Department of Chemistry
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Item Syntheses and characterization of N,N′-dipropyl/diisopropylethane-1,2-diamine complexes of nickel(II) nitrate: Thermal studies and X-ray single crystal structure analysis of cis-nitratobis (N,N′-dipropylethane-1,2-diamine)nickel(II) nitrate(Elsiever, 1998) Laskar, Inamur RahamanThe blue complex cis-[Ni(dipren)2(NO3)](NO3) 1 and the greenish blue cis-[Ni(dipren)2(H2O2](NO3)2 · 2H2O2 (dpren/dpren = dipropyl/diisopropylethane-1,2-diamine) have been synthesized. Complex 2 upon heating loses four water molecules in a single step and undergoes melting accompanied with colour change, greenish blue to deep green, 2a. Configuration of the complexes 1,2 and 2a have been proposed to be cis-octahedral on the basis of magnetic, IR and electronic spectroscopic studies and confirmed in case of complex 1 by X-ray single crystal structure analysis. The role of steric factor of the alkyl groups on the selectivity of coordinating mode of nitrate ion is studied.Item Synthesis and Single-Crystal Structure of an Unusual Heptacoordinate Cadmium(II) Complex, [Cd(medien)(NO3)2] (medien = bis(2-aminoethyl)methylamine).(ACTA, 1998) Laskar, Inamur RahamanMolecular geometry and coordination number play the key role in exploring the chemistry of a coordination compound.Item Synthesis, Characterization and Thermal Studies of Bis(2-aminoethyl)methylamine(medien) Complexes of Cadmium(II). Single Crystal Structure of Cd(medien)I2.(ACTA, 1998) Laskar, Inamur RahamanThe synthesis and characterization of bis complexes of bis(2-aminoethyl) amine (dien) with transition and non transition metals are of interest as these complexes can potentially exist in three isomeric formsItem First structural characterisation of nitro–nitrito linkage isomers of nickel(II): synthesis and single crystal structures of [NiL2(NO2)2] and [NiL2(ONO)2] [L = 1-(2-aminoethyl)piperidine](RSC, 1998) Laskar, Inamur RahamanThe linkage isomers trans-bis[1-(2-aminoethyl)piperidine]dinitronickel(II) (brown) 1 and trans-bis[1-(2-aminoethyl)piperidine]dinitritonickel(II) (blue) 2 have been synthesized and characterised by X-ray single crystal structure analysis.Item Synthesis of s-fac/mer bis(N2-methyldiethylenetriamine, L) nickel(II): X-ray single crystal structures of s-fac[NiL2](NO3)2 and mer[NiL2](CF3CO2)2(Springer, 1999-06) Laskar, Inamur Rahaman[NiL2](NO3)2 (1) and [NiL2](CF3CO2)2 (2) (L = N2-methyldiethylenetriamine] have been synthesized and their X-ray single crystal structures have been determined. The triamines are ligated to NiII s-facially in (1) and meridionally in (2), with a NiN6 chromophore in each complex.Item A three dimensional network of Cadmium"(Wiley, 1999) Laskar, Inamur RahamanIn attempts to build molecular materials with interesting properties, such as catalysis clathration etc., much attention has been given to the synthesis of one-, two- and three-dimensional extended solids involving cadmium. Rigid bridged ligands are frequently employed to construct these materials (Abrahams et al., 1994[Abrahams, B. F., Hardie, M. J., Hoskins, B. F., Robson, R. & Sutherland, E. E. (1994). J. Chem. Soc. Chem. Commun. pp. 1049-1050.]; Soma et al., 1994[Soma, T., Yuge, H. & Iwamoto, T. (1994). Angew. Chem. Int. Ed. Engl. 33, 1665-1666.]; Fujita et al., 1994[Fujita, M., Kwon, Y. J., Miyazawa, M. & Ogura, K. (1994). J. Chem. Soc. Chem. Commun. pp. 1977-1978.]; Yuge & Iwamoto, 1995[Yuge, H. & Iwamoto, T. (1995). Acta Cryst. C51, 374-377.]). The ambidentate thiocyanate ion which is usually S-bonded to a soft and N-bonded to a hard metal centre can also act as a bridging bidentate ligand to satisfy the coordination number of the metal ion, although the thiocyanate anion has not been widely used in the construction of inorganic polymeric networks. In order to synthesize uncharged three-dimensional polymers where channels remain unblocked by anions and free for solvent inclusion, we have chosen cadmium(II) thiocyanate as an effective building block. Cadmium is well suited to this as its d10 configuration permits a wide variety of symmetries and coordination numbers. Recently, we reported the syntheses of the inorganic polymer [Cd3(dien)2(μ-NCS)6]n·nH2O (dien is diethylenetriamine), (II[link]) (Mondal et al., 1999[Mondal, A., Mostafa, G., Ghosh, A., Laskar, I. R. & Ray Chaudhuri, N. (1999). J. Chem. Soc. Dalton Trans. pp. 9-10.]), which utilizes the full bridging potential of the anion. The structure of complex (II[link]) is a polymeric network which contains solvent-filled channels. Channel-containing solids have been and continue to be investigated intensively because of their potential applications, viz. as heterogeneous catalysts and molecular sieves. As part of a continuing investigation into control over the channels, we are currently studying the corresponding cadmium compounds. In this paper, we report the structure of the title CdII complex (I[link]), where medien [medien is N,N-bis(2-aminoethyl)methylamine] ligands replace the dien ligands of complexItem Cis–trans isomerism in nickel(II)–diamine nitrite: synthesis and single crystal structure of an unusual cis-dinitronickel(II) complex, [NiL2(NO2)2] (L=1,2-diamino-2-methylpropane)(Elsiever, 2000-04-30) Laskar, Inamur RahamanThe complexes [NiL3](NO2)2·2H2O (violet, 1) and cis-[NiL2(NO2)2]·0.5H2O (pink, 1b) (L=1,2-diamino-2-methylpropane) have been synthesized from solution. The X-ray single crystal structure analysis of compound 1b has been carried out, but the presence of a water molecule cannot be detected. Upon heating, complex 1b undergoes dehydration followed by an endothermic phase transition to produce trans-[NiL2(NO2)2] (1d). The violet species (1) also undergoes dehydration upon heating with deamination resulting (1d).Item Synthesis and characterization of cis and trans isomers of [NiL2(NCS)2] [L=1-(2-aminoethyl)pyrrolidine]: X-ray single-crystal structures(Elsiever, 2000-07-30) Laskar, Inamur RahamanThe isomeric complexes trans-[NiL2(NCS)2] (violet) (1) and cis-[NiL2(NCS)2] (blue) (2) [L=1-(2-aminoethyl)pyrrolidine] have been synthesized, varying solvents and temperature, and their X-ray crystal structures have been determined. Both the isomers possess the same space group, P21/c, having distorted octahedral geometry.Item A 1D thiocyanato bridge nickel(II) system: crystal structure and magnetic property(Elsiever, 2001-04) Laskar, Inamur RahamanA one-dimensional coordination polymer of nickel(II), [(μN,S-NCS)2{Ni(ampy)}]n (ampy=1-(2-aminoethyl)pyrrolidine) has been synthesized and characterized by X-ray single crystal analysis. Structure analysis reveals that each nickel(II) center is coordinated in a distorted octahedral fashion with four bridging thiocyanato ligands and one mesocyclic diamine ligand. The low temperature (300–18 K) magnetic measurement shows that the system is ferromagnetically coupled. The magnetic data are fitted to the de Neef equation, giving the parameters J=1.4 cm−1 and g=2.08.Item First report on thermally induced nitro → nitrito(O,O) linkage isomerization in diamine complexes of nickel(II) in the solid state: X-ray single crystal structural analyses of nitro and nitrito isomers(RSC, 2001) Laskar, Inamur RahamanThe brown nitro isomer, trans-[NiL2(NO2)2], 1 (L = N,N′-dipropyl-1,2-diaminoethane), was synthesized by adding L to a suspension of K4[Ni(NO2)6]·H2O in methanol. Complex 1 is metastable at ca. 298 K and transforms slowly to the greenish blue nitrito(O,O) isomer, cis-[NiL2(O2N)](NO2), 2. This transformation is accelerated with increasing temperature and slowed down on lowering the temperature (< 283 K). Complex 2 shows a reversible phase transition, 2↔3 (cooling: ΔH = 8.150 ± 0.004 kJ mol−1; 266–255 K; heating: ΔH = −7.960 ± 0.003 kJ mol−1; 257–268 K), whereas complex 1 does not exhibit any such transition. The structures of 1, 2 and 3 have been characterized by X-ray single crystal structure analyses, which reveal that 1 and 2/3 are nitro and nitrito(O,O) linkage isomers, respectively. Complexes 2 and 3 have essentially similar structures and their reversible transformation is supposed to be due to the change in thermal motion of the side chains on variation of temperature.