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)(μ 2 -C≡P)Ni( Me I i Pr) 2 ( Me I i Pr=1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) and Au(IDipp)(μ 2 -C≡P)Rh(Cp*)(PMe 3 ). These studies reveal that, in contrast to the cyanide ion, bimetallic cyaphido complexes strongly favor a η 1  : η 2 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)(μ 2 -C≡P)Rh(Cp*)(PMe 3 ) with an electrophilic transition metal reagent, W(CO) 5 (THF), which affords the heterotrimetallic compound Au(IDipp)(μ 3 -C≡P)[Rh(Cp*)(PMe 3 )][W(CO) 5 ].