Bhattacharjee Jayeeta, Peters Marius, Bockfeld Dirk, Tamm Matthias
Institut für Anorganische und Analytische Chemie, Technische Universität Braunschweig, Hagenring 30, 38106, Braunschweig, Germany.
Chemistry. 2021 Apr 1;27(19):5913-5918. doi: 10.1002/chem.202100482. Epub 2021 Mar 3.
The N-heterocyclic carbene-phosphinidene adducts (NHC)PH were reacted with AlMe in toluene to afford the monoaluminum complexes [{(IDipp)PH}AlMe ] and [{(IMes)PH}AlMe ] (IDipp=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene, IMes=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene). In contrast, the dialuminum complex [{( IMes)PH}(AlMe ) ] was obtained for IMes=1,3-bis(2,4,6-trimethylphenyl)-4,5-dimethylimidazolin-2-ylidene. These complexes served as initiators for the efficient ring-opening polymerization of rac-lactide in toluene at 60 °C. High degrees of isoselectivity were found for the poly(rac-lactide) obtained in the presence of the monoaluminum complexes (P up to 0.92, T up to 191 °C), whereas almost atactic polymers were produced by the dialuminum complex. Detailed mechanistic studies reveal that the polymerization proceeds via a coordination-insertion mechanism with the carbene-phosphinidene ligands acting as stereodirecting groups.
将N-杂环卡宾-磷烯加合物（NHC）PH与AlMe在甲苯中反应，得到单铝配合物[{(IDipp)PH}AlMe ]和[{(IMes)PH}AlMe ]（IDipp = 1,3-双（2,6-二异丙基苯基）咪唑啉-2-亚基，IMes = 1,3-双（2,4,6-三甲基苯基）咪唑啉-2-亚基）。相比之下，当IMes = 1,3-双（2,4,6-三甲基苯基）-4,5-二甲基咪唑啉-2-亚基时，得到二铝配合物[{(IMes)PH}(AlMe ) ]。这些配合物在60 °C下作为引发剂用于在甲苯中高效引发外消旋丙交酯的开环聚合。在单铝配合物存在下得到的聚（外消旋丙交酯）具有高度的等规选择性（P高达0.92，T高达191 °C），而二铝配合物则生成几乎无规的聚合物。详细的机理研究表明，聚合反应通过配位插入机理进行，其中卡宾-磷烯配体作为立体定向基团。
