A new look at the similarities of the conjugative ability and reactivity of phosphorus-carbon and carbon-carbon double bonding

Phospha‐Organic Chemistry: Panorama and Perspectives

“…[6] The conjugative properties are similar for P ¼ C and C ¼ C bonds, [7] and that the P ¼ C p bond is apolar has already been mentioned. [4] A typical phosphaalkene has a P¼C bond length in the range 1.60-1.70 .…”

Cycloaddition reactions of heterophospholes

“…In the neutral heterophosphole ring, besides sp 2 -phosphorus, there must be at least one heteroatom like NR, O, or S(Se,Te) contributing two -electrons. In view of the close resemblance between carbon and phosphorus [5][6][7][8], heterophosphole ring may be thought as derived from the classical heteroles such as pyrrole, furan, or thiophene by substituting one ring CH by P . Furthermore, as in diazoles, oxazoles, thiazoles, or triazoles, the heterophosphole ring may contain one or more two-coordinate nitrogen atoms or even more than one two-coordinate phosphorus atom.…”

Complexes of Azaphospholes: Synthesis and Structure of Pentacarbonyl-(η1)-2-phosphaindolizine)chromium(0), -molybdenum(0), and -tungsten(0)

“…and 2-phosphaindolizine [14] have been reported, which exhiMono-, di-, and triphosphole anions exhibit different coorbit even lower 31 P-coordination shifts than related η 1 -didination modes but, like cyclopentadienyl anions, they prefand -triazaphosphole [11] [15] and η 1 -phosphabenzene comerably form η 5 -complexes [1] [2] [6] emphasizing the similarities plexes [16] with sp 2 (p π ) hybridized phosphorus. This may be of PϭC and CϭC structural units [7] . Pyrroles and pyrrole viewed in association with the reduced σ-and the increased anions also form various types of complexes with π-and σ-π-charge density at phosphorus [10] [14] in these π-excess hetcoordination.…”