Ajay Pal Singh Pannu

Syntheses and structures of cobalt(II), nickel(II), and copper(II) complexes with N,N,N′,N′-tetraalkylpyridine-2,6-dicarboxamides (O-daap) containing nitrate as the counter ion

Reactions of M(NO3)2 · xH2O [M = Co(II), Ni(II), and Cu(II)] with N,N,N′,N′-tetraalkylpyridine-2,6-dicarboxamides(O-daap) in CH3CN yield [Co(O-dmap)(NO3)2] (1), [Co(O-deap)(NO3)2] (2), [Co(O-dpap)(NO3)2] (3), [Ni(O-dmap)(H2O)3](NO3)2] (4), [Ni(O-deap)(H2O)2(NO3)](NO3)] (5), [Cu(O-deap)(NO3)2] (6), and [Cu(O-dpap)(NO3)2] (7). X-ray crystal structures of 1, 2, 4, 5, and 7 reveal that O-daap ligands coordinate tridentate to each metal, O–N–O, with nitrate playing a vital role in molecular and crystal structures of all the complexes. The coordination geometry in the two Co(II) complexes, 1 and 2, is approximately pentagonal bipyramidal with nitrate bonded in a slightly unsymmetrical bidentate chelating mode. [Ni(dmap)(H2O)3](NO3)2 (4) and [Ni(deap)(H2O)2(NO3)](NO3) (5) exhibit octahedral geometry, the former containing uncoordinated nitrate while the latter has one nitrate coordinated unidentate and the other nitrate outside the coordination sphere. The Cu(II) in [Cu(dpap)(NO3)2] (7) occupies a distorted square pyramidal geometry and is linked to two unidentate nitrates, although one nitrate is also involved in a weak interaction with the metal through its other oxygen. IR spectra and other physical studies are consistent with their crystal structural data. O-dmap = N,N,N′,N′-tetramethylpyridine-2,6-dicarboxamides; O-deap = N,N,N′,N′-tetraethylpyridine-2,6-dicarboxamides; and O-dpap = N,N,N′,N′-tetraisopropylpyridine-2,6-dicarboxamides.

A self assembled 3-D network propagated by coordination polymerization and H-bonding: synthesis and X-ray crystal structure of [{Co(L)2(H2O)2}(ClO4)2(CH3COCH3)2(H2O)2] n , where L = N,N-diisopropylisonicotinamide

Reaction of Co(ClO4)2 · 6H2O with N,N-diisopropylisonicotinamide (L) has yielded a 1-D coordination polymer [{Co(L)2(H2O)2}(ClO4)2(CH3COCH3)2(H2O)2] n (1). Complex 1 has been characterized by infrared (IR) and UV-Vis spectroscopies, thermal analysis, and single crystal X-ray diffraction techniques. The structure has alternate arrangement of parallel 1-D cationic metal-ligand chains and H-bonded anionic chains containing perchlorate, acetone and water in the lattice. Further hydrogen bonding among both chains leads to formation of 2-D networks along almost perpendicular planes. Interpenetrations of such perpendicular 2-D sheets create a 3-D supramolecular structure.

Syntheses and X-ray crystal structures of five- and six-coordinate copper(II) complexes of N,N,N′,N′-tetraalkylpyridine-2,6-dicarboxamides containing–OClO3 and–OSO2CF3 counter ions

Reactions of anhydrous copper(II) chloride with NaX (1 : 1 or 1 : 2) and AgX (1 : 2) containing appropriate N,N,N′,N′-tetraalkylpyridine-2,6-dicarboxamides(O-daap) in CH3CN yield monosubstituted five-coordinate [Cu(L1)Cl(CF3SO3)] (1), [Cu(L2)Cl(ClO4)] (2), [Cu(L3)Cl(ClO4)] (3), and six-coordinate [Cu(L2)(CF3SO3)2] · H2O (4) (X = −OClO3 and–OSO2CF3; L1 = N,N,N′,N′-tetraethylpyridine-2,6-dicarboxamides; L2 = N,N,N′,N′-tetraisopropylpyridine-2,6-dicarboxamides; L3 = N,N,N′,N′-tetraisobutylpyridine-2,6-dicarboxamides). The structures of these complexes have been determined by X-ray crystallography. The Cu2+ in 1–3 adopts distorted square-pyramidal geometry, while 4 exhibits octahedral structure. Steric factors in conjunction with lattice effects and the nature of the anions are responsible for the variety in coordination spheres. These compounds undergo extensive intermolecular H-bonding to give to 2-D sheets extending along various planes.

Entrapment and kinetic resolution of stabilized axial and equatorial conformers of spiro-β-lactams.

The facile synthesis of the stabilized axial and equatorial conformers of spiro-β-lactams was achieved via entrapment of cyclohexanone imines (Schiff bases) with acetoxyacetyl chloride in a [2 + 2]-cycloaddition reaction followed by their kinetic resolution. The immobilization of the racemic substrates on an inert solid support significantly reduced the reaction time and improved the enantioselectivity of conformers during kinetic resolution. The mechanism of the formation of the spiro-β-lactams was explored using B3LYP/6-31+G* level quantum chemical calculations.