Dehydrochlorination of alpha-Chlorophosphines, a Simple and General Route to Phosphaalkenes

Diels-Alder reactions of 1-phosphabutadienes: a highly selective route to P[double bond, length as m-dash]C-substituted phosphacyclohexenes

Kinetically stabilized 1-phosphahaloprenes (2-halo-1-phosphabutadienes) as well as 1-phosphaisoprene undergo a hitherto unknown phospha-Diels-Alder dimerization of the P[double bond, length as m-dash]C-C[double bond, length as m-dash]C units upon heating. The [4+2] cyclodimerization is highly stereo- and regio-selective. The phosphaalkene-substituted phosphacyclohexene product is an unprecedented P(sp²),P(sp³) ligand that is of interest in polymer/materials science and catalysis.

Theoretical study of the tautomerism, structures, and vibrational frequencies of the phosphaalkenes XP=C(CH3)2 (X = H, F, Cl, Br, OH, Ar(F) (Ar(F) = 2,6-(CF3)2C6H3))

Ab initio theoretical calculations have been used to study the influence of phosphorus substituents, Y, on the tautomerism between the vinylphosphine XP(H)C(CH(3))=CH(2) and the phosphaalkene XP=C(CH(3))(2) (X = H, F, Cl, Br, OH, and Ar(F); Ar(F) = 2,6-(CF(3))(2)C(6)H(3)) and on the acidity of the aforementioned vinylphosphine. The stabilization of the phosphaalkene and the increased acidity of the vinylphosphine by Ar(F) are possible factors in the successful synthesis of certain isolable phosphaalkenes. In this work, the properties of Ar(F) are assessed theoretically. Density functional theory using the B3LYP functional has been used for all substituents. In addition, coupled-cluster singles and doubles with noniterative triples (CCSD(T)) has been used for X = H, F, Cl, Br, and OH. The phosphaalkene is favored over the vinylphosphine for all substituents, with F having the strongest stabilizing effect. Cl, Br, and OH have stronger stabilizing effects than Ar(F). In contrast, the most acidic vinylphosphine is that with Ar(F). To aid in the interpretation and analysis of future experimental work, CCSD(T) calculations were used to provide structures and vibrational frequencies for the series XP=C(CH(3))(2) (X = H, F, Cl, Br). The influence of the substituent on geometries and C=P and X-P stretching frequencies was examined, and comparisons were made with the CH(2)=PX series.