Fulminate anion

Singh and Palkar [726] identified an initial deceleratory reaction in the decomposition of silver fulminate. This obeyed first-order kinetics (E = 27 kJ mole-1) and overlapped with the acceleratory period of the main reaction, which obeyed the power law [eqn. (2), n = 2] with E = 119 kj mole-1. The mechanism proposed included the suggestion that two-dimensional growth of nuclei involved electron transfer from anion to metal. 

As shown in the introduction, the DNM anion can be regarded as a resonance stabilized, nonlinear planar pseudohalide, which forms an insoluble, highly explosive brownish silver salt upon addition of silver nitrate to an aqueous solution of 7. The DNM anion is related to the linear fulminate ion (CNO ) and can formally be regarded as the addition product of NO to fulminic acid (HCNO). Starting from CH4, NO containing nonlinear pseudohalides can be derived by successive substitution of H by NO, e.g. H3C(NO)/H2C(NO), H2C(N0)2/HC(N0)2 and HC(NO)3/C(NO)3, whereas the linear pseudohalide CNO is formally formed by replacing three H atoms by one NO unit and deprotonation. 

As a rule explosives were listed and described under their parent compounds arranged in alphabetical order, as for example 2,4,6-Trinitroaniline or Picramide is described under ANILINE in Vol I of Encycl. Most of the metallic salts are described under the names of their anions as, for example, Lead Azide (LA) is described under AZIDES, Mercuric Fulminate (MF), under FULMINATES, whereas some salts are described under the names of their cations- as for example Ammonium Nitrate (AN) is described under AMMONIUM in Vol 1... 

Hg(CNO)2 is decomposed by heat (equation 8).4 It crystallizes in the orthorhombic form and contains linearly coordinated mercury.21 It reacts with alkali metal fulminate solutions to form the highly explosive compounds M2Hg(CNO)4 (M = K, Rb, Cs) with larger cations such as Ph4As+ more stable complexes are formed.219,220 Besides the homogeneous anionic mercury(II) fulminato complexes there are a few mixed species with unknown structures, e.g. Na Hg(CNO)2X (X = Cl, Br) or Na2S203-2Hg(CNO).221... 

The only directly accessible metal fulminates are those of mercury(II) and silver(I), very dangerously exposive solids obtained by the action of nitric acid and ethanol on the metals or their salts. Most modern preparations of fulminato complexes involve the conversion of a known amount of mercury fulminate into aqueous sodium fulminate by the action of sodium amalgam and ice-cold water the sodium fulminate solution is then allowed to react with the appropriate amount of a transition metal salt, and the resulting complex fulminato ion is precipitated as the salt of a large cation, most frequently Ph4As+ or R4N+ these are not explosive,4,35 Alkali and alkaline earth metal salts containing complex fulminato anions may be isolated from aqueous solutions, but they are reported to be as exposive as the binary silver and mercury fulminates, and are therefore usually avoided. 

Other aqueous preparative methods include aerial oxidation of an alkaline solution of CoS04 and NaCNO to give the fulminatocobaltate(III) anion [Co(CNO)6]3-, reduction of ruthenate(VI) by excess of fulminate to give [Ru(CNO)6]4, and displacement of 2,2 -bipyridyl or 1,10-phenan-throline from nickel(II) or cobalt(III) complexes to give [Ni(CNO)4]2 or [Co(CNO)6]3. Liquid ammonia may replace water as solvent [Ni(NH3) ]2+ and [Co(NH3)6]3+, for example, react with sodium fulminate in this solvent to form [Ni(CNO)4]2 and [Co(CNO)6]3. In all these reactions fulminate behaves very like cyanide with [AuClJ-, however, reduction to form the gold(I) complex [Au(CNO)2] takes place and no gold(III) complex can be isolated. 

The list of ligands covered by Ref. 1 (vol. 2) starts with the exotic mercury ligand (Dean, p. 1). Silicon and a series of metals (Ge, Ti, Pb) (Harrison, p. 15) also reveal ligand properties. Hydrogen and a variety of hydride anion complexes (Crabtree, p. 689), as well as the complexes formed by anions with a carbon-donor center (cyanides, fulminates, etc.) (Sharpe, p. 25) are briefly discussed. 

Ambident reactivity was shown by oximate anions normally, Oarylation predominated over N-arylation, with ratios of oxime ethers to nitrones ranging from 9 1 (for the benzophenone oxime anion) to 1.7 1 (for the fluorenone oxime anion) [77]. The arylation of two heterocyclic oximes was performed under mild conditions and led mainly to the corresponding oxime ethers which served as good precursors for the generation of unstable aryl fulminates, ArONC [79,80],... 

Burning under reduced pressure Initiating properties of mercuric fulminate Other salts of fulminic acid Manufacture of mercuric fulminate Esters of fulminic acid I lydra >ic acid, its derivatives and salts Decomposition of azides HctcrtK yclics from azides Other react ions of azide anion amt radical Some organic azides Danger of handling a/ides Cyanic triazide... 

Singh and Palkar [71] studied the decomposition of silver fulminate across the interval 463 to 483 K. The initial deceleratory reaction (E, = 27 kJ mol" ) was much more significant than the corresponding process in the mercury salt and overlapped with the onset of the subsequent acceleratory process, which fitted the power law, with n = 2 and = 119 kJ mol. The suggested mechanism is an initial electron-transfer step from the anion to the product metal during the two-dimensional advance of the interface. 

The heavy metal pseudohtilides fall in this group since covalent forces are partially present. The structural parameters listed in Table 4 show that thallous azide, fulminate and cycmate are isostructural with the tetragonal alkali metal salts, while thallous thiocyanate is isostructural with the room temperature phase of potassium thiocyanate. The lattice constants of the salts axe all indicative of abnormally short metal-anion distances. The silver salts form an interesting series where the subtle interactions which result as a function of the electron affinity, electronic structure and size of the anions, stimulate somewhat predictable variations of crystal geometry. Silver azide is an example of a distortion of the tetragonal D4 (Fig. 1) lattice due to covalent metal-emion interaction which lowers the space symmetry of the crystal to D2 (29), while silver thiocyanate is mainly covalent with bidentate metal-anion chains... 

Detailed crystal structures of only a few of the other heavy metal pseudohalides are available in the literature. Among them are, cuprous azide which has a relatively simple tetragonal lattice and cupric azide, mercuric fulminate and a-lead azide which have increasingly complex orthorhombic lattices. a-Lead azide has four types of anion sites of varying amounts of as5nnmetry (33) while cupric azide (35) and mercuric fulminate (72) have two such sites. The structure of cupric azide which is built up of distorted octahedra of asymmetric Ns ions about the central cupric ion is analogous to that of a transition metal complex. 

Hydroxamic acids react with diaryliodonium salts to afford the O-phenyl derivatives. number of heterocyclic compounds containing A -hydroxyamino groups were selectively arylated on the oxygen atom. 0 (Table 5.4) In the case of oximate anions, ambident behaviour was observed, with predominant 0-arylation. With heterocyclic oximes, the 0-aryl ethers were mainly formed and served as precursors to prepare unstable aryl fulminates, 19 (Table 5.5) In the reaction of quinolone derivatives with diaryliodonium salts, the products of O- or C-arylation were obtained.(Table 5.6)... 

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