Palladium complexes bearing monodentate and bidentate phosphine ligands (1–7) were synthesised and used as catalyst precursors in the methoxycarbonylation of norbornene. The catalytic systems bearing ligands 1, 3 and 4 afforded excellent conversions (>99%) and selectivity of the ester (>99%). NMR investigations showed that using complex 1a as the precursor resulted in the protonated phosphine, 1-H+, being formed under catalytic conditions and thus the addition of acid is not required for the activation of this system since the reaction involving the precursor with methanol under CO pressure produces 2 equivalents of HCl and leads to the formation of the active species. The protonation of ligand 4 under methoxycarbonylation conditions was also observed and the diprotonated diphosphine was isolated and characterised. This compound was tested as a ligand and acid source in a catalysis and provided excellent conversion and high selectivity to the ester.
合成了带有单齿和双齿
膦配体(1-7)的
钯配合物,并将其用作
降冰片烯甲氧基羰基化反应的催化剂前体。含有
配体 1、3 和 4 的催化体系具有优异的酯转化率(大于 99%)和选择性(大于 99%)。核磁共振研究表明,使用配合物 1a 作为前体,在催化条件下会形成质子化的膦 1-H+,因此该体系的活化不需要添加酸,因为在 CO 压力下,前体与
甲醇反应会产生 2 个当量的 HCl,从而形成活性物质。此外,还观察到
配体 4 在甲氧基羰基化条件下发生质子化,并分离和鉴定了二质子化的
二膦。该化合物作为
配体和酸源在催化反应中进行了测试,并提供了极佳的酯转化率和高选择性。