Phosphorus‐Atom Transfer from Phosphaethynolate to an Alkylidyne

Abstract

A low‐spin and mononuclear vanadium complex, (Menacnac)V(CO)(η2‐P≡CtBu) (2) (Menacnac−=[ArNC(CH3)]2CH, Ar=2,6‐iPr2C6H3), was prepared upon treatment of the vanadium neopentylidyne complex (Menacnac)V≡CtBu(OTf) (1) with Na(OCP)(diox)2.5 (diox=1,4‐dioxane), while the isoelectronic ate‐complex [Na(15‐crown‐5)]{([ArNC(CH2)]CH[C(CH3)NAr])V(CO)(η2‐P≡CtBu)} (4), was obtained via the reaction of Na(OCP)(diox)2.5 and ([ArNC(CH2)]CH[C(CH3)NAr])V≡CtBu(OEt2) (3) in the presence of crown‐ether. Computational studies suggest that the P‐atom transfer proceeds by [2+2]‐cycloaddition of the P≡C bond across the V≡CtBu moiety, followed by a reductive decarbonylation to form the V−C≡O linkage. The nature of the electronic ground state in diamagnetic complexes, 2 and 4, was further investigated both theoretically and experimentally, using a combination of density functional theory (DFT) calculations, UV/Vis and NMR spectroscopies, cyclic voltammetry, X‐ray absorption spectroscopy (XAS) measurements, and comparison of salient bond metrics derived from X‐ray single‐crystal structural characterization. In combination, these data are consistent with a low‐valent vanadium ion in complexes 2 and 4. This study represents the first example of a metathesis reaction between the P‐atom of [PCO]− and an alkylidyne ligand.

Deciphering the Differences in Ambident Reactivity between the Cyanate, Thiocyanate Ions, and their P‐ and As‐Containing Analogues

“…During the past decade, the P‐containing analogue of cyanate anion, the phosphaethynolate, [PCO] − anion, first reported by Becker et al [26] . (Figure 1B), has also attracted significant interest, [27–44] accelerated by the recent development of straightforward synthetic methods leading to the sodium salt of this anion [45] . Indeed, the chemical reactivity of the [PCO] − anion has been explored extensively: In general, the [PCO] − anion can participate in various reactions, including cycloadditions, P − ‐transfer reactions, and nucleophilic substitutions (S N ) [46–48] …”