Cyaphide (P≡C−) is the isolobal and isoelectronic phosphorus analogue of cyanide. Cyaphide ligands could be useful, e.g., in molecular electronic and magnetic materials. So far, there had been no example of multiple cyaphide ligands at the same metal center, i.e., direct analogues of poly-cyano systems.
Ian R. Crossley, University of Sussex, Brighton, UK, and colleagues have synthesized the first example of a biscyaphido complex, [Ru(dppe)2(C≡P)2] (pictured, dppe 1,2-bis(diphenylphosphino)ethane). The team started from the stable, five-coordinate cation [Ru(dppe)2(C≡P)]+ as a precursor. The triflate salt of this cation was suspended 1,4-dioxane and reacted with P≡CSiMe3 (in a toluene solution) to give the cyaphidophosphaalkyne complex cation trans-[Ru(dppe)2(η1-P≡CSiMe3)(C≡P)]+.
The researchers then desilylated the phosphaalkyne using NaOPh to obtain [Ru(dppe)2(C≡P)2]. They also prepared [Ru(dppe)2(CN)(C≡P)] to allow for comparison between cyanide and cyaphide, using [Ru(dppe)2(C≡P)]+ and NaCN. According to the team, the structural features of the synthesized complexes provide the first direct experimental support for an enhanced π-acceptor character of −C≡P over −C≡N.
- A Monometallic Bis(cyaphido) Complex,
Madeleine C. Levis, Monte L. Helm, John F. C. Turner, Ian R. Crossley,
Chem. Eur. J. 2024.
https://doi.org/10.1002/chem.202303370
