An interesting phenomenon of ligand exchange is observed in the DMSO solution of certain self-assembled molecules generated from cis-protected PdII and organic ligands. Upon heating, assemblies such as [{Pd(en)}x(ligand)y](NO3)2x change to [Pdm(ligand)n](NO3)2m and [Pd(en)2](NO3)2. The change is also possible at room temperature when 0.5 equiv. Pd(en)(NO3)2 is added in excess to the system. The transformation is incomplete when the ligand moiety is monodentate in nature, for example in the case of 4-phenylpyridine. However, multinuclear assemblies containing nonchelating, polydentate ligands used in this study entirely favor the transformation. This process is not possible with some related PtII compounds. © Wiley-VCH Verlag GmbH &amp; Co. KGaA, 2005.

Dillip Kumar Chand

Department Of Chemistry

Kandasamy Jeyakumar

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

European Journal of Inorganic Chemistry

A series of binuclear palladium(II)-based self-assembled metallomacrocycles of Pd2L′2L2 type compositions were synthesized by complexation of an imidazole appended non-chelating bidentate ligand L with different cis-protected palladium(II) components (i.e. PdL′). The complexes [Pd2(en)2(L)2](NO3)4, 1, [Pd2(tmeda)2(L)2](NO3)4, 2, [Pd2(bpy)2(L)2](NO3)4, 3, and [Pd2(phen)2(L)2](NO3)4, 4 were characterized by NMR spectroscopy and their nuclearities were established with the help of ESI-MS. Solid state structures of the complexes 2, 3 and [Pd2(phen)2(L)2](OTf)4, 4′ were established by the single-crystal XRD technique. These metallomacrocycles could act as tectons for crystal engineering by using the available π-surface on their architectures. The crystal packing of these molecules revealed the importance of the π-surface on the ligand moiety as well as on the cis-protecting moiety. Utilization of the π-surfaces afforded 1D to 3D supramolecular networks in solid state. © 2018 Elsevier B.V.

Inorganica Chimica Acta

Crystal engineering with palladium(II)-based self-assembled binuclear complexes as tectons

One-pot synthesis of self-assembled heteroleptic complexes of general formula [Pdx(tmeda)x(L)y](NO3) 2x is achieved by combining required amount of tmeda, a chosen ligand L and Pd(NO3)2 under suitable reaction conditions. The strategy is devised using our understanding of a special variety of ligand exchange reactions (LER) around palladium(II) centers as modeled in this work. The one-pot synthesis technique is thus considered as an application of the unique LER. © 2013 Elsevier B.V.

Inorganic Chemistry Communications

One-pot synthesis of self-assembled heteroleptic palladium(II) complexes with tmeda: An application of ligand exchange reactions

Ligand N,N′-bis(3-pyridylformyl)piperazine, L1, exists in syn and anti conformers in solution state almost in equal proportion. Formation of a saturated quadruple stranded helicate is observed when Pd(NO 3)2 is reacted with ligand L1. In the complexed form the ligand exists in a flattened boat conformation with anti form. © 2010 The Royal Society of Chemistry.

Dalton Transactions

Conformation of N,N′-bis(3-pyridylformyl)piperazine and spontaneous formation of a saturated quadruple stranded metallohelicate

A remarkable upfield shift of the pyα protons of complexed 2,2′-bipyridine in [cis-Pd(bpy)(NO3)2] is observed which is considered to originate from the anisotropic influence of suitably positioned coordinated nitrate anions around the Pd(II) centre of the molecule. A typical complexation-induced downfield shift is observed for the NH2 protons in [cis-Pd(en)(NO3)2] where 'en' stands for ethylenediamine. © 2006 Elsevier Ltd. All rights reserved.

Tetrahedron Letters

Manifestation of diamagnetic chemical shifts of proton NMR signals by an anisotropic shielding effect of nitrate anions

Polynuclear self-assembly molecules of general formula [{Pd(en)}x(ligand)y](NO3)2x (A) undergo ligand exchange reaction when heated in DMSO. A mixture of [Pdm(ligand)n](NO3)2m (B) and [Pd(en)2](NO3)2 (C) is generated in this process. The binuclear compound (A) containing a bidentate, non-chelating ligand 1,4-bis(4′-pyridylmethyl)-2,3,5,6-tetrafluorobenzene, is subjected to ligand exchange where upon the compound (A) remains in a dynamic equilibrium with the mixture of ensuing (B) and (C). Combination of separately prepared (B) and (C) also generates (A), thus equilibrium of (A) with (B) and (C) is again observed. We predict [{Pd(bpy)}x(ligand)y](NO3)2x (A′) where 2,2′-bipyridyl (bpy) is the cis-protecting group would not probably undergo ligand exchange. The idea was conceived from the fact that (bpy) is more rigid compared to (en) moreover one of the expected products in the event of ligand exchange [Pd(bpy)2](NO3)2 (C′) is not really very stable unlike (C). In fact, when (A′) is heated in DMSO no ligand exchange is observed at all. More interestingly combination of (B) and (C′) generated (A′) smoothly. Mononuclear complexes obtained from the ligand 4-phenylpyridine are also used for similar study for comparison. It is suggested that (bpy) could serve as a better cis-protecting group for Pd(II)-based self-assembly coordination cage compounds particularly when dissolution of the assemblies in polar solvents and heating of the resultant solution is required. © 2006 Elsevier B.V. All rights reserved.

Journal	European Journal of Inorganic Chemistry
ISSN	14341948
Open Access	No