Methylsemicarbazide as a Ligand in Late 3d Transition Metal Complexes

Abstract

Most ignition and initiation systems nowadays still contain poisonous chemicals such as lead styphnate and lead azide but also chromates and other compounds of high concern. Therefore, methylsemicarbazide (1, MSC), which can be prepared in a one-step reaction and in an extraordinary high yield of 95 %, has been evaluated as ligand in energetic coordination compounds. For the first time 25 new transition metal complexes (Mn , Ni , Co , Cu , and Zn ) using methylsemicarbazide (1) as the ligand were prepared and comprehensively analyzed by, for example, XRD, IR, EA, UV/Vis and DSC/DTA/TGA. Many show a strong energetic character, which can be tuned by using different anions such as Cl , SO , NO , ClO , picrate or styphnate. Selected compounds were additionally evaluated as lead-free primary explosives in initiation tests (nitropenta filled detonators) and in laser ignition systems. Especially compound 7 showed very promising results during these tests and could be a potential candidate for future applications.

N2-Alkylation of semicarbazones. A general and efficient protocol for the synthesis of 2-alkylsemicarbazides from semicarbazide

“…Similarly, 2-benzyl-2h,i,k and 2-(4-methoxybenzyl)-substituted semicarbazones of aliphatic aldehydes 2j,l were prepared in 66-78% yields by alkylation of semicarbazones of propanal, butanal, or 2-methylpropanal 1e,f, (E)-1g after their deprotonation with NaH in MeCN (entries [11][12][13][14][15]. Only a single stereoisomer of 2h-l presumably with (E)-configuration was obtained in each case.…”

“…The first is based on nitrosonation of N-alkylureas with nitrous acid or its anhydride followed by reduction of nitroso group in the obtained N-alkyl-N-nitrosoureas with Zn in aqueous AcOH, [6][7][8] H2 over Pd/C, 9 or using electrochemical method. 10 The second approach involves carbamoylation of the corresponding monosubstituted hydrazines with trimethylsilyl isocyanate, 4,[11][12][13] urea, 14 or cyanic acid generated by reaction of Brønsted acid and metal cyanate. [15][16][17][18] Scheme 1.…”

Substitution of Nitrogen-Rich Linkers with Insensitive Linkers in Azide-Based Energetic Coordination Polymers toward Safe Energetic Materials

“…Primary explosives as an important component of energetic materials have been applied to initiate less sensitive and higher energetic secondary explosives. , Nowadays, metal-based explosives including mercury fulminate (MF), lead styphnate (LS), and lead azide (LA) are the most extensively used primary explosives, but the Hg- and Pb-based primary explosives have high risks to the environment and health. , Since the development of weapons has gone toward security and miniaturization, traditional primary explosives with high mechanical and electrostatic sensitivities and low heats of detonation have been losing their competitive edge. − Many terrible accidents have been caused by primary explosives due to high sensitivities. , Advancements in primary explosives have been motivated by requiring the achievement of remarkable energetic performance with relatively acceptable mechanical and electrostatic sensitivities (but not too insensitive to ignite) for the safe handling of energetic materials. ,− …”

A New Efficient Route to 2-Alkylsemicarbazides

“…The first is based on nitrosonation of N-alkylureas with nitrous acid or its anhydride, followed by reduction of the nitroso group in the obtained N-Alkyl-N-nitrosoureas with Zn in aqueous AcOH [6][7][8], H2 over Pd/C [9], or using the electrochemical method [10]. The second approach involves carbamoylation of the corresponding monosubstituted hydrazines with trimethylsilyl isocyanate [4,[11][12][13], urea [14], or cyanic acid generated by reaction of Brønsted acid and metal cyanate [15][16][17][18]. In addition, there are some particular syntheses of 2-alkylsemicarbazides.…”