Thermal Chemistry of Cp*W(NO)(CHCMe)(H)(L) Complexes (L = Lewis Base).

The complexes trans-Cp*W(NO)(CHCMe)(H)(L) (Cp* = η-CMe) result from the treatment of Cp*W(NO)(CHCMe) in n-pentane with H (∼1 atm) in the presence of a Lewis base, L. The designation of a particular geometrical isomer as cis or trans indicates the relative positions of the alkyl and hydrido ligands in the base of a four-legged piano-stool molecular structure. The thermal behavior of these complexes is markedly dependent on the nature of L.

Effects of the η(5)-C5H4(i)Pr Ligand on the Properties Exhibited by Its Tungsten Nitrosyl Complexes.

Reaction of Na[η(5)-C5H4(i)Pr] with W(CO)6 in refluxing THF for 4 days generates a solution of Na[(η(5)-C5H4(i)Pr)W(CO)3] that when treated with N-methyl-N-nitroso-p-toluenesulfonamide at ambient temperatures affords (η(5)-C5H4(i)Pr)W(NO)(CO)2 (1) that is isolable in good yield as an analytically pure orange oil. Treatment of 1 with an equimolar amount of I2 in Et2O at ambient temperatures affords (η(5)-C5H4(i)Pr)W(NO)I2 (2) as a dark brown solid in excellent yield. Sequential treatment at low temperatures of 2 with 0.

Surface Composition of Silver Nanocubes and Their Influence on Morphological Stabilization and Catalytic Performance in Ethylene Epoxidation.

Silver nanocubes with exposed (100) facets are reported to have improved selectivity with respect to their spherical counterparts for ethylene epoxidation. In the present study, we observe that the surface composition of the silver nanocubes also has a critical impact on activity. Detailed investigation of the surface composition of silver nanocubes has been carried out using HRTEM, SEM, EDS, EELS, and EFTEM.

Synthesis, Characterization, and Some Properties of Cp*W(NO)(H)(η(3)-allyl) Complexes.

Sequential treatment at low temperatures of Cp*W(NO)Cl2 in THF with 1 equiv of a binary magnesium allyl reagent, followed by an excess of LiBH4, affords three new Cp*W(NO)(H)(η(3)-allyl) complexes, namely, Cp*W(NO)(H)(η(3)-CH2CHCMe2) (1), Cp*W(NO)(H)(η(3)-CH2CHCHPh) (2), and Cp*W(NO)(H)(η(3)-CH2CHCHMe) (3). Complexes 1-3 are isolable as air-stable, analytically pure yellow solids in good to moderate yields by chromatography or fractional crystallization. In solutions, complex 1 exists as two coordination isomers in an 83:17 ratio differing with respect to the endo/exo orientation of the allyl ligand.

Green synthesis of Ni-Nb oxide catalysts for low-temperature oxidative dehydrogenation of ethane.

The straightforward solid-state grinding of a mixture of Ni nitrate and Nb oxalate crystals led to, after mild calcination (T<400 °C), nanostructured Ni-Nb oxide composites. These new materials efficiently catalyzed the oxidative dehydrogenation (ODH) of ethane to ethylene at a relatively low temperature (T<300 °C). These catalysts appear to be much more stable than the corresponding composites prepared by other chemical methods; more than 90 % of their original intrinsic activity was retained after 50 h with time on-stream.

Synthesis and reactivity of [(silox)2Mo=NR]2Hg (R=tBu, tAmyl; silox=OSitBu3): unusual thermal stability and ready nucleophilic cleavage rationalized by electronic factors.

Treatment of (DME)Cl2Mo(=NR)2 (R=tBu, (1-tBu), tAmyl (1-tAmyl)) with 2 equiv of tBu3SiOH (siloxH) and 1 equiv of HCl produced (silox)2Cl2Mo=NR (R=tBu, (3-tBu), tAmyl (3-tAmyl)); subsequent reduction by Na/Hg afforded the Mo(V) chloride, (silox)2ClMo=NtBu (4-tBu), and the Mo(IV) mercury derivatives, [(silox)2Mo=NR]2Hg (R=tBu ((5-tBu)2Hg), tAmyl ((5-tAmyl)2Hg)). Reductions of 3-tBu and 3-tAmyl in the presence of L (L=PMe3, pyridine, 4-picoline) led to the isolation of adducts (silox)2(Me3P)Mo=NR (R=tBu (6-tBu), tAmyl (6-tAmyl)) and (silox)2L2Mo=NtBu (L=py (7-py), 4-pic (7-4-pic)). Single-crystal X-ray structural investigations of pseudo-tetrahedral 4-tBu, Hg-capped, pseudo-trigonal planar (5-tBu)2Hg, pseudo-tetrahedral 6-tBu, and trigonal bipyramidal 7-4-pic reveal that all possess a closed O-Mo-O angle when compared to the N=Mo-O angles.

Hydroamination and hydroalkoxylation catalyzed by triflic acid. Parallels to reactions initiated with metal triflates.

Intermolecular additions of the O-H bonds of phenols and alcohols and the N-H bonds of sulfonamides and benzamide to olefins catalyzed by 1 mol % of triflic acid and studies to define the relationship between these reactions and those catalyzed by metal triflates are reported. Cyclization of an alcohol containing pendant monosubstituted and trisubstituted olefins catalyzed by either triflic acid or metal triflates form products from addition to the more substituted olefin, and additions of tosylamide catalyzed by triflic acid or metal triflates form indistinguishable ratios of the two N-alkyl sulfonamides.

3-center-4-electron bonding in [(silox)2Mo=NtBu]2(mu-Hg) controls reactivity while frontier orbitals permit a dimolybdenum pi-bond energy estimate.

Na/Hg reduction of (silox)2Cl2Mo=NtBu (3) afforded C2h [(silox)2Mo=NtBu]2(mu-Hg) (12-Hg), which consists of two distorted trigonal monoprisms with Hg at the each apex (d(MoHg) = 2.6810(5) A). Calculations reveal 3c4e bonding in the linear MoHgMo linkage that renders 12-Hg susceptible to nucleophilic cleavage.