Atomically precise copper nanoclusters (NCs) are of immense interest for a variety of applications, but have remained elusive. Herein we report the isolation of a copper NC, [Cu 25 H 22 (PPh 3 ) 12 ]Cl (1), from the reaction of Cu(OAc) and CuCl with Ph 2 SiH 2 , in the presence of PPh 3 . Complex 1 has been fully characterized, including analysis by X-ray crystallography, XANES, and XPS. In the solid state, complex 1 is constructed around a Cu 13 centered-icosahedron and formally features partial Cu(0) character. XANES of 1 reveals a Cu K-edge at 8979.6 eV, intermediate between the edge energies of Cu (0) and Cu(I), confirming our oxidation state assignment. This assignment is further corroborated by determination of the Auger parameter for 1, which also falls between those recorded for Cu(0) and Cu(I).

ABSTRACT:The copper hydride nanocluster (NC) [Cu 29 Cl 4 H 22 (Ph 2 phen) 12 ]Cl (2; Ph 2 phen = 4,7-diphenyl-1,10-phenanthroline) was isolated cleanly, and in good yields, by controlled growth from the smaller NC, [Cu 25 H 22 (PPh 3 ) 12 ]Cl (1), in the presence of Ph 2 phen and a chloride source at room temperature. Complex 2 was fully characterized by singlecrystal X-ray diffraction, XANES, and XPS, and represents a rare example of an N* = 2 superatom. Its formation from 1 demonstrates that atomically precise copper clusters can be used as templates to generate larger NCs that retain the fundamental electronic and bonding properties of the original cluster. A time-resolved kinetic evaluation of the formation of 2 reveals that the mechanism of cluster growth is initiated by rapid ligand exchange. The slower extrusion of CuCl monomer, its transport, and subsequent capture by intact clusters, resemble elementary steps in the reactant-assisted Ostwald ripening of metal nanoparticles.

The redox entity comprising two Schiff base groups attached to a phenyl ring (NCHArHCN) is reported to be active for sodium‐ion storage (Ar=aromatic group). Electroactive polymeric Schiff bases were produced by reaction between non‐conjugated aliphatic or conjugated aromatic diamine block with terephthalaldehyde unit. Crystalline polymeric Schiff bases are able to electrochemically store more than one sodium atom per azomethine group at potentials between 0 and 1.5 V versus Na+/Na. The redox potential can be tuned through conjugation of the polymeric chain and by electron injection from donor substituents in the aromatic rings. Reversible capacities of up to 350 mA h g−1 are achieved when the carbon mixture is optimized with Ketjen Black. Interestingly, the “reverse” configuration (CHNArNHC) is not electrochemically active, though isoelectronic.

Lithium enolates derived from carboxylic acids are ubiquitous intermediates in organic synthesis. Asymmetric transformations with these intermediates, a central goal of organic synthesis, are typically carried out with covalently attached chiral auxiliaries. An alternative approach is to utilize reagents that form discrete, well-defined aggregates with lithium enolates, providing a chiral environment conducive of asymmetric bond formation. These reagents effectively act as non-covalent, or traceless, chiral auxiliaries. Lithium amides are an obvious choice for such reagents as they are known to form mixed aggregates with lithium enolates. We demonstrate here that mixed aggregates can effect highly enantioselective transformations of lithium enolates in several types of reactions most notably in transformations forming tetrasubstituted and quaternary carbon centers. Easy recovery of the chiral reagent by aqueous extraction is another practical advantage of this one-step protocol. Crystallographic, spectroscopic, and computational studies of the central reactive aggregate, which provide insight into the origins of selectivity, are also reported.

ABSTRACT:The group 11 hydride clusters [Ag 6 H 4 (dppm) 4 (OAc) 2 ](1) and(2) (dppm = 1,1-bis(diphenylphosphino)methane) were synthesized in moderate yields from the reaction of M(OAc) (M = Ag, Cu) with Ph 2 SiH 2 , in the presence of dppm. Complex 1 is the first structurally characterized homometallic polyhydrido silver cluster to be isolated. Both 1 and 2 catalyze the hydrosilylation of (,-unsaturated) ketones. Notably, this represents the first example of hydrosilylation with an authentic silver hydride complex.

Two synthetic strategies for incorporating diiron analogues of [FeFe]-hydrogenases into short peptides via phosphine functional groups are described. First, utilizing the amine side chain of lysine as an anchor, phosphine carboxylic acids can be coupled via amide formation to resin-bound peptides. Second, artificial, phosphine-containing amino acids can be directly incorporated into peptides via solution phase peptide synthesis. The second approach is demonstrated using three amino acids each with a different phosphine substituent (diphenyl, diisopropyl, and diethyl phosphine). In total, five distinct monophosphine-substituted, diiron model complexes were prepared by reaction of the phosphine-peptides with diiron hexacarbonyl precursors, either (μ-pdt)Fe2(CO)6 or (μ-bdt)Fe2(CO)6 (pdt = propane-1,3-dithiolate, bdt = benzene-1,2-dithiolate). Formation of the complexes was confirmed by UV/Vis, FTIR and (31)P NMR spectroscopy. Electrocatalysis by these complexes is reported in the presence of acetic acid in mixed aqueous-organic solutions. Addition of water results in enhancement of the catalytic rates.

We report a critical re-evaluation of the synthesis and characterization of Cu(MPP). This product was reportedly formed by the reaction of Cu(NO) with 2-mercapto-5-n-propylpyrimidine (HMPP) and NaBH, in ethanol, in the presence of [N(CH)][Br]. In our hands, we found no experimental evidence to support the existence of Cu(MPP) in the reaction mixture. Instead, we demonstrate that the material isolated from this reaction is a complex mixture containing [N(CH)], Br, NO, and 2-mercapto-5-n-propyl-1,6-dihydropyrimidine (HMPP*), along with the Cu(I) coordination polymer, [Cu(MPP)]. To support our conclusions, we have independently synthesized HMPP* and [Cu(MPP)], as well as the related Cu(I) coordination complexes, [Cu(HMPP*)] and [Cu(MPP*)]. All new materials were characterized by NMR spectroscopy and mass spectrometry, while HMPP*, [Cu(HMPP*)] (n = 4), and [Cu(MPP)] (n = 6) were also characterized by X-ray crystallography.

The reactivity of MCl 3 (η 1 -TEMPO) (M = Fe, 1; Al, 2; TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl) with a variety of alcohols, including 3,4-dimethoxybenzyl alcohol, 1phenyl-2-phenoxyethanol, and 1,2-diphenyl-2-methoxyethanol, was investigated using NMR spectroscopy and mass spectrometry. Complex 1 was effective in cleanly converting these substrates to the corresponding aldehyde or ketone. Complex 2 was also able to oxidize these substrates; however, in a few instances the products of overoxidation were also observed. Oxidation of activated alkanes, such as xanthene, by 1 or 2 suggests that the reactions proceed via an initial 1-electron concerted proton−electron transfer (CPET) event. Finally, reaction of TEMPO with FeBr 3 in Et 2 O results in the formation of a mixture of FeBr 3 (η 1 -TEMPOH) ( 23) and [FeBr 2 (η 1 -TEMPOH)] 2 (μ-O) (24), via oxidation of the solvent, Et 2 O.