Phosphorescent Thiazol-2-ylidene Platinum(II) Complexes with β‑Ketoiminates: Single Isomer Formation by Ligand Architecture

We present the synthesis and photophysical properties of six novel N-phenyl-1,3-thiazol-2-ylidene platinum­(II) complexes with sterically demanding N-aryl-β-ketoiminate ligands. Diverse aryl substituents at the coordinating nitrogen atom (phenyl, mesityl, 2,6-diisopropylphenyl, 4-cyanophenyl, 1-naphthyl, and 2,4-difluorophenyl) of the N-aryl-(3Z)-4-amino-3-penten-2-ones exclusively yielded the SP-4-3 coordinated C∧C* cyclometalated platinum­(II) complexes as single isomers as a consequence of the low steric demand of the C∧C* cyclometalating thiazole ligand and the bulkiness of the β-ketoiminate ligands. The formation of this isomer was confirmed by 195Pt NMR and extensive 2D NMR experiments, two solid-state structures, and the results of DFT calculations. As a proof of principle, two complexes with the sterically less demanding β-ketoiminate ligands (3Z)-4-amino-3-penten-2-onato and (2Z)-3-amino-1-phenyl-2-buten-1-onato were synthesized and isolated as an isomeric mixture.本工作报道了六种新型N-苯基-1,3-噻唑-2-亚基铂(II)配合物的合成与光物理性质，该类配合物搭载空间位阻较大的N-芳基-β-酮亚胺配体。针对N-芳基-(3Z)-4-氨基-3-戊烯-2-酮的配位氮原子引入多种芳基取代基（苯基、均三甲苯基、2,6-二异丙基苯基、4-氰基苯基、1-萘基及2,4-二氟苯基），最终仅得到SP-4-3配位型C∧C*环金属化铂(II)配合物单一异构体，这一结果源于C∧C*环金属化噻唑配体的空间位阻较低，而β-酮亚胺配体具有较大空间位阻。 该异构体的生成通过195Pt核磁共振（195Pt NMR）、多组二维核磁共振（2D NMR）实验、两套固态晶体结构解析结果以及密度泛函理论（DFT）计算得到了确证。 作为原理性验证，本工作合成并分离得到了两组搭载空间位阻较小的β-酮亚胺配体的配合物：(3Z)-4-氨基-3-戊烯-2-酮合配体与(2Z)-3-氨基-1-苯基-2-丁烯-1-酮合配体，二者以异构体混合物形式存在。