Metal complexes of small cyano anions and their derivatives
2017-02-28T00:58:50Z (GMT) by
This thesis examines the chemistry of Small Cyano Anions (SCAs), specifically dicyanonitrosomethanide (dcnm) and dicyanonitromethanide (dcnom). The aims of this work are to observe the coordination modes offered by these SCAs and their derivatives as well as the propensity of both anions to undergo transition metal promoted nucleophilic addition as a means for in situ ligand synthesis. Chapter Two of this thesis illustrates the chemistry of the carbamoylcyanonitrosomethanide (ccnm) anion, which is the product of water addition to a nitrile arm of dcnm. In some cases the formation of ccnm was observed in our attempts to induce nucleophilic addition of aromatic amines and a primary alcohol. The structure of the octanuclear manganese cluster [MnII4MnIII4O4(ccnm)12]•4MeCN•7H2O was found to possess a rare tetra-capped distorted cubane topology that displayed dominant antiferromagnetic interactions. The addition of base to a reaction involving ccnm caused deprotonation, yielding amidocarbonyl(cyano)nitrosomethanide (acnm) species. Chapter Three discusses the ability of alcohol addition products to construct a diverse range of metal complexes, ranging from mononuclear to polymeric structures. A series of coordination networks structures were obtained by reacting dcnm anions with FeII and a range of alkali metals in methanol. The unprecedented coordination mode displayed by cyano[imino(methoxy)methyl]nitrosomethanide (cmnm) in these structures allowed the formation of 2D network structures, containing cmnm bridging both FeII and alkali metal centres. Also observed was a new coordination mode of cmnm, a syn-isomeric form as opposed to the predominant anti-isomeric form, in the 1D polymeric structure [Zn(cmnm)2(4,4′-bpy)]•2H¬2O. The nucleophilic addition of alcohols was not just limited to small alcohols, as demonstrated by the formation of hydroxyethylaminobis(ethoxy(imino)methyl(cyano)nitrosomethanide (hbnm) and methylaminobis(ethoxy(imino)methyl(cyano)nitrosomethanide (mbnm) from the addition of triethanolamine (teaH¬3) and N-methyldiethanolamine (mdeaH2) respectively. With attempts to observe the nucleophilic additions of aromatic amines with pyridyl functionalities unsuccessful, attention was turned to aliphatic amines (while retaining the pyridyl functionality), and specifically n-aminomethylpyridines (n = 2, 3, 4). The results of this study are given in Chapter Four. Each of the primary amines was observed to undergo nucleophilic addition to the nitrile arm of dcnm, with solution studies for a zinc complex suggesting that water is necessary in this reaction. The addition of m-xylenediamine to dcnm resulted in the formation of a “triple-decker” structure, with the orthogonal arrangement of Cu(dx2-dy2) orbital yielding ferromagnetic coupling. Another notable feature of this compound was that deprotonation of the cmnm ligand was observed for the first time. Chapter Five discusses the formation of pyrazole (Hpz) addition products, which are the first examples of addition of solid nucleophiles to dcnm. A series of mononuclear, metal cluster and 1D zigzag chain structures were obtained from these reactions, although the reaction was observed only for copper ions. Magnetic studies on these complexes revealed the imido bridge with a bridging angle of ~120o led to very strong antiferromagnetic interactions. Chapter Six describes the chemistry of dcnom anion. Two reaction procedures were conducted involving this anion, conventional bench top and solvothermal reactions, each of which resulted in different products being obtained.