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

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-(diphenylphosphino)ethoxy]- and -25,27-bis(diphenylphosphinomethoxy)-26,28-bis(3-oxabutyloxy)calix[4]arene} react with [Rh(nbd)(THF)(2)]BF4 (nbd=1,5-norbornadiene; THF=tetrahydrofuran) 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)-C3H4Me)(THF)(2)]BF4 gave the corresponding cationic chelate complexes [Pd(eta (3)-C3H4Me)L-i]BF4 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, the achiral calixarene subunits of some of these complexes are no longer C-2v-symmetrical, as evidenced by the H-1 and C-13 NMR spectra that show non-equivalent side groups. Selective chelation via the two phosphorus atoms was also observed in the complexes [RuCl(p-MeC6H4Pri)L-i]BF4 (L-i=L-3 or L-4) obtained by reaction of the amide phosphines L-i with [RuCl(p-MeC6H4Pri)(THF)(2)]BF4 [L-3=5,11,17,23-tetra-tert-butyl-25,27-bis(diethylcarbamoylmethoxy)-26,28-bis(diphenylphosphinomethoxy)- and L-4=5,11,17,23-tetra-tert-butyl-25,27-bis(diphenylphosphinomethoxy)-26,28-bis{(1-(R)-phenylethyl)carbamoylmethoxy}-calix[4]arene]. Reaction of L-3 or L-4 with neutral [RuCl2(p-MeC6H4Pri)](2) afforded the bimetallic complexes [{RuCl(p-MeC6H4Pri)}(2)L-i] where the calixarene acts as a P,P' bridging ligand. Reaction of AgBF4 with calix-crown L-9 {25,27-bis(diethoxyphosphinoxy)-26,28-(3,6,9-trioxaundecane-1,11-dioxy)calix[4]arene} resulted in quantitative formation of the complex [AgL9]BF4 in which the silver(I) ion lies inside the cavity constituted by the crown ether fragment and the two phosphorus arms. As revealed by a single crystal X-ray diffraction study, the Ag+ ion has a trigonal P2O coordination environment with a P-Ag-P angle of 134.74(4)degrees.