At last, terminal cyaphide ligand

The quest is over for making an isolable cyaphide metal complex--a compound with a terminal -C≡P ligand, the phosphorus equivalent of cyanide. Following attempts by a number of chemists over several decades, Hansjörg Grützmacher and his coworkers at the Swiss Federal Institute of Technology, Zurich, finally devised a synthetic strategy capable of transferring the -C≡P moiety to a transition-metal ion (Angew. Chem. Int. Ed. 2006, 45, 6159). Phosphaalkynes (R-C≡P) and bimetallic complexes with a bridging ligand (M-C≡P-M) were previously known. The researchers first synthesized a silyl-substituted phosphaalkyne, Ph₃Si-C≡P (Ph = phenyl), in which the silyl group functions as a protecting group. This phosphaalkyne was coordinated to a ruthenium bis(1,2-diphenylphosphinoethane) complex via the phosphorus atom. Reacting that complex with sodium phenoxide cleaved the silyl group and flipped the C≡P group to coordinate to ruthenium via the carbon atom, generating the cyaphide complex shown. The researchers hope their synthesis of Ph₃Si-C≡P will be generally useful to make other cyaphide complexes, they note.