Silicon-Containing Formal 4 pi-Electron Four-Membered Ring Systems: Antiaromatic, Aromatic, or Nonaromatic?

Density functional theory calculations (B3LYP) have been carried out to investigate the 4π-electron systems of 2,4-disila-1,3-diphosphacyclobutadiene (compound 1) and the tetrasilacyclobutadiene dication (compound 2). The calculated nucleus-independent chemical shift (NICS) values for these two compounds are negative, which indicates that the core rings of compounds 1 and 2 have a certain amount of aromaticity.

An Isotope (O-18, N-15, and H-2) Technique to Investigate the Metal Ion Interactions Between the Phosphoryl Group and Amino Acid Side Chains by Electrospray Ionization Mass Spectrometry

Cationic metal ion-coordinated N-diisopropyloxyphosphoryl dipeptides (DIPP-dipeptides) were analyzed by electrospray ionization multistage tandem mass spectrometry (ESI-MS n ). Two novel rearrangement reactions with hydroxyl oxygen or carbonyl oxygen migrations were observed in ESI-MS/MS of the metallic adducts of DIPP-dipeptides, but not for the corresponding protonated DIPP-dipeptides.

Fragmentation of pentacoordinate spirobicyclic aminoacylphosphoranes (P-AAs) by electrospray ionization tandem mass spectrometry concerning P-O and P-N bond cleavage

The fragmentation pathways of both protonated and sodiated pentacoordinate spirobicyclic aminoacylphosphoranes (P-AAs) have been studied by electrospray ionization multi-stage mass spectrometry (ESI-MSn) in positive mode. The possible pathways and their mechanisms are elucidated through the combination of ESI-MS/MS, isotope (15 N and 2H) labeling and high-resolution Fourier transform ion cyclotron resonance (FTICR)-MS/MS. The relative Gibbs free energies (ΔG) of the product ions and possible fragmentation pathways are estimated at the B3LYP/6-31 G(d) level of theory.

Interpolation of Atomically Thin Hexagonal Boron Nitride and Graphene: Electronic Structure and Thermodynamic Stability in Terms of All-Carbon Conjugated Paths and Aromatic Hexagons

Two-dimensional hexagonal composite materials (BN)n(C2)m (n, m = 1, 2, ...), which all are isoelectronic with graphene and hexagonal boron nitride (h-BN), have been studied by density functional theory (DFT) with a focus on the relative energies of different material isomers and their band gaps. The well-established chemical concepts of conjugation and aromaticity were exploited to deduce a rationale for identifying the thermodynamically most stable isomer of the specific composites studied.

Stable Iso-osmabenzenes from a Formal [3+3] Cycloaddition Reaction of Metal Vinylidene with Alkynols

The magic of Os: An unprecedented formal [3+3] cycloaddition reaction of 1 with alkynols affords stable iso-osmabenzenes at room temperature (see scheme). The phosphonium substituent at the Cβ position and the 18e− nature of the compound play key roles in the origin of the high thermal stability of the products. Isomerization of iso-osmabenzenes into η5-cyclopentadienyl complexes through metalated cyclopentadiene intermediates is also described.

On the Importance of Clar Structures of Polybenzenoid Hydrocarbons as Revealed by the π-Contribution to the Electron Localization Function

The degree of p-electron (de)localization and aromaticity of a series of polybenzenoid hydrocarbons (PBHs) has been analyzed through the π-contribution to the electron localization function (ELFπ), calculated at the B3LYP/6-311G(d,p) hybrid density functional theory level. The extent of p-electron delocalization in the various hexagons of a PBH was determined through analysis of the bifurcation values of the ELFp basins (BV(ELFp)), the spans in the bifurcation values in each hexagon (ΔBV(ELFπ)), and the ring-closure bifurcation values of the ELFπ (RCBV(ELFπ)).

Insertion reactions of allenes with palladium aryl complexes [PdI(Ph)(PPh3)](2) and PdI(Ph)(dppe)

Treatment of [PdI(Ph)(PPh3)]2 with allenes CH2═C═CHR (R = CMe3, CO2Et, P(O)(OEt)2, and SO2Ph) in dichloromethane at room temperature produces a mixture of cis and trans isomers of the π-allyl palladium complexes PdI(η3-CH2C(Ph)CHR)(PPh3) in which the R group is anti to the Ph group. The disubstituted allenes MeCH═C═CHR (R = P(O)(OEt)2 and SO2Ph) similarly react with [PdI(Ph)(PPh3)]2 to give the π-allyl palladium complexes PdI(η3-MeCHC(Ph)CHR)(PPh3) in which the R group is anti and the Me group is syn to the Ph group.

A metallanaphthalyne complex from zinc reduction of a vinylcarbyne complex

Cl prevents insertion: The first metallanaphthalyne 2 has been obtained by Zn reduction of Os carbyne complex 1. The key to its isolation was the use of o-chlorophenyl instead of phenyl substituents to avoid formation of a putative hydrido metallanaphthalyne intermediate (supported by DFT calculations), which undergoes migratory insertion of the carbyne into the OsH bond and rearrangement to give an indenyl complex as the final product.

Ligand effect on the insertion reactions of allenes with MHCl(CO)(PPh3)(3)and MHCl(PPh3)(3) (M = Ru, Os)

Treatment of RuHCl(CO)(PPh3)(3) with CH2=C=CHCO2Me gives the allyl complex Ru(77 3 -CH2CHCHCO2Me)CI(CO)(PPh3)(2). The analogous allyl complexes Os(eta(3)-CH2CHCHR)Cl(CO)(PPh3)(2) (R = Ph, CH2Ph) are also produced from the reactions of OsHCI(CO)(PPh3)(3) with CH2=C=CHR. In contrast, MHCl(PPh3)(3) (M = Ru, Os) react with CH2=C=CHR to give the vinyl complexes MCl((C(CH3)=CHR)(CH2 C=CHR)(PPh3)(2) (M = Ru, R = CMe3, M = Os, R = CMe3, Ph, CO2Et).