Revealing the Role of the Cyaphide Ion as a Bridging Ligand in Heterometallic Complexes.

The synthesis of heterometallic transition metal complexes featuring bridging cyaphide ions (C≡P^- ) is reported. These are synthesized from reactions of Au(IDipp)(CP) (IDipp=1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with electron-rich, nucleophilic transition metal reagents, affording Au(IDipp)(μ₂ -C≡P)Ni(^Me Iⁱ Pr)₂ (^Me Iⁱ Pr=1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) and Au(IDipp)(μ₂ -C≡P)Rh(Cp*)(PMe₃ ). These studies reveal that, in contrast to the cyanide ion, bimetallic cyaphido complexes strongly favor a η¹  : η² coordination mode that maximizes the interaction of the second metal (Ni, Rh) with the π-manifold of the ion (and not the phosphorus atom lone pair). End-on bridging can be effectively unlocked by blocking the π-manifold, as demonstrated by reaction of Au(IDipp)(μ₂ -C≡P)Rh(Cp*)(PMe₃ ) with an electrophilic transition metal reagent, W(CO)₅ (THF), which affords the heterotrimetallic compound Au(IDipp)(μ₃ -C≡P)[Rh(Cp*)(PMe₃ )][W(CO)₅ ].