Peculiarities of p_πp_π conjugation in aminosubstituted phosphaalkenes

Abstract

Effects of p,,-pm conjugation in phosphaalkenes have

Reactivity of Carbonyl-Functionalized Phosphaalkenes RC(O)P=C(NMe2)2 (R =tBu, Ph) towards Electrophiles

“…Low-field shifted singlets in the 31 P{ 1 H} NMR spectra at δ ϭ 68.3 (6a) (∆δ ϭ 41.9) and δ ϭ 5.0 ( 1 J PC ϭ 11.7 Hz), respectively, which is consistent with an alkylation at the P-atom of the P-acyl phosphaal-72.6 (6b) (∆δ ϭ 41.5), and the absence of ν(CϭO) bands in the IR spectra of the adducts agree with the ligation of the kenes. Upon methylation, the 13 [5] This is presumably because of the steric hinderance between the cis-oriented diaminocarbenium group and the phenyl ring which means that the valence angle P(1)ϪC (1)ϪC (41) [127.5(2)°] is markedly more obtuse than P(1)ϪC (1)ϪO (1) Scheme 4. Reaction of 2a,b with B(C 6 F 5 ) 3…”

“…Here we report on the reactions of 2a As has been found previously [2] the calculations predict that the parent phosphaalkene should have a nonpolar π-and 2b with protic acids, alkylating and silylating reagents, organometallic compounds of group 13 elements, and tranbond (NBO charges and populations), [4d] although one amino group or, to a greater extent, two amino groups at the sition metal carbonyl complexes. carbon atom [5] induce an inverse electron-density distribution at the π-bond, i.e. the charge at the phosphorus is increased relative to the parent methylenephosphane.…”

“…Thus, only dimerization and isomerization processes of several phosphatriafulvenes, as well as the formation of the complex [tBuC(O)P-{W(CO) 5 We decided to study in more detail the chemical reactivity of tBuC(O)PϭC(NMe 2 ) 2 (2a) and PhC(O)PϭC(NMe 2 ) 2 Scheme 2. Charge distribution in HPϭCH 2 and amino-substi-(2b), which are readily available from Me 3 SiPϭC(NMe 2 ) 2 tuted phosphaalkenes (1) and carboxylic acid chlorides, especially with respect to the related carbonyl-stabilized phosphorus ylides RC(O)CHϭPPh 3 .…”

“…Phosphaalkenes with an inverse electron density exhibit pe- 5 ] group, a trigonal-pyramidal phosphorus atom (sum of angles 346.1°) forms a single soluble in CH 2 Cl 2 and CHCl 3 . In chloroform, however, slow decomposition occurred at ambient temperature.…”

“…In the W(CO) 5 complex of the inversely polarized phosphatriafulvene MesPϭC a C b (tBu)ϪC c tBu(C a ϪC c ), however, the PC double bond [1.679(5) Å ] is retained, and the phosphorus atom is pyramidalized to a lesser extent (sum of angles 352.9°). [2b] From carbanion and ylide chemistry [8] it is well documented that the negative charge on a carbon center is effectively stabilized by adjacent carbonyl groups via π-delocalization.…”