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A novel bis-1,2,4-benzothiadiazine pincer ligand: synthesis, characterization and first row transition metal complexes.

Authors :
Pringouri, Konstantina
Anwar, Muhammad U.
Mansour, Liz
Doupnik, Nathan
Beldjoudi, Yassine
Gavey, Emma L.
Pilkington, Melanie
Rawson, Jeremy M.
Source :
Dalton Transactions: An International Journal of Inorganic Chemistry; 11/28/2018, Vol. 47 Issue 44, p15725-15736, 12p
Publication Year :
2018

Abstract

Reaction of 2,6-dicyanopyridine with 2 equiv. of 2-(propylthio)benzenamine in the presence of lithium bis(trimethylsilyl)amide, followed by ring-closing oxidation with N-chlorosuccinimide affords the novel tridentate ligand, 2,6-bis-(1′,2′,4′-benzothiadiazinyl)pyridine (LH<subscript>2</subscript>). Electrochemical studies on the free ligand LH<subscript>2</subscript> reveal a single well-defined 2e<superscript>−</superscript> oxidation process with E<subscript>1/2</subscript> = +0.90 V. EPR studies of the in situ chemical oxidation of LH<subscript>2</subscript> reveal the generation of a benzotriazinyl radical. Reactions of ligand LH<subscript>2</subscript> with a range of divalent transition metal salts in either MeOH or MeCN in a 2 : 1 ratio at ambient temperatures afforded mononuclear complexes with general formula [M(LH<subscript>2</subscript>)<subscript>2</subscript>][X]<subscript>2</subscript> (M = Mn, X = CF<subscript>3</subscript>SO<subscript>3</subscript> (1); Fe, X = CF<subscript>3</subscript>SO<subscript>3</subscript> (2); Fe, X = BF<subscript>4</subscript> (3); Co, X = Cl (4); Ni, X = Cl (5); Zn, X = CF<subscript>3</subscript>SO<subscript>3</subscript> (6)) and the 1 : 1 complex [Cu(LH<subscript>2</subscript>)(NO<subscript>3</subscript>)<subscript>2</subscript>] (7). In all cases the LH<subscript>2</subscript> ligand binds in a tridentate N,N′,N′′ chelate fashion via benzothiadiazinyl N<subscript>BTDA</subscript> and pyridyl N<subscript>py</subscript> atoms. The low spin Fe<superscript>II</superscript> complexes (2 and 3) were implemented for NMR and UV-Vis solution studies of ligand reactivity as well as cyclic voltammetry which reveal two 1e-oxidation waves. The metal complexes 1–6 are discussed and reveal a range of geometries between octahedral and trigonal prismatic with the greatest deviation from octahedral symmetry apparent for ions with no crystal field stabilisation energy, i.e. d<superscript>10</superscript> Zn<superscript>II</superscript> and high spin d<superscript>5</superscript> Mn<superscript>II</superscript> ions. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
14779226
Volume :
47
Issue :
44
Database :
Complementary Index
Journal :
Dalton Transactions: An International Journal of Inorganic Chemistry
Publication Type :
Academic Journal
Accession number :
132994677
Full Text :
https://doi.org/10.1039/c8dt03346c