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.

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.

A spectroscopic study of sulphide, selenide, and telluride complexes of palladium(II) and mercury(II)

1973 ◽  
Vol 26 (12) ◽  
pp. 2615 ◽  
Author(s):  
JE Fergusson ◽  
KS Loh
Keyword(s):  
Low Temperature ◽  
Low Frequency ◽  
Temperature Inversion ◽  
Spectroscopic Techniques ◽  
Electronic Effects ◽  
Sulphur Atom ◽  
Spectral Bands ◽  
Bonding System ◽  
Square Planar ◽  
Square Planar Complexes

trans-Square planar complexes of the type PdX2L2 (X = Cl, Br, I, NO3, NO2 and L = R2S, Et2Se, Et2Te, PhRS, PhEtSe) have been prepared and studied using low-frequency i.r., 1H N.M.R., and u.v.-visible spectroscopic techniques. The i.r. and u.v.-visible spectral bands have been assigned. The 1H N.M.R. spectra have proved informative in separating out the different electronic effects transmitted through both the bonding system as well as through space. Evidence for low temperature inversion about the pyramidal sulphur atom has been obtained for a number of complexes. The dimeric, halogen-bridged mercury(II) complexes [HgX2L]2 (X = Cl, Br; L = R2S Et2S, Et2Te and X = I; L = Et2Se) have been isolated and studied in a similar manner.

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-.

The trans influence of F, Cl, Br and I ligands in a series of square-planar Pd(II) complexes. Relative affinities of halide anions for the metal centre in trans-[(Ph3P)2Pd(Ph)X]

1998 ◽  
Vol 280 (1-2) ◽  
pp. 87-98 ◽  
Author(s):  
Jeffrey P. Flemming ◽  
Mark C. Pilon ◽  
Oleg Ya. Borbulevitch ◽  
Mikhail Yu. Antipin ◽  
Vladimir V. Grushin
Keyword(s):  
Metal Centre ◽  
Trans Influence ◽  
Halide Anions ◽  
Square Planar ◽  
In Trans

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.

Extended X-ray absorption fine structure and multiple-scattering simulation of nickel dithiolene complexes Ni[S2C2(CF3)2]2n(n= −2, −1, 0) and an olefin adduct Ni[S2C2(CF3)2]2(1-hexene)

2015 ◽  
Vol 22 (1) ◽  
pp. 124-129 ◽  
Author(s):  
Weiwei Gu ◽  
Hongxin Wang ◽  
Kun Wang
Keyword(s):  
Fine Structure ◽  
Multiple Scattering ◽  
Edge Structure ◽  
X Ray ◽  
Absorption Fine ◽  
Square Planar ◽  
Square Planar Complexes ◽  
Uv Visible ◽  
Edge Features ◽  
X Ray Absorption

A series of Ni dithiolene complexes Ni[S2C2(CF3)]2n(n= −2, −1, 0) (1,2,3) and a 1-hexene adduct Ni[S2C2(CF3)2]2(C6H12) (4) have been examined by NiK-edge X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine-structure (EXAFS) spectroscopies. Ni XANES for1–3reveals clear pre-edge features and approximately +0.7 eV shift in the NiK-edge position for `one-electron' oxidation. EXAFS simulation shows that the Ni—S bond distances for1,2and3(2.11–2.16 Å) are within the typical values for square planar complexes and decrease by ∼0.022 Å for each `one-electron' oxidation. The changes in NiK-edge energy positions and Ni—S distances are consistent with the `non-innocent' character of the dithiolene ligand. The Ni—C interactions at ∼3.0 Å are analyzed and the multiple-scattering parameters are also determined, leading to a better simulation for the overall EXAFS spectra. The 1-hexene adduct4presents no pre-edge feature, and its NiK-edge position shifts by −0.8 eV in comparison with its starting dithiolene complex3. Consistently, EXAFS also showed that the Ni—S distances in4elongate by ∼0.046 Å in comparison with3. The evidence confirms that the neutral complex is `reduced' upon addition of olefin, presumably by olefin donating the π-electron density to the LUMO of3as suggested by UV/visible spectroscopy in the literature.

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