Yang Feng-Zhao, Wang Yu-Heng, Chang Mu-Chieh, Yu Kuo-Hsuan, Huang Shou-Ling, Liu Yi-Hung, Wang Yu, Liu Shiuh-Tzung, Chen Jwu-Ting
Department of Chemistry, National Taiwan University, Taipei 106, Taiwan.
Inorg Chem. 2009 Aug 17;48(16):7639-44. doi: 10.1021/ic900296y.
A series of hemilabile ligands of alpha-aminoaldimines and their methylpalladium complexes have been prepared and characterized. Neutral square-planar methylpalladium complexes in the form of [R(1)R(2)NCMe(2)CH horizontal lineNR]Pd(Me)Cl (R = Me, R(1) = R(2) = Me (3a); R = Me, R(1) = R(2) = Et (3b); R = Et, R(1) = R(2) = Me (4a); R = (n)Pr, R(1) = R(2) = Me (5a); R = (i)Pr, R(1) = R(2) = Me (6a); R = (i)Pr, R(1) = R(2) = Et (6b); R = (i)Pr, (R(1), R(2)) = c-C(4)H(8) (6c); R = (i)Pr, R(1) = (i)Pr, R(2) = H (6d); R = (i)Pr, R(1) = (t)Bu, R(2) = H (6e); R = (t)Bu, R(1) = R(2) = Me (7a); R = (t)Bu, R(1) = R(2) = Et (7b); R = (t)Bu, (R(1), R(2)) = c-C(4)H(8) (7c); R = (t)Bu, R(1) = (i)Pr, R(2) = H (7d); R = (t)Bu, R(1) = (t)Bu, R(2) = H (7e); R = Ph, R(1) = R(2) = Me (8a); R = Ph, R(1) = R(2) = Et (8b)) show geometrical isomerism. The relative ratios of trans/cis isomers appear to be predominated by the steric hindrance between the Pd-bound methyl group and imino or amino substituents (R and R(1) and R(2)). The NMR studies for the substitution reaction of (COD)Pd(Me)Cl with Et(2)NCMe(2)CH horizontal lineN(i)Pr at -20 degrees C indicate that cis-6b is the major kinetic product, which isomerizes to the thermodynamic product in trans form quantitatively above -5 degrees C. Kinetic results show that the ligand substitution reaction likely undergoes an associative pathway, and the isomerization reaction proceeds via an intramolecular process that comprises imine dissociation and recoordination.
一系列α-氨基醛亚胺的半不稳定配体及其甲基钯配合物已被制备和表征。呈[R(1)R(2)NCMe(2)CH横线NR]Pd(Me)Cl形式的中性平面正方形甲基钯配合物（R = Me，R(1) = R(2) = Me (3a)；R = Me，R(1) = R(2) = Et (3b)；R = Et，R(1) = R(2) = Me (4a)；R = (n)Pr，R(1) = R(2) = Me (5a)；R = (i)Pr，R(1) = R(2) = Me (6a)；R = (i)Pr，R(1) = R(2) = Et (6b)；R = (i)Pr，(R(1), R(2)) = c-C(4)H(8) (6c)；R = (i)Pr，R(1) = (i)Pr，R(2) = H (6d)；R = (i)Pr，R(1) = (t)Bu，R(2) = H (6e)；R = (t)Bu，R(1) = R(2) = Me (7a)；R = (t)Bu，R(1) = R(2) = Et (7b)；R = (t)Bu，(R(1), R(2)) = c-C(4)H(8) (7c)；R = (t)Bu，R(1) = (i)Pr，R(2) = H (7d)；R = (t)Bu，R(1) = (t)Bu，R(2) = H (7e)；R = Ph，R(1) = R(2) = Me (8a)；R = Ph，R(1) = R(2) = Et (8b)）表现出几何异构现象。反式/顺式异构体的相对比例似乎主要由与钯相连的甲基与亚氨基或氨基取代基（R以及R(1)和R(2)）之间的空间位阻决定。在-20℃下对(COD)Pd(Me)Cl与Et(2)NCMe(2)CH横线N(i)Pr的取代反应进行的核磁共振研究表明，顺式-6b是主要的动力学产物，在高于-5℃时它定量地异构化为反式的热力学产物。动力学结果表明，配体取代反应可能通过缔合途径进行，而异构化反应则通过包含亚胺解离和重新配位的分子内过程进行。
