Organometallics

Understanding nonplanarity in metallabenzene complexes

The nonplanarity found in metallabenzene complexes has been investigated theoretically via density functional theory (DFT) calculations. A metallabenzene has four occupied π molecular orbitals (8 π electrons) instead of three that benzene has. Our electronic structure analyses show that the extra occupied π molecular orbital, which is the highest occupied molecular orbital (HOMO) in many metallabenzenes, has antibonding interactions between the metal center and the metal-bonded ring-carbon atoms, providing the electronic driving force toward nonplanarity.

Activation of the S-S bonds of alkyl disulfides RSSR (R = Me, Et, Pr, Bu-n) by heterodinuclear phosphido-bridged CpW(Co)(2)(mu-PPh2)Mo(CO)(5)

Reactions of CpW(CO)(2)(mu-PPh2)Mo(CO)(5) (1) with alkyl disulfides RSSR (R = Me, Et, Pr, Bu-n) in refluxing dichloromethane yielded the series of new mixed-metal and mixed-ligand bridged compounds CpW(CO)(mu-SR)(2)(mu-PPh2)Mo(CO)(3) (R = Me (4a), Et (4b), Pr (4c), Bun (4d)), CpW(CO)(mu-SR)2(mu-PPh2)Mo(CO)(mu-SR)(2) (R = Me (5a), Et (5b), Pr (5c), Bu-n (5d)), and CpW(CO)(mu-SR)(2)(mu-PPh2) Mo(CO)(2)(PPh2SR) (R = Me (6a), Et (6b), Pr (6c), Bu-n (6d)). All except 6c were characterized by single-crystal X-ray diffraction analysis.

Reactions of [Cp*Ru(H2O)(NBD)](+) with dihydrogen, silanes, olefins, alkynes, and allenes

Formal [2+2+2] addition reactions of the NBD ligand in [Cp*Ru(H2O)(NBD)]BF4 (NBD = norbornadiene) with H-2, Ph3SiH, ArCH=C=CH2, and RC=-CPh were observed. In contrast, olefins such as styrene and NBD do not undergo similar [2+2+2] addition reactions with [Cp*Ru(H2O)(NBD)]BF4. [Cp*Ru(H2O)(NBD)]BF4 reacts with H-2 in benzene to give [Cp*Ru(eta(6)-C6H6)]BF4 and nortricyclene. Similarly, [Cp*Ru(H2O)(NBD)]BF4 reacts with Ph3SiH to give [Cp*Ru(eta(6)-C6H5SiPh2OH)]BF4 and nortricyclene.

Theoretical Investigation of Alkyne Metathesis Catalyzed by W/Mo Alkylidyne Complexes

In this paper, the mechanism of alkyne metathesis catalyzed by W/Mo alkylidyne complexes has been theoretically investigated with the aid of density functional theory calculations. Calculations on various model alkylidyne complexes M( CMe)(OR)(3) (M = W, Mo; R = Me, CH2F), W( CMe)(NMe2)(3), and W( CMe)(Cl)(3) allow us to examine the factors that influence the reaction barriers. In the reaction mechanism, metallacyclobutadienes are initially formed from a ring-closing step between alkynes and alkylidyne complexes. A ring-opening step then gives the metathesis products.

β-Hydrogen Elimination of Five-Membered-Ring Metallacycles. Is It Possible?

B3LYP density functional theory calculations have been carried out to examine the structural and energetic aspects of β-hydrogen elimination in several metallacyclic complexes of ruthenium and platinum. Factors affecting barriers of the elimination reactions have been examined. It was found that favorable structural arrangements, in which the transferring β-hydrogen is in close proximity to the metal center, for β-hydrogen elimination exist in certain ring conformations of metallacyclic complexes.

Reactions of Hydrotris(pyrazolyl)borate (Tp)-Supported Ruthenium Dihydrogen Complexes [TpRu(L2)(H2)]+ (L2 = dppm, dppp, (PPh3)2) with O2

The η2-dihydrogen complex [TpRu(L2)(H2)]+ (L2 = dppm, dppp, or (PPh3)2) prepared in situ by protonation of the hydride precursor reacts with O2 to yield the paramagnetic RuIII-superoxo complex [TpRuIII(L2)(O2)]+, in which antiferromagnetic coupling between the RuIII ion (d5, S = 1/2) and the coordinated superoxide radical (S = 1/2) does not seem to be present.

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