Synthesis of some very bulky N,N′-disubstituted amidines and initial studies of their coordination chemistry †
作者:René T. Boeré、Vicki Klassen、Gotthelf Wolmershäuser
DOI:10.1039/a805548c
日期:——
N,Nâ²-Bis(2,6-diisopropylphenyl)-4-toluamidine, -4-anisylamidine and -acetamidine have been prepared for the first time from 2,6-diisopropylaniline and the acid chlorides via the corresponding imidoyl chlorides. The crystal structures of all three amidines were determined, indicating that the first is a disordered mixture of Z-anti and E-syn tautomeric forms, the second Z-anti, and the third E-anti in the solid state. Despite these differences, all three form identical coordination complexes with Mo(CO)3 in which the ligand is in the Z-anti geometry, and the metal is Ï-coordinated to the imino 2,6-diisopropylphenyl ring, and the amino NâH unit is directed towards metal. The coordination mode was confirmed by single-crystal X-ray structure determination of the toluamidine and methylamidine complexes with Mo(CO)3. In the case only of the methylamidine, an isolable intermediate is first formed in which the neutral amidine is coordinated in a monodentate fashion to an Mo(CO)5 unit. The crystal structure of this complex shows that the ligand is in the E-anti geometry, with the imino nitrogen coordinated to Mo, d(MoâN)Â =Â 2.352(2) Ã
. The structures are closely related in that the initial Mo(CO)5 N-coordination sets up the metal for conversion to the more thermodynamically stable Ï-coordinated Mo(CO)3 complex. The high steric bulk of these superamidine ligands is seen in the failure of any of them to form the metalâmetal bonded Mo2(amidinate)4 complexes typically prepared using common, less bulky, amidines.
首次以 2,6-二异丙基苯胺和酸氯化物为原料,通过相应的亚胺酰氯制备出了 N,Nâ²-双(2,6-二异丙基苯基)-4-甲苯胺、-4-甲脒和-乙脒。这三种脒的晶体结构均已确定,表明在固态下,第一种脒是 Z-反式和 E-syn 同分异构体的无序混合物,第二种脒是 Z-反式,第三种脒是 E-反式。尽管存在这些差异,但这三种化合物都与 Mo(CO)3 形成了相同的配位复合物,其中配体呈 Z-anti 几何结构,金属与 2,6-二异丙基苯基亚氨基环配位,氨基 NâH 单元朝向金属。这种配位模式通过测定甲脒和甲脒与 Mo(CO)3 的单晶 X 射线结构得到了证实。仅就甲脒而言,首先形成了一个可分离的中间体,其中的中性脒以单配位方式与 Mo(CO)5 单元配位。该复合物的晶体结构显示,配体呈 E-anti 几何结构,亚氨基氮与 Mo 配位,d(MoâN)Â =Â 2.352(2) Ã。这两种结构密切相关,最初的 Mo(CO)5 N 配位使金属转化为热力学上更稳定的 Ï 配位 Mo(CO)3 复合物。这些超脒配体的高立体体积体现在它们中的任何一种都无法形成通常使用体积较小的普通脒制备的金属键 Mo2(脒基)4 复合物。