycling need to be elucidated. This work describes a new organometallic Mg(II)Co(II) catalyst that combines high productivity, low loading tolerance, the highest polymerization control and yields polycarbonates with molar mass values from 4-130 kg mol-1, with narrow, monomodal distributions. Used in the ROCOP of CO2 with cyclohexene oxide (CHO), vinyl-cyclohexene oxide (vCHO) or cyclopentene oxide (CPO) to produce a series of samples, each with Mn>100 kg mol-1, of poly(cyclohexene carbonate) (PCHC), poly(vinyl-cyclohexene carbonate) (PvCHC), poly(ethyl-cyclohexene carbonate) (PeCHC, produced by hydrogenation of PvCHC) and poly(cyclopentene carbonate) (PCPC). All these materials are amorphous thermoplastics, with high glass transition temperatures (85 < Tg < 126 °C, by DSC) and high thermal stability (Td > 260 °C). The cyclic ring substituents mediate the materials’ chain entanglements, viscosity and the glass transition temperatures. Specifically, PCPC shows an entanglement molar mass (Me = 4-5 kg mmol-1) which is 10x lower than PCHC (Me ~ 50 kg mol-1) and has a zero-shear viscosity (0.78 MPa s) which is 100x lower than PCHC (90 MPa s). PCPC also shows higher tensile strength (59 MPa) and toughness (3.3 MJ m-3) compared with PCHC; its properties are competitive with thermoplastics like polystyrene and improve upon the high temperature application window for poly(L-lactide). All the new polymers are fully recyclable, either by re-processing using compression molding or by using the Mg(II)Co(II) catalyst for highly selective depolymerizations to epoxides and CO2. PCPC shows the fastest depolymerization rates, achieving an activity of 2500 h-1 and >99% selectivity for CPO and CO2 (1:5000, [catalyst]:[PCPC], neat films, 140 °C). In future, CO2/epoxide-thermoplastic research should prioritize alkyl-substituted cyclohexenes or cyclopentenes since these show the highest chain entanglements, optimal processing and properties. Furthermore, the highly controlled, organometallic Mg(II)Co(II) catalyst should access other polycarbonates, terpolymers or block copolymers from CO2.

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Pentafluorophenylcobalt(II) complexes

Cited by 10 publications

References 8 publications

Homoleptic Organocobalt(III) Compounds with Intermediate Spin

Homoleptic Organocobalt(III) Compounds with Intermediate Spin

High Molar Mass Polycarbonates as Closed-Loop Recyclable Thermoplastics

High Molar Mass Polycarbonates as Closed-Loop Recyclable Thermoplastics

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