Unusually Large Bite Angle of a Distally Diphosphanylated Calix[4]arene Chelator

5,17‐Diphenylphosphanyl‐11,23‐bis(4‐tolyl)‐25,26,27,28‐tetrapropoxycalix[4]arene ( 6 ), a semi‐rigid, calixarene‐based diphosphane in which the phosphorus atoms are separated by 12 chemical bonds, reacts with [Ni(η 5 ‐C 5 H 5 )(1,5‐cyclooctadiene)]BF 4 or AgBF 4 to afford the corresponding chelate complexes [Ni(η 5 ‐C 5 H 5 )( 6 )]BF 4 and [Ag( 6 )]BF 4 quantitatively. These complexes were both characterised by a single‐crystal X‐ray diffraction study. In the nickel complex the ligand shows a bite angle of 104.5°, which lies in the range expected for this kind of diphosphane with a large P ··· P separation. In the silver(I) complex the diphosphane displays a much larger bite angle of 138.8°, which was unexpected and reflects the flexilibilty of the calix[4]arene skeleton. Furthermore, in solution the silver complex shows dynamic behaviour. One of the observed motions corresponds to the silver atom switching reversibly from a linear to a bent AgP 2 cordination geometry.