New synthetic strategies leading to [RNPNR]− anions and the isolation of the [P(Nt-Bu)3]3− trianion

Abstract

New and straightforward synthetic paths for the syntheses of [RNPNR]⁻ anions (R = t-Bu (1) or CPh₃ (6)) in the form of their tmeda- or thf-coordinated lithium salts are described. The attempts to isolate the sodium analogue [(Ph₃CNPNCPh₃)Na·(thf)_x] (8) remained unsuccessful probably due to its high reactivity although its formation in the reaction of the parent cis-[(Ph₃CNP)₂(Ph₃CNH)₂] (5) with 2 eq. of sodium naphthalenide was corroborated by NMR spectroscopy. Importantly, when an excess of sodium naphthalenide was used in the reaction with 5, [(Ph₃C)Na(thf)₃] (9) was obtained along with a complex mixture of other by-products indicating the cleavage of the C–N bond in the starting material. Furthermore, the synthesis and the structural characterization of the [P(Nt-Bu)₃]³⁻ trianion as its trilithium salt [P(Nt-Bu)₃Li₃]₂ (10) has been successfully achieved.