The Chemistry of the 2‐Phosphaethynolate Anion

Abstract

In all likelihood the first synthesis of the phosphaethynolate anion, PCO , was performed in 1894 when NaPH was reacted with CO in an attempt to make Na(CP) accompanied by elimination of water. This reaction was repeated 117 years later when it was discovered that Na(OCP) and H are the products of this remarkable transformation. Li(OCP) was synthesized and fully characterized in 1992 but this salt proved to be too unstable to allow for a detailed investigation of its chemistry. It was not until the heavier analogues of this lithium salt were isolated, Na(OCP) and K(OCP) (both of which are remarkably stable and can be even dissolved in water), that the chemistry of this new functional group could be explored. Here we review the chemistry of the 2-phosphaethynolate anion, a heavier phosphorus-containing analogue of the cyanate anion, and describe the wide breadth of chemical transformations for which it has been thus far employed. Its use as a ligand, in decarbonylative and deoxygenative processes, and as a building block for novel heterocycles is described. In the mere twenty-six years since Becker first reported the isolation of this remarkable anion, it has become a fascinating reagent for the synthesis of a vast library of, often unprecedented, molecules and compounds.

Trapping of a Highly Bent and Reduced Form of 2‐Phosphaethynolate in a Mixed‐Valence Diuranium–Triamidoamine Complex

“…TheUV/Vis/NIR spectrum of 2 is dominated by charge transfer bands in the UV/Vis regions,and weak f-f absorptions are observed in the NIR region. [1] With complex 2 in-hand, we examined its reduction chemistry.A ddition of 2 to ap reformed mixture of KC 8 and 2,2,2-cryptand in THF in a1:1:1 ratio resulted in adark green solution, from which, after work-up,d ark brown [{U-(Tren TIPS )} 2 {m-h 2 (OP):h 2 (CP)-OCP}][K(2,2,2-cryptand)] (3) was isolated from toluene in 43 %c rystalline yield (based on uranium content, Scheme 1). [14] When considered together,t hese data are consistent with other U IV -OCP complexes, [6,9] and are indicative of the presence of uranium(IV) and the dominance of P C À O À ,r ather than À P = C = O, resonance forms as is common when this anion is coordinated to electropositive metal ions.…”

“…[1] However,e ven though the inception of the OCP À anion may date back to 1894, [2] and it certainly moved to afirmer footing in 1992, [3] it has not been until within the past decade that reliable,accessible routes to OCP À have become widely available. [1] However,e ven though the inception of the OCP À anion may date back to 1894, [2] and it certainly moved to afirmer footing in 1992, [3] it has not been until within the past decade that reliable,accessible routes to OCP À have become widely available.…”

“…[1] However,e ven though the inception of the OCP À anion may date back to 1894, [2] and it certainly moved to afirmer footing in 1992, [3] it has not been until within the past decade that reliable,accessible routes to OCP À have become widely available. [1] Although the oxidation chemistry of the OCP À anion is now quite established, [1] reports of its formal reduction chemistry are exceedingly scarce. [1] Although the oxidation chemistry of the OCP À anion is now quite established, [1] reports of its formal reduction chemistry are exceedingly scarce.…”

“…[4] Consequently,d espite the increasingly burgeoning nature of the area there are still many unanswered questions about the intrinsic properties and coordination chemistry of the OCP À anion. [1,5] This is perhaps unsurprising since as aclosed-shell anion OCP À would be expected to inherently resist reduction as this would populate antibonding orbitals,a nd indeed where examples of reduction have been reported fragmentation of the OCP À unit is usually the decisive,inevitable result. [1,5] This is perhaps unsurprising since as aclosed-shell anion OCP À would be expected to inherently resist reduction as this would populate antibonding orbitals,a nd indeed where examples of reduction have been reported fragmentation of the OCP À unit is usually the decisive,inevitable result.…”

Oxidative Coupling of Terminal Rhenium Pnictide Complexes

“…[22] Thes ymmetric one-dimensional Laplacian distribution profile between P3 and P4 (Figure 3b,m iddle) shows two valence shell charge concentrations (VSCCs) originating from the overlapping valence shells of the interacting atoms,w ith two minima on both sides of the bcp,i ndicating essentially homopolar covalent bonding (see P 2 H 2 in Figure S68). (pz) bonding pattern with Pn=Pn double bonds.This binding mode corresponds to push/pull stabilized, neutral {P 2 } 0 and {As 2 } 0 ligands as compared to push/push NHC-stabilized dipnictides with Pn À Pn single bond character, [4] dinuclear Pn 2 -bridged complexes with increasingly reduced {P=P} 2À to {PÀP} 4À ligands, [5] or mononuclear complexes with diphosphenyl {P=PÀR} À ligands. [23] In both cases,t he bcp resides close to the nodal surface in the Laplacian distribution (Figure 3c)s uch that the sign of 5 2 1 at the bcp is unsuitable for ab ond classification.…”