Molecular studies of the initiation and termination steps of the anionic polymerization of P=C bonds

Abstract

The initiation and termination steps of the anionic polymerization of P=C bonds have been modeled. The initiation step was investigated through the stoichiometric reaction of MesP=CPh2 (1) with RLi (R = Me or n-Bu). In each case, the addition was highly regioselective with the formal attack of R– at phosphorus to give the carbanion Li[Mes(R)P–CPh2] (3a, R = Me; 3b, R = n-Bu). To simulate the termination step in the anionic polymerization of 1, carbanions 3a and 3b were quenched in situ with various electrophiles. Through these reactions, several new tertiary phosphines have been prepared, namely, Mes(Me)P–CPh2H (4a), Mes(n-Bu)P–CPh2H (4b), Mes(Me)P–CPh2Me (6a), Mes(Me)P–CPh2–P(NEt2)2 (7a), Mes(Me)P–CPh2–SiMe2H (8a), and Mes(Me)P–CPh2–SiMe3 (9a). In addition, compounds 4a, 7a, 8a, and 9a were characterized by X-ray crystallography. Most of the metrical parameters are typical of tertiary phosphines; however, the P–CPh2H bonds were elongated in all cases reflecting the considerable steric bulk surrounding this bond. Unexpectedly, an unusually large 31P–31P coupling constant (2JPP > 200 Hz) was observed for 7a both in solution and the solid state. This observation may be rationalized by a through space P···P interaction. This rationale is further supported by the short P···P distance [P(1)—P(2) = 2.966(1) Å; cf. Σ rvdw = 3.7 Å] and a small P–C–P bond angle for 7a [P(1)–C(11)–P(1) = 99.17(9)°].Key words: phosphaalkenes, phosphorus polymers, phosphines, anionic polymerization.

Isomerization Polymerization of the Phosphaalkene MesPCPh2: An Alternative Microstructure for Poly(methylenephosphine)s

“…In our earlier studies, the broadening of the signals assigned to the ortho ‐bound CH 3 groups in 3 was rationalized as arising from restricted rotation of the Mes group. Similar broadening had been noted in the 13 C{ 1 H} NMR spectra of the phosphines MesRP‐CPh 2 R′ (R=Bu, R′=H; R=Me, R′=Me, P(NEt 2 ) 2 , SiHMe 2 , SiMe 3 ), the structures of which were confirmed by X‐ray crystallography 17. In light of the CH activated 2 ⋅AuCl, a 13 C APT (attached‐proton test) NMR experiment was conducted on the polymer.…”

Reaction of an Enantiomerically Pure Phosphaalkene-Oxazoline with MeM Nucleophiles (M = Li and MgBr): Stereoselectivity and Noninnocence of the P-Mesityl Substituent

“…Crystals of the desired complex, 2 a,a ·PdCl 2 , were formed by slow diffusion of hexanes into the reaction mixture. The molecular structure is shown in Figure 4b, and the product was fully characterized using NMR spectroscopy ( 1 H, 13 The isolation of both 2 a,s ·PdCl 2 and 2 a,a ·PdCl 2 provided further insight into the composition of the quenched MeMgBr and MeLi reaction mixtures analyzed by 31 P{ 1 H} NMR spectroscopy (Figure 1, panels c and d). There are only two resonances common to both reactions (δ = −39.5 and −40.3), the former being unequivocally assigned to isolable 2 a,a .…”

Isomerization Polymerization of the Phosphaalkene MesPCPh2: An Alternative Microstructure for Poly(methylenephosphine)s

“…Similar broadening had been noted in the 13 C{ 1 H} NMR spectra of the phosphines MesRP-CPh 2 R' (R = Bu, R' = H; R = Me, R' = Me, P(NEt 2 ) 2 , SiHMe 2 , SiMe 3 ), the structures of which were confirmed by X-ray crystallography. [17] In light of the CÀH activated 2·AuCl, a 13 C APT (attached-proton test) NMR experiment was conducted on the polymer. Remarkably, this experiment suggested that the signal at 33.0 ppm could not result from a CH 3 moiety and must result from either a quaternary carbon atom or a CH 2 group.…”