NUCLEAR MAGNETIC RESONANCE STUDIES OF THE P³¹ NUCLEUS IN PHOSPHORUS COMPOUNDS

NMR isotope shift and perturbational MO study of conformation and hyperconjugation in cyclopentyl cations

“…Deuterium substitution at carbon atoms adjacent to the cation center in classical tertiary alkylcarbenium ions induces a downfield shift of the 13C NMR signal of the carbenium carbon.2 Similar long-range, downfield NMR isotope shifts due to deuterium substitution at a carbon atom adjacent to the cation center in phenyldialkylcarbenium ions have been documented. [3][4][5][6][7] These NMR isotope shifts due to /3-deuteration have been postulated to be related to the hyperconjugative interaction and in this sense are analogous to /3-deuterium kinetic isotope effects. [2][3][4][5][6][7] In an effect fundamentally arising from vibrational differences, the C-D bond behaves as a poorer electron donor than a C-H bond in cationic hyperconjugation, resulting in decreased electron density in the ir system of the cation and hence NMR deshielding.…”

“…[3][4][5][6][7] These NMR isotope shifts due to /3-deuteration have been postulated to be related to the hyperconjugative interaction and in this sense are analogous to /3-deuterium kinetic isotope effects. [2][3][4][5][6][7] In an effect fundamentally arising from vibrational differences, the C-D bond behaves as a poorer electron donor than a C-H bond in cationic hyperconjugation, resulting in decreased electron density in the ir system of the cation and hence NMR deshielding.…”

Phosphinotrihydroborate(1-), H2P.BH3-, the conjugate Broensted base of phosphine-borane. Synthesis, reactions, and stability of the lithium salt

“…The /p_H' coupling constant of 175 Hz is quite different from the value found in H2P(BH3)2~(/p-h = 320 Hz) or in H3P-BH3 (Jp-h = 372 Hz)12 and is within the range expected for compounds with tricoordinated phosphorus. 13 Exact peak intensities could not be determined because both components of the PH2 doublet superimpose a signal of the BH3 quartet. H2P-BH3~as a Lewis Base.-The Lewis base character of H2P • BH3~i s demonstrated by its reaction with diborane to form H2P(BH3)2~(eq 13).…”

“…H2P-BH3~as a Lewis Base.-The Lewis base character of H2P • BH3~i s demonstrated by its reaction with diborane to form H2P(BH3)2~(eq 13). Another Lewis H2P-BH3-+ 0.5B2H6 ->-H2P(BH3)2- (13) base reaction is the formation of H2P(BH3)2_ as a byproduct of the (H2P-BH3)Li preparation, which most probably proceeds via eq 8 as a base displacement. These reactions of H2P • BHS~are in agreement with a mechanism for the formation of (NH4+)(H2P(BH3)2~) from phosphine-borane and ammonia which was presented by Parry2 (eq 14 and 15).…”

Über Pentafluorphenyl-Verbindungen der V. Hauptgruppe V

“…Es hat sich gezeigt, daß mehrere Faktoren wie z. B. der Hybridisierungszustand, der ionische Charakter und die damit verbundene Änderung der Asymmetrie in der Besetzung der p-Funktionen oder die Ausbildung von Mehrfachbindungen Einfluß haben [3][4][5][6][7][8] …”