192229-09-7Relevant academic research and scientific papers
Variable-Valent Re≡NAr Species. A Family of ReVINAr Amide Complexes and Their RevNAr Imine Precursors Related by Oxygen Atom Transfer
Dirghangi, Bimal Kumar,Menon, Mahua,Banerjee, Sangeeta,Chakravorty, Animesh
, p. 3595 - 3601 (2008/10/09)
Imide complexes of type RevCl3(X-SB)(NC6H4Y(p)), with X, Y= H, Me, OMe, Cl have been synthesized where X-SB is the Schiff base of pyridine-2-carboxaldehyde (the corresponding complex is 4), 2-acetylpyridine (5), 2-benzoylpyridine (6), and anilines, p-XC6H4NH2. Treatment of 4 or 5 (but not 6) with aqueous nitric acid in acetonitrile afforded ReVICl3(X-PA)(NC6H4Y(p)), 7, via oxygen atom transfer (X-PA -monoanionic picolinamide). In the structures of 5(X=C1,Y=C1), 6(OMe,OMe), and 7(Me,Me), the chlorine atoms are meridionally disposed in a ReCl3N3 coordination sphere. The trans influence of the imide nitrogen considerably lengthens the ReN(pyridine) bond. The ReNC6H4Y(p) group has the triple-bonded linear moiety, Re≡N-C. The amide group in 7(Me,Me) is planar. In 6(OMe,OMe) the two aryl rings on the imine function block water attack and hence amide formation. The rhenium(VI)-rhenium(V) E1/2 values for 4-6 (0.7-1,0 V vs SCE) are much higher than that for 7 (E1/2 ～ 0.15 V), which displays the rhenium(VH)-rhenium(VI) couple near 1.6 V. Six EPR hyperfine lines are observed for solutions of 7 at room temperature (giso ～ 1.91 ; Aav ～ 490 G). Crystal data for the complexes are as follows: 5(C1,C1), empirical formula C19H15Cl5N3Re, crystal system monoclinic, space group P21/c, a = 13.360(6) ?, b = 12.110(3) ?, c = 14.954(9) ?, β= 111.41(4)°, V = 2252.4(1.7) ?3,Z = 4; 6(OMe,OMe), empirical formula C26H23Cl3N3O2Re, crystal system orthorhombic, space group Pbca, a = 12.079(5) ?, b = 17.083(9) ?, c = 26.049(9) ?, V = 5375.4(4.0) ?3, Z = 8; 7(Me,Me), empirical formula C20H18Cl3N3ORe, crystal system monoclinic, space group P21/c, a = 7.071(2) ?, b = 17.541(6) ?, c = 16.857(8) ?, β= 100.59(3)°, V = 2055.3(1.3) ?3, Z = 4.
Pyridine-2-carboxamide complexes of arylimidorhenium(VI) derived from 2-pyridylmethyleneamine complexes of arylimidorhenium(V) via oxygen-atom transfer
Banerjee, Sangeeta,Dirghangi, Bimal Kumar,Menoh, Mahua,Pramanik, Amitava,Chakravorty, Animesh
, p. 2149 - 2153 (2007/10/03)
Complexes of type [ReVL(NC6H4Y-p)Cl3] (Y = H or Cl) have been synthesized where L is the Schiff base formed from pyridine-2-carbaldehyde and the aniline p-XC6H4NH2 (X = Me or Cl). Treatment with aqueous nitric acid in acetonitrile converts them into [ReVIL′(NC6H4Y-p)Cl3], where L′ is a monoanionic pyridine-2-carboxamide. The latter complexes display hyperfine-split six-line solution EPR spectra at room temperature. The crystal structures of [ReL(NC6H4Cl)Cl3] and [ReL′(NC6H4Cl)Cl3] (X = Me in both cases) revealed the presence of severely distorted and meridionally configured ReCl3N3 co-ordination spheres. The effective metal radius decreases only marginally upon metal oxidation and the imide fragment is approximately linear and triple bonded, Re≡N-C, in both cases. The rhenium(VI)-rhenium(V) reduction potentials in the two types of complex are ≈1.0 and ≈0.2 V respectively.
