Late Transition Metal Complexes with Pincer Ligands that Comprise N-Heterocyclic Carbene Donor Sites

The incorporation of N-heterocyclic carbenes into the well-established pincer ligand platform entails a number of attractive benefits. For example, NHCs are strong donors, and the metal–carbene bond is often remarkably robust towards oxidative and hydrolytic conditions and thus sustains in air, moisture, and even highly acidic environments. Moreover, NHCs can be readily functionalized and modulated and thus provide excellent opportunities for fine-tuning the properties of a coordinated metal center. As a consequence, the combination of the concepts of pincer ligands and of NHCs has much appeal and continues to attract considerable interest. This chapter summarizes accomplishments over the last 5 years in the domain of pincer carbene complexes containing Group 8–10 metals, including synthetic aspects as well as application of these complexes, which has included in particular catalysis and to a lesser extent materials science and medicinal areas

Addition of Pt(IPr) Groupings to Ru5 Carbide Gives New Mixed-Metal Pt–Ru Cluster Complexes

The reaction of Pt(IPr)(SnBu 3 t )(H), 1 [IPr = N-heterocylic carbene ligand N,N ′-bis-(2,6-(diisopropyl) phenyl)imidazol-2-ylidene] with Ru5(μ 5 -C)(CO)15, 2, in 1.2:1 (and 2.2:1) ratio in benzene solvent at refluxing temperature afforded the octahedral monoplatinum–pentaruthenium cluster complexes PtRu5(IPr)(CO)15(μ 6 -C), 3 in 54 % (10 %) yield, PtRu5(IPr)(CO)14(H)2(μ 6 -C), 4 in 6 % (10 %) yield and the diplatinum–pentaruthenium cluster complex Pt2Ru5(IPr)2(CO)15(μ 6 -C), 5 in 2 % (36 %)yield. Complex 3 readily reacts with H2 at room temperature to give complex 4. Compound 5 exhibits dynamical activity in solution where the two Pt(IPr) groups are exchanging rapidly. All three compounds were structurally characterized by single-crystal X-ray diffraction analyses