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Here we report novel catalysts for nitrobenzene hydrogenation based on Ru/RuO2nanoparticles (NPs) and including iron oxide NPs, allowing magnetic recovery. The solvent type, reaction temperature, and the size and composition of initial iron oxide NPs are demonstrated to be the control factors determining synthesis outcomes including the degree of NP aggregation and catalytic properties. A complete characterization of the catalysts using transmission electron microscopy (TEM), X-ray powder diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and energy dispersive x-ray spectroscopy (EDS) allowed assessment of the structure–property relationships. It is revealed that coexistence of the Ru/RuO2and iron oxide NPs in the catalyst as well as the proximity of two different NP types lead to significantly higher aniline yields and reaction rates. The catalytic properties are also influenced by the type of iron oxide NPs present in the catalytic samples.

(R-IAN)2ZrX2 complexes, where X = NMe2, Cl, have recently emerged as effective olefin polymerization precatalysts bearing chiral ligands formally of the β-diketimine class. An attempt to exchange dimethylamido ligands for alkyl (methyl) using the Jordan protocol resulted in a surprisingly facile transmetalation of the bidentate Me-IAN ligands from zirconium(IV) to aluminum(III). An initial study of the process and the finding that the (R-IAN)AlMe2 complexes that result are more potent precatalysts themselves provide a case study within the rapidly growing area of catalysis based on β-diketiminate metal complexes.

(PNP^tBu)Re(H)4, where PNP^tBu is (^tBu2PCH2SiMe2)2N, reacts at 23 °C with RC&tbd1;CH (R = ^tBu, SiMe3, Ph) to give first H2 and mirror-symmetric (PNP^tBu)ReH3(CCR), then H2 and C2ν symmetric (PNP^tBu)Re(CCR)2. The diacetylide compounds show temperature-independent paramagnetism and ¹³C and ³¹P chemical shifts far beyond their normal values for other (PNP^tBu)ReXn compounds. Single-crystal X-ray diffraction shows very similar structures for the cases R = Ph and R = SiMe3, each having an approximately C2v geometry with equivalent acetylides with ∠C−Re−C approximately 108°. No hydride or H2 ligands are detected in final difference Fourier maps. DFT(B3PW91) calculations give minimum energy geometries of these species, of their products upon adding H2, and of mechanistically significant analogues [(H2PCH2SiH2)2N]ReHnR‘mH2-m, with n = 0, 2, m = 1, 2, and R‘ = H or Ph. These calculated geometries, when compared to those from X-ray diffraction, indicate that the isolated compounds have no hydride or H2 ligands and are thus (PNP)Re^III(CCR)2, making them more unsaturated than the reagent (PNP)Re^V(H)4 by two electrons. Triplet state geometries of (PNP)ReXY are calculated and analyzed, as are their frontier orbitals.

An efficient method has been developed for the stereocontrolled construction of polycyclic and spirocyclic compounds, including the spirocyclic core of the antitumor agent fredericamycin A. The strategy involves a one-pot aldol addition/Brook rearrangement/cyclization sequence beginning from arene chromium tricarbonyl complexes and can formally be described as a [3 + 2] annulation.

We have prepared the yttrium(III) alkoxides [(L^Me2)(HL^Me2)Y3(OCH2C6H5)4] (3) and [(S-L^Me)Y]2·2(HOCH2C6H5) (1·2BnOH) through treatment of two previously developed complexes with benzyl alcohol. Complex 3 possesses a novel cluster structure that appears to be retained in solution and is capable of polymerizing both dl-lactide (LA) and ε-caprolactone (CL). The polymerizations are controlled as evidenced by the linear nature of molecular weight versus conversion plots and [M]/[3] ratios. The kinetics of LA polymerization using 3 are first-order with respect to the monomer at low [LA]/[Y] ratios. The polymerization of CL is zero-order in monomer. Complex 1·2BnOH possesses a dimeric structure previously seen in both the solid and solution state. However, the added presence of benzyl alcohol moieties in 1·2BnOH increases the rate of LA polymerization and allows for control over the molecular weights of isolated polylactide, a feature unseen in earlier reported dimers. The complex 1·2BnOH is not active for the polymerization of CL.

Palladium(II) and ruthenium(II) complexes containing aminoxyl radical-substituted triphenylphosphine ligands are reported. The novel spin-labeled phosphine ligands [(p-(4,4,5,5,-tetramethylimidazolinyl-1-oxyl-3-oxide)phenyl)diphenylphosphine] (1) and [(p-(N-oxyl-tert-butylamino-2-)phenyl)diphenylphosphine] (2) react with PdCl2 to yield trans-Pd[1]2Cl2 and trans-Pd[2]2Cl2 (complexes 3 and 4, respectively), which show exchange-coupled EPR spectra. This through-space, intramolecular coupling provides a method of determining the number of radical phosphines coordinated to the Pd(II) center. Systems with only one coordinated phosphine show EPR spectra typical of the ligand. Phosphine 2 reacts with [(η³-C3H5)PdCl]2 and [(η⁶-p-cymene)RuCl2]2 to form the mononuclear metal phosphine adducts (η³-C3H5)Pd[2]Cl (5) and (η⁶-p-cymene)Ru[2]Cl2 (6). All complexes show broad, shifted ¹H NMR spectra, and magnetic susceptibility measurements confirm the presence of one (complexes 5, 6) or two (complexes 3, 4) radicals per complex accordingly. The X-ray crystal structures of Pd[2]2Cl2 and (η³-C3H5)Pd[2]Cl are also reported. Complexes 5 and 6 are unusual examples of stable organometallic systems with peripheral free radicals, i.e., spin-labeled organometallics.

The medial collateral ligaments is a common site of injury in baseball pitchers, causing substantial morbidity and loss of pitching time. Twenty-six skilled baseball pitchers with medial collateral ligament insufficiency were studied before surgery with high-speed cinematography and fine-wire electromyography of eight muscles around the elbow. Data from the pitchers with injured elbows were compared with data obtained from uninjured pitchers. The flexor carpi radialis muscle in the pitchers with medial collateral ligment deficiencies revealed significantly decreased firing during the acceleration and deceleration phase of the fastball when compared with that of the pitchers with normal elbows, and the flexor carpi radialis muscle was significantly depressed during the early cocking and deceleration phases. The extensor muscles revealed slightly increased activity in the injured elbows; however, this was not statistically significant. Although the muscles of the flexor pronator group (especially the flexor carpi ulnaris muscle and the flexor digitorum superficialis muscles) are anatomically positioned to provide dynamic stability of the elbow, they did not demonstrate increased electrical activity in pitchers with medial collateral ligament deficiencies. This finding suggests that the muscles on the medial side of the elbow do not supplant the role of the medial collateral ligament during the fastball pitch.

The reaction of alkynes RC&tbd1;CH (R = H, Ph) with (PNP)RuCl, where PNP is (^tBu2PCH2SiMe2)2N, occurs rapidly below 23 °C to give first an η²-alkyne adduct and then a final product with a vinylidene group, C&dbd;CHR, inserted into the N−Ru bond. Characterization included X-ray diffraction (R = Ph) and DFT calculations to probe mechanistic aspects of the reaction.