Chelated fluoroboron cations. III. Spectroscopic evidence for ring size and steric limitations to chelate formation by amine chelating donors

2001 ◽  
Vol 79 (4) ◽  
pp. 426-436 ◽  
Author(s):  
J Stephen Hartman ◽  
James AW Shoemaker
Keyword(s):  
Mass Spectrometry ◽  
Nmr Spectroscopy ◽  
Fast Atom Bombardment ◽  
Ring Size ◽  
Chelating Ligands ◽  
Factors Affecting ◽  
Spectroscopic Evidence ◽  
Chelate Formation ◽  
Amine Ligands ◽  
Chelate Rings

Factors affecting the ability of potentially chelating amine ligands to form chelated fluoroboron cations are explored by 19F and 11B NMR spectroscopy and fast atom bombardment mass spectrometry (FAB-MS). Five-membered chelate rings form much more readily than six-membered. Some potentially chelating ligands give rise to additional fluoroboron species by various redistribution and decomposition reactions.Key words: chelated fluoroboron cations, 19F NMR, 11B NMR; FAB-MS, N,N,N',N'-tetraethylethylenediamine.

Chelated fluoroboron cations. I. Synthesis and NMR studies involving the tertiary-amine ligands N,N,N',N'-tetramethylethylenediamine and N,N,N',N",N''-pentamethyldiethylenetriamine

1999 ◽  
Vol 77 (11) ◽  
pp. 1856-1868 ◽  
Author(s):  
James AW Shoemaker ◽  
J Stephen Hartman
Keyword(s):  
Mass Spectrometry ◽  
Chemical Shifts ◽  
Chelating Ligands ◽  
Donor Molecule ◽  
Nmr Studies ◽  
Fab Mass Spectrometry ◽  
Methods Of Synthesis ◽  
Amine Ligands ◽  
Positive Ion ◽  
Nmr Signals

Several possible methods of synthesis of chelated fluoroboron cations are explored, using the tert-amines N,N,N',N'-tetramethylethylenediamine (Me4en) and N,N,N',N",N"-pentamethyldiethylenetriamine (Me5dien) as model chelating ligands. Both ligands displace pyridine from (pyr)2BF2+ (as its PF6- salt) to form the bidentate (Me4en)BF2+ and (Me5dien)BF2+ cations. The same cations, as well as the corresponding BFCl+ and BFBr+ cations, can also be prepared by displacement of the donor molecule (D = pyridine or isoxazole) and the heavy halide ion (Cl- or Br-) from the neutral D·BF2X and D·BFX2 adducts. The central nitrogen of Me5dien becomes chiral when it and one terminal nitrogen are coordinated, and the prochiral and magnetically nonequivalent fluorines of (Me5dien)BF2+ give 19F NMR signals separated by 1.2 ppm. In (Me5dien)BFCl+ the boron is a second chiral centre and the two diastereomers, distinguishable by NMR with 19F chemical shifts differing by 3.0 ppm, form in a 3:1 ratio. The bidentate BFBr+ cations of Me4en and Me5dien are insoluble in non-coordinating solvents but have been detected by positive ion FAB mass spectrometry and 11B MAS NMR. The tridentate complex (Me5dien)BF+2 does not form under our conditions.Key words: N,N,N',N'-tetramethylethylenediamine, N,N,N',N",N"- pentamethyldiethylenetriamine, chelated fluoroboron cations, fluorine-19 NMR, boron-11 NMR, pyridine, isoxazole, chiral, magnetically nonequivalent.

Synthesis and Caracterization of some New 1H-3-aryl-7-etoxycarbonyl-6-methyl-pyrazolo[5,1-c][1,2,4]triazoles

2008 ◽  
Vol 59 (1) ◽  
pp. 41-44
Author(s):  
Maria-Daniela Sofei ◽  
Maria Ilici ◽  
Valentin Badea ◽  
Carol Csunderlik ◽  
Vasile-Nicolae Bercean
Keyword(s):  
Mass Spectrometry ◽  
Acetic Acid ◽  
Nmr Spectroscopy ◽  
Sodium Acetate ◽  
Glacial Acetic Acid ◽  
Ir And Nmr Spectroscopy

The synthesis of 1H-3-aryl-7-ethoxycarbonyl-6-methyl-pyrazolo[5,1-c][1,2,4]triazoles (2) was carried out by cyclization of 1H-5-arylidenehydrazino-4-ethoxycarbonyl-3-methyl-pyrazoles (1) in the presence of bromine using glacial acetic acid as solvent and sodium acetate as base. The new nine obtained compounds were characterized by IR and NMR spectroscopy and mass spectrometry.

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