Arunendu Mondal

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)

Abstract The 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).

Syntheses of [Ni2(dien)2(NCS)4(H2O)] and [Ni(aepn)(NCS)2]n ((dien = bis(2-aminoethyl)amine and aepn = N-(2-aminoethyl)-1,3-propanediamine): single crystal structure analysis and thermal behaviour in the solid state

Abstract [Ni 2 (dien) 2 (NCS) 4 (H 2 O)] ( 1 ) and [Ni(aepn)(NCS) 2 ] n ( 2 ) (where dien = bis(2-aminoethyl)amine and aepn = N -(2-aminoethyl)-1,3-propanediamine) have been synthesised from solution. Single crystal X-ray structure analyses of 1 and 2 reveal that the metal atoms in both the complexes display distorted octahedral geometry with the triamine coordinating facially in 1 and meridionally in 2 . The dinuclear [Ni 2 (dien) 2 (NCS) 4 (H 2 O)] unit in 1 is bridged via a thiocyanate moiety while in 2 the nickel(II) octahedra form a polymeric chain. The species 1 on deaquation at ∼ 165°C followed by cooling yields a conglomerated mass ( 1a ). The species 2 melts at ∼ 230°C which on cooling yields conglomerated mass ( 2a ). Both 1a and 2a are amorphous; the former reverts to 1 in a humid atmosphere.

Synthesis, characterization of triamine complexes of nickel(II)selenocyanate and their thermally induced dimerization: X-ray single crystal structures of [Ni(dpt)(SeCN)2(H2O)] and [Ni(aepn)(SeCN)2(H2O)] (dpt=bis(3-aminopropyl)amine and aepn=(2-aminoethyl)(3-aminopropyl)amine)

Abstract [NiL(SeCN) 2 (H 2 O)] [L=bis(3-aminopropyl)amine (dpt), ( 1 ), (2-aminoethyl)(3-aminopropyl)amine (aepn), ( 2 ) and bis(2-aminoethyl)methylamine) (medien), ( 3 )] have been synthesized and characterized in the solid state by X-ray single crystal analysis ( 1 and 2 ), IR, electronic spectra and magnetic measurement. Structure analyses of ( 1 ) and ( 2 ) reveal that the nickel(II) center is coordinated in a distorted octahedral fashion and the two SeCN groups are attached in trans position. Upon heating they undergo deaquation followed by color change, yielding dinuclear species bridging through selenocyanate. The deaquated dinuclear complexes have been characterized by IR, electronic spectra and magnetic susceptibility measurement.

A dimeric form of the nickel(II) thiocyanate complex of bis(3-aminopropyl)methylamine

The structure of bis[N,N-bis(3-aminopropyl)methylamine]-1κ 3 N,2κ 3 N-di-μ-thiocyanato-1:2κ 2 N:S;1:2κ 2 S:N-dithiocyanato-κN,2κN-dinickel(II), [Ni 2 (NCS) 4 (C 7 H 19 N 3 ) 2 ] or [Ni 2 (μ-SCN) 2 (medpt) 2 (NCS) 2 ], where medpt is bis(3-aminopropyl)methylamine, consists of two crystallographically independent dimer types differing in their orientations. In each dimer, the two Ni II ions are bridged by two SCN- ligands in an end-to-end fashion. The coordination polyhedra about the Ni II atoms are distorted octahedra consisting of three N atoms of the medpt ligand coordinating meridionally, one N atom of the non-bridging thiocyanate ligand, and one N and one S atom of two bridging thiocyanate ligands. The six-membered chelate rings display chair conformations.

STRUCTURAL EXPLORATION OF HYDROXO BRIDGED TRIAMINE COMPLEXES OF ZINC(II)

Abstract Single crystal structure of [Zn2(dpt)2(μ-OH)](ClO4)3 (dpt = bis(3-aminopropyl) amine) shows that two units of Zn(dpt) are bridged by oxygen atom of the hydroxo group. Each Zn-atom possesses distorted tetrahedral geometry. Analogous complexes [Zn2L2(μ-OH)](ClO4)3 [L = bis(3-aminopropyl) methylamine(medpt), bis(2-aminoethyl)methylamine(medien)] have been synthesised.

Thermal studies N-(2-aminoethyl)-1,3-propanediamine and N-(3-aminopropyl)-1,3-propanediamine complexes of cadmium(II)

Abstract [Cd(aepn) 2 ]X 2 · n H 2 O (where aepn is N -(2-aminoethyl)-1,3-propanediamine, and n = 1 when X is Cl − and Br − , n = 0 when X is 0.5SO 2− 4 , 0.5SeO 2− 4 , NO − 3 and I − ), Cd(aepn)X 2 (where X is Cl − , Br − , I − , 0.5SeO 2− 4 , 0.5SO 2− 4 and SCN − ), and Cd(dpt)X 2 · n H 2 O (where dpt is N -(3-aminopropyl)-1,3-propanediamine, and n = 1 when X is 0.5SO 2− 4 and 0.5SeO 2− 4 , n = 0 when X is Cl − , Br − , I − and SCN − ) have been synthesised and investigated thermally in the solid state. The species Cd(aepn)Cl 2 , Cd(aepn)SO 4 and Cd(aepn)SeO 4 have also been synthesised pyrolytically in the solid state from the corresponding parent bis-complexes. Cd(aepn) (SCN) 2 and Cd(dpt) (SCN) 2 melt on heating and exist as supercooled liquids at ambient temperature. On heating and after deaquation, Cd(dpt)SO 4 ·H 2 O shows two endothermic phase transitions (172–190°C, ΔH = 8.0 kJ mol −1 and 210–245°C, ΔH = 3.5 kJ mol −1 and the low-temperature transition is reversible (182–165°C, ΔH = −7.8 kJ mol −1 ). Conversely, the selenate analogue undergoes an irreversible endothermic phase transition (240–257°C, ΔH = 13.2 kJ mol −1 ). [Cd(aepn) 2 ] (NO 3 ) 2 and Cd(aepn)I 2 show irreversible endothermic phase transitions (198–218°C, ΔH = 5.9 kJ mol −1 for nitrate, and 195–202°C, ΔH = 8.3 kJ mol −1 for iodide). The transitions are assumed to be due to the conformational changes in the triamine chelate rings. The thermal stabilities are rationalized with respect to the carbon chain lengths of the triamine ligands.

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

Abstract[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.

Thermal Studies of Nickel(II) Squarate Complexes of Triamines in the Solid State

Abstract[NiL2]C4O4·nH2O [where n=2 when L=diethylenetriamine(dien) and N-(3-aminopropyl)-1,3-propanediamine (dpt); n=3 when L=N-(2-aminoethyl)-1,3-propanediamine (aepn); n=0 when L=N2-methyldiethylenetriamine (medien)] and Ni(tmdien)C4O4·2H2O (where tmdien=1,4,7 trimethyl-diethylenetriamine) have been synthesised and investigated thermally in the solid state. Ni(dpt)C4O4·H2O has also been synthesised pyrolytically in the solid state from the corresponding bis complex. All the complexes possess octahedral geometry. The squarate anion takes part in coordination only in monotriamine species. [Ni(medien)2]C4O4 upon heating undergoes phase transition (270–285°C; ΔH=4.9 kJ mol−1) accompanied by colour change pink to grey. Thermal stability decreases with increase in chain length of the triamines.

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]

The 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.

A Hyperbranched Polymer of Cadmium

Crystal structure analysis of Cd(aepn)(NCS)2 [aepn=(2-aminoethyl)(3-aminopropyl)amine] reveals that each cadmium(II) possesses distorted octahedral geometry and is linked to four different nearest cadmium centres via thiocyanate groups and non-chelated arms of the triamine ligands forming a chain linked system of a hyperbranched polymeric molecule.