MO study of Td-D4h equilibrium in complexes of transition metals. Equilibrium in tetrachloro complexes of atoms of the first transition row

1982 ◽  
Vol 47 (6) ◽  
pp. 1556-1569 ◽  
Author(s):  
Petr Pelikán ◽  
Marek Liška
Keyword(s):  
Experimental Data ◽  
Electronic Structure ◽  
Chemical Reactions ◽  
Central Atom ◽  
Equilibrium Constants ◽  
Cndo Method ◽  
Oxidation Degree ◽  
Square Planar ◽  
Complexes Of Transition Metals ◽  
Square Planar Complexes

The CNDO method in UHF version has been used for study of equilibrium of configuration isomers of tetrahedral and square-planar tetrachloro complexes of the first transition row atoms in the oxidation degree II (Mn(II), Fe(II), Co(II), Ni(II), Cu(II)). From the results it follows that the ability (conditioned by electronic structure of the central atom) to form the square-planar complexes decreases in the series Mn(II) > Fe(II) > Co(II) > Ni(II) > Cu(II). Several authors state the fact that the most important task of quantum chemistry is to develop procedures for calculation of rate and equilibrium constants of chemical reactions1,2. At the same time it is emphasized that these procedures should be independent of experimental data. By this term the authors mean such experimental data which are in some way connected with the reaction studied, and not the general experimental experience which (after transformation into axioms) can represent a basis of the used method.

MO study of Td-D4h equilibrium in complexes of transition metals. II. Equilibrium in tetrafluoro and tetrabromo complexes of atoms of the first transition row

1984 ◽  
Vol 49 (12) ◽  
pp. 2837-2856 ◽  
Author(s):  
Peter Pelikán ◽  
Marek Liška
Keyword(s):  
Electronic Structure ◽  
Transition Metals ◽  
Central Atom ◽  
Spin States ◽  
Cndo Method ◽  
Oxidation Degree ◽  
High Spin States ◽  
Square Planar ◽  
Complexes Of Transition Metals ◽  
Square Planar Complexes

The CNDO method for transition metals in the UHF version has been used to study the equilibrium of configuration isomers of tetrahedral and square-planar tetrafluoro and tetrabromo complexes of the first transition row atoms in the oxidation degree II (Mn(II), Fe(II), Co(II), Ni(II), Cu(II) both in low-spin and in high-spin states. The results show that the ability (given by electronic structure of the central atom) to form the square-planar complexes decreases monotonously in the series: Mn(II) > Fe(II) > Co(II) > Ni(II) > Cu(II). With respect to the effect of the electronic structure of ligands, the same ability decreases in the series: F- > Cl- > Br-.

π-BONDING IN INORGANIC COMPOUNDS: II. THE TRANSMISSION OF ELECTRONIC EFFECTS THROUGH SQUARE-PLANAR COMPLEXES

1961 ◽  
Vol 39 (2) ◽  
pp. 324-330 ◽  
Author(s):  
A. D. Westland ◽  
L. Westland
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Central Atom ◽  
Inorganic Compounds ◽  
Electron Drift ◽  
Electronic Effects ◽  
Trans Effect ◽  
Pyridine Ligands ◽  
Square Planar ◽  
In Trans ◽  
Square Planar Complexes

Measurement of the transmission of electronic effects through square-planar complexes of platinum has provided evidence of double bonding to halogen and nitro ligands. The nuclear magnetic resonance chemical shift of the β-protons in pyridine ligands serves as an indicator of electron drift in the complexes. Justification is thus provided for the assumed mechanism of the trans effect involving π-bonding. The observations are in accord with the assumption that the increase in trans-directing powers with atomic number of the halogen is due to an increasing tendency to accept d-electrons from the central atom.

The exchange of pyridine on bis-pyridine adducts of square-planar nickel(II) complexes containing dithiocarbamate, xanthate, dithiophosphate and monothioacetylacetonate ligands. A nitrogen-14 magnetic resonance study

1983 ◽  
Vol 36 (10) ◽  
pp. 2019 ◽  
Author(s):  
J Sachinidis ◽  
MW Grant
Keyword(s):  
Magnetic Resonance ◽  
Equilibrium Constants ◽  
Substituent Effects ◽  
Adduct Formation ◽  
Lewis Acidity ◽  
Magnetic Resonance Study ◽  
Square Planar ◽  
Square Planar Complexes ◽  
The Relationship

14N n.m.r. has been used to measure the rates of pyridine exchange of a series of bis pyridine adducts of square-planar nickel(II) complexes containing dithiocarbamate, xanthate, dithiophosphate and monothioacetylacetonate ligands. Substantial variations in the lability of the coordinated pyridine are observed, k,, at 298 K varying from about 103 to 107 s-1. In the monothioacetylacetonate series the lability of pyridine decreases as the electron withdrawing power of the substituents increases. Both the lability and the sensitivity to substituent effects are greater than for the analogous acetylacetonate derivatives. The relationship between the intrinsic Lewis acidity of the nickel(II) centre in the parent square-planar complexes as measured by equilibrium constants for bis pyridine adduct formation and the lability of pyridine in the adducts is explored.

A Nuclear Magnetic Resonance Study of the Conformation of Six-membered Chelate Rings in Four-coordinate Complexes

1975 ◽  
Vol 53 (3) ◽  
pp. 366-372 ◽  
Author(s):  
William R. Cullen ◽  
Laurance D. Hall ◽  
John T. Price ◽  
Gregory Spendjian
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Central Atom ◽  
Nuclear Magnetic Resonance Study ◽  
Dihedral Angles ◽  
Group Viii ◽  
Magnetic Resonance Study ◽  
Square Planar ◽  
Square Planar Complexes ◽  
Chelate Rings

The ditertiary arsine (CH3)2AsCH2CH(C(CH3)3)CD2As(CH3)2 (L–L) forms 'tetrahedral' (L–L)Ni(CO)2 and square planar (L–L)NiOC(CF3)2C(CF3)2O. In both complexes the conformations of the chelate rings are locked with the t-butyl groups equatorial. The dihedral angles are very similar in spite of the anticipated differences in angles at the central atom. The square planar complexes (L–L)′PtbipyCl2 and (L–L)2′PtCl2 and their palladium analogs ((L–L)′ = H2NCH2CH(C(CH3)3)CD2NH2) also have their chelate rings in locked chair conformations. This results in the identification of isomers in the case of (L–L)2′M2+. The 3JH–H couplings indicate that the dihedral angles are similar in the group VIII complexes with a degree of puckering which could be less than in related complexes of L–L. The 3JPt–H couplings indicate changes in the puckering about the N … N axis.

Electronic Structure Benchmark Calculations of Inorganic and Biochemical Carboxylation Reactions

2018 ◽  
Author(s):  
Oscar A. Douglas-Gallardo ◽  
David A. Sáez ◽  
Stefan Vogt-Geisse ◽  
Esteban Vöhringer-Martinez
Keyword(s):  
Electronic Structure ◽  
Chemical Reactions ◽  
Density Functional ◽  
Correlation Energy ◽  
Electronic Energy ◽  
Basis Sets ◽  
Electronic Correlation ◽  
Correct Description ◽  
Carbon Dioxide Co2 ◽  
High Level

<div><div><div><p>Carboxylation reactions represent a very special class of chemical reactions that is characterized by the presence of a carbon dioxide (CO2) molecule as reactive species within its global chemical equation. These reactions work as fundamental gear to accomplish the CO2 fixation and thus to build up more complex molecules through different technological and biochemical processes. In this context, a correct description of the CO2 electronic structure turns out to be crucial to study the chemical and electronic properties associated with this kind of reactions. Here, a sys- tematic study of CO2 electronic structure and its contribution to different carboxylation reaction electronic energies has been carried out by means of several high-level ab-initio post-Hartree Fock (post-HF) and Density Functional Theory (DFT) calculations for a set of biochemistry and inorganic systems. We have found that for a correct description of the CO2 electronic correlation energy it is necessary to include post-CCSD(T) contributions (beyond the gold standard). These high-order excitations are required to properly describe the interactions of the four π-electrons as- sociated with the two degenerated π-molecular orbitals of the CO2 molecule. Likewise, our results show that in some reactions it is possible to obtain accurate reaction electronic energy values with computationally less demanding methods when the error in the electronic correlation energy com- pensates between reactants and products. Furthermore, the provided post-HF reference values allowed to validate different DFT exchange-correlation functionals combined with different basis sets for chemical reactions that are relevant in biochemical CO2 fixing enzymes.</p></div></div></div>

Voltammetric Studies of Some Novel Fe(III) Complexes with Quadridentate Ligands. The Axial Ligand-Exchange Reactions in DMF and DMSO

1995 ◽  
Vol 60 (7) ◽  
pp. 1140-1157 ◽  
Author(s):  
Ljiljana S. Jovanovic ◽  
Luka J. Bjelica
Keyword(s):  
Oxidation State ◽  
Chemical Reactions ◽  
Ligand Exchange ◽  
Kinetic Data ◽  
Central Atom ◽  
Axial Ligand ◽  
Exchange Reactions ◽  
Ligand Effect ◽  
Condensation Products ◽  
Voltammetric Studies

The electrochemistry of four novel Fe(III) complexes of the type [Fe(L)Cl], involving quadridentate ligands based on the condensation products of benzoylacetone-S-methylisothiosemicarbazone with salicylaldehyde, 5-chlorosalicylaldehyde, 3,5-dichlorosalicylaldehyde or 5-nitrosalicylaldehyde, was studied in DMF and DMSO at a GC electrode. All complexes undergo a two-step one-electron reductions, usually complicated by chemical reactions. In solutions containing Cl-, the ligand-exchange reactions Cl--DMF and Cl--DMSO take place. Stability of the chloride-containing complexes was discussed in terms of the coordinated ligand effect, oxidation state of the central atom and, in particular, of the donor effect of the solvent. Some relevant kinetic data were calculated.

Chlorine nuclear quadrupole resonance in some chloro complexes of divalent copper

1971 ◽  
Vol 24 (10) ◽  
pp. 1993 ◽  
Author(s):  
DE Scaife
Keyword(s):  
Nuclear Quadrupole Resonance ◽  
Covalent Bonding ◽  
Divalent Copper ◽  
Chloro Complexes ◽  
35Cl Nucleus ◽  
Square Planar ◽  
Bonding Interaction ◽  
Quadrupole Resonance ◽  
Square Planar Complexes ◽  
Nuclear Quadrupole

Nuclear quadrupole resonance for the 35Cl nucleus has been observed in some chloro complexes of divalent copper. Square-planar complexes each show two resonance lines, with the following frequencies (at 77�K): (CH3NH3)2CuCl4, 10.780, 12.157 MHz; (C2H5NH3)2CuCl4, 10.817, 12.074 MHz; (enH2)CuCl4, 10.271, 11.901 MHz; and (C3H7NH3)2CuCl4 at 223�K, 11.290 and 11.781 MHz. NH4CuCl3, containing dimeric Cu2Cl62- units, has resonances, at 77�K, at 11.907, 11.993, and 12.448 MHz. The trigonal pyramidal anion in Co(NH3)6CuCl5 has two resonances at 9.642 and 10.352 MHz at 77�K. ��� These results are compared with previous results for copper chloro complexes, and the implications of covalent bonding are discussed. In particular, it is suggested that the long-bond interaction between units in square-planar complexes amounts to 7-16% of the bonding interaction within the units.

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