| Institution: | 1. Organic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Faculty of Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht (The, Netherlands
These authors contributed equally to this work;2. Structural Biochemistry, Bijvoet Centre for Biomolecular Research, Faculty of Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht (The, Netherlands;3. NMR Spectroscopy, Bijvoet Centre for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht (The, Netherlands;4. Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, 94025 Menlo Park, California, USA;5. Organic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Faculty of Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht (The, Netherlands |
| Abstract: | The synthesis, characterization and catalytic activity of a new class of diruthenium hydrido carbonyl complexes bound to the t Bu PNNP expanded pincer ligand is described. Reacting t Bu PNNP with two equiv of RuHCl(PPh3)3(CO) at 140 °C produces an insoluble air-stable complex, which was structurally characterized as Ru2(tBuPNNP)H(μ-H)Cl(μ-Cl)(CO)2] ( 1 ) using solid-state NMR, IR and X-ray absorption spectroscopies and follow-up reactivity. A reaction with KOtBu results in deprotonation of a methylene linker to produce Ru2(tBuPNNP*)H(μ-H)(μ-OtBu)(CO)2] ( 3 ) featuring a partially dearomatized naphthyridine core. This enables metal-ligand cooperative activation of H2 analogous to the mononuclear analogue, Ru(tBuPNP*)H(CO)]. In contrast to the mononuclear system, the bimetallic analogue 3 catalyzes the E-selective semi-hydrogenation of alkynes at ambient temperature and atmospheric H2 pressure with good functional group tolerance. Monitoring the semi-hydrogenation of diphenylacetylene by 1H NMR spectroscopy shows the intermediacy of Z-stilbene, which is subsequently isomerized to the E-isomer. Initial findings into the mode of action of this system are provided, including the spectroscopic characterization of a polyhydride intermediate and the isolation of a deactivated species with a partially hydrogenated naphthyridine backbone. |
