Well-defined, solvent-free cationic barium complexes: Synthetic strategies and catalytic activity in the ring-opening polymerization of lactide

作者：Liu Bo; Roisnel Thierry; Sarazin Yann^*

来源：Inorganica Chimica Acta, 2012, 380: 2-13.

DOI：10.1016/j.ica.2011.09.020

• Barium
• Well-defined cations
• Secondary interactions
• Ring-opening polymerization

Well-defined, solvent-free cationic barium complexes of the type [{LnX}Ba](+)center dot[H2N{B(C6F5)(3)}(2)] stabilized by multidentate amino-ether phenoxide or fluorinated amino-ether alkoxide ligands {LnX} are available according to original, general and high-yield protocols. These cations have been prepared by (i) hydrolysis of heteroleptic complexes {LnX}BaN(SiMe2H)(2) stabilized by Ba center dot center dot center dot H-Si interactions with [H(OEt2)(2)](+)center dot[H2N{B(C6F5)(3)}(2)], or (ii) reaction of {Ba[N(SiMe2H)(2)](2)}(n) with the doubly acidic pro-ligands [{LnX}HH](+)center dot[H2N{B(C6F5)(3)}(2)]. The solid-state structures of [{LO2}Ba(THF)(2)](+)center dot[H2N{B(C6F5)(3)}(2)] ({LO2} H = 2-[(1,4,7,10-tetraoxa-13-azacyclopentadecan-13-yl)methyl]-4,6-di-tert-butylphenol) and [{RO2}Ba](+)center dot[H2N{B(C6F5)(3)}(2)] {RO2}H = 2-[(1,4,7,10-tetraoxa-13-azacyclopentadecan-13-yl)methyl]-1,1,1,3,3,3-hexafluoropropan-2-ol) are described, highlighting the key role of internal secondary Ba center dot center dot center dot F-C interactions in these highly electrophilic species. In combination with an excess of an external nucleophile (chosen from benzyl alcohol, 1,3-propanediol, benzyl amine or an hydroxyl-functionalized alkoxy-amine) as a co-initiator, some of these Ba cations provide extremely efficient catalysts for the immortal ring-opening polymerization of L-lactide in the temperature range 0-30 degrees C, converting rapidly up to 5000 equiv. of monomer in a controlled fashion and with excellent end-group fidelity.

• 出版日期2012-1-15