Calix[4]arene-derived diphosphines, diphosphinites and diphosphites as chelating ligands for transition metal ions. Encapsulation of silver(I) in a calix-crown diphosphite

摘要

A series of lower rim-functionalised calix[4]arenes bearing 1,3-positioned phosphorus(III) ligands L~1-L~9 have been synthesized and their coordinative properties examined. L~1 and L~2 { 5,11,17,23-tetra-tert-butyl-25,27-bis[2-(diphenyl- phosphino)ethoxy]- and -25,27-bis(diphenylphosphinomethoxy)-26.28-bis(3-oxabutyloxy)calix[4]arene} react with [Rh(nbd)(THF)_2]BF_4 (nbd = 1,5-norbomadiene; THF= tetrahydroturan) to afford in high yield the complexes [Rh(nbd)L~1]BF4 and [Rh(nbd)L~2]BF4, respectively, where the calixarene behaves as a P,P' chelator. Both complexes catalyse hydroformylation of styrene at comparable rates, the linear : branched aldehyde ratio being 5 : 95. The presence of the ether side groups did not exert a noticeable effect on the selectivity nor the catalytic activity. Reaction of L~1-L~8 with [Pd(#eta#~3-C_3H_4Me)(THF)_2]BF_4 gave the corresponding cationic chelate complexes [Pd(#eta#~3-C_3H_4Me)L~i]BF_4 that are active in the catalytic alkylation of 1 ,3-diphenylprop-2-enyl acetate with dimethyl malonate. Owing to the presence of a non-planar Pd-allyl fragment, theachiral calixarene subunits of some of these complexes are no longer C_(2v)-symmetrical, as evidenced by the ~1H and ~(13)C NMR spectra that show non-equivalerit side groups. Selective chelation via the two phosphorus atoms was also observed in the complexes [RuCl(p-MeC_6H_4Pr~i)L~i]BF_4 (L~i = L~3 or L~4) obtained by reaction of the amide phosphines L~i with [RuCl(p-MeC_6H_4Pr~i)(THF)_2]BF_4 [L~3 = 5,11,17,23-tetra- tert-butyl-25,27 -bis(diethylcarbamoylmethoxy)-26,28-bis( diphenylphosphinomet and L~4 = 5,11,17,23-tetra-tert-butyl-25,17-bis(diphenylphosphinomethoxy)-26,28-bis{(1-(R)-phenylethyl)carbamoylmethyoxy}-calix[4]arene] Reaction of L~3 or L~4 with neutral [RuCl_2(p-MeC_6H_4Pr~i)]_2 afforded the bimetallic complexes [{RuCl(p-MeC_6H_4Pr~i)}_(2-) L~i] where the calixarene acts as a P,P' bridging ligand. Reaction of AgBF_4 with calix-crown L~9 {25,27-bis(diethoxy- phosphinoxy)-26,28-(3.6,9-trioxaundecane-1 , Il-dioxy)calix[4]arene} resulted in quantitative formation of the complex [AgL~9]BF_4 in which the silver(I) ion lies inside the cavity constituted by the crown ether fragment and the two phosphorus arms. As revealed bya single crystal X-ray diffraction study. the Ag~- ion has a trigonal P_2O coordination environment with a P-Ag-P angle of 134.74(4)deg.