The preparation and coordinative properties of two upper-rim functionalized calixarenes, 5,17-bis(tert-butyl)-11,23-bis(diethoxyphosphinomethoxy)-25,26,27,28-tetrakis(2-ethoxyethoxy)calix [4] arene (4) and 5,17-bis(tert-butyl)-11,23-bis(diphenylphosphinomethyl)-25,26,27,28-tetrakis(2-ethoxyethoxy)calix[4]arene (6) are presented. Diphosphine 6 was oxidized by air to the corresponding di(phosphine oxide) 7. The molecular structure of 7.2CHCl(3) was elucidated by X-ray crystallography: C78H94O10P2. 2CHCl(3), a = 16.313(5) Angstrom, b = 16.553(5) Angstrom, c = 17.068(6) Angstrom, alpha = 108.04(2)degrees, beta = 93.13(2)degrees, gamma = 100.27(2)degrees, Z = 2. The calixarene matrix displays a pinched cone conformation, with the two Bu-t-phenoxy rings of the macrocycle lying almost perpendicular (interplanar angle 84.7 degrees) and the other two phenoxy rings making an angle of 20.9 degrees. Reaction of 6 with 2 equiv of [AuCl(SC4H8)] (SC4H8 = tetrahydrothiophene) in CH2Cl2 afforded the digold complex 6 .(AuCl)(2) (8). Reaction of 6 with [RuCl2(p-cymene)](2) resulted in formation of the dinuclear complex 6 .[RuCl2(p-cymene)](2) (9) while the rhodium complex 6 .[RhCl(norbornadiene)](2) (10) was formed by reaction of 6 with [RhCl(norbornadiene)](2). Complex 10 catalyzes hydroformylation of styrene (CO/H-2 = 1, P = 40 bar, 70 degrees C, styrene/Rh similar to 585) in the presence of NEt3, from which linear and branched aldehydes were obtained in a 9:91 ratio. Diphosphite 4 was found to be suitable for chelate formation; thus [Pd(eta(3)-MeC3H4)(thf)(2)]BF4 (thf = tetrahydrofuran) reacts with 4 to yield the mononuclear complex [4 .{Pd(eta(3)-MeC3H4)}]BF4 (11), where the metal is located at the mouth of the cavity. All complexes were characterized by elemental analyses and by H-1, C-13, and P-31 NMR spectroscopy.