Heterofunctionalised phosphites built on a calix[4]arene scaffold and their use in 1-octene hydroformylation. Formation of 12-membered P,O-chelate rings
作者:St??phane Steyer、Catherine Jeunesse、Dominique Matt、Richard Welter、Marcel Wesolek
DOI:10.1039/b204604k
日期:2002.11.12
The calixarene phosphites L1–L4 were obtained in high yield through reaction of PCl3/NEt3 with the monofunctionalised cone-calixarenes p-tert-butylcalix[4]arene(OH)3OR, in which the R substituents bear an oxygen donor ligand [R = CH2P(O)Ph2 (L1), CH2CO2Et (L2), CH2C(O)NEt2 (L3), CH2CH2OMe (L4)]. The calixarene core of the four ligands adopts a cone conformation and, hence, the phosphites become potential P,O-chelating systems. Phosphite L1 is remarkably stable towards aqueous NaOH, but the presence of slightly acidic water results in phosphonate formation. Slow oxidation of L1 in air afforded the corresponding mixed phosphine oxide–phosphate. In the complexes [RuCl2(p-cymene)L1], [cis-PtCl2(L1)2]
(9), trans-[PdCl2(L1)2], [Pd(8-mq)Cl(Ln)]
(8-mqH = 8-methylquinoline, n
= 1–3), [Pd(dmba)Cl(L1)]
(dmbaH =
N,N-dimethylbenzylamine), [Pd(η3-C4H7)Cl(L2)], [Rh(acac)(CO)Ln] (n
= 1–3) and [RhCl(CO)(L1)2], the phosphites behave as a monodentate phosphorus donor ligands. Owing to their steric crowding, the two cis-disposed ligands of complex 9 cannot freely rotate about their coordination axis. In the solid state, the calixarene backbones of complex 9 display a so-called ‘up-up-out-up’ conformation. Chelating phosphite behaviour was found in the cationic complexes [Pd(8-mq)Ln]BF4 (n
= 1–3). In solution, the large, chelating P,O-loop of the latter complexes swings from one side of the metal plane to the other, the dynamics possibly being facilitated by the flexibility of the calixarene backbone. The four oxo-functionalised phosphites were tested as catalysts for 1-octene hydroformylation. The observed reaction rates lie in the range reported for other medium-bulky phosphites. Furthermore, the hydroformylation rate decreases as the donor strength of the side group increases, suggesting binding of the O-donor during catalysis. The L/B ratios lie in the range 1.4–3.6, the highest linear aldehyde selectivity being observed with the phosphite ester L3.
通过 PCl3/NEt3 与单官能化锥杯芳烃对叔丁基杯[4]芳烃(OH)3OR 反应,高产率地获得了杯芳烃亚磷酸酯 L1–L4,其中 R 取代基带有氧供体配体 [R = CH2P(O)Ph2 (L1)、CH2CO2Et (L2)、CH2C(O)NEt2 (L3)、CH2CH2OMe (L4)]。四个配体的杯芳烃核心采用锥形构象,因此亚磷酸酯成为潜在的 P,O 螯合系统。亚磷酸盐 L1 对 NaOH 水溶液非常稳定,但微酸性水的存在会导致膦酸盐形成。 L1 在空气中缓慢氧化得到相应的混合氧化膦-磷酸盐。在配合物 [RuCl2(p-cymene)L1]、[cis-PtCl2(L1)2] 中
(9)、反式-[PdCl2(L1)2]、[Pd(8-mq)Cl(Ln)]
(8-mqH = 8-甲基喹啉,n
= 1–3), [Pd(dmba)Cl(L1)]
(dmbaH =
N,N-二甲基苄胺), [Pd(η3-C4H7)Cl(L2)], [Rh(acac)(CO)Ln] (n
= 1–3) 和 [RhCl(CO)(L1)2],亚磷酸酯充当单齿磷供体配体。由于空间拥挤,配合物 9 的两个顺式配置的配体不能绕其配位轴自由旋转。在固态下,复合物 9 的杯芳烃主链显示出所谓的“向上-向上-向外-向上”构象。在阳离子配合物 [Pd(8-mq)Ln]BF4 (n
= 1–3)。在溶液中,后者配合物的大的螯合 P,O 环从金属平面的一侧摆动到另一侧,杯芳烃主链的柔性可能促进了动力学。测试了四种氧代官能化亚磷酸酯作为 1-辛烯加氢甲酰化的催化剂。观察到的反应速率位于其他中等体积亚磷酸酯报道的范围内。此外,随着侧基供体强度的增加,加氢甲酰化速率降低,这表明在催化过程中O-供体的结合。 L/B 比率在 1.4–3.6 范围内,亚磷酸酯 L3 观察到最高的直链醛选择性。