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Instead of reductive elimination of aldehyde, or decarbonylation to give a trifluoroalkyl hydride, heating Cp*(PMe3)Ir(H)[C(O)CF3] (1) leads to the quantitative formation of Cp*(PMe3)Ir(CO) (2) and CF3H. Kinetic experiments, isotope labeling studies, solvent effect studies, and solvent-inclusive DFT calculations support a mechanism that involves initial dissociation of trifluoromethyl anion to give the transient ion-pair intermediate [Cp*(PMe3)Ir(H)(CO)]+[CF3]-. Further evidence for the ability of CF-3 to act as a leaving group came from the investigation of the analogous methyl and chloride derivatives Cp*(PMe3)Ir(Me)[C(O)CF3] and Cp*(PMe3)Ir(Cl)[C(O)CF3]. Both of these compounds undergo a similar loss of trifluoromethyl anion, generating an iridium carbonyl cation and CF3D in CD3OD. Three additional acyl hydrides, Cp*(PMe3)Ir(H)[C(O)RF] (where RF = CF2CF3, CF2CF2CF3, or CF2(CF2)6CF3) undergo RF--H elimination to give 2 at a faster rate than CF3H elimination from 1. Stereochemical studies using a chiral acyl hydride with a stereocenter at the β-position reveal that ionization of the carbanion occurs to form a tight ion-pair with high retention of configuration and enantiomeric purity upon proton transfer from iridium. [ABSTRACT FROM AUTHOR]

Addition of BF3·OEt2 to ethereal solutions of the Ni(ll) β-diketiminates (Me2NN]Ni(F1)(2,4-lutidine) (R = Et (1), Pr (2)) allows the isolation of the neutral β-H agostic monoalkyls (Me2NN]Ni(R) (R = Et (3), Pr (4)). X-ray studies of primary alkyls 3 and 4a reveal acute Ni-Cα-Cβ angles with short Ni-Cβ distances, indicating structures along the β-H elimination pathway. Positional disorder of the alkyl group in the X-ray structure of 4 corresponds to partial (22%) occupancy by the secondary alkyl [Me2NN)Ni(CHMe2) (4b). Variable-temperature NMR spectra of 3 and 4 reveal fluxional behavior that result from β-H elimination, in-plane rotation of the β-CH3 group, and a tetrahedral triplet structure for 3 that were investigated by density functional theory calculations at the Becke3LYP/6-31 G* level of theory without simplifications on the β-diketiminate ancillary ligand. Calculations support low temperature NMR studies that identify the linear β-H agostic propyl isomer 4a as the ground state with the branched β-H agostic isomer 4b slightly higher in energy. NMR studies and calculations show that the β-agostic 3 reluctantly coordinates ethene and that 3 is the ground state for this ethylene oligomerization catalyst. The thermodynamic isotope effect KH/KD = 1.3(2) measured for the loss of 2,4-lutidine from 1 to form β-agostic 3 was also examined by DFT calculations. [ABSTRACT FROM AUTHOR]

The article presents a study on the competitive reductive elimination (RE) from a [RhIII(CH3)(CN)][I] complex to give CH3CN in protic olvents and CH3I in aprotic solvents. It states that the reductively eliminated CHI undergoes selective electrophilic attack on the cyano ligand of the RhI complex in an aprotic solvent to give the corresponding alkyl isonitrile complex.

New hafnocene triarylstannyl complexes were prepared and were shown to undergo clean thermal decompositions via α-aryl-elimination to produce the corresponding stannylene and a hafnocene aryl complex. The rate of the decomposition is highly dependent on the nature of the ancillary ligand, with the stabilities of the CpCp*Hf(SnPh3)X compounds following the order X = NMe2 > Np (α-agostic) > OMe > Cl > Me. Mechanistic information suggests that α-aryl-elimination may be viewed as a concerted process involving nucleophilic attack of the migrating aryl group onto the electrophilic metal center. [ABSTRACT FROM AUTHOR]

(CpMoμ-S)2S2CH2, 2, and related derivatives serve as electrocatalysts for the reduction of protons with current efficiencies near 100%. The kinetics of the electrochemical reduction process has been studied, and the effects of varying the proton source, the solvent, the cyclopentadienyl substituents, and the sulfur substituents on the catalyst have been examined. The reduction of excess p-cyanoanilinium tetrafluoroborate under a hydrogen atmosphere in 0.3 M Et4NBF4/acetonitrile buffered at pH 7.6 is catalyzed by 2 at -0.64 V versus ferrocene, with an overpotential of 120 mV. Protonation of the sulfido ligand in 2 is an initial step in the catalytic process, and the rate-determining step at high acid concentrations appears to be the elimination of dihydrogen. The elimination may occur either from adjacent hydrosulfido sites or from a hydrosulfido-molybdenum hydride intermediate. [ABSTRACT FROM AUTHOR]

This article describes an efficient synthesis of a potent trehalase inhibitor, 1,1'-N-linked pseudodisaccharide 1 (consisting of two valienamines), in 14 steps with an overall yield of 12% and a first synthesis of 2 (consisting of two 2-epi-valienamines) in 15 steps with an overall yield of 24% from (-)-quinic acid. The synthesis involves a stereospecific palladium-catalyzed coupling reaction between an allylic amine and an allylic chloride as the crucial step. The acetonide blodking groups were shown to be the best hydroxyl protecting groups, compatible with the palladium-catalyzed allylic amination reaction that afforded high yields of the 1,1'-N-linked pseudodisaccharicles with a minimum amount of an elimination diene side product. [ABSTRACT FROM AUTHOR]