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.
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.
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.
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.
P-Arylation in water has been developed via cross-coupling of aryl halides with diphenylphosphine oxide (Ph2P(O)H) and (RP)-(−)-menthyl benzylphosphinate catalyzed by NiCl2·6H2O/Zn under relatively mild conditions.
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.
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)).
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.
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.
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).