Synthesis, Structural Characterization, Hirshfeld Analysis and AIM Analysis of 2,4,8,10-tetra-tert-butyl-6-phenyldibenzo[d,g][1,3,6,2]-dioxa-selenaphosphocine and its Oxide and Selenide Derivatives

The reaction of 2,2′-selenobis(4,6-di-tert-butyl phenol) with equimolar amount of dichlorophenylphosphine afforded the 8-membered cyclic phosphonite, PhP{-OC₆H₂(^tBu)₂(µ-Se)(^tBu)₂C₆H₂O-} (1). The reaction of 1 with 30% aq H₂O₂ resulted in the oxidation of both phosphorus and selenium to give PhP(O){-OC₆H₂(^tBu)₂(µ-Se(O))(^tBu)₂C₆H₂O-} (2) in quantitative yield. Similar reaction of 1 with one equivalent of trimethylamine-N-oxide yielded the phosphine oxide derivative, PhP(O){-OC₆H₂(^tBu)₂(µ-Se)(^tBu)₂C₆H₂O-} (3). The reaction of 1 with gray selenium in 1:1 molar ratio afforded PhP(Se){-OC₆H₂(^tBu)₂(µ-Se)(^tBu)₂C₆H₂O-} (4) in good yield. All the derivatives have been structurally characterized. Both the compounds 2 and 3 crystallized with the asymmetric unit containing a whole molecule, whereas the compound 4 crystallized with a CH₂Cl₂ molecule. All of these molecules showed intermolecular C−H⋅⋅⋅O and C−H⋅⋅⋅Se hydrogen bonding interactions which play major role in the crystal packing to form a three-dimensional array. Hirshfeld surface analysis, d_norm and two-dimensional fingerprint plots were investigated to validate the contributions of the different intermolecular contacts within the supramolecular structure. A Hirshfeld surface analysis indicated that the most significant contributions to the crystal packing of 2 are from H⋅⋅⋅H (72%), C⋅⋅⋅H/H⋅⋅⋅C (15%), O⋅⋅⋅H/H⋅⋅⋅O (10.1%) and Se⋅⋅⋅H/H⋅⋅⋅Se (2.8%) contacts, and those for 3 are from H⋅⋅⋅H (74.1%), C⋅⋅⋅H/H⋅⋅⋅C (14.2%), O⋅⋅⋅H/H⋅⋅⋅O (5.7%) and Se⋅⋅⋅H/H⋅⋅⋅Se (5.7%) contacts, while those for 4 are from H⋅⋅⋅H (75.9%), C⋅⋅⋅H/H⋅⋅⋅C (10.5%), O⋅⋅⋅H/H⋅⋅⋅O (1%) and Se⋅⋅⋅H/H⋅⋅⋅Se (12.5%) contacts. Non-covalent interactions between C–H and O were observed in the molecular structures of 2–4. These weak interactions were also assessed by DFT calculations in terms of their non-covalent interaction plots and QTAIM analysis.

Graphical Abstract

This paper describes the synthesis and crystal structures of three selenaphosphocine derivatives. The reaction of 2,2′-selenobis(4,6-di-tert-butyl phenol) with equimolar amount of dichlorophenylphosphine produce the 8-membered cyclic phosphonite 1. The reaction of 1 with 30% aq H₂O₂ and elemental selenium afford three different macrocyclic compounds.