A series of uranyl compounds with the redoxactive iminoquinone ligand have been synthesized, and their electronic structures elucidated using multinuclear NMR, EPR, electronic absorption spectroscopies, SQUID magnetometry, and X-ray crystallography. Characterization and analysis of the iminoquinone (iq 0 ) complex, ( dipp iq)UO 2 (OTf) 2 THF (1-iq), the iminosemiquinone (isq 1− ) complex, ( dipp isq) 2 UO 2 THF (2i s q ) , a n d t h e a m i d o p h e n o l a t e ( a p 2 − ) complex, [( dipp ap) 2 UO 2 THF][K(18-crown-6)(THF) 2 ] 2 (3-ap crown) show that reduction events are ligand-based, with the uranium center remaining in the hexavalent state. Reactivity of 2-isq with B-chlorocatecholborane or pivaloyl chloride leads to U−O uranyl bond scission and reduction of U(VI) to U(IV) concomitant with ligand oxidation along with organic byproducts. 18 O isotopic labeling experiments along with IR spectroscopy, mass spectrometry, and multinuclear NMR spectroscopy confirm that the organic byproducts contain oxygen atoms which originate from U−O uranyl bond activation.

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 initiation sensitivity of the explosive and lead to the development of a new class of sensitivity switchable materials. To explore this relationship, the well-known spin crossover compound [Fe(Htrz) 3 ] n [ClO 4 ] 2n (1) was re-evaluated for its explosive properties, and its mechanical impact sensitivity was correlated to spin transition. A variable temperature impact test was developed and used to evaluate the impact sensitivity of 1 in the low spin (LS, S = 0), thermally accessed high spin (HS, S = 2), and mixed LS and HS states. For comparison, the structurally similar Ni compound, [Ni(Htrz) 3 ] n [ClO 4 ] 2n (2), which does not undergo a spin transition at accessible temperatures, was synthesized and characterized, and its explosive properties and variable temperature impact sensitivity measured. These results reveal a correlation between impact sensitivity and spin transition, where 1 exhibits lower impact sensitivity in the LS state and increases in sensitivity upon transition to the HS state. Density functional theory was used to predict structural changes that occur upon spin transition that correlate to the change in sensitivity. This demonstrates, for the first time, an explosive spin crossover compound (ExSCO) that exhibits switchable impact sensitivity with a fully reversible internal switching mechanism.

A set of organolanthanide(III) complexes featuring Ce(III)−C aryl σ-bonds have been synthesized and characterized. The syntheses follow salt metathesis reactions of the salts: ortholithiated oxazoline (Li-ortho-oxa) (L1) and Li 2 -biphenyl (L2) with t h e c o r r e s p o n d i n g m e t a l l o c e n e p r e c u r s o r s : 1 -L n ([(C 5 Me 5 ) 2 LnKCl 2 (THF)] n ) Ln = La and Ce, 2-La, ( [ ( C 5 M e 4 S i M e 3 ) 2 L a K C l 2 ( T H F ) ] n ) a n d 2 -C e ([((C 5 Me 4 SiMe 3 ) 2 CeKCl 2 )(Et 2 O) 0.5 ] n ). Electrochemical studies were performed for the organolanthanide(III) complexes. Reversible Ce(III)/Ce(IV) redox couples were observed for (C 5 Me 5 ) 2 Ce(κ 2 -ortho-oxa) (3-Ce) and [Li(DME) 3 ][(C 5 Me 5 ) 2 Ce-( b i p h e n ) ] ( 5 -C e ) c o m p l e x e s . H o w e v e r , c o m p l e x (C 5 Me 4 (SiMe 3 )) 2 Ce(κ 2 -ortho-oxa) (4-Ce) showed an irreversible Ce(III/IV) oxidation wave.A DFT-computed redox potential for 3-Ce showed good agreement with experiment. For 5-Ce, calculations indicated that the redox potential may be influenced strongly by speciation changes associated with the Li(DME) 3 + cation becoming outer-sphere. Bonding analysis suggests strong bond polarization in the title complexes (3-Ce and 5-Ce) with weights of 7−8% from Ce in the Ce−C aryl donation-bond orbitals. Attempts to isolate Ce(IV) species from these complexes resulted into the decomposition of the products into unidentified Ce(III) species, indicating that the bulky and electron-donating cyclopentadienide derivatives, ortho-oxazolide ligand, and/or the biphenylide ligand do not effectively stabilize the organocerium(IV) complexes against decomposition under the conditions employed.

Ce(iv) complexes with multiple bonds display similar f0 fractions, but different f/d hybridization, 5d-orbital energies, and TIP levels.

The separation and purification of niobium and tantalum, which co-occur in natural sources, is difficult due to their similar physical and chemical properties. The current industrial method for separating Ta/Nb...