An Unusual Calix[4]arene Derivative Containing Phosphorus with Coordination Numbers 4, 5 and 6

The title compound, chloro[5,11,17,23-tetra-tert-butyl-28-(tetraphosphoranyloxy)calix[4] arene-25,26,27-trioxy]phosphonium hexachlorophosphate dichloromethane solvate, C₄₄H₅₂Cl₅O₄P₂⁺.PCl₆^-.CH₂Cl₂, contains pentavalent phosphorus with three different coordination numbers, 4, 5 and 6. The calixarene adopts a non-standard conformation between the partial cone and 1,2-alternate conformations.

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