peri-Interactions in Naphthalenes, 10 [1]. In Search of Independent Criteria for N→P Bonding: Protonation Studies on (8-Diethylamino-naphth-1-yl)-diphenyl-phosphine

Abstract

Enhancement of the basicity of the amino group in (8-dialkylamino-naphth-1-yl)-diphenylphosphines diverts protonation from the P to the N atom. Thus the cation 8-Et2N+(H)-C10H6-PPh2 becomes available whose 1H and 31P NMR spectra provide arguments against dative N→P interactions in the phosphines and their quaternary phosphonium salts. Likewise, the X-ray structure of 8-Et2N-C10H6-PPh2 does not indicate such interactions.

Naphthalene and Related Systems peri‐Substituted by Group 15 and 16 Elements

“…Sceptical of the claims made by Corriu, Chuit and others, they reinvestigated the structure and properties of DAN-phosphines and related compounds. [53,[62][63][64][65][66] Several structural and spectroscopic properties of the DAN-phosphorus compounds led them to conclude that an intramolecular dative bond was highly unlikely and no hypercoordination would be anticipated. Firstly, they believe N···P distances shorter than sum of van der Waals radii of the respective elements are not an indication of a bonding interaction, instead they are enforced by the geometry of the rigid naphthalene backbone.…”

“…Other arguments, such as high-field shift of the phosphorus NMR signal on intramolecular DAN coordination (or its absence) were questioned by Schiemenz; additional support for non-existence of the dative bond was found in analysing the J(CH) coupling constants of NMe 2 groups [64] or the study of NMR properties of protonated DAN-phosphines. [62] During these comparative studies a range of DAN-phosphines and related compounds were synthesized by Schiemenz (Scheme 38) [62,63,[67][68][69] and (Scheme 34). [55] Schiemenz concluded that under favourable conditions DAN-phosphorus compounds can form dative N!P bonds and hexacoordination at phosphorus can occur, an example of this is molecule 64 (Scheme 34).…”

“…The varying stoichiometry of these reactions leads to mono-, bis-and trisA C H T U N G T R E N N U N G (DAN) species, illustrative examples of these reactions are shown in Scheme 40. [56,59,74,75] peri-Lithiation is also the critical step in preparations starting with other 1-(dialkylamino)naphthalenes, namely 1-(diethylamino)naphthalene [63] and 1-[(isopropyl)A C H T U N G T R E N N U N G (methyl)]aminonaphthalene. [69] Phosphonium salts, phosphine oxides and sulfides can be obtained from DANphosphines by standard procedures known from general phosphine chemistry.…”

peri-Interactions in Naphthalenes, 12 [1]. The Significance of Linear and T-Shaped Arrangements in peri-Substituted Naphthalenes

“…In the perfect naphthalene system, the available intersubstituent distance is only 247 pm [4, 5, 39 -42] so that even strong distortion of the C 10 system does not permit Σr(vdW) distances [1, 11,42]. To accommodate bulky peri-substituents, the C 10 system resorts to an enlargement of the bay angles substituent-C(1/8)-C(9) and C(1)-C(9)-C(8) (predominantly of the latter one [4,5,11,12,43]) whereas the C 10 skeleton frequently remains virtually planar [12,18,42,44,45]. In 1a, the planarity is borne out by the sum of the angles around C(1), C(8) and C(9), consistently 360 • .…”

peri-Interactions in Naphthalenes, 14 [1]. Pyramidalization versus Planarization at Nitrogen in 8-Dialkylamino-naphth-1-yl Compounds as a Measure of peri Bond Formation

“…265 and ca. 310 pm are typical when no attractive forces are operative [3,8] -distances much shorter than the sum of the respective van der Waals radii, ∑ r vdW [N, X], which the GPF do not permit to reach even in cases of strong steric hindrance [9]. Consequently, conclusions in favour of weak bonding interaction drawn from experimentally found PD < d(N···X)< ∑ r vdW [N, X] are void [5].…”