Nickel-catalyzed selective conversion of two different aldehydes to cross-coupled esters

In the presence of a Ni(0)/NHC catalyst, an equimolar mixture of aliphatic and aryl aldehydes can be employed to selectively yield a single cross-coupled ester. This reaction can be applied to a variety of aliphatic (1°, 2°, cyc-2°, and 3°) and aryl aldehyde combinations. The reaction represents 100% atom efficiency and generates no waste. Mechanistic studies have revealed that the striking feature of the reaction is the simultaneous coordination of two aldehydes to Ni(0).     

Formation and coordination modes of the C4E4 moiety (E = COOMe) bound to two palladium(II) moieties

The transmetallation of the palladacyclopentadiene complex Pd{C(COOMe)C(COOMe)C(COOMe)C(COOMe)}(bipy) with the dicationic Pd(II) complex [Pd(bipy)(CH(3)CN)(2)][BF(4)](2) afforded a terminally σ-palladated diene complex [Pd(2){μ-η(1):η(1)-C(COOMe)C(COOMe)C(COOMe)C(COOMe)}(bipy)(2)(CH(3)CN)(2)][BF(4)](2). It was revealed by X-ray crystallographic analysis that replacement of the acetonitrile ligands in a terminally σ-palladated diene complex with PPh(3) ligands resulted in the conformation change of the σ-palladated diene moiety from skewed s-cis to planar s-trans. Treatment of a bis-triphenylphosphine dipalladium complex [Pd(2)(PPh(3))(2)(CH(3)CN)(4)][PF(6)](2) with dimethoxyacetylene dicarboxylate (DMAD) (1 equiv.) in acetonitrile resulted in the insertion of DMAD to the Pd-Pd bond to afford [Pd(2){μ-η(1):η(1)-C(COOMe)C(COOMe)}(PPh(3))(2)(CH(3)CN)(4)][PF(6)](2). Addition of the second DMAD gave the ylide-type complex [Pd(2){μ-η(2):η(3)-C(COOMe)C(COOMe)C(COOMe)C(COOMe)(PPh(3))}(PPh(3))(2)(CH(3)CN)(3)][PF(6)](2) of which the structure was determined by X-ray crystallographic analysis.     

Synthesis and structure of dipalladium complexes containing cyclooctatetraene and bicyclooctatrienyl ligands

The reaction of a substitutionally labile dipalladium(I) complex [Pd₂(CH₃CN)₆][BF₄]₂ (1) with 1,3,5,7-cyclooctatetraene (COT) in acetonitrile afforded [Pd₂(μ-η³:η³-C₈H₈)(CH₃CN)₄][BF₄]₂ (2). The reaction of 2 with COT in acetonitrile yielded [Pd₂(μ-η³:η³-C₁₆H₁₆)(CH₃CN)₄][BF₄]₂ (4), where COT is dimerized via C-C bond formation. Complexes 2 and 4 were structurally characterized by X-ray diffraction analyses. In dichloromethane, COT isomerized to styrene at room temperature in the presence of catalytic amount of 1, 2, or 4.     

para-Bridged symmetrical pillar[5]arenes: their Lewis acid catalyzed synthesis and host-guest property

Condensation of 1,4-dimethoxybenzene (DMB) with paraformaldehyde in the presence of BF3.O(C2H5)2 gave novel para-bridged pentacyclic pillar DMB (DMpillar[5]arene). Moreover, para-bridged pentacyclic hydroquinone (pillar[5]arene) was prepared. Pillar[5]arene formed 1:1 host-guest complexes with dialkyl viologen and alkyl pyridinium derivatives. However, pillar[5]arene did not form complexes with the diadamantyl viologen derivative since a bulky adamantyl group was unable to thread the cavity of pillar[5]arene.     

Dynamic-to-Static Planar Chirality Conversion in Pillar[5]arenes Regulated by Guest Solvents or Amplified by Crystallization

Controlling dynamic chirality and memorizing the controlled chirality are important. Chirality memory has mainly been achieved using noncovalent interactions. However, in many cases, the memorized chirality arising from noncovalent interactions is erased by changing the conditions such as the solvent and temperature. In this study, the dynamic planar chirality of pillar[5]arenes was successfully converted into static planar chirality by introducing bulky groups through covalent bonds. Before introducing the bulky groups, pillar[5]arene with stereogenic carbon atoms at both rims existed as a pair of diastereomers, and thus showed planar chiral inversion that was dependent on the chain length of the guest solvent. The pS and pR forms, regulated by guest solvents, were both diastereomerically memorized by introducing bulky groups. Furthermore, the diastereomeric excess was amplified by crystallization of the pillar[5]arene. The subsequent introduction of bulky groups yielded pillar[5]arene with an excellent diastereomeric excess (95 % de).     

Study of the ‘Raman spectroscopic signature of life’ in mitochondria isolated from budding yeast

The ‘Raman spectroscopic signature of life’ is a Raman band at 1602 cm⁻¹ that sharply reflects the metabolic activity of cell mitochondria. Here we report the study of thissignature in isolated yeast mitochondria. The existence and behaviour of the 1602 cm⁻¹ band in isolated mitochondria have been confirmed to be the same as in living yeast cells: the intensity of the band decreases with timewhen a respiration inhibitor, sodium azide, is added. The present study shows the significance of isolated mitochondria in elucidating the origin of this still unassigned Raman band. Copyright © 2009 John Wiley & Sons, Ltd.     

A Square‐Planar Complex of Platinum(0)

The Pt⁰ complex [Pt(PPh₃)(Eind₂‐BPEP)] with a pyridine‐based PNP‐pincer‐type phosphaalkene ligand (Eind₂‐BPEP) has a highly planar geometry around Pt with ∑(Pt)=358.6°. This coordination geometry is very uncommon for formal d¹⁰ complexes, and the Pd and Ni homologues with the same ligands adopt distorted tetrahedral geometries. DFT calculations reveal that both the Pt and Pd complexes are M⁰ species with nearly ten valence electrons on the metals whereas their atomic orbital occupancies are evidently different from one another. The Pt complex has a higher occupancy of the atomic 6s orbital because of strong s–d hybridization due to relativistic effects, thereby adopting a highly planar geometry reflecting the shape and orientation of the partially unoccupied orbital.