CO2/ethylene oxide copolymerization and ligand variation for a highly active salen-cobalt(III) complex tethering 4 quaternary ammonium salts.

A cobalt(III) complex (1) of a salcy-type ligand tethering 4 quaternary ammonium salts, which is thought to act as a highly active catalyst for CO2/propylene oxide (PO) copolymerization, also shows high activity (TOF, 25,900 h(-1); TON, 518,000; 2.72 kg polymer per g cat) and selectivity (>98%) for CO2/ethylene oxide (EO) copolymerization that results in high-molecular-weight polymers (M(n), 200,000-300,000) that have strictly alternating repeating units. The related cobalt(III) complexes 11-14 were prepared through variations of the ligand framework of 1 by replacing the trans-1,2-diaminocyclohexane unit with 2,2-dimethyl-1,3-propanediamine, trans-1,2-diaminocyclopentane, or 1,1'-binaphthyl-2,2'-diamine or by replacing the aldimine bond with ketimine.

Anion variation on a cobalt(III) complex of salen-type ligand tethered by four quaternary ammonium salts for CO2/epoxide copolymerization.

Anion exchange of BF(4)(-) occurs by stirring a cobalt(III) complex of salen-type ligand tethered by four quaternary ammonium BF(4)(-) salts over a slurry of NaX in CH(2)Cl(2), affording a complex containing four X's per cobalt (X = 2,4,5-trichlorophenolate, 6; X = 4-nitrophenolate, 10; X = 2,4-dichlorophenolate, 12). The (1)H and (13)C NMR spectra are in agreement with an unusual imine uncoordinated structure. The two salen-phenoxys and the two X's persistently coordinate with cobalt(III) to form a square planar cobaltate complex while the other two X's scramble through coordination and decoordination to the axial sites of the square plane.

Elucidation of the structure of a highly active catalytic system for CO2/epoxide copolymerization: a salen-cobaltate complex of an unusual binding mode.

Salen-type ligands comprised of ethylenediamine or 1,2-cyclohexenediamine, along with an salicylaldehyde bearing a methyl substituent on its 3-position and a -[CR(CH(2)CH(2)CH(2)N(+)Bu(3))(2)] (R = H or Me) on its 5-position, unexpectedly afford cobalt(III) complexes with uncoordinated imines. In these complexes, two salen-phenoxys and two 2,4-dinitrophenolates (DNPs), which counter the quaternary ammonium cations, coordinate persistently with cobalt, while two other DNPs are fluxional between a coordinated and an uncoordinated state in THF at room temperature. The complexes of this binding mode show excellent activities in carbon dioxide/propylene oxide copolymerization (TOF, 8300-13,000 h(-1)) but with some fluctuation in induction times (1-10 h), depending on how dry the system is.

Bimetallic anilido-aldimine zinc complexes for epoxide/CO2 copolymerization.

Acyclic o-phenylene-bridged bis(anilido-aldimine) compounds, o-C(6)H(4){C(6)H(2)R(2)N=CH-C(6)H(4)-(H)N(C(6)H(3)R'(2))}(2) and related 30-membered macrocyclic compounds, o-C(6)H(4){C(6)H(2)R'(2)N=CH-C(6)H(4)-(H)N-C(6)H(2)R(2)}(2) (o-C(6)H(4)) are prepared. Successive additions of Me(2)Zn and SO(2) gas to the bis(anilido-aldimine) compounds afford quantitatively dinuclear mu-methylsulfinato zinc complexes, o-C(6)H(4){(C(6)H(2)R(2)N=CH-C(6)H(4)-N(C(6)H(3)R'(2))-kappa(2)-N,N)Zn(mu-OS(O)Me)}(2) (R = iPr and R' = iPr, 29; R = Et and R' = Et, 30; R = Me and R'= Me, 31; R = Me and R' = iPr, 32; R = Et and R' = Me, 33; R = Et and R' = iPr, 34; R = iPr and R' = Et, 35) and o-C(6)H(4){C(6)H(2)R'(2)N=CH-C(6)H(4)-N-C(6)H(2)R(2)-kappa(2)-N,N)Zn(mu-OS(O)Me)}(2) (o-C(6)H(4)) (R = Et and R'= Et, 36; R = Me and R' = Me, 37; R = iPr and R' = Me, 38; R = Et and R' = Me, 39; R = Me and R'= iPr, 40). Molecular structures of 34 and 40 are confirmed by X-ray crystallography.