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Imidazol-2-ylidene-N′-phenylureate ligands in alkali and alkaline earth metal coordination spheres - heterocubane core to polymeric structural motif formation
K. Naktode, J. Bhattacharjee, H.P. Nayek,
Published in
2015
Volume: 44
   
Issue: 16
Pages: 7458 - 7469
Abstract
The synthesis and isolation of two potassium, one lithium and two calcium complexes of imidazol-2-ylidene-N′-phenylureate ligands [ImRNCON(H)Ph] [(R = tBu (1a); Mes (1b) and Dipp (1c); Mes = mesityl, Dipp = 2,6-diisopropylphenyl] are described. Potassium complexes, [{κ2-(ImMesNCONPh)K}4] (2b) and [{κ3-(ImDippNCONPh)K}2{KN(SiMe3)2}2]n (2c), were prepared in good yields by the reactions of 1b and 1c, respectively, with potassium bis(trimethyl)silyl amide at ambient temperature in toluene. Lithium complex [{(2,6-tBu2-4-Me-C6H2O)Li(ImtBuNCON(H)Ph)}2{ImtBuNCON(H)Ph}] (3a) was isolated by a one-pot reaction between 1a and LiCH2SiMe3, followed by the addition of 2,6-tBu2-4-Me-C6H2OH in toluene. Calcium complex [{κ2-(ImtBuNCONPh)Ca{N(SiMe3)2}-{KN(SiMe3)2}]n (4a) was isolated by the one-pot reaction of 1a with [KN(SiMe3)2] and calcium diiodide in THF at ambient temperature. The solid-state structures of ligand 1a and complexes 2b, 2c, 3a and 4a were confirmed by single-crystal X-ray diffraction analysis. It was observed that potassium was coordinated to the oxygen atom of urea group and to the nitrogen atom of the imidazolin-2-imine group, in the solid-state structure of 2b. In complex 4a, the calcium ion was ligated to the monoanionic imidazol-2-ylidene-N′-phenylureate ligand in a bi-dentate (κ2) fashion through the oxygen and nitrogen atoms of the isocyanate building block leaving the imidazolin-2-imine fragment uncoordinated. In the solid state of the potassium complex 2c, tri-dentate (κ3) coordination from the imidazol-2-ylidene-N′-phenylureate ligand was observed through the oxygen and nitrogen atoms of the isocyanate building block and of the imidazolin-2-imine fragment. In contrast, in the dimeric lithium complex 3a, the neutral imidazol-2-ylidene-N′-phenylureate ligand was bound to the lithium centre in a mono-dentate fashion (κ1) through an oxygen atom of the isocyanate moiety. It is to be noted that in each complex thus observed, the elongated carbon-nitrogen bond distances indicate substantial electron delocalisation from the imidazole ring to the ureate group present in ligand 1. © The Royal Society of Chemistry 2015.}, keywords={Alkalinity; Atoms; Calcium; Chelation; Crystal atomic structure; Ligands; Lithium; Nitrogen; Nitrogen compounds; Oxygen; Single crystals; Synthesis (chemical); Temperature; Toluene; Urea; X ray diffraction analysis, Building blockes; Carbon nitrogen bonds; One-pot reaction; Oxygen and nitrogens; Potassium complex; Single crystal X-ray diffraction analysis; Solid-state structures; Structural motifs, Coordination reactions}, correspondence_address1={Panda, T.K.; Department of Chemistry, Indian Institute of Technology Hyderabad, Ordnance Factory EstateIndia}, publisher={Royal Society of Chemistry}, issn={14779226}, coden={DTARA}, language={English}, abbrev_source_title={Dalton Trans.}, document_type={Article}, source={Scopus},
About the journal
JournalDalton Transactions