Metallation nitrogen stabilization

Important aspects of the coordination chemistry of binary chalcogen-nitrogen ligands include (a) the ability of metals to stabilize labile neutral and anionic binary S-N ligands, (b) the applications of metal complexes as reagents for the preparation of other S-N compounds, and (c) the possible incorporation of metals into sulfur-nitrogen chains to produce conducting materials. 

Schiff bases having two nitrogen atoms as donors may be derived either from condensation of dialdehydes and diketones with two molecules of an amine, or from reaction of diamines with aldehydes or ketones. In Section 20.1.2.1, it has been pointed out that coordination through the N atom may occur only under particular circumstances. However, in the case of diimines the formation of chelate rings stabilizes the metal-nitrogen bond. Thus, they can form both mono-41 and bis-chelate42 complexes. 

In a series of tetrabenzoazaporphyrins there are tendencies coupled to the increase in the number of meso nitrogens, such as the decrease in stability, the increase in sublimability, the decrease in basicity, the increase in oxidizability, the red shift of main absorption bands and the increase in metal complex stability.195... 

Until recently, the synthesis of ionic/covalent nitrides was relatively unexplored except for the pioneering work of Juza on ternary lithium nitrides.11 However, within the last decade, several groups have begun to explore ternary nitride systems, many of which have relied on the inductive effect. The inductive effect is based on the donation of electron density from an electropositive element to an adjacent metal-nitrogen bond, thereby increasing the covalency and stability of that bond and of the nitride material itself. The success of this method is illustrated by the fact that almost all of the known ionic/covalent ternary nitrides contain electropositive elements. Only recently has a small number of transition metal ternary nitrides been synthesized in the absence of the inductive effect at moderate temperatures, by taking advantage of low temperature techniques, such as the ammonolysis of oxide precursors and metathesis reactions.6,12-17... 

If the photolysis takes place in an inert gas matrix, both the homolytic splitting of the metal-metal bond and the breaking of a metal-nitrogen bond will be followed by a fast backreaction to the parent compound. The radicals formed by homolysis of the metal-metal bond can not diffuse from the matrix site and will recombine to the parent compound. Moreover, the photoproduct obtained by breaking of a metal nitrogen bond, will not be stabilized by a coordinating solvent molecule and therefore react back to the parent compound. Because of this the photochemistry of some of these complexes has also been studied in a Cl-k-matrix at 10K and for comparison in a PVC film, which is a less rigid medium than the matrix especially at room temperature. 

Vogtle et al. have demonstrated the formation of solid 1 1 adducts between terpy and MSCN (M = Li or Na) in contrast, [NH4][SCN] forms a 2 1 adduct with terpy. Although stability constants were not reported, it was shown by Na NMR studies that terpy is superior to bipy, but inferior to phen, as a ligand for the sodium cation 455). Presumably, the metal-nitrogen interaction is predominantly ionic in character. 

Chlorophylls are a subgroup of the cyclic tetrapyrroles. They are large, relatively rigid aromatic molecules. They are planar, but deviations from planarity are observed for most Chls in photosynthetic proteins. The four central nitrogens can bind a variety of central metals. The stabilities of these metal complexes vary widely. The Mg++ characteristic of Chls is lost... 

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