Diazene structure

Diazenes of the type REN=C(R )N=NC(R )=NER have a rich structural chemistry. The selenium derivatives 15.11a,b display a cis,trans,cis conformation with two short l,5-Se N contacts (2.65 A). Several sulfur analogues, e.g., 15.1c, have the same structure, but a different cis,trans,cis conformer 15.12 with two 1,4-S N contacts (2.83 A) has also been characterized. A third type of diazene is the trans,trans,trans isomer 15.13a,b with no intramolecular short contacts. ... 

Compounds of the form RN2 X are named by adding the suffix -diazonium to the name of the parent compound RH, the whole being followed by the name of X- (Rule C-931.1, e.g., methanediazonium tetrafluoroborate, benzenediazonium chloride, not phenyldiazonium). Following RC- 82.2.2.3 (IUPAC, 1993), diazonium ions may also be named structurally on the basis of the parent cation diazenylium HNJ, e.g., benzenediazenylium ion. We name the substituent — NJ diazonio (not diazonium) following the same rule. Diazonio describes both mesomeric structures — N = N and — N = N. If one wants to describe one of these structures only, diazyn-l-ium-l-yl or diazen-2-ylium-l-yl has to be used for -N = N or -N = N, respectively. In the General Subject Index of Chemical Abstracts and in Beilstein, diazonium compounds as a class are indexed under this heading. 

Equation 6 would hold for a family of free radical initiators of similiar structure (for example, the frarw-symmetric bisalkyl diazenes) reacting at the same rate (at a half-life of one hour, for example) at different temperatures T. Slope M would measure the sensitivity for that particular family of reactants to changes in the pi-delocalization energies of the radicals being formed (transition state effect) at the particular constant rate of decomposition. Slope N would measure the sensitivity of that family to changes in the steric environment around the central carbon atom (reactant state effect) at the same constant rate of decomposition. 

More entries were used to test the valT3ity of equation 6 for reaction 1 than for the other families of initiators (Table I). Six of the thirteen entries for reaction 1 have AE(x) values bunched between -21 and -24 kcal/mole. It was felt that, by using all of these six entries, any bias in structure activity relationships would be decreased for this region of radical pi-delocalization energies. This group also includes those diazenes which are most used commercially, such as 2,2 -azobisisobutyronitrile (AIBN - entry 16 ) and dimethyl 2,2 -azobisisobutyrate (entry 14). 

Irons-phenyl, alkyl diazenes (2), peresters (3) and hydrocarbons (4). These equations are intended to be used for their predictive value for applications especially in the area of free radical polymerization chemistry. They are not intended for imparting deep understanding of the mechanisms of radical forming reactions or the properties of the free radical "products". Some interesting hypotheses can be made about the contributions of transition state versus reactant state effects for the structure activity relationships of the reactions of this study, as long as the mechanisms are assumed to be constant throughout each family of free radical initiator. 

Meso- and (+ )-azobis[6-(6-cyanododecanoic acid)] were synthesized by Porter et al. (1983) as an amphipathic free radical initiator that could deliver the radical center to a bilayer structure controllably for the study of free radical processes in membranes. The decomposition pathways of the diazenes are illustrated in Fig. 36. When the initiator was decomposed in a DPPC multilamellar vesicle matrix, the diazenes showed stereo-retention yielding unprecedented diastereomeric excesses, as high as 70%, in the recombination of the radicals to form meso- and (+ )-succinodinitriles (Brittain et al., 1984). When the methyl esters of the diazene surfactants were decomposed in a chlorobenzene solution, poor diastereoselectivity was observed, diastereomeric excesses of 2.6% and 7.4% for meso- and ( )-isomers respectively, which is typical of free radical processes in isotropic media (Greene et al, 1970). 

To explain the behavior of the meso- and ( )-diazenes upon micellization, the differences in the molecular structures and the aggregates they form must both be examined since either (or both) may be responsible for the anomaly. 

Copper (continued) cynates, 17 322, 323 diaminodithioether complexes, 17 185 diazene complexes, 27 232 difluoride, structure, 27 85, 86, 87, 88 dinuclear sites, 40 362-367 diphosphine complexes of, 14 235-239 electron-density distributions of complexes, 27 34, 41... 

Mdssbauer spectra of bonding and structure in, 15 184-187 reactions with diborane, 16 213 stabilization of, 5 17, 18-19 cyanates, 17 297, 298 cyanide complexes of, 8 143-144 cyclometallated bipyridine complex, 30 76 diazene complexes, 27 231-232 dinitrogen complexes, 27 215, 217 diphosphine complexes of, 14 208-219 dithiocarbamates, 23 253-254 -1,2-dithiolene complexes, 22 323-327 hydrogen bonding, 22 327 halide complexes with phosphine, etc., 6 25 hexaflouride, structure, 27 104 hydride complexes, 20 235, 248-281, see also Transition metal-hydride complexes... 

The electrochemistry of dinitrogen bridging two porphyrin ligated ruthenium centers has been studied as a possible route to fixed nitrogen [45 -47]. Diazene stabilized by bonding to two iron centers in a FeS system has been advanced as a structural model of a plausible intermediate in biological nitrogen fixation [48-50]. 

Two older systems of nomenclature name aliphatic azo compounds diazenes or diimines, as in structure VII. 

The reaction of bis(trimethylsilyl)diazene with chromocene or CpCrCl2 affords the dark violet crystalline imide with structure (297). The imide shows distinct trimethylsilyl signals in the NMR spectrum, and in methanol forms [CpCr(NH)(NSiMe3)]2.1425... 

The effect of structure on the rates of hydrogenations catalyzed by Pt, Pd, and Ni is compared with the effects upon the rates of reduction by diimide (diazene) (Garbisch) and the association constants with a Ni(0) complex (Tolman). These later reactions serve as models for the effect of structure on certain of the elementary reactions of catalysis by metals. Some of the factors which determine the selectivity of a catalyst are reviewed including the kinetics, the metal, and the importance of isomerization as a competing reaction. 

Pd and Ni catalysts with the structural effects on reductions with diimide (diazene) (ref. 6) and the equilibrium constants for the association of substituted ethylenes with a Ni(0) complex (ref. 7). These particular reactions were chosen because of our perception of their relation to the mechanisms of catalytic hydrogenation, and the insightful analysis of the relationship between structure and reactivity provided by the authors of these studies. 

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