2-Hydro-2-aminophosphasilene with N–Si–P π Conjugation

Abstract

The first 2-aminophosphasilene, [Ar(Me 3 Si)-N]HSiPAr′ (4, Ar = 2,6-iPr 2 C 6 H 3 , Ar′ = 2,6-Mes 2 C 6 H 3 ), bearing a hydride ligand on the three-coordinate silicon atom has been synthesized and structurally characterized. Both X-ray data of 4 and DFT calculations on the model compound (H 2 N)HSiPH (4′) disclosed that the amino group on the silicon atom results in significant N−Si−P π conjugation.

A Persistent 1,2‐Dihydrophosphasilene Adduct

“…TheNBO analysis indicated only one s-type bond between the Si and Pa toms and two lone pairs residing on the phosphorus center.T he NPAc harges (Si: + 1.05;P :À0.60) and the natural resonance theory (NRT) analysis (Si-P:7 8.9 %, Si = P: 21.1 %) reflect this bonding situation. These computational results and the high-fieldshifted 31 Pr esonance suggest that the zwitterionic resonance structure 2B is the dominant contribution to the electronic features of 2 (Scheme 3).…”

“…The 1 J(P,H) coupling constant is 12 Hz smaller than that of the Me 4 -NHC-stabilized form of II (NHC-II), [30] indicating lower 3s character of the PÀ Hbond. The 31 Psignal of 2 is shifted to higher field compared with the resonance of NHC-II (d( 31 P) = À259.8 ppm) and is even more shielded than signals of existing "half-parent" phosphasilenes.T he upfield-shifted 29 Si signal (d( 29 Si) = À25.6 ppm, 1 J(Si,P) = 120.7 Hz) is similar to the 29 Si resonance signal of III (d( 29 Si) = À21.1 ppm). [31] In the 1 HNMR spectrum the signal for the hydrogen nucleus at the phosScheme 1.…”

“…The 31 Psignal of 2 is shifted to higher field compared with the resonance of NHC-II (d( 31 P) = À259.8 ppm) and is even more shielded than signals of existing "half-parent" phosphasilenes.T he upfield-shifted 29 Si signal (d( 29 Si) = À25.6 ppm, 1 J(Si,P) = 120.7 Hz) is similar to the 29 Si resonance signal of III (d( 29 Si) = À21.1 ppm). [31] In the 1 HNMR spectrum the signal for the hydrogen nucleus at the phosScheme 1. Phosphasilenes bearing ah ydrogen atom at the Si and/or P center.C ompounds of type IV are currently unknown.…”

“…These species and related low-valent Group 14 compounds are stabilized either by taking advantage of steric congestion through the presence of bulky substituents and/or by pushpull electronic effects. Only recently,t he first isolable "half-parent" phosphasilenes I, [28] II, [29,30] and III [31] of the type R 2 Si = PH or R(H)Si = PR could be realized (Scheme 1). However,a1,2-dihydrophosphasilene IV with hydrogen atoms at silicon and phosphorus R(H)Si=PH, which are closer to the parent system, has not been reported to date.…”

“…dme (dme = 1,2-dimethoxyethane) at room temperature in THF afforded, after 18 h, the 1,2-dihydrophosphasilene 2,p resumably through tautomerization of its elusive phosphanylsilylene isomer (Scheme 2). The 31 PNMR spectrum of 2 shows adoublet of doublets with 29 Si satellites at d( 31 P) = À301.4 ppm ( 1 J(P,H) = 132.0 Hz, 2 J(P,H) = 11.3 Hz, 1 J(Si,P) = 120.7 Hz). The 1 J(P,H) coupling constant is 12 Hz smaller than that of the Me 4 -NHC-stabilized form of II (NHC-II), [30] indicating lower 3s character of the PÀ Hbond.…”