Calix[4]arene Ligands with Phosphorus-Containing Groups Tethered at the Upper Rim

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: C 78 H 94 O 10 P 2 ·2CHCl 3, a = 16.313 (5) Å, b = 16.553(5) Å, c = 17.068(6) Å, α = 108.04(2)°, β = 93.13(2)°, γ = 100.27(2)°, Z = 2. The calixarene matrix displays a pinched cone conformation, with the two t Bu-phenoxy rings of the macrocycle lying almost perpendicular (interplanar angle 84.7°) and the other two phenoxy rings making an angle of 20.9°. Reaction of 6 with 2 equiv of [AuCl(SC 4 H 8 )] (SC 4 H 8 = tetrahydrothiophene) in CH 2 Cl 2 afforded the digold complex 6 ·(AuCl) 2 ( 8 ). Reaction of 6 with [RuCl 2 ( p -cymene)] 2 resulted in formation of the dinuclear complex 6 ·[RuCl 2 ( 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 °C, styrene/Rh ∼ 585) in the presence of NEt 3, 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( η 3 -MeC 3 H 4 )(thf) 2 ]BF 4 (thf = tetrahydrofuran) reacts with 4 to yield the mononuclear complex [ 4 ·{Pd( η 3 -MeC 3 H 4 )}]BF 4 ( 11 ), where the metal is located at the mouth of the cavity. All complexes were characterized by elemental analyses and by 1 H, 13 C, and 31 P NMR spectroscopy.