Transition metal complexes perchlorates

Numerous explosives are based on hydrazine and its derivatives, including the simple azide, nitrate, perchlorate, and diperchlorate salts. These are sometimes dissolved in anhydrous hydrazine for propeUant appUcations or in mixtures with other explosives (207). Hydrazine transition-metal complexes of nitrates, azides, and perchlorates are primary explosives (208). 

Cationic complexes of rran.s-chelating tridentate ligand, (/ ,/ )-4,6-dibenzo-furandiyl-2,2 -bis(4-phenyloxazoline), with transition metal(II) perchlorates as effective catalysts for asymmetric cycloaddition of nitrones 98YGK368. 

The cationic aqua complexes prepared from traws-chelating tridentate ligand, R,R-DBFOX/Ph, and various transition metal(II) perchlorates induce absolute enantio-selectivity in the Diels-Alder reactions of cyclopentadiene with 3-alkenoyl-2-oxazoli-dinone dienophiles. Unlike other bisoxazoline type complex catalysts [38, 43-54], the J ,J -DBFOX/Ph complex of Ni(C104)2-6H20, which has an octahedral structure with three aqua ligands, is isolable and can be stored in air for months without loss of catalytic activity. Iron(II), cobalt(II), copper(II), and zinc(II) complexes are similarly active. 

Because trifluoromethanesulfonic acid is a stronger acid than perchloric acid, under no circumstances should perchlorate salts be used with the neat acid, because the hot anhydrous perchloric acid so formed represents an extreme explosion hazard, especially in contact with transition metal complexes (or with organic materials). See Perchloric acid Dehydrating agents See other ORGANIC ACIDS... 

One possible strategy in the development of low-overpotential methods for the electroreduction of C02 is to employ a catalyst in solution in the electrochemical cell, A few systems are known that employ homogeneous catalysts and these are based primarily on transition metal complexes. A particularly efficient catalyst is (Bipy)Re[CO]3Cl, where Bipy is 2,2 bipyridine, which was first reported as such by Hawecker et al. in 1983. In fact, this first report concerned the photochemical reduction of C02 to CO. However, they reasoned correctly that the complex should also be capable of catalysing the electrochemical reduction reaction. In 1984, the same authors reported that (Bipy)Re[C013CI catalysed the reduction of C02 to CO in DMF/water/ tetraalkylammonium chloride or perchlorate with an average current efficiency of >90% at —1.25 V vs. NHE (c. —1.5V vs. SCE). The product analysis was performed by gas chromatography and 13C nmr and showed no other products. 

Perchlorate Frequencies of Early Transition Metal Complexes... 

This method was successfully applied using acetates [64,65], acetylacetonates [66,67], alkoxides [16,68,69] and [Pd2(dba)j] [70]. In fact, the first NHC transition metal complex reported by WanzUck and Schonherr in 1968 [3] used mercury(II) acetate and 1,3-diphenylimidazolium perchlorate as the starting materials. 

Even though both Hohenberg-Kohn and Kohn-Sham papers have been subsequently recognized as extremely important for Chemistry, that recognition came late in the community of theoretical chemists. Meanwhile, the MS-Xa method received much more attention. Por example, in 1970, Johnson and Smith addressed polyatomic molecules such as perchlorate and sulphate ions for the first time [13]. A landmark application of MS-Xa was the first investigation by Johnson and Smith of the electronic structure of a coordination compound, namely the permanganate ion [22]. The interest in the MS-Xa method for calculating the electronic structure of transition metal complexes increased rapidly and realistic results were soon obtained [23-25]. 

Caution. Under no circumstances should perchlorate salts be used in any of the reactions involving neat triflic acid. The anhydrous hot perchloric acid thus produced represents an extremely explosive hazard, especially in contact with transition metal complexes. Addition of anhydrous diethyl ether to such solutions would represent an additional explosive hazard. Trifluoromethanesulfonic acid, its salts, and its complexes are extremely stable thermally, and no explosive hazards are known. However, consideration should be given to the thermal stability of other components of the complex before any new reactions are attempted at elevated temperatures. 

Fairly little is known about self-assembly of transition metal complexes via Tr-arene interactions. A prominent example, [AgC104(C6H6)] , 94, was structurally characterized at a time when X-ray crystallography was still far from being a routine method [87]. Crystals of 94 can be obtained by recrystallizing silver(I) perchlorate... 

Strained Carbocyclic Systems.—A large number of examples of catalysis of valence isomerization of strained ring compounds by transition-metal complexes has been considered during the period covered by this Report. The most commonly used metal centres are rhodium and silver, and much of the interest in this field is concentrated on determining and accounting for the differences, in effectiveness and in the nature of the products, between rhodium catalysts and silver catalysts. Thus, for instance, in the presence of [RhCl(nor)]2 or [RhCl(cod)]2, cubane (1) isomerizes to the diolefin (2), but in the presence of silver perchlorate cubane isomerizes to cuneane (3). ... 

Transition metal hydrazine perchlorate, nitrate, and azide complexes are explosive in nature, as indicated by DTA experiments and impact sensitivity measurements. Special precautions have to be taken during the synthesis and characterization of these materials. Small quantities of up to 1 g can be prepared without any explosion. Special mention should be made of the nickel hydrazine azide complex, which is prepared from NiCli + NaNa-I-2N2H4 H2O. The product is highly friction sensitive, especially in dry state, and so samples are to be handled with a Teflon spatula. A few milligrams are used for DTA and impact sensitivity tests. 

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