A Well‐Defined Anionic Dicopper(I) Monohydride Complex that Reacts like a Cluster**

Low-nuclearity copper hydrides are rare and few well-defined dicopper hydrides have been reported. Herein, we describe the first example of a structurally characterized anionic dicopper hydride complex. This complex does not display typical reactivity associated with low-nuclearity copper hydrides, such as alcoholysis or insertion reactions. Instead, its stoichiometric and catalytic reactivity is akin to that of copper hydride clusters. The distinct reactivity is ascribed to the robust dinuclear core that is bound tightly within the dinucleating ligand scaffold

Tuning the Bonding of a μ-Mesityl Ligand on Dicopper(I) through a Proton-Responsive Expanded PNNP Pincer Ligand

We report the synthesis and characterization of a series of cationic, neutral, and anionic dicopper(I) complexes featuring a μ-mesityl ligand and a naphthyridine-derived PNNP expanded pincer ligand. Structural characterization showed that the protonation state of the dinucleating ligand has a pronounced effect on the bending and tilting of the μ-mesityl ligand. DFT calculations indicate that the varying orientations of the μ-mesityl ligand are inherent due to changes in electronic structure rather than crystal-packing effects. NBO analysis reveals how the interactions that contribute to the three-center–two-electron bond between the μ-mesityl ligand and the dicopper core change for the various degrees of observed bending and tilting

Cooperative H2 Activation on Dicopper(I) Facilitated by Reversible Dearomatization of an “Expanded PNNP Pincer” Ligand

A naphthyridine‐derived expanded pincer ligand is described that can host two copper(I) centers. The proton‐responsive ligand can undergo reversible partial and full dearomatization of the naphthyridine core, which enables cooperative activation of H2 giving an unusual butterfly‐shaped Cu4H2 complex

Tuning the Bonding of a μ-Mesityl Ligand on Dicopper(I) through a Proton-Responsive Expanded PNNP Pincer Ligand

We report the synthesis and characterization of a series of cationic, neutral, and anionic dicopper(I) complexes featuring a μ-mesityl ligand and a naphthyridine-derived PNNP expanded pincer ligand. Structural characterization showed that the protonation state of the dinucleating ligand has a pronounced effect on the bending and tilting of the μ-mesityl ligand. DFT calculations indicate that the varying orientations of the μ-mesityl ligand are inherent due to changes in electronic structure rather than crystal-packing effects. NBO analysis reveals how the interactions that contribute to the three-center–two-electron bond between the μ-mesityl ligand and the dicopper core change for the various degrees of observed bending and tilting

Cooperative H2 Activation on Dicopper(I) Facilitated by Reversible Dearomatization of an “Expanded PNNP Pincer” Ligand

A naphthyridine‐derived expanded pincer ligand is described that can host two copper(I) centers. The proton‐responsive ligand can undergo reversible partial and full dearomatization of the naphthyridine core, which enables cooperative activation of H2 giving an unusual butterfly‐shaped Cu4H2 complex

Unexpected reactivity of a PONNOP ‘expanded pincer’ ligand

We report the synthesis, characterization and coordination chemistry of a new naphthyridine-derived phosphinite PONNOP expanded pincer ligand. As envisioned, the dinucleating ligand readily binds two copper(I) centers in close proximity, but undergoes an unexpected rearrangement in the presence of nickel(II) salts to form an interesting PONNP pincer platform

Persistence of a Ru3(μ-CO)3(CO)5 Cluster Bound to a PNNP “Expanded Pincer” Ligand in Different Protonation States

We report the synthesis and characterization of Ru3(μ-CO)3(CO)5-type cluster complexes bound to a dinucleating PNNP ‘expanded pincer’ ligand. Each bidentate PN pocket of the ligand chelates a single ruthenium center of the cluster and can undergo deprotonation concomitant with dearomatization of its naphthyridine core. Although the cluster bearing a partially dearomatized ligand reacts with H2, we found no indication that this proceeds via a pathway involving metal-ligand cooperativity

Allylpalladium(II) Histidylidene Complexes and Their Application in Z-Selective Transfer Semihydrogenation of Alkynes

We have studied the use of amino acid histidine as a precursor for N-heterocyclic carbene (NHC) ligands. This natural amino acid possesses an imidazole substituent, which makes it an interesting NHC precursor that contains both an acid and an amino functionality. These functionalities may be used for further tuning of NHC complexes. We have developed routes for the synthesis of symmetric and dissymmetric alkyl, benzyl, and aryl-substituted histidinium salts. Subsequently, the corresponding Ag and Pd histidylidenes were synthesized and the palladium complexes were tested in the Z-selective transfer semihydrogenation of alkynes. Histidylidene palladium complexes that contain additional donor functionalities were found to display good selectivities. The best catalytic results were obtained with a Pd-histidylidene complex that contains two picolyl functional groups

Intramolecular redox-active ligand-to-substrate single-electron transfer: Radical reactivity with a palladium(II) complex

Coordination of the redox-active tridentate NNO ligand LH2 to PdII yields the paramagnetic iminobenzosemiquinonato complex 3. Single-electron reduction of 3 yields diamagnetic amidophenolato complex 4, capable of activating aliphatic azide 5. Experimental and computational studies suggest a redox-noninnocent pathway wherein the redox-active ligand facilitates intramolecular ligand-to-substrate single-electron transfer to generate an open-shell singlet nitrene-substrate radical, ligand radical , enabling subsequent radical-type C-H amination reactivity with PdII