English
 
Help Privacy Policy Disclaimer
  Advanced SearchBrowse

Item

ITEM ACTIONSEXPORT
  Square Planar vs Tetrahedral Coordination in Diamagnetic Complexes of Nickel(II) Containing Two Bidentate π-Radical Monoanions

Blanchard, S., Neese, F., Bothe, E., Bill, E., Weyhermüller, T., & Wieghardt, K. (2005). Square Planar vs Tetrahedral Coordination in Diamagnetic Complexes of Nickel(II) Containing Two Bidentate π-Radical Monoanions. Inorganic Chemistry, 44(10), 3636-3656. doi:10.1021/ic040117e.

Item is

Basic

show hide
Genre: Journal Article

Files

show Files

Locators

show

Creators

show
hide
 Creators:
Blanchard, Sebastian1, Author              
Neese, Frank1, Author              
Bothe, Eberhard1, Author              
Bill, Eckhard1, Author              
Weyhermüller, Thomas1, Author              
Wieghardt, Karl1, Author              
Affiliations:
1Research Department Wieghardt, Max Planck Institute for Bioinorganic Chemistry, Max Planck Society, ou_3023881              

Content

show
hide
Free keywords: -
 Abstract: The reaction of three different 1-phenyl and 1,4-diphenyl substituted S-methylisothiosemicarbazides, H2[L1-6], with Ni(OAc)2·4H2O in ethanol in the presence of air yields six four-coordinate species [Ni(L1-6•)2] (1−6) where (L1-6•)1- represent the monoanionic π-radical forms. The crystal structures of the nickel complexes with 1-phenyl derivatives as in 1 reveal a square planar structure trans-[Ni(L1-3•)2], whereas the corresponding 1,4-diphenyl derivatives are distorted tetrahedral as is demonstrated by X-ray crystallography of [Ni(L5•)2] (5) and [Ni(L6•)2] (6). Both series of mononuclear complexes possess a diamagnetic ground state. The electronic structures of both series have been elucidated experimentally (electronic spectra magnetization data). The square planar complexes 1−3 consist of a diamagnetic central Ni(II) ion and two strongly antiferromagnetically coupled ligand π-radicals as has been deduced from correlated ab initio calculations; they are singlet diradicals. The tetrahedral complexes 4−6 consist of a paramagnetic high-spin NiII ion (SNi = 1), which is strongly antiferromagnetically coupled to two ligand π-radicals. This is clearly revealed by DFT and correlated ab initio calculations. Electrochemically, complexes 1−6 can be reduced to form stable, paramagnetic monoanions [1−6]- (S = 1/2). The anions [1−3]- are square planar Ni(II) (d,8 SNi = 0) species where the excess electron is delocalized over both ligands (class III, ligand mixed valency). In contrast, one-electron reduction of 4, 5, and 6 yields paramagnetic tetrahedral monoanions (S = 1/2). X-band EPR spectroscopy shows that there are two different isomers A and B of each monoanion present in solution. In these anions, the excess electron is localized on one ligand [NiII(L4-6•)(L4-6)]- where (L4-6)2- is the closed shell dianion of the ligands H2[L4-6] as was deduced from their electronic spectra and broken symmetry DFT calculations. Oxidation of 1 and 5 with excess iodine yields octahedral complexes [NiII(L1,ox)2I2] (7), [NiII(L1,ox)3](I3)2 (8), and trans-[NiII(L5,ox)2(I3)2] (9), which have been characterized by X-ray crystallography; (L1-6,ox) represent the neutral, two-electron oxidized forms of the corresponding dianions (L1-6)2-. The room-temperature structures of complexes 1, 5, and 7 have been described previously in refs 1−5.

Details

show
hide
Language(s): eng - English
 Dates: 2004-10-182005-04-162005-05-01
 Publication Status: Published in print
 Pages: 21
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1021/ic040117e
 Degree: -

Event

show

Legal Case

show

Project information

show

Source 1

show
hide
Title: Inorganic Chemistry
  Abbreviation : Inorg. Chem.
Source Genre: Journal
 Creator(s):
Affiliations:
Publ. Info: Washington, DC : American Chemical Society
Pages: - Volume / Issue: 44 (10) Sequence Number: - Start / End Page: 3636 - 3656 Identifier: ISSN: 0020-1669
CoNE: https://pure.mpg.de/cone/journals/resource/0020-1669