High- and low-spin complexes with similar, ligands. II. Iron(II) complexes with sterically hindered analogues of 2,2'-bipyridyl

1972 ◽  
Vol 25 (8) ◽  
pp. 1631 ◽  
Author(s):  
CM Harris ◽  
S Kokot ◽  
HRH Patil ◽  
E Sinn ◽  
H Wong
Keyword(s):  
Spectral Data ◽  
High Spin ◽  
Steric Hindrance ◽  
Field Potential ◽  
Ligand Field ◽  
Apparent Difference ◽  
Field Splitting ◽  
Analogous Complex ◽  
Sterically Hindered ◽  
Direct Change

Benzo substitution cis to the nitrogen of 2,2'-bipyridyl (bipy), to form 2-(2'-pyridyl)quinoline (pq), transforms the tris-complex with iron(11) from low spin in Fe(bipy)32+ to essentially high spin but near the crossover in Fe(pq)32+. For this complex, the ligand field splitting near the crossover, Δc is estimated from magnetic and spectral data as c. 12000 cm-l. A similar value but 150 cm-l lower is estimated for the analogous complex with the sterically related ligand 2-methyl-1,10-phenanthroline. This apparent difference in Δ values could arise from a direct change in ligand field potential, or from other factors, such as a change in distortion effects. Due to steric hindrance, pq prefers to form bis-complexes Fe(pq)2X2, pseudooctahedral and high spin, with suitable monodentates, X = Cl2 Br, NCS, ClO4. Double benzo substitution of bipy to form 2,2'-biquinolyl (biq) so increases steric hindrance that the tris-complex could not be formed. Instead biq forms pseudotetrahedral complexes Fe(biq)22+ and Fe(biq)X2 (X = Cl, Br).

Ligand field transitions and the origin of zero field splitting in [PPh4][FeCl4] and [NEt4][Fe(SR)4] (R = 2,3,5,6-Me4C6H): a model for the high-spin Fe(III) site in rubredoxin

1988 ◽  
Vol 110 (18) ◽  
pp. 6241-6243 ◽  
Author(s):  
Joseph C. Deaton ◽  
Matthew S. Gebhard ◽  
Stephen A. Koch ◽  
Michelle. Millar ◽  
Edward I. Solomon
Keyword(s):  
High Spin ◽  
Ligand Field ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Field Splitting

Synthesis of Conjugated Triynes via Alkyne Metathesis

2019 ◽  
Author(s):  
Idriss Curbet ◽  
Sophie Colombel-Rouen ◽  
Romane Manguin ◽  
Anthony Clermont ◽  
Alexandre Quelhas ◽  
...  
Keyword(s):  
Steric Hindrance ◽  
High Selectivity ◽  
Alkyne Metathesis ◽  
Cross Metathesis ◽  
Synthetic Strategy ◽  
Sterically Hindered ◽  
Site Selective

<div> <div> <div> <div> <p>The synthesis of conjugated triynes by molybdenum-catalyzed alkyne metathesis is reported. Strategic to the success of this approach is the utilization of sterically-hindered diynes that allowed for the site- selective alkyne metathesis to produce the desired con- jugated triyne products. The steric hindrance of alkyne moiety was found to be crucial in preventing the for- mation of diyne byproducts. This novel synthetic strategy was amenable to self- and cross-metathesis providing straightforward access to the corresponding symmetrical and dissymmetrical triynes with high selectivity. </p> </div> </div> </div> </div>

Theory Of 3d Transition Metal Defects In 3C SiC

1996 ◽  
Vol 442 ◽  
Author(s):  
Harald Overhof
Keyword(s):  
Electronic Structure ◽  
Transition Metal ◽  
Electronic Properties ◽  
Crystal Field ◽  
High Spin ◽  
Crystal Field Splitting ◽  
Large Crystal ◽  
Field Splitting ◽  
Vacancy Model ◽  
The Difference

AbstractThe electronic properties of 3d transition metal (TM) defects located on one of the four different tetrahedral positions in 3C SiC are shown to be quite site-dependent. We explain the differences for the 3d TMs on the two substitutional sites within the vacancy model: the difference of the electronic structure between the carbon vacancy VC and the silicon vacancy VSi is responsible for the differences of the 3d TMs. The electronic properties of 3d TMs on the two tetrahedral interstitial sites differ even more: the TMs surrounded tetrahedrally by four Si atoms experience a large crystal field splitting while the tetrahedral C environment does not give rise to a significant crystal field splitting at all. It is only in the latter case that high-spin configurations are predicted.

Coordination of 2,2'-Biimidazole with Iron, Cobalt, Nickel and Copper

1979 ◽  
Vol 32 (3) ◽  
pp. 513 ◽  
Author(s):  
AS Abushamleh ◽  
HA Goodwin
Keyword(s):  
Spectral Data ◽  
High Spin ◽  
Weak Field ◽  
Trivalent Iron ◽  
Iron Cobalt ◽  
Cobalt Nickel ◽  
Bivalent Iron

Complexes of 2,2'-biimidazole with bivalent iron, cobalt, nickel and copper, and trivalent iron are described. The ligand produces a relatively weak field and all complexes are high-spin and markedly less stable than corresponding complexes of 2,2'-bipyridine or 2-(2-pyridyl)imidazole. Inner complexes, M(L-H)2, derived from the monoanion of biimidazole are also described. The complexes are characterized by magnetic and spectral data.

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