D.K. Rastogi

Stereochemical features of some nickel(II) and cobalt(II) complexes of amino ligand—2-(2-aminoethyl) pyridine—VII

Abstract Nickel(II) and cobalt(II) complexes of the composition [ M ( L ) 2 . X 2 ] [ L = 2—(2-aminoethyl) pyridine; X = NO 3 , NCS] have been isolated and characterized by elemental analyses, magnetic, conductometric, electronic and i.r. spectral studies. The electronic spectral studies indicate that the complexes are tetragonally distorted from their regular cubic symmetry and it has been concluded that this distortion is produced due to unequal donor strengths of NO 3 and NCS ligands. A possible correlation of it has been sought with the low values of magnetic moments observed in these complexes. I.R. spectral studies show that the metals are coordinated through the nitrogen of the amino group and the heterocyclic nitrogen atom. These studies in the far i.r. region indicate that the strength of the metal-nitrogen bond in 2-(2-aminoethyl) pyridine complexes shifts as a function of X in the spectrochemical sereries: NCS > NO 3 > halides.

Stereochemical features vis-a-vis spectral data on some nickel(II) complexes of amino ligands viz. 3,3′-Diamino-4,4′-dihydroxy diphenyl sulphone and 8-amino-7-hydroxy-4-methylcoumarin. I.

Abstract Nickel(II) complexes of 3,3′-diamino-4,4′-dihydroxy diphenyl sulphone (abbreviated as D(AHP)S) viz. [Ni(C 12 H 10 N 2 O 4 S)(H 2 O) 3 ], [Ni(C 12 H 19 N 2 O 4 S)(NH 3 ) 2 ], and 8-amino-7-hydroxy-4-methylcoumarin (AHMC) viz. H[Ni(C 10 H 8 NO 3 ) 2 (Cl)(H 2 O)], K 2 [Ni(C 10 H 8 NO 3 ) 2 (CN) 2 ] have been isolated and characterised by analyses, magnetic, conductivity, electronic and infrared spectral studies. The electronic spectral studies indicate the effect of distortion in case of AHMC complexes,, which is probably produced due to the unequal donor strengths of chloride and cyanide ligands. A possible correlation of which has been sought with the low values of magnetic moments observed in these complexes. Other ligand field parameters have also been calculated.

Electronic spectral data vis-a-vis nephelauxetic effect-calculation and accuracy of the interelectronic repulsion parameter in some vanadium(II), chromium(III), cobalt(II) and nickel(II) complexes of amino ligands—V

Abstract The preparation and properties of a series of V(II), Co(II) and Ni(II) complexes of the composition [M(L2)(X2)] [where (L = AEP; X = Cl, Br, I) and (L = AHMC, D(AHP)S; X = H2O, NH3)]; Cr(III) complexes of the composition [M(L2)(X2)] X (where L = AEP; X = Cl, Br) are reported. Analytical, conductometric (wherever possible), magnetic and electronic spectral data show that all the complexes have octahedral geometries except [Co(AEP)(Cl2)], which has been found to have tetrahedral structure. An intercomparison of Dq and B values for AEP complexes shows that in the spectrochemical series Dq increases in the sequence Cl > Br > I. A comparison of Dq for the analogous complexes of AEP; AHMC and D(AHP)S indicates that the order of these three ligands in the spectrochemical series is AHMC > D(AHP)S > AEP.

Studies on square planar complexes of 3,3′-diamino-4,4′-dihydroxy diphenyl sulphone with copper(II), platinum(II) and palladium(II)—IV

Abstract Complexes of the composition [ M (C 12 H 10 N 2 O 4 S)][ M = Cu(II), Pt(II) and Pd(II)] with 3,3′-diamino-4,4′-dihydroxy diphenyl sulphone D(AHP)S have been isolated and characterized. Analytical, magnetic, i.r. and electronic spectral data show that all the complexes have square planar geometries. Electronic spectral studies indicate that σ-bonding in D(AHP)S complexes increases in the order 3dσ

Platinum metal complexes of 8-amino-7-hydroxy-4-methylcoumarin with osmium(VIII), osmium(IV) and platinum(IV)

Abstract Complexes of Os(VIII), Os(IV) and Pt(IV) with 8-amino-7-hydroxy-4-methyl-coumarin have been isolated and characterised. Magnetic, conductivity and electronic spectral data show that all the complexes have octahedral geometries. The osmium-(IV) complex reveals an anomalous magnetic behaviour which may possibly be attributed to a large spin-orbit coupling. Relevant ligand field parameters have been evaluated where possible. I.R. spectral studies have also been made.

Correlation in magnetic and spectral studies on cobaltous complexes of 8-amino-7 hydroxy-4 methylcoumarin

Abstract 8-Amino-7 hydroxy-4 methylcoumarin (AHMC) has been found to form two distinct complexes with cobalt(II), viz. Co[(C 10 H 8 NO 3 ) 2 (H 2 O) 2 ] H 2 O and Co[(C 10 H 8 NO 3 ) 2 (NH 3 ) (H 2 O)] 3H 2 O at pH 8·5 and 12·0 respectively. Magnetic studies on powder form of these complexes reveal rather low values of magnetic moment for high-spin octahedral complexes, a possible correlation of which has been sought in nephelauxetic ratio of these complexes. Other ligand field parameters have also been evaluated. The i.r. spectra of the complexes have been discussed.

Metal complexes of 8-amino-7-hydroxy-4-methylcoumarin. I. Chromium(III), iron(III), cobalt(III), nickel(II) and copper(II) complexes

8-Amino-7-hydroxy-4-methylcoumarin has been found to form distinct coloured complexes with CrIII, FeIII, CoIII, NiII, and CuII metal ions. These complexes have been isolated and characterized by analyses, magnetic, electronic and infrared spectral studies. All the complexes are octahedral except the copper(II) complex which has square planar stereochemistry. The values of splitting energy, ligand field stabilization energy, Racahs parameters and nephelauxetic ratio, have been evaluated in most of the cases. Iron(III) complex is trimeric in nature involving chlorine bridges as evidenced by i.r. studies. Also these studies indicate the coordination of ligand through nitrogen atom. The stability order for metal ions has been drawn on the basis of νassym(NH2) vibrations.

Correlation of the 1.R. data with the stability of transition metal complexes of 8-amino-7-hydroxy-4-methylcoumarin

Abstract The i.r. spectra of a number of solid transition metal complexes of AHMC have been investigated and it has been possible to determine three vibrations of the ligated molecules in these complexes. The decrease in stretching NH2 vibrations have been observed in the region 3320-3200 cm−1; the NH2 rocking deformation in the region 790-650 cm −1 and the metal-nitrogen stretching frequencies in the region 510−480 cm−1. On the basis of these frequencies a correlation has been sought in with the stability of transition metal complexes which is supported by their 10 Dq values.