The effect of number and position of P=O/P=S bridging units on cavitand selectivity toward methyl ammonium salts

Nitrosonium complexation by the tetraphosphonate cavitand 5,11,17,23-tetramethyl-6,10:12,16:18,22:24,4-tetrakis(phenylphosphonato-κ2O,O)resorcin(4)arene

Resorcinarene-based tetra­phospho­nate cavitands are versatile mol­ecular receptors which combine a π-basic aromatic cavity with hydrogen-bond acceptor groups at their upper rim. Their complexation properties span from neutral mol­ecules to cationic species, and have been extensively studied both in solution and in the solid state. In this paper, we report the NMR solution studies and the crystal structure of a new supra­molecular complex between a tetra­phospho­nate cavitand and the nitrosyl cation NO⁺. The cation is disordered over two equivalent positions, and inter­acts with two adjacent P=O groups at the upper rim of the cavitand through a dipole–charge inter­action.

The crystal structure of a new supra­molecular complex between the tetra­phos­pho­nate cavitand 5,11,17,23-tetra­methyl-6,10:12,16:18,22:24,4-tetra­kis(phenyl­phospho­nato-κ²O,O′)resorcin(4)arene and the nitrosyl cation NO⁺, as the BF₄⁻ salt, is reported. The complex, of general formula [(C₅₆H₄₄P₄O₁₂)(NO)]BF₄·CH₂Cl₂ or NO@Tiiii[H, CH₃, C₆H₅] BF₄·CH₂Cl₂, crystallizes in the space group P-1. The nitrosyl cation is disordered over two equivalent positions, with occupancies of 0.503 (2) and 0.497 (2), and inter­acts with two adjacent P=O groups at the upper rim of the cavitand through dipole–charge inter­actions. In the lattice, the cavitands are connected through a series of C—H⋯π inter­actions involving the methyl and methyl­enic H atoms and the aromatic rings of the macrocycle. The structure is further stabilized by the presence of C—H⋯F inter­actions between the hydrogen atoms of the cavitands and the F atoms of the tetra­fluorido­borate anion. As a result of the disorder, the lattice di­chloro­methane mol­ecules could not be modelled in terms of atomic sites, and were treated using the PLATON SQUEEZE procedure [Spek (2015 ▸). Acta Cryst. C71, 9–18]. The complexation process has also been studied in solution through NMR titrations.