Complexes of the type [VO(L)(H 2 gl)] and [VO(L)(Hpd)] have been synthesized in excellent yields by reacting bis(acetylacetonato)oxovanadium() with H 2 L in the presence of excess glycerol (H 3 gl) and propane-1,3-diol (H 2 pd) in methanol-acetone (hydroxyphenylmethylenehydrazones of 4-hydroxy-4-phenylbut-3-en-2-one, salicylaldehyde and 2-hydroxynaphthaldehyde are respectively abbreviated as H 2 L 1 , H 2 L 2 and H 2 L 3 and generally as H 2 L). The crystal structures ofϪ and [Hpd] Ϫ form fiveand six-membered V(O,O) chelate rings respectively. In the distorted octahedral VO 5 N co-ordination sphere the V᎐O (alkoxide) bond is 0.5-0.6 Å shorter than the V᎐O (alcoholic) bond which lies trans to the oxo oxygen atom. In [VO(L 2 )(Hpd)] the lattice consists of dimers held together by O ؒ ؒ ؒ N hydrogen bonding between the OH group of [Hpd] Ϫ in one molecule and the unco-ordinated [L 2 ] 2Ϫ nitrogen in an adjacent molecule. In the [VO(L 2 )(H 2 gl)] lattice such dimers self-assemble into an infinite pattern via additional O ؒ ؒ ؒ O hydrogen bonding between the unco-ordinated OH group of [H 2 gl] Ϫ of one molecule with the co-ordinated alkoxidic oxygen of the adjacent molecule. In [VO(L)(H 2 gl)] both the metal site and the [H 2 gl] Ϫ ligand are chiral and the two equally abundant diastereoisomers are present in solution ( 1 H NMR). The 51 V chemical shifts are diagnostic of the alkoxidic chelate ring size: the shifts of [VO(L)(H 2 gl)] being ≈30 ppm downfield from that of [VO(L)(Hpd)]. The complexes have low VO 3ϩ -VO 2ϩ reduction potentials.
The present report exemplifies two novel aromatic ring amination reactions via metal mediation. A rationale with respect to site selection for the above amination reactions, based on relative labilities of the coordinated coligands, has been established.
Dinuclear (V(IV)V(V)) oxophenoxovanadates of general formula [V2O3L] have been synthesized in excellent yields by reacting bis(acetylacetonato)oxovanadium(IV) with H3L in a 2:1 ratio in acetone under an N2 atmosphere. Here L3- is the deprotonated form of 2,6-bis[{{(2-hydroxybenzyl)(N',N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenol (H3L1), 2,6-bis[{{(5-methyl-2-hydroxybenzyl)(N',N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenol (H3L2), 2,6-bis[{{(5-tert-butyl-2-hydroxybenzyl)(N',N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenol (H3L3), 2,6-bis[{{(5-chloro-2-hydroxybenzyl)(N',N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenol(H3L4), 2,6-bis[{{(5-bromo-2-hydroxybenzyl)(N'N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenol (H3L5), or 2,6-bis[{{(5-methoxy-2-hydroxybenzyl)(N'N'-(dimethylamino)ethyl)}methyl]-4-methylphenol (H3L6). In [V2O3L1], both the metal atoms have distorted octahedral geometry. The relative disposition of two terminal V=O groups in the complex is essentially cis. The O=V...V=O torsion angle is 24.6(2) degrees . The V-O(oxo)-V and V-O(phenoxo)-V angles are 117.5(4) and 93.4(3) degrees , respectively. The V...V bond distance is 3.173(5) A. X-ray crystallography, IR, UV-vis, and 1H and 51V NMR measurements show that the mixed-valence complexes contain two indistinguishable vanadium atoms (type III). The thermal ellipsoids of O2, O4, C10, C14, and C15 also suggests a type III complex in the solid state. EPR spectra of solid complexes at 77 K display a single line indicating the localization of the odd electron (3d(xy)1). Valence localization at 77 K is also consistent with the 51V hyperfine structure of the axial EPR spectra (3d(xy)1 ground state) of the complexes in frozen (77 K) dichloromethane solution: S = 1/2, g(parallel) approximately 1.94, g(perpendicular) approximately 1.98, A(parallel) approximately 166 x 10(-4) cm(-1), and A(perpendicular) approximately 68 x 10(-4) cm(-1). In contrast isotropic room-temperature solution spectra of the family have 15 hyperfine lines (g(iso) approximately 1.974 and A(iso) approximately 50 x 10(-4) cm(-1)) revealing that the unpaired electron is delocalized between the metal centers. Crystal data for the [V2O3L1].CH2Cl2 complex are as follows: chemical formula, C32H43O6N4Cl2V2; crystal system, monoclinic; space group, C2/c; a = 18.461(4), b = 17.230(3), c = 13.700(3) A; beta = 117.88(3) degrees ; Z = 8.
The N4O3 coordinating heptadentate ligand afforded binuclear complex [Cu 2(H 2L)(mu-OH)](ClO4)2 (1) and [Cu2(L)(H2O)2]PF6 (2). In complex 1, two copper ions are held together by mu-phenoxo and mu-hydroxo bridges, whereas in complex 2, the copper centers are connected only by a mu-phenoxo bridge. In 1, both the Cu(II) centers have square pyramidal geometry (tau=0.01-0.205), whereas in the case of 2, one Cu(II) center has square pyramidal (tau=0.2517) and other one has square based pyramidal distorted trigonal bipyramidal (tau=0.54) geometry. Complexes 1 and 2 show an strong intramolecular and very weak antiferromagnetic interaction, respectively. Density-functional theory calculations were performed to establish the magneto structural correlation between the two paramagnetic copper(II) centers. Both of the complexes display a couple of one-electron reductive responses near -0.80 and -1.10 V. The complexes show significant catalytic activity at pH 8.5 on the oxidation of 3,5-di- tert-butylcatechol (3,5-DTBC) to 3,5-di- tert-butylquinone (3,5-DTBQ), and the activity measured in terms of kcat=29-37 h(-1).
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