Metal complexes containing dicyanonitrosomethanide and its derivatives
Creators: name: Chesman, Anthony
Publisher: name: Monash University
Year: 2017
Subjects: Uncategorized

description: This thesis examines the chemistry of the dicyanonitrosomethanide (dcnm) anion and how it may undergo the transition metal promoted addition of a nucleophile as a means of in situ ligand formation. A computational study indicated that the addition of water to a nitrile group of the dcnm anion only gives the anti-isomer of the carbamoylcyanonitrosomethanide (ccnm) anion, with the syn isomer resulting from the subsequent rotation of the nitroso group of the anti-isomer. The addition of a molecule of water to the ccnm or dicyanonitromethanide (dcnom) anions was not experimentally observed, and appears electronically disfavoured. The in situ transition metal promoted additions of ethanol, n-propanol and ethylene glycol methyl ether to the dcnm anion were observed for the first time, with the presence of ammonia causing the deprotonation of the ccnm anion to give the dianionic amidocarbonyl(cyano)nitrosomethanide species. The reaction path for the addition and subsequent cyclisation of two molecules of 1,2-diaminoethane to the dcnm anion to give the di(imidazolinyl)nitrosomethanide (dinm) ligand has been deduced. Ethanolamine was shown to add to the dcnm anion via the NH2 moiety, demonstrating higher reactivity of amines than alcohols in transition metal promoted reactions with the dcnm anions. Coordinatively divergent derivatives of the dcnm anion in conjunction with bridging co-ligands give a range of topologically diverse coordination polymers. The facile loss of methanol molecules residing in the lattice of a 1D coordination polymer results in its transformation into a 3D network. The nitroso group has proven to be ideal for bridging between metal centres to aid in the formation of polynuclear homometallic complexes, with these clusters predominantly displaying antiferromagnetic coupling. An octanuclear dysprosium cluster displayed behaviour indicative of slow magnetisation reversal. The heterofunctionalised nature of derivatives of dcnm makes them ideal for forming 3d/4f heterobimetallic clusters such as [{Gd(OH)(ccnm)2(H2O)4}2MnIII](ClO4)3 and [Ln2MnIII2O2(ccnm)6(dcnm)2(H2O)2]. The viability of using the carbonate anion of as a cluster forming agent has been demonstrated during the synthesis of the polynuclear complexes [Ln13(H2O)6(phen)18(ccnm)6(CO3)14]•Cl3•CO3 (Ln = La, Ce, Pr) and [Gd14(CO3)13(ccnm)9(OH)(H2O)6(phen)13(NO3)](CO3)2.5•phen. In the homoleptic 12-coordinate complex [Ln(ccnm)6]3− there is strong intramolecular hydrogen bonding between the nitroso and carbamoyl groups of adjacent ligands. The use of the dcnm ligand results in the formation of an analogous trianionic lanthanoid complex. The presence of intra- and intermolecular hydrogen bonding and sterically crowding co-ligands have been used to probe the nature of the nitroso groups of dcnm and ccnm ligands coordinating to lanthanoids. The [Ln(dcnm)6]3− trianion has been incorporated into a range of ionic liquids (ILs). The use of counter-cations that may act as hydrogen bond donors resulted in an increase in the melting points of the ILs. Synchrotron based in situ powder diffraction studies were used to determine that the observed change in the melting point of complexes [N4444]3[Ln(dcnm)6] over several heating and cooling cycles was due to the recrystallisation of the product giving a less thermodynamically stable polymorph. <br>Awards: Winner of the Mollie Holman Doctoral Medal for Excellence, Faculty of Science, 2011.