η²-Edge-Bridging and η³-Face-Capping Coordination of Conjugated Ynenyl Ligands in Triruthenium Carbonyl Cluster Complexes Derived from 1,1-Dimethylhydrazine

The reactions of the 1,1-dimethylhydrazine-derived cluster [Ru3(μ-H)(μ3-η2-HNNMe2)(CO)9] with conjugated diynes, RC4R (R = Me, Ph), afford the ynenyl derivatives [Ru3(μ3-η2-HNNMe2)(μ-η2-RCCCCHR)(μ-CO)2(CO)6] (R = Me) and [Ru3(μ3-η2-HNNMe2)(μ3-η3-RCCCCHR)(μ-CO)(CO)7] (R = Me, Ph), featuring η2-edge-bridging and η3-face-capping coordination modes for their ynenyl ligands. DFT calculations have revealed that the face-capped products are slightly more stable than the edge-bridged ones. The regioselectivity of the reactions is affected by the nature of the R groups of the diynes.