Monoclinic and Triclinic Tetraisopropyl‐p‐phenylenediamine: To what Extent do n_N/π Interactions Determine Structures?

Polydentate Phosphane Ligands Featuring N,N,N’‐Trialkylformamidines

“…In such cases, a C−N bond length should have a typical value of 1.45 Å. For example, tetraisopropyl‐p‐phenylenediamine (CCDC ref codes PIDFEN and PIDFEN01) can be crystallized in two crystal polymorphs [14] . The first possesses approximately coplanar (PIDFEN) and the second (PIDFEN01) has orthogonal arrangement of the benzene ring and the i ‐Pr 2 N groups.…”

“…Thus, the reaction of silylformamidine 3 c with phosphorus trichloride in a 2 : 1 ratio exhibited a signal at δ p =45 ppm in 31 P NMR, that we assigned to chlorophosphane 16 . Recently, an analogous chlorophosphane was separated and characterized with δ p =31 ppm [10,14] . The signal attributed to chlorophosphane 16 disappeared in 4 days at room temperature and the signal of the final diazaphospholium salt 13 c (δ p =155 ppm) emerged (Scheme 6).…”

Computational elucidation of the reaction mechanism for synthesis of pyrrolidinedione derivatives via Nef-type rearrangement – cyclization reaction

“…Computational studies of the Nef reaction mechanism and the rearrangement are rather rare. Bock et al 19 reported that the activation energy of the tautomerization process of a single nitromethane molecule is very high, 335 kJ mol −1 , at HF/6-31G** level. By this reason, aci -nitro compounds are obtained by acidification of their salts.…”

Pseudopolymorphic crystals of sodium tetraphenyl-p-benzosemiquinone containing two or three tetrahydropyran solvent molecules

“…7 According to the principle of advantageous dense lattice packing'-3 therefore, the monoclinic pseudopolymorphic modification should also contain the larger negative lattice (sublimation) energy. [1][2][3] To rationalize the unexpected higher density of the monoclinic inclusion lattice, the ring centroid distances (in pm) are shown in Fig. 2.…”

“…The shortest of these nonbonded distances, between the centroid of tetrahydropyran selected in (1) and the centroids of the other rings, are 493 pm to benzoquinone radical anion with an interplanar angle of 75", 526 pm to the Na+ solvating ether ligands, 532 pm to the benzoquinone phenyl substituents and 614 pm between each other. Van der Waals interactions are treated in force field models often based on Lennard-Jones potentials, EvdW = cr-6 + dr-12, with the attractive dispersion dominating at longer distances.7 For herringbonetype interactions, e.g.…”