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Spin crossover complexes are known to undergo bond length, volume, and enthalpy changes during spin transition. In an explosive spin crossover complex, these changes could affect the mechanical and...

Metal nitrides are strong refractory ceramic materials known for applications in the coatings, catalysis, and semiconductor industries. Lanthanide nitrides are difficult to prepare in high purity and often require high temperatures and sophisticated equipment. In this work, we present an approach to the synthesis of high-purity f-element nitrides through the use of simple lanthanide salts and the nitrogen-rich ligand 5,5'-bis(1H-tetrazolyl)amine (H

Enhanced safety, with the ability to control detonation behavior, while maintaining energy output are highly desirable characteristics for new high explosive (HE) materials. The use of switchable explosive spin crossover (ExSCO) compounds is a potentially powerful strategy to access on-demand mechanical sensitivity. Spin crossover is a transition between the low spin (LS) and high spin (HS) state electron configurations in a metal complex. We present our variable temperature impact sensitivity results on [Fe(Htrz)3]n[ClO4]2n, a high nitrogen Fe(II) ExSCO compound, and compare its mechanical sensitivity in the LS vs HS states. In addition, we describe the synthesis and properties of energetic acrylate monomers that will be used to develop custom materials for use in the additive manufacturing of explosives.

We report a critical re-evaluation of the synthesis and characterization of Cu8(MPP)4. This product was reportedly formed by the reaction of Cu(NO3)2 with 2-mercapto-5-n-propylpyrimidine (HMPP) and NaBH4, in ethanol, in the presence of [N(C8H17)4][Br]. In our hands, we found no experimental evidence to support the existence of Cu8(MPP)4 in the reaction mixture. Instead, we demonstrate that the material isolated from this reaction is a complex mixture containing [N(C8H17)4]+, Br–, NO3–, and 2-mercapto-5-n-propyl-1,6-dihydropyrimidine (H2MPP*), along with the Cu(I) coordination polymer, [Cu(MPP)]n. To support our conclusions, we have independently synthesized H2MPP* and [Cu(MPP)]n, as well as the related Cu(I) coordination complexes, [Cu(HMPP*)]n and [Cu2(MPP*)]n. All new materials were characterized by NMR spectroscopy and mass spectrometry, while H2MPP*, [Cu(HMPP*)]n (n = 4), and [Cu(MPP)]n (n = 6) were also characterized by X-ray crystallography.

The group 11 hydride clusters [Ag6H4(dppm)4(OAc)2] (1) and [Cu3H(dppm)3(OAc)2] (2) (dppm = 1,1-bis(diphenylphosphino)methane) were synthesized in moderate yields from the reaction of M(OAc) (M = Ag, Cu) with Ph2SiH2, 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 (α,β-unsaturated) ketones. Notably, this represents the first example of hydrosilylation with an authentic silver hydride complex.

The copper hydride nanocluster (NC) [Cu29Cl4H22(Ph2phen)12]Cl (2; Ph2phen = 4,7-diphenyl-1,10-phenanthroline) was isolated cleanly, and in good yields, by controlled growth from the smaller NC, [Cu25H22(PPh3)12]Cl (1), in the presence of Ph2phen and a chloride source at room temperature. Complex 2 was fully characterized by single-crystal 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.

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, [Cu25H22(PPh3)12]Cl (1), from the reaction of Cu(OAc) and CuCl with Ph2SiH2, in the presence of PPh3. 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 Cu13 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).

The copper hydride clusters [Cu14 H12 (phen)6(PPh3)4][X]2 (X=Cl or OTf; OTf=trifluoromethanesulfonate, phen=1,10-phenanthroline) are obtained in good yields by the reaction of [(Ph3P)CuH]6 with phen, in the presence of a halide or pseudohalide source. The complex [Cu14H12 (phen)6(PPh3)4][Cl]2 reacts with CO2 in CH2Cl2 , in the presence of excess Ph3 P, to form the formate complex [(Ph3P)2Cu(κ(2)-O2CH)], along with [(phen)(Ph3 P)CuCl].

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.

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 chiral reagents that form discrete, well-defined aggregates with lithium enolates, providing a chiral environment conducive of asymmetric bond formation. These reagents effectively act as noncovalent, 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 classes 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.

© 2014 American Chemical Society. The reactivity of MCl3(η1O) (M = Fe, 1; Al, 2; TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl) with a variety of alcohols, including 3,4-dimethoxybenzyl alcohol, 1-phenyl-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 FeBr3 in Et2O results in the formation of a mixture of FeBr3(η1OH) (23) and [FeBr2(η1OH)]2(μ-O) (24), via oxidation of the solvent, Et2O.

Phosphite, which often exists in growth solutions obtained directly from commercial P 2 O 5 , was found to have significant inhibiting effects on the growth of pyramidal face of KDP crystals. K(D x H 1-x ) 2 PO 4 (referred to as DKDP) crystals with different deuterium fraction x were grown and the optical performances were investigated. The absorption coefficients at 1.05 μm decreases monotonically with the increase of x. The transmission threshold shift from 1.65μm at x=0 to 2.10 μm at x=0.96. The high temperature phase transition temperature and latent heat were measured using the method of differential scanning calorimetry (DSC). Thermal conditioning experiments were carried out at 180°C and 140°C for KDP and DKDP, respectively. After conditioning, a different degree of improvement was observed in the optical homogeneity of the samples, while the laser damage threshold and light absorption coefficient showed no significant change.