Sodium Phosphaethynolate as a Building Block for Heterocycles

Abstract

Phosphorus-containing heterocycles have evolved from laboratory curiosities to functional components, such as ligands in catalytically active metal complexes or molecular constituents in electronic devices. The straightforward synthesis of functionalized heterocycles on a larger scale remains a challenge. Herein, we report the use of the phosphaethynolate (OCP)(-) anion as a building block for various sterically unprotected and functionalized hydroxy substituted phosphorus heterocycles. Because the resulting heterocycles are themselves anions, they are building blocks in their own right and allow further facile functionalization. This property may be of interest in coordination chemistry and material science.

η1:η2-P-Pyrazolylphosphaalkene Complexes of Ruthenium(0)

“…This is consistent with 13 C-NMR studies of vinyl- [49] and aryl-silanes [50], for which enhanced deshielding of the α-carbon follows from increasing methyl substitution at silicon, presumably reflecting the relative "inductive effect", given the greater electronegativity of carbon relative to silicon. While carbocentric systems show the reverse shielding trend for the β-center, in the case of 2-6 enhanced deshielding of phosphorus is again noted for the SiMe3 Assignment of the isomeric preference in 6a and 6d is a more complex undertaking, given the lack of any direct spectroscopic handle, though the same steric arguments can reasonably be applied.…”

“…Supplementary Materials: The following are available online at http://www.mdpi.com/2304-6740/4/4/30/s1, crystal data for compound 3d in cif format (CCDC 1502285); supplementary file containing illustrative 13 C and 31 P NMR spectra for compounds 3c (Figures S1 and S2), 4c (Figures S3 and S4), 5d ( Figures S5 and S6), 6a ( Figures S7 and S8). …”

“…Moreover, even bulky phosphaalkynes, e.g., R 3 SiC≡P (R = Ph [9], Me [10,11]) often exhibit only limited stability, in some instances comparable to that of unencumbered systems (e.g., MeC≡P [12]). Significantly, the formally related phosphaethynyloate ion "O-C≡P − " is isolable as a sodium salt [13,14], which exhibits appreciable stability despite the lack of any steric "protection"; this fact is attributed to electronic influences, with alongside computational studies of the isolated cyaphide ion ("C≡P − "), which indicate an intrinsically unstable hypovalent "[C=P] − " structure [15], this would imply that electronics serve an equally important role in imparting stability to low-coordinate phosphacarbons. Indeed, in the context of phosphaalkenes-which remain the longest and most heavily studied of the phosphacarbons-the incorporation of π-donor substituents (e.g., NR2, OR) and/or conjugate π-systems has long been employed as an alternative means of stabilization [16].…”

Annulated 1,3,4‐Azadiphospholides: Heterocycles with Widely Tunable Optical Properties

“…[9g, 12] Phosphorus-containing p-conjugated heterocycles are often easier to handle, [8] and sodium phosphaethynolate,N a(OCP), proved to be av ersatile building block for those (see selected examples in Scheme 1). )o r[ 2 + +4] cycloadditions (VI [15] ), respectively,w hich are likewise formed by incorporating ac omplete (OCP) À anion into the cycle.[14c]Thef ive-membered heterocycles VII-IX are special because they are formed in reactions between carboxylic acid chloride derivatives,RC(= X)Cl (X = NR, O, S) with two (OCP) À anions,but only one is fully included while the other serves as source of a" P À "i on after loss of CO.[17] Herein we report as imple access to annulated 1,3,4-azadiphospholes with aw idely tunable p-conjugated electronic structure, which have,i nc ontrast to well-studied diazaphospholes, [18] only rarely been investigated before. [19] These new compounds may find applications in electronic devices or chemical sensors.…”

“…[9g, 12] Phosphorus-containing p-conjugated heterocycles are often easier to handle, [8] and sodium phosphaethynolate,N a(OCP), proved to be av ersatile building block for those (see selected examples in Scheme 1). )o r[ 2 + +4] cycloadditions (VI [15] ), respectively,w hich are likewise formed by incorporating ac omplete (OCP) À anion into the cycle.…”