Carbon–phosphorus triple bond formation through multiple bond metathesis of an anionic niobium phosphide with carbon dioxide

A novel borane-capped niobium phosphide anion ([B(C6F5)3-1]) has been prepared in 87% yield by reaction of [PNb(N[Np]Ar)3]− (1, Ar = 3,5-C6H3Me2 and Np = neopentyl) with the Lewis acidic borane B(C6F5)3. Room-temperature reaction of this adduct with carbon dioxide readily yields the OCP− ion 3, isolated as its sodium salt, [Na(dme)2][OCP] (dme = dimethoxyethane), in 70% yield, with concomitant formation of a borane-substituted niobium oxo complex [B(C6F5)3-2] (2 = ONb(N[Np]Ar)3).

Graphical abstractThe niobium phosphide anion complex [PNb(N[Np]Ar)3]−, where Np = neopentyl and Ar = 3,5-C6H3Me2, was converted to its fluorinated borane adduct, [(F5C6)3BPNb(N[Np]Ar)3]−. Upon reaction of the latter anion with CO2, formation of phosphaethynolate, [OCP]−, was confirmed, together with formation of borane-capped niobium oxo, (F5C6)3BONb(N[Np]Ar)3.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A niobium phosphide anion complex was complexed with perfluorotriphenylborane. ► Carbon dioxide was transformed into the sodium salt of phosphaethynolate. ► Sodium phosphaethynolate was formed in good yield and isolated in pure form.