Can Tetrylone Act in a Similar Fashion to Tetrylene in Ni(CO)2 Complexes? A Theoretical Study based on a Comparison using DFT Calculations

A comparison was made to investigate the structures and bonding of nickel complex that carry tetrylone and tetrylene ligands [(CO)₂Ni‐{E(PH₃)₂}] ( Ni1E ) and [(CO)₂Ni‐{NHE_Me}] ( Ni2E ) (E = C to Pb) using quantum chemical calculations at the BP86 level with various basis sets (SVP, TZVPP, TZ2P+). The nature of the Ni–E bonds was analyzed with charge‐ and energy decomposition methods. The structures of tetrylone complexes Ni1E exhibit an interesting trend with the ligands E(PH₃)₂ are bonded in a tilted orientation relative to the fragment Ni(CO)₂. In contrast, the calculated equilibrium structures of complexes Ni2E exhibit the NHE_Me ligands (E = C to Sn) bonded in a head‐on way to the Ni(CO)₂ fragment, while the bending angle gives the strongest side‐on bonded ligand NHPb_Me when E = Pb. The interesting trend of the bond dissociation energy (BDE) is observed for the tetrylone, which has the same trend BDEs compared with tetrylene complexes. The EDA‐NOCV results indicate that the tetrylone ligands {E(PH₃)₂} in complexes are similar to the tetrylene ligands NHE_Me as strong σ‐donors and weak π‐acceptors. The BDEs calculated for the Ni–E bonds in Ni1E and Ni2E show that the effect of bulky ligands may obscure the intrinsic Ni–E bond strength. The bonding analysis shows that the tetrylone ligands in Ni1E may act in a similar fashion to the tetrylene ligands in Ni2E . All complexes Ni1E and Ni2E are suitable targets for synthesis.     

Rh(I)-catalyzed ring-opening of hetaryne-furan Diels-Alder adducts: rapid access to stereochemically defined heterocyclic scaffolds

Probing the nucleophilic ring-opening of various bicyclic [2.2.1] hetaryne-furan Diels-Alder adducts revealed that efficient reactivity could be observed with heteroatom nucleophiles by using a cationic Rh(I) complex in combination with a chiral Josiphos-type phosphine ligand. Remarkably, this catalyst system was not impeded by the incorporation of a heteroatom into the substrate. Racemic materials afforded separable mixtures of enantioenriched regioisomers, indicating that strong reagent control is operative.     

Detection of point-like scatterers using one type of scattered elastic waves

In this paper, we are concerned with the detection of point-like obstacles using elastic waves. We show that one type of waves, either the P or the S scattered waves, is enough for localizing the points. We also show how the use of S incident waves gives better resolution than the P waves. These affirmations are demonstrated by several numerical examples using a MUSIC type algorithm.     

Remarkable shifts of Csp2-H and O-H stretching frequencies and stability of complexes of formic acid with formaldehydes and thioformaldehydes

Thirty-six stable complexes of formic acid with formaldehydes and thioformaldehydes were determined on the potential energy surface, in which the XCHO···HCOOH complexes are found to be more stable than the XCHS···HCOOH counterparts, with X = H, F, Cl, Br, CH₃, NH₂. All complexes are stabilized by hydrogen bonds, and their contribution to the total stabilization energy of the complexes increases in going from C-H···S to C-H···O to O-H···S and finally to O-H···O. Remarkably, a significant blueshift of C_sp2-H bond by 81–96 cm⁻¹ in the C_sp2-H···O hydrogen bond has hardly ever been reported, and a considerable redshift of O-H stretching frequency by 206–544 cm⁻¹ in the O-H···O/S hydrogen bonds is also predicted. The obtained results in our present work and previous literatures support that a distance contraction and a stretching frequency blueshift of C-H bond involving hydrogen bond depend mainly on its polarity and gas phase basicity of proton acceptor, besides the rearrangement of electron density due to complex formation. Markedly, we suggest the ratio of deprotonation enthalpy to proton affinity (R _c) as an indicator to prospect for classification of hydrogen bonds. The symmetry adapted perturbation theory results show a larger role of attractive electrostatic term in XO-n as compared to that in XS-n and the electrostatic interaction is overwhelming dispersion or induction counterparts in stabilizing XO-n and XS-n , with n = 1, 2, 3. © 2019 Wiley Periodicals, Inc.     

Asymptotic linear bounds for the Castelnuovo-Mumford regularity

We prove asymptotic linear bounds for the Castelnuovo-Mumford regularity of certain filtrations of homogeneous ideals whose Rees algebras need not be Noetherian.

     

Über allgemeine Hyperflächenschnitte einer algebraischen Varietät

LetV/k be an irreducible algebraic variety over a fieldk in an affinen-space andF _u a generic hypersurface defined byu ₁ f ₁ (X)+...+u r f _r(X)=0, whereu ₁...,u _r are indeterminates overk andf ₁(X), ...,f _r(X) are polynomials ink[X ₁, ...,X _n]. Let (E) be a property which an arbitrary algebraic variety could have, e. g. irreducibility, normality (local or global), ... Then it will be studied under which conditions off ₁(X), ...,f _r(X) (E) may be transfered fromV/k toVF _u /k(u) (and conversely).