peri-Interactions in Naphthalenes, 4 [1]. Hypercoordination in 8-Dimethylamino-naphth-1-yl Phosphorus Compounds

Abstract

Hypercoordination, Bond Length Alterations, Sub-van der Waals Interatomic DistancesIn an 8-dimethylamino-naphth-l-yl-phosphorane a dative N-P bond forms in spite of the spacer properties of the naphthalene skeleton. Its "normal" length, 213.2 pm, much too short to fill the peri space, forces the Cio skeleton into severe distortion. In the light of these properties peri distances d(N-P/Si) 250 pm in 8-dimethylamino-naphth-l-yl-phosphines, -silanes etc.are recognized as evidence for steric hindrance.für Naturforschung, Tübingen -www.znaturforsch.com K

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

“…The crucial C-N-C angles (subset A) amount to only 328.4 − 1.9 • (−6.0%) and thereby confirm the earlier conclusion that a full covalent bond (albeit dative, N→P, and hypercoordinate) exists between N and P [3]. An excess of 1.9 • in subset B (the C-N-P angles) brings the total to perfect tetrahedrality (656.8 • ).…”

“…Nevertheless, d(N···P) = 286.9 pm, the splay angle (+8.6 • ) and PL = 25.0% exclude a N→P bond. In (DAN) 3 As [72] (entry 51), both the low electronegativity of As and the increased length of the As-C(1) bond render N→As bonds unfavourable; indeed, all criteria indicate the absence of such interaction. Not surprisingly, (4-Me-C 6 H 4 ) 2 Sb-DAN [29] (entry 52) shows essentially the same behaviour.…”

“…In the pyrocatechol derivative DAN-P(O 2 C 6 H 4 ) 2 (Table 1, entry 60) with hexacoordinate P (including N→P coordination) [3], d(N-P) = 213.2 pm is 37 pm shorter than PD, but 33 pm (18%) longer than the sum of the single bond covalent radii, ∑ r cov [N, P] = 180 pm [73]. The crucial C-N-C angles (subset A) amount to only 328.4 − 1.9 • (−6.0%) and thereby confirm the earlier conclusion that a full covalent bond (albeit dative, N→P, and hypercoordinate) exists between N and P [3].…”

“…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].…”

“…Their high bond energy and stout resistance against bond stretching enables covalent bonds between the peri-bound atoms X and Y in 1-X-8-Y-substituted naphthalenes to cope with the FSR and the GPF and to enforce interatomic distances d(X···Y)< PD [2,3,5,22]. However, such distances are not necessarily restricted to classical covalent bonds.…”