CAVITY-SHAPED PHOSPHANE LIGANDS - PHOSPHANE-AMIDE HYBRIDS BASED ON A CALIX[4]ARENE MATRIX AND THEIR CHELATING BEHAVIOR TOWARDS PLATINUM ANDRHODIUM

The di(amide)-diphosphane hybrids )-26,28-bis(diphenylphosphinomethoxy )calix[4]arene (cone) 7 and (R,R)-(+)-5,11, 17,23-tetra-tert-butyl-25, 27-bis[(1-phenylethyl) thoxy]-26,28-bis(diphenylphosphinomethoxy)calix [4] arene (cone) 8 were prepared in three steps from p-tert-butylcalix [4]arene 1. Reaction of 1 with 1.1 equiv K2CO3 and 2 equiv BrCH2C(O)NR (1)R(2) (R(1) = R(2) = Et and R(1) = (R)-CHMePh, R(2) = H) proceeds vi a the selective alkylation of two diametrically located phenol rings a nd gave the di(amide)-di(hydroxy) compounds 2 and 3, respectively, bot h in a cone conformation. Deprotonation of 2 and 3 with 2 equiv (t)BuO Na followed by alkylation with 2 equiv Ph(2)P(O)CH(2)OTs yielded the p hosphane oxides 4 and 5 respectively (cone conformers). The structure of 4 was confirmed by an X-ray diffraction study. Crystal data for 4 : triclinic, space group P (1) over bar, with a = 14.316 (4) Angstrom, b = 15.272 (4) Angstrom, C = 18.100 (5) Angstrom, alpha = 86.98(2)degr ees, beta = 74.93(2)degrees, gamma = 87.61(2)degrees, and Z = 2. The s tructure was solved by direct methods and refined to R = 0.060. Functi onalization of 2 with (t)BuKO instead of (t)BuNaO led to the partial c one isomer 6 in which one phosphoryl group is positioned anti with res pect to the three other pendant groups. The quantitative reduction of 4 and 5, leads to the diphosphanes 7 and 8, respectively, and was perf ormed in refluxing PhSiH(3). The sequential reaction of [RhCl(norborna diene)](2) with 2 equiv AgBF4 and 2 equiv 8 gave the cationic complex cis-[RhCl(norbornadiene) 8](BF4) 9. Complex 9 catalyzes the hydroformy lation of styrene at 40 degrees C, under a CO/H-2-pressure of 40 bar, leading to 2-phenylpropanal and 3-phenylpropanal in a ratio 95:5. Reac tion of 7 with [PtCl2(cycloocta-1,5-diene)] gave the chelate complex 1 0. The structure of 10 has been determined from three-dimensional X-ra y data. Crystal data for 10 . CH2Cl2 : triclinic, space group P1 (1) o ver bar, with a = 12.481 (9) Angstrom, b = 17.558 (5) Angstrom, c = 20 .43 (1) Angstrom, alpha = 95.20 (4)degrees, beta = 103.68 (8)degrees, gamma = 92.79 (4)degrees, and Z = 2. The structure was refined to R = 0.096. The phosphorus atoms are cis-bonded to the metal center and the platinum atom lies above the cavity defined by the four substituents of the calixarene. All compounds have been characterized by elemental analyses, IR and H-1, C-13{H-1} and P-31{H-1} NMR spectroscopy.