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Lutz, Martin

Publications and source records attributed to Lutz, Martin.

4 records
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DOE OSTI2024

Chloride, Alkoxide, or Silicon: The Bridging Ligand Dictates the Spin State in Dicobalt Expanded Pincer Complexes

We report the synthesis and characterization of a series of high- and low-spin dicobalt complexes of the tBu PNNP expanded pincer ligand. Reacting this dinucleating ligand in its neutral form with two equiv of CoCl 2 (tetrahydrofuran) 1.5 yields a high-spin dicobalt complex featuring one Co inside and one Co outside of the dinucleating pocket. Performing the same reaction in the presence of two equivalents of KOtBu provides access to a high-spin dicobalt complex wherein both Co centers are bound within the PNNP pocket, and this complex also features a bridging OtBu ligand. Reacting either of the high-spin complexes with excess diethyl silane affords a low-spin dicobalt complex containing two unusual bridging Si-based ligands. These complexes were investigated using NMR spectroscopy, XAS, single crystal X-ray structure determination, and computational methods, showing that the Si-based ligands are best described as base-stabilized silylenes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

E ‐selective Semi‐hydrogenation of Alkynes under Mild Conditions by a Diruthenium Hydride Complex

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(PPh 3 ) 3 (CO) at 140 °C produces an insoluble air‐stable complex, which was structurally characterized as [Ru 2 ( t Bu PNNP)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 KO t Bu results in deprotonation of a methylene linker to produce [Ru 2 ( t Bu PNNP * )H(μ‐H)(μ‐O t Bu)(CO) 2 ] ( 3 ) featuring a partially dearomatized naphthyridine core. This enables metal‐ligand cooperative activation of H 2 analogous to the mononuclear analogue, [Ru( t Bu PNP*)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 H 2 pressure with good functional group tolerance. Monitoring the semi‐hydrogenation of diphenylacetylene by 1 H 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.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗